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Shaktism

2023-03-20T16:13:52Z

173.165.237.1: /* Theology */

{{Short description|Goddess-centric sect of Hinduism}}
{{Good article}}
{{EngvarB|date=March 2015}}
{{Use dmy dates|date=March 2015}}
[[File:Statues of Vaishnavi, Varahi, Indrani and Camunda, National Museum, New Delhi.jpg|thumb|260px|Shaktism is a goddess-centric tradition of Hinduism.<ref name="Klostermaier2010p30"/><ref name="flood174">{{citation|last=Flood|first=Gavin D. |title=An Introduction to Hinduism |url=https://books.google.com/books?id=KpIWhKnYmF0C&pg=PA82 |pages=174–176 |year=1996 |publisher=Cambridge University Press|isbn=978-0-521-43878-0}}</ref> Relief statues of [[Vaishnavi (Matrika goddess)|Vaishnavi]], [[Varahi]], [[Indrani]] and [[Chamunda]]]]
{{Saktism}}
{{Hinduism}}

'''Shaktism''' ({{lang-sa|शाक्त}}, {{IAST3|Śākta}}, {{lit|doctrine of energy, power, the eternal goddess}}) is one of several major [[Hindu denominations]], wherein the metaphysical reality is considered metaphorically a woman and Shakti ([[Mahadevi]]) is regarded as the supreme godhead. It includes many goddesses, all considered aspects of the same supreme goddess.<ref name="Klostermaier2010p30">{{cite book|first=Klaus K. |last=Klostermaier |title=Survey of Hinduism, A: Third Edition |year=2010|publisher=State University of New York Press|isbn=978-0-7914-8011-3 |pages=30, 114–116, 233–245}}</ref><ref name="Melton2010p2600">{{cite book|author1=J. Gordon Melton|first2=Martin|last2=Baumann|title=Religions of the World: A Comprehensive Encyclopedia of Beliefs and Practices, 2nd Edition|url=https://books.google.com/books?id=v2yiyLLOj88C&pg=PA2600 |year=2010|publisher=ABC-CLIO|isbn=978-1-59884-204-3|pages=2600–2602}}</ref> Shaktism has different sub-traditions, ranging from those focused on most worshipped [[Durga]], gracious [[Parvati]] to that of fierce [[Kali]].<ref name=britannicashakti/><ref>{{cite book|author=Yudit Kornberg Greenberg|title=Encyclopedia of Love in World Religions |year=2008|publisher=ABC-CLIO|isbn=978-1-85109-980-1|pages=254–256}}</ref>

The [[Sruti]] and [[Smriti]] texts of Hinduism are an important historical framework of the Shaktism tradition. In addition, it reveres the texts ''[[Devi Mahatmya]]'', the ''[[Devi-Bhagavata Purana]]'', ''[[Kalika Purana]]'' and [[Shakta Upanishads]] such as the [[Devi Upanishad]].<ref>{{cite book |first1=Constance|last1=Jones|first2=James|last2=Ryan|title=Encyclopedia of Hinduism |year=2014|publisher=Infobase Publishing |isbn=978-0816054589 |page=399}}</ref> The ''Devi Mahatmya'' in particular, is considered in Shaktism to be as important as the ''[[Bhagavad Gita]]''.{{sfn|Rocher|1986|p=[https://archive.org/details/historyindianlit00roch_770/page/n199 193]}}

Shaktism is known for its various sub-traditions of [[tantra]],<ref>{{cite book |author1=Katherine Anne Harper |first2=Robert L. |last2=Brown |title=The Roots of Tantra |year=2012 |publisher=State University of New York Press |isbn=978-0-7914-8890-4 |pages=48, 117, 40–53}}</ref> as well as a galaxy of goddesses with respective systems. It consists of the Vidyapitha and [[Kulamārga]]. The pantheon of goddesses in Shaktism grew after the [[decline of Buddhism in India]], wherein [[Hindu]] and [[Buddhist]] goddesses were combined to form the [[Mahavidya]], a list of ten goddesses.<ref>Sanderson, Alexis. [http://www.alexissanderson.com/uploads/6/2/7/6/6276908/sanderson_2014_the_saiva_literature_jist_kyoto_(1).pdf "The Śaiva Literature"]. {{Webarchive|url=https://web.archive.org/web/20160304104838/http://www.alexissanderson.com/uploads/6/2/7/6/6276908/sanderson_2014_the_saiva_literature_jist_kyoto_(1).pdf |date=4 March 2016 }} ''Journal of Indological Studies'' (Kyoto), Nos. 24 & 25 (2012–2013), 2014, pp. 80.</ref> The most common aspects of Devi found in Shaktism include Durga, Kali, [[Saraswati]], [[Lakshmi]], Parvati and [[Tripura Sundari|Tripurasundari]].<ref name="Melton2010p2600"/> The goddess-focused tradition is very popular in eastern India particularly [[West Bengal]], [[Odisha]], [[Bihar]], [[Jharkhand]], [[Tripura]] and [[Assam]], which it celebrates festivals such as the [[Durga puja]], which is popular in West Bengal and Odisha.<ref name=britannicashakti>[https://www.britannica.com/topic/Shaktism "Shaktism"], ''Encyclopædia Britannica'' (2015).</ref>

Shaktism also emphasizes that intense love of deity is more important than simple obedience, thus showing the influence of [[Vaishnavism|Vaishnava]] idea where passionate relationship between [[Radha]] and [[Krishna]] is also the ideal relationship. These older ideas still influence modern Shaktism.{{sfn|McDaniel|2004|p=11}} Similarly, Shaktism's ideas have also influenced [[Vaishnavism]] and [[Shaivism]] traditions. In Shaktism, the goddess is considered as the ''Shakti/Energy'' of [[Vishnu]] and [[Shiva]] respectively, and revered prominently in numerous [[Hindu temple]]s and festivals.<ref name="flood174" />

==Origins and history==
{{main|History of Shaktism}}
The earliest archaeological evidence of what appears to be an [[Upper Paleolithic]] shrine for Shakti worship were discovered in the terminal upper paleolithic site of Baghor I ([[Baghor stone]]) in [[Sidhi district]] of [[Madhya Pradesh]], India. The excavations, carried out under the guidance of noted archaeologists [[G. R. Sharma]] of [[Allahabad University]] and [[J. Desmond Clark]] of [[University of California, Berkeley|University of California]] and assisted by [[Jonathan Mark Kenoyer]] and J.N. Pal, dated the Baghor formation to between 9000 B.C and 8000 B.C.<ref>{{citation |last=Kenoyer |first=J.M.|title=An upper paleolithic shrine in India? |url=https://www.harappa.com/sites/default/files/pdf/Kenoyer1983_An%20Upper%20Palaeolithic%20Shrine%20in%20India.pdf}}</ref>
The origins of Shakti worship can also be traced to [[Indus Valley civilization]].<ref>{{Cite journal |last=Singh |first=Akhileshwar |date=2018-04-10 |title=Goddess Durga: Origin, iconography and mythology |url=http://scientificresearchjournal.com/wp-content/uploads/2018/05/Social-Science-5_A-627-632-Full-Paper.pdf |journal=International Journal of Applied Social Science |volume=5 |number=5}}</ref>
Among the earliest evidence of reverence for the female aspect of God in Hinduism is this passage in chapter 10.125 of the ''[[Rig Veda]]'', also called the [[Devīsūkta|Devi Suktam]] hymn:{{Sfn|McDaniel|2004|p=90}}{{Sfn|Brown|1998|p=26}}<ref name="Hymn 125"/>

{{blockquote|
I am the Queen, the gatherer-up of treasures, most thoughtful, first of those who merit worship.
Thus Gods have established me in many places with many homes to enter and abide in.
Through me alone all eat the food that feeds them, – each man who sees, breathes, hears the word outspoken.
They know it not, yet I reside in the essence of the Universe. Hear, one and all, the truth as I declare it.
I, verily, myself announce and utter the word that Gods and men alike shall welcome.
I make the man I love exceeding mighty, make him nourished, a sage, and one who knows [[Brahman]].
I bend the bow for Rudra [Shiva], that his arrow may strike, and slay the hater of devotion.
I rouse and order battle for the people, I created Earth and Heaven and reside as their Inner Controller.
On the world's summit I bring forth sky the Father: my home is in the waters, in the ocean as Mother.
Thence I pervade all existing creatures, as their Inner Supreme Self, and manifest them with my body.
I created all worlds at my will, without any higher being, and permeate and dwell within them.
The eternal and infinite consciousness is I, it is my greatness dwelling in everything.|[[Devi]] Sukta, ''Rigveda 10.125.3 – 10.125.8'',{{Sfn|McDaniel|2004|p=90}}{{Sfn|Brown|1998|p=26}}<ref name="Hymn 125">[https://en.wikisource.org/wiki/The_Rig_Veda/Mandala_10/Hymn_125 The Rig Veda/Mandala 10/Hymn 125] Ralph T.H. Griffith (Translator); for Sanskrit original see: [https://sa.wikisource.org/wiki/ऋग्वेद:_सूक्तं_१०.१२५ ऋग्वेद: सूक्तं १०.१२५]</ref>}}

The Vedic literature reveres various goddesses, but far less frequently than Gods [[Indra]], [[Agni]] and [[Soma (deity)|Soma]]. Yet, they are declared equivalent aspects of the neutral Brahman, of [[Prajapati]] and [[Purusha]].{{citation needed|date=August 2022}} The goddesses often mentioned in the Vedic layers of text include the Ushas (dawn), [[Vāc]] (speech, wisdom), Sarasvati (as river), Prithivi (earth), Nirriti (annihilator), Shraddha (faith, confidence).<ref name="Melton2010p2600"/> Goddesses such as Uma appear in the [[Upanishad]]s as another aspect of divine and the knower of ultimate knowledge (Brahman), such as in section 3 and 4 of the ancient ''[[Kena Upanishad]]''.<ref name=pauldeussen34>{{cite book |first=Paul |last=Deussen |title=Sixty Upaniṣads of the Veda, Part 1 |year=1980| publisher=Motilal Banarsidass |isbn=978-81-208-1468-4|pages=207–208, 211–213 verses 14–28}}</ref><ref name=charleskenaprose>Charles Johnston, Kena Upanishad in The Mukhya Upanishads: Books of Hidden Wisdom, (1920–1931), The Mukhya Upanishads, Kshetra Books, {{ISBN|978-1-4959-4653-0}} (Reprinted in 2014), [http://www.universaltheosophy.com/pdf-library/Kena%20Upanishad_Johnston.pdf Archive of Kena Upanishad - Part 3 as published in Theosophical Quarterly, pages 229–232]</ref>

Hymns to goddesses are in the ancient Hindu epic ''Mahabharata'', particularly in the ''Harivamsa'' section, which was a late addition (100 to 300 CE) to the work.<ref name="FulkersonBriggs139"/> The archaeological and textual evidence implies, states Thomas Coburn, that the goddess had become as prominent as God in Hindu tradition by about the third or fourth century.{{Sfn|Coburn|2002|p=7}} The literature on Shakti theology grew in ancient India, climaxing in one of the most important texts of Shaktism called the ''Devi Mahatmya.'' This text, states C. Mackenzie Brown – a professor of Religion, is both a culmination of centuries of Indian ideas about the divine woman, as well as a foundation for the literature and spirituality focussed on the female transcendence in centuries that followed.<ref name="FulkersonBriggs139">{{cite book|first=N. B. |last=Saxena |title=The Oxford Handbook of Feminist Theology |editor1-first=Mary McClintock |editor1-last=Fulkerson |editor2-first=Sheila |editor2-last=Briggs |year=2012 |publisher=Oxford University Press |isbn=978-0-19-927388-1 |page=139}}</ref> The ''Devi-Mahatmya'' is not the earliest literary fragment attesting to the existence of devotion to a goddess figure, states [[Thomas B. Coburn]] – a professor of Religious Studies, but "it is surely the earliest in which the object of worship is conceptualized as goddess, with a capital G".{{Sfn|Coburn|1991|p=16}}

Other important texts of Shaktism include the ''[[Shakta Upanishads]]'',{{sfn|Krishna Warrier|1999|pages=ix-x}} as well as Shakta-oriented [[Puranas|Upa Puranic literature]] such as the ''Devi Purana'' and ''[[Kalika Purana]]'',{{sfn|Bhattacharyya|1996|page=164}} the ''[[Lalita sahasranama|Lalita Sahasranama]]'' (from the ''[[Brahmanda Purana]]'').{{sfn|Dikshitar|1999|pages=1–36}}{{sfn|Brown|1998|pages=8, 17, 10, 21, 320}} The ''[[Tripura Upanishad]]'' is historically the most complete introduction to Shakta Tantrism,{{Sfn|Brooks|1990|pp=xiii–xiv}} distilling into its 16 verses almost every important topic in Shakta Tantra tradition.{{Sfn|Brooks|1990|pp=xvi}} Along with the ''Tripura Upanishad'', the ''[[Tripuratapini Upanishad]]'' has attracted scholarly [[bhasya]] (commentary) in the second half of 2nd-millennium, such as the work of [[Bhaskararaya]],{{Sfn|Brooks|1990|pp=37-38}} and Ramanand.{{Sfn|Brooks|1990|p=221 with note 64}} These texts link the Shakti [[Tantra]] tradition as a Vedic attribute,{{Sfn|Dasgupta|1996|p=3}} however this link has been contested by scholars.{{Sfn|Brooks|1990|pp=xiii–xiv, xvi, 21}}<ref name=hughurban/>

The 18th-century Shakta [[bhakti]] poems and songs were composed by two Bengal court poets, [[Bharatchandra Ray]] and [[Ramprasad Sen]],{{sfn|McDermott|2005|p=826}} as well as the Tamil collection [[Abhirami Anthadhi]].{{Citation needed|date=July 2021}}

Shakta-universalist [[Sri Ramakrishna]], one of the most influential figures of the [[Hindu reform movements]], believed that all Hindu goddesses are manifestations of the same [[mother goddess]].{{sfn|McDermott|2005|p=826}}

==Theology==
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| footer = In Shakta theology, the female and male are interdependent realities, represented with [[Ardhanarishvara]] icon. Left: A 5th century art work representing this idea at the [[Elephanta Caves]]; Right: a painting of Ardhanarishvara.
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{{Quote box
|quote = The central conception of Hindu philosophy is of the Absolute; that is the background of the universe. This Absolute Being, of whom we can predicate nothing, has Its ''powers'' spoken of as ''She'' — that is, the real personal God in India is She.<ref>{{cite web
|url=http://www.ramakrishnavivekananda.info/vivekananda/volume_9/lectures_and_discourses/the_women_of_india.htm
|title=Complete-Works/Volume 9/Lectures and Discourses/THE WOMEN OF INDIA|access-date=2021-12-21}}</ref>
|author = — [[Swami Vivekananda]]
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Shaktas conceive the goddess as the supreme, ultimate, eternal reality of all existence, or same as the Brahman concept of Hinduism. She is considered to be simultaneously the source of all creation, its embodiment and the energy that animates and governs it, and that into which everything will ultimately dissolve.{{sfn|Bhattacharyya|1996|page=1}}<ref name="Melton2010p2600"/> Maha Devi said in Devi Upanishad, verse 2, "I am essentially Brahman".<ref>{{cite web | url=https://bharatabharati.in/2016/10/10/devi-upanishad-rishi-atharvan-3/ | title=Devi Upanishad – Rishi Atharvan | date=10 October 2016 }}</ref><ref>{{cite web | url=http://www.vyasaonline.com/devi-upanishad/ | title=Devi Upanishad – Vyasa Mahabharata }}</ref><ref>{{cite web|url=https://www.astrojyoti.com/deviupanishad.htm |title=Devi Upanishad |publisher=Astrojyoti.com |date=2022-05-30 |accessdate=2022-09-01}}</ref><ref>{{cite web|url=https://archive.org/stream/1UpanishadsRigVeda/5Upanishads%20-%20Atharva%20Veda_djvu.txt |title=Full text of "108 Upanishads English Translation" |date=2022-01-14 |accessdate=2022-09-01}}</ref> According to V. R. Ramachandra Dikshitar – a professor of Indian history, in Shaktism theology "Brahman is static Shakti and Shakti is dynamic Brahman."{{sfn|Dikshitar|1999|pages=77-78}}

Shaktism views the Devi as the source, essence and substance of everything in creation.<ref name="Melton2010p2600"/> Its texts such as the ''[[Devi-Bhagavata Purana]]'' states:

{{Blockquote|I am Manifest Divinity, Unmanifest Divinity, and Transcendent Divinity. I am Brahma, Vishnu and Shiva, as well as Saraswati, Lakshmi and Parvati. I am the Sun and I am the Stars, and I am also the Moon. I am all animals and birds, and I am the outcaste as well, and the thief. I am the low person of dreadful deeds, and the great person of excellent deeds. I am Female, I am Male in the form of Shiva.{{efn|''Srimad Devi Bhagavatam'', VII.33.13-15, cited in Brown 1991{{sfn|Brown|1991|page=186}}}} }}

Shaktism's focus on the Divine Female does not imply a rejection of the male. It rejects masculine-feminine, male-female, soul-body, transcendent-immanent dualism, considering nature as divine. Devi is considered to be the cosmos itself – she is the embodiment of energy, matter and soul, the motivating force behind all action and existence in the material universe.<ref>{{cite book|author=Neela B Saxena| editor1=Mary McClintock Fulkerson|editor2=Sheila Briggs|title=The Oxford Handbook of Feminist Theology |year=2012|publisher=Oxford University Press|isbn=978-0-19-927388-1|pages=134–138, 140}}</ref> Yet in Shaktism, states C. MacKenzie Brown, the cultural concepts of masculine and the feminine as they exist among practitioners of Shaktism are aspects of the divine, transcendent reality.{{sfn|Brown|1991|page=217}} In Hindu iconography, the cosmic dynamic of male-female or masculine-feminine interdependence and equivalence, is expressed in the half-Shakti, half-Shiva deity known as [[Ardhanari]].{{sfn|Yadav|2001}}

The philosophical premises in many Shakta texts, states professor of Religious Studies June McDaniel, is syncretism of [[Samkhya]] and [[Advaita Vedanta]] schools of [[Hindu philosophy]], called ''Shaktadavaitavada'' (literally, the path of nondualistic Shakti).{{Sfn|McDaniel|2004|pp=89–91}}

The Hindu monk [[Swami Vivekananda]], remarked thus; about being an actual Shakti worshipper:
"Do you know who is the real "Shakti-worshipper"? It is he who knows that God is the omnipresent force in the universe and sees in women the manifestation of that Force."
<ref>{{cite web
|url=https://www.ramakrishnavivekananda.info/vivekananda/volume_5/epistles_first_series/006_haripada.htm
|title=Complete-Works/Volume 5/Epistles-First Series
|access-date=2021-12-21}}</ref>

===Devi Gita===
The seventh book of the ''Srimad Devi-Bhagavatam'' presents the theology of Shaktism.{{Sfn|Rocher|1986|p=170}} This book is called ''Devi Gita'', or the "Song of the Goddess".{{Sfn|Rocher|1986|p=170}}{{Sfn|Brown|1998|p=1-2, 85-98}} The goddess explains she is the Brahman that created the world, asserting the Advaita premise that spiritual liberation occurs when one fully comprehends the identity of one's soul and the Brahman.{{Sfn|Rocher|1986|p=170}}{{Sfn|Brown|1998|p=12-17}} This knowledge, asserts the goddess, comes from detaching self from the world and meditating on one's own soul.{{Sfn|Rocher|1986|p=170}}{{Sfn|Pintchman|2015|pp=131-138}}

The ''Devi Gita'', like the ''Bhagavad Gita'', is a condensed philosophical treatise.{{Sfn|Brown|1990|pp=179-198}} It presents the divine female as a powerful and compassionate creator, pervader and protector of the universe.{{Sfn|Brown|1998|pp=1-3}} She is presented in the opening chapter of the ''Devi Gita'' as the benign and beautiful world-mother, called ''Bhuvaneshvari'' (literally, ruler of the universe).{{Sfn|Pintchman|2014|p=26-28}}{{Sfn|Brown|1990|pp=179-198}} Thereafter, the text presents its theological and philosophical teachings.{{Sfn|Brown|1998|pp=1-3}}

{{Quote box
|quote = '''The soul and the Goddess'''
<poem>
My sacred syllable ह्रीम्] transcends,{{efn|ह्रीम् is pronounced as hrīm, it is a tantric mantra bīja, and it identifies a "Shakti".<ref>{{cite book |first=Antonio |last=Rigopoulos |title=Dattatreya: The Immortal Guru, Yogin, and Avatara: A Study of the Transformative and Inclusive Character of a Multi-faceted Hindu Deity |year=1998 |publisher=State University of New York Press |isbn=978-0-7914-3696-7 |page=72 }}</ref>{{sfn|Brooks|1992|p=94 }}}}
the distinction of name and named,
beyond all dualities.
It is whole, infinite [[satcitananda|being, consciousness and bliss]].
One should meditate on that reality,
within the flaming light of consciousness.
Fixing the mind upon me,
as the Goddess transcending all space and time,
One quickly merges with me by realizing,
the oneness of the soul and Brahman.
</poem>
|source = —''Devi Gita'', Transl: Lynn Foulston, Stuart Abbott ''Devibhagavata Purana'', Book 7{{Sfn|Foulston|Abbott|2009|pp=74-75}}
|bgcolor=#FFE0BB
|align = right
}}
The ''Devi Gita'' describes the Devi (or goddess) as "universal, cosmic energy" resident within each individual. It thus weaves in the terminology of [[Samkhya]] school of [[Hindu philosophy]].{{Sfn|Brown|1998|pp=1-3}} The text is suffused with [[Advaita Vedanta]] ideas, wherein nonduality is emphasized, all dualities are declared as incorrect, and interconnected oneness of all living being's soul with Brahman is held as the liberating knowledge.{{Sfn|Brown|1998|pp=1-3, 12-17}}{{Sfn|Pintchman|2015|pp=9, 34, 89-90, 131-138}}{{Sfn|Foulston|Abbott|2009|pp=15-16}} However, adds Tracy Pintchman – a professor of Religious Studies and Hinduism, ''Devi Gita'' incorporates Tantric ideas giving the Devi a form and motherly character rather than the gender-neutral concept of Adi Shankara's Advaita Vedanta.{{Sfn|Pintchman|2014|p=9-10}}

===List of 8 Shakta Upanishads===
{| class="wikitable sortable" style="margin:auto; background:none;"
|+List of the Shakta Upanishads according to [[Muktikā]] anthology{{citation needed|date=July 2021}}
|- style="text-align: center;"
! width=220px style="background" | '''Title'''
! width=60px | '''Muktika serial #'''
! width=150px | '''Attached Veda'''
! width= 300px | '''Period of creation'''
|- style="text-align: center;"
| width=120px |''[[Sita Upanishad]]''
| 45
| width=40px | [[Atharva Veda]]
| width= 200px |At least 10,000 Years Before
|- style="text-align: center;"
| width=120px |''[[Tripuratapini Upanishad]]''
| 80
| width=40px |Atharva Veda
| width= 200px | At least 10,000 Years Before
|- style="text-align: center;"
| width=120px |''[[Devi Upanishad]]''
| 81
| width=40px | Atharva Veda
| width= 200px | At least 10,000 Years Before
|- style="text-align: center;"
| width=120px |''[[Tripura Upanishad]]''
| 82
| width=40px | [[Rigveda]]
| width= 200px |At least 10,000 Years Before
|- style="text-align: center;"
| width=120px |''[[Bhavana Upanishad]]''
| 84
| width=40px | Atharva Veda
| width= 200px |At least 10,000 Years Before
|- style="text-align: center;"
| width=120px |''[[Saubhagyalakshmi Upanishad]]''
| 105
| width=40px | Rigveda
| width= 200px | Unknown
|- style="text-align: center;"
| width=120px |''[[Sarasvati-rahasya Upanishad]]''
| 106
| width=40px | [[Krishna Yajurveda]]
| width= 200px |At least 10,000 Years Before
|- style="text-align: center;"
| width=120px |''[[Bahvricha Upanishad ]]''
| 107
| width=40px | Rigveda
| width= 200px | At least 10,000 Years Before
|}

===Tantra===
Sub-traditions of Shaktism include "Tantra", which refers to techniques, practices and ritual grammar involving ''[[mantra]]'', ''[[yantra]]'', ''[[nyasa (ritual)|nyasa]]'', ''[[mudra]]'' and certain elements of traditional [[kundalini yoga]], typically practiced under the guidance of a qualified [[guru]] after due initiation (''[[diksha]]'') and oral instruction to supplement various written sources.{{sfn|Brooks|1990|pages=47-72}} There has been a historic debate between Shakta theologians on whether its tantric practices are Vedic or non-Vedic.{{sfn|Brooks|1990|page=xii}}{{Sfn|Brooks|1990|pp=xiii–xiv, xvi, 21}}<ref name=hughurban/>

The roots of Shakta Tantrism are unclear, probably ancient and independent of the Vedic tradition of Hinduism. The interaction between Vedic and Tantric traditions trace back to at least the sixth century,{{Sfn|Brooks|1990|p=xii}} and the surge in Tantra tradition developments during the late medieval period, states Geoffrey Samuel, were a means to confront and cope with Islamic invasions and political instability in and after the 14th century CE.<ref>{{cite book |last=Samuel |first=Geoffrey |year=2010 |title=Tantric Revisionings |publisher=Motilal Banarsidass |isbn=978-8120827523 |pages=60–61, 87–88, 351–356}}</ref>

Notable Shakta [[Tantras (Hinduism)|tantras]] are ''Saradatilaka Tantra'' of Lakshmanadesika (11th century), ''Kali Tantra'' (c. 15th century), [[Yogini Tantra]], Sarvanandanatha's ''Sarvolassa Tantra'', Brahmananda Giri's ''Saktananda Tarangini'' with ''Tararahasya'' and Purnananda Giri's ''Syamarahasya'' with ''Sritattvacintamani'' (16th century), Krishananda Agamavagisa's ''Tantrasara'' and Raghunatna Tarkavagisa Bhattacarya ''Agamatattvavilasa'' (17th century), as well as works of Bhaskaracharya (18th century).{{sfn|McDermott|2005|p=827}}

==Principal deities==
[[File:Durga_Loro_Jonggrang_copy.jpg|thumb|180px|A 9th-century Durga Shakti idol, victorious over demon Mahishasura, at the Shiva temple, [[Prambanan]], Indonesia.<ref>{{cite book|author=Keat Gin Ooi|title=Southeast Asia: A Historical Encyclopedia, from Angkor Wat to East Timor|url=https://books.google.com/books?id=QKgraWbb7yoC&pg=PA1101 |year=2004|publisher=ABC-CLIO|isbn=978-1-57607-770-2|pages=1101–1102}}</ref>]]
Shaktas approach the Devi in many forms; however, they are all considered to be but diverse aspects of the one supreme goddess.{{sfn|Kinsley|1987}}{{sfn|Kali|2003|page=149}} The primary Devi form worshiped by a Shakta devotee is his or her ''[[Ishta-deva|ishta-devi]]'', that is a personally selected Devi.<ref>{{cite book|first=Patricia|last=Monaghan|title=Goddesses in World Culture |year=2011|publisher=ABC-CLIO|isbn=978-0-313-35465-6|pages=26, 94}}</ref> The selection of this deity can depend on many factors such as family tradition, regional practice, guru lineage and personal resonance.{{sfn|Kinsley|1987|pp=102-104}}

Some forms of the goddess are widely known in the Hindu world. The common goddesses of Shaktism, popular in the Hindu thought at least by about mid 1st-millennium CE, include Parvati, Durga, Kali, [[Yogmaya]], Lakshmi, Saraswati, [[Gayatri]], [[Radha]] and [[Sita]].{{sfn|Kinsley|1987|pp=1-5}}<ref name="Melton2010p2600"/> The rarer forms of Devi found among tantric Shakta are the [[Mahavidyas]], particularly Tripura Sundari, [[Bhuvaneshvari]], [[Tara (Devi)|Tara]], [[Bhairavi]], [[Chhinnamasta]], [[Dhumavati]], [[Bagalamukhi]], [[Matangi]] and [[Kamalatmika|Kamala]].{{sfn|Kinsley|1987|pp=161-165}}{{sfn|Kinsley|1998}} Other major goddess groups include the ''[[Matrikas|Sapta-Matrika]]'' ("Seven Little Mothers"), "who are the energies of different major Gods, and described as assisting the great Shakta Devi in her fight with demons", and the 64 ''[[Yogini]]s''. Eight forms of goddess Lakshmi are called [[Ashtalakshmi]] and the nine forms of goddess Durga, the [[Navadurga]]s worshipped in [[Navratri]].{{sfn|Bhattacharyya|1996|page=126}}

==Tantric traditions==
===Vidyāpīṭha===
The Vidyāpīṭha is subdivided into Vāmatantras, Yāmalatantras, and Śaktitantras.<ref>Sanderson, Alexis. [http://www.alexissanderson.com/uploads/6/2/7/6/6276908/sanderson_2014_the_saiva_literature_jist_kyoto_(1).pdf "The Śaiva Literature."] {{Webarchive|url=https://web.archive.org/web/20160304104838/http://www.alexissanderson.com/uploads/6/2/7/6/6276908/sanderson_2014_the_saiva_literature_jist_kyoto_(1).pdf |date=4 March 2016 }} Journal of Indological Studies (Kyoto), Nos. 24 & 25 (2012–2013), 2014, pp. 35, 37.</ref>

===Kulamārga===
The [[Kulamārga]] preserves some of the distinctive features of the [[Kāpālika]] tradition, from which it is derived.<ref>Sanderson, Alexis. [http://www.alexissanderson.com/uploads/6/2/7/6/6276908/sanderson_2014_the_saiva_literature_jist_kyoto_(1).pdf "The Śaiva Literature."] {{Webarchive|url=https://web.archive.org/web/20160304104838/http://www.alexissanderson.com/uploads/6/2/7/6/6276908/sanderson_2014_the_saiva_literature_jist_kyoto_(1).pdf |date=4 March 2016 }} Journal of Indological Studies (Kyoto), Nos. 24 & 25 (2012–2013), 2014, pp.4-5, 11, 57.</ref> It is subdivided into four subcategories of texts based on the goddesses Kuleśvarī, Kubjikā, Kālī and Tripurasundarī respectively.<ref>Sanderson, Alexis. [http://www.alexissanderson.com/uploads/6/2/7/6/6276908/sanderson_2014_the_saiva_literature_jist_kyoto_(1).pdf "The Śaiva Literature."] {{Webarchive|url=https://web.archive.org/web/20160304104838/http://www.alexissanderson.com/uploads/6/2/7/6/6276908/sanderson_2014_the_saiva_literature_jist_kyoto_(1).pdf |date=4 March 2016 }} Journal of Indological Studies (Kyoto), Nos. 24 & 25 (2012–2013), 2014, pp. 57-65.</ref> The [[Trika]] texts are closely related to the Kuleśvarī texts and can be considered as part of the Kulamārga.<ref>Sanderson, Alexis. [http://www.alexissanderson.com/uploads/6/2/7/6/6276908/sanderson_2014_the_saiva_literature_jist_kyoto_(1).pdf "The Śaiva Literature."] {{Webarchive|url=https://web.archive.org/web/20160304104838/http://www.alexissanderson.com/uploads/6/2/7/6/6276908/sanderson_2014_the_saiva_literature_jist_kyoto_(1).pdf |date=4 March 2016 }} Journal of Indological Studies (Kyoto), Nos. 24 & 25 (2012–2013), 2014, pp. 59-60, 68.</ref>

==Worship==
Shaktism encompasses a nearly endless variety of beliefs and practices – from animism to philosophical speculation of the highest order – that seek to access the Shakti (Divine Energy or Power) that is believed to be the Devi's nature and form.{{sfn|Subramuniyaswami|2002|page=1211}} Its two largest and most visible schools are the ''Srikula'' (family of ''Tripura Sundari''), strongest in [[South India]], and the ''Kalikula'' (family of ''Kali''), which prevails in northern and eastern India.{{sfn|Subramuniyaswami|2002|page=1211}}

=== Srikula: family of Lalita Tripura Sundari ===
[[File:Lalita sm.JPG|upright|thumb|Sri Lalita-Tripurasundari enthroned with her left foot upon the [[Sri Chakra]], holding her traditional symbols, the sugarcane bow, flower arrows, noose and goad.]]
The ''Srikula'' (family of ''Sri '') tradition (''[[sampradaya]]'') focuses worship on Devi in the form of the goddess ''Lalita-Tripura Sundari''. Rooted in first-millennium. Srikula became a force in South India no later than the seventh century, and is today the prevalent form of Shaktism practiced in South Indian regions such as [[Kerala]], [[Tamil Nadu]] and Tamil areas of [[Sri Lanka]].{{sfn|Brooks|1992|page=back cover}}

The Srikula's best-known school is [[Shri Vidya|Srividya]], "one of Shakta Tantrism's most influential and theologically sophisticated movements." Its central symbol, the ''[[Sri Chakra]]'', is probably the most famous visual image in all of Hindu Tantric tradition. Its literature and practice is perhaps more systematic than that of any other Shakta sect.{{sfn|Brooks|1990|page=xiii}}

Srividya largely views the goddess as "benign [''saumya''] and beautiful [''saundarya'']" (in contrast to Kalikula's focus on "terrifying [''ugra''] and horrifying [''ghora'']" Goddess forms such as Kali or Durga). In Srikula practice, moreover, every aspect of the goddess – whether malignant or gentle – is identified with Lalita.{{sfn|Brooks|1992|pages=59-60}}

Srikula adepts most often worship Lalita using the abstract ''Sri Chakra'' [[yantra]], which is regarded as her subtle form. The Sri Chakra can be visually rendered either as a two-dimensional diagram (whether drawn temporarily as part of the worship ritual, or permanently engraved in metal) or in the three-dimensional, pyramidal form known as the ''Sri Meru''. It is not uncommon to find a ''Sri Chakra'' or ''Sri Meru'' installed in South Indian temples, because – as modern practitioners assert – "there is no disputing that this is the highest form of Devi and that some of the practice can be done openly. But what you see in the temples is not the ''srichakra'' worship you see when it is done privately."{{efn|A senior member of Guru Mandali, Madurai, November 1984, cited in Brooks 1992.{{sfn|Brooks|1992|page=56}} }}

The Srividya ''[[parampara]]s'' can be further broadly subdivided into two streams, the ''[[Kaula (Hinduism)|Kaula]]'' (a ''[[vamachara|vamamarga]]'' practice) and the ''Samaya'' (a ''[[dakshinachara|dakshinamarga]]'' practice). The ''Kaula'' or ''Kaulachara'', first appeared as a coherent ritual system in the 8th century in central India,{{sfn|White|2003|page=219}} and its most revered theorist is the 18th-century philosopher [[Bhaskararaya]], widely considered "the best exponent of Shakta philosophy."{{sfn|Bhattacharyya|1996|page=209}}

The ''Samaya'' or ''Samayacharya'' finds its roots in the work of the 16th-century commentator Lakshmidhara, and is "fiercely puritanical [in its] attempts to reform Tantric practice in ways that bring it in line with high-caste [[brahmin|brahmanical]] norms."{{sfn|Brooks|1990|page=28}} Many Samaya practitioners explicitly deny being either Shakta or Tantric, though scholars argues that their cult remains technically both.{{sfn|Brooks|1990|page=28}} The Samaya-Kaula division marks "an old dispute within Hindu Tantrism,"{{sfn|Brooks|1990|page=28}} and one that is vigorously debated to this day.{{citation needed|date=June 2015}}

===Kalikula: family of Kali===
[[File:Indian - Kali as the Supreme Deity - Walters W897.jpg|thumb|Kali as the supreme deity worshiped by Indra, Brahma, Vishnu and Shiva]]
[[File:Kali_lithograph.jpg|thumb|upright|Kali in her ''Dakshina Kali'' form]]

The ''Kalikula'' (Family of ''Kali'') form of Shaktism is most dominant in northeastern India, and is most widely prevalent in [[West Bengal]], [[Assam]], [[Bihar]] and [[Odisha]], as well as [[Nepal]] and [[Kerala]]. The goddesses Kubjika, Kulesvari, [[Chamunda]], [[Chandi]], Shamshan Kali (goddess of the cremation ground), Dakshina Kali, and Siddheshwari are worshipped in the region of Bengal to protect against disease and smallpox as well as ill omens. ''Kalikula'' lineages focus upon the Devi as the source of wisdom (''vidya'') and liberation (''[[moksha]]''). The tantric part generally stand "in opposition to the brahmanic tradition," which they view as "overly conservative and denying the experiential part of religion."{{sfn|McDaniel|n.d.}}

The main deities of the Kalikula tradition are ''Kali'', ''[[Chandi]]'', ''Bheema'' and ''Durga''. Other goddesses that enjoy veneration are ''Tara'' and all the other ''[[Mahavidyas]]'', [[Kaumari]] as well as regional goddesses such as ''[[Manasa]]'', the snake goddesses, ''Ṣaṣṭī'', the protectress of children, ''[[Shitala|Śītalā]]'', the smallpox goddess, and ''[[Umā]]'' (the Bengali name for Parvati) — all of them, again, considered aspects of the Divine Mother.{{sfn|McDermott|2005|p=826}}{{sfn|McDaniel|n.d.}}

In [[Nepal]] devi is mainly worshipped as the goddess Bhavani. She is one of the important Hindu deities in Nepal.
Two major centers of Shaktism in West Bengal are [[Kalighat]] where the skull of Kali is believed to be worshipped along with her 25 forms. The kali ghat temple is located in [[Calcutta]] and [[Tarapith]] in [[Birbhum district]]. In Calcutta, emphasis is on devotion (''bhakti'') to the goddess as ''Kali''. Where the goddess(kali) is seen as the destroyer of evil.:

{{Blockquote|She is "the loving mother who protects her children and whose fierceness guards them. She is outwardly frightening – with dark skin, pointed teeth, and a necklace of skulls – but inwardly beautiful. She can guarantee a good rebirth or great religious insight, and her worship is often communal – especially at festivals, such as ''Kali Puja'' and ''Durga Puja''. Worship may involve contemplation of the devotee's union with or love of the goddess, visualization of her form, chanting [of her] ''mantras'', prayer before her image or ''yantra'', and giving [of] offerings."{{sfn|McDaniel|n.d.}} }}

At Tarapith, Devi's manifestation as ''Tara'' ("She Who Saves") or ''Ugratara'' ("Fierce Tara") is ascendant, as the goddess who gives liberation (''kaivalyadayini''). [...] The forms of ''sadhana'' performed here are more ''[[yogic]]'' and ''tantric'' than devotional, and they often involve sitting alone at the [cremation] ground, surrounded by ash and bone. There are [[shamanic]] elements associated with the Tarapith tradition, including "conquest of the Goddess, exorcism, trance, and control of spirits."{{sfn|McDaniel|n.d.}}

The philosophical and devotional underpinning of all such ritual, however, remains a pervasive vision of the Devi as supreme, absolute divinity. As expressed by the 19th-century saint [[Ramakrishna]], one of the most influential figures in modern Bengali Shaktism:

{{Blockquote|Kali is none other than Brahman. That which is called Brahman is really Kali. She is the Primal Energy. When that Energy remains inactive, I call It Brahman, and when It creates, preserves, or destroys, I call It Shakti or Kali. What you call Brahman I call Kali. Brahman and Kali are not different. They are like fire and its power to burn: if one thinks of fire one must think of its power to burn. If one recognizes Kali one must also recognize Brahman; again, if one recognizes Brahman one must recognize Kali. Brahman and Its Power are identical. It is Brahman whom I address as Shakti or Kali.{{sfn|Nikhilananda|2000|page=734}} }}

===Festivals===
Shaktas celebrate most major Hindu festivals, as well as a huge variety of local, temple- or deity-specific observances. A few of the more important events are listed below:{{sfn|Pattanaik|2000|pages=103-109}}

====Navaratri====
{{Main|Navaratri}}

The most important Shakta festival is ''[[Navratri|Navaratri]]'' (lit., "Festival of Nine Nights"), also known as "Sharad Navaratri" because it falls during the Hindu month of [[Sharad (Indian season)|Sharad]] (October/November). This is the festival that worships the [[Navadurgas]], forms of [[Devi]]. This festival – often taken together with the following tenth day, known as ''Dusshera'' or ''[[Vijayadashami]]'' – celebrates the goddess Durga's victory over a series of powerful demons described in the ''[[Devi Mahatmya]]''.{{Sfn|Kinsley|1987|pp=95-115}} In [[Bengal]], the last four days of Navaratri are called Durga Puja, and mark one episode in particular: Durga's iconic slaying of [[Mahishasura]] (lit., the "Buffalo Demon").{{sfn|McDermott|2005|p=826}}<ref>"Durga Puja," [http://www.durga-puja.org/ DurgaPuja.org].</ref> Durga Puja also became the main religio-cultural celebration within the Bengal diaspora in the West (together with Kali and [[Saraswati Pooja|Sarasvati]] Pujas, if a community enough big and rich).{{sfn|McDermott|2005|p=830}}

While Hindus of all denominations celebrate the autumn Navratri festival, Shaktas also celebrate two additional Navratris – one in the spring and one in the summer. The spring festival is known as ''Vasanta Navaratri'' or ''Chaitra Navatri'', and celebrated in the Hindu month of [[Chaitra]] (March/April). Srividya lineages dedicate this festival to Devi's form as the goddess Tripura Sundari. The summer festival is called ''Ashada Navaratri'', as it is held during the Hindu month of [[Ashadha]] (June/July). The [[Vaishno Devi]] temple in [[Jammu]], with Vaishno Devi considered an aspect of Durga, celebrates Navaratri.{{Sfn|Kinsley|1987|pp=95-115}}<ref>{{cite book|author=Susan Snow Wadley|title=Raja Nal and the Goddess: The North Indian Epic Dhola in Performance |year=2004|publisher=Indiana University Press|isbn=0-253-11127-7|pages=103–104}}</ref> ''Ashada Navaratri'', on the other hand, is considered particularly auspicious for devotees of the boar-headed Goddess [[Varahi]], one of the seven Matrikas named in the ''Devi Mahatmya''.<ref>"Regaling Varahi with different 'alankarams' in 'Ashada Navaratri'," 24 July 2007, [https://web.archive.org/web/20071114233110/http://www.hindu.com/2007/07/24/stories/2007072456270200.htm The Hindu].</ref>

====Vasant Panchami====
{{Main|Vasant Panchami}}

====Diwali and others====
{{Main|Diwali}}
[[Lakshmi Puja]] is a part of Durga Puja celebrations by Shaktas, where Laksmi symbolizes the goddess of abundance and autumn harvest.{{Sfn|Kinsley|1987|p=33}} Lakshmi's biggest festival, however, is ''[[Diwali]]'' (or ''Deepavali''; the "Festival of Lights"), a major Hindu holiday celebrated across India and in Nepal as Tihar. In North India, Diwali marks the beginning of the traditional New Year, and is held on the night of the new moon in the Hindu month of [[Kartika (month)|Kartik]] (usually October or November). Shaktas (and many non-Shaktas) celebrate it as another Lakshmi Puja, placing small oil lamps outside their homes and praying for the goddess's blessings.<ref>"Diwali Festival", [http://www.diwalifestival.org/ DiwaliFestival.org].</ref> Diwali coincides with the celebration of [[Kali Puja]], popular in Bengal,{{sfn|McDermott|2005|p=826}} and some Shakta traditions focus their worship on Devi as Parvati rather than Lakshmi.<ref>"Kali Pooja in Bengal," [http://www.diwalifestival.org/kali-pooja-in-bengal.html Diwali Festival.org].</ref>

[[File:India Meenakshi Temple.jpg|thumb|A [[gopuram]] (tower) of the [[Meenakshi Amman Temple]], a Shakta temple at Madurai, Tamil Nadu, [[India]]]]

''[[Jagaddhatri]] Puja'' is celebrated on the last four days of the Navaratis, following Kali Puja. It is very similar to Durga Puja in its details and observance, and is especially popular in Bengal and some other parts of Eastern India. ''[[Parvati|Gauri]] Puja'' is performed on the fifth day after [[Ganesh Chaturthi]], during [[Ganesha]] Puja in Western India, to celebrate the arrival of Gauri, Mother of Ganesha where she brings her son back home.{{citation needed|date=October 2016}}

Major Shakta temple festivals are ''Meenakshi Kalyanam'' and ''[[Ambubachi Mela]]''. The ''Meenakshi Kalyanam'' is a part of the [[Chithirai Thiruvizha]] festival in [[Madurai]] around April/May, one of the largest festivals in South India, celebrating the wedding of goddess [[Minakshi|Meenakshi]] (Parvati) and Shiva. The festival is one where both the Vaishnava and Shaiva communities join the celebrations, because Vishnu gives away his sister Parvati in marriage to Shiva.<ref>{{cite book|first1=Constance|last1=Jones|first2=James D.|last2=Ryan|title=Encyclopedia of Hinduism |year=2006|publisher=Infobase Publishing|isbn=978-0-8160-7564-5| pages=112–113}}</ref> ''[[Ambubachi Mela]]'' or Ameti is a celebration of the menstruation of the goddess, by hundreds of thousands of devotees, in a festival held in June/July (during the monsoon season) at [[Kamakhya Temple]], Guwahati, Assam. Here the Devi is worshiped in the form of a [[yoni]]-like stone, and the site is one of Shakta Pitha or pilgrimage sites in Shaktism.<ref>{{cite book|first=Roshen|last=Dalal|title=The Religions of India: A Concise Guide to Nine Major Faiths|url=https://books.google.com/books?id=pNmfdAKFpkQC&pg=PA184 |year=2010 |publisher=Penguin Books |isbn=978-0-14-341517-6|page=184}}</ref>

===Animal sacrifice===
{{multiple image
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| image1 = Durga slaying the Buffalo demon Mahisuramardini LACMA M.70.42.8.jpg
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| image2 = Immolation Sacrifice, Mouh Boli, Durga Puja.jpg
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| footer = In Shaktism mythology, Durga slays an evil buffalo demon (left, 18th century statue).<ref name="Fuller Christopher John 2004 83"/> Right: A buffalo about to be sacrificed by a villager during Durga puja festival. The buffalo sacrifice practice, however, is rare in contemporary India.<ref>{{cite book|author=Christopher John Fuller|title=The Camphor Flame: Popular Hinduism and Society in India |year=2004|publisher=Princeton University Press|isbn=0-691-12048-X|page=141}}</ref>
}}
Shaktism tradition practices animal sacrifice to revere goddesses such as Kali in many parts of India but particularly in the eastern states of India and Nepal. This is either an actual animal, or a vegetable or sweet dish substitute considered equivalent to the animal.<ref>{{cite book|first=Rachel Fell|last=McDermott|title=Revelry, Rivalry, and Longing for the Goddesses of Bengal: The Fortunes of Hindu Festivals |year=2011|publisher=Columbia University Press|isbn=978-0-231-12919-0|pages=204–205}}</ref> In many cases, Shaktism devotees consider animal sacrifice distasteful, and practice alternate means of expressing devotion while respecting the views of others in their tradition.<ref>{{cite book|first1=Ira|last1=Katznelson|first2=Gareth Stedman |last2=Jones|title=Religion and the Political Imagination |year=2010|publisher=Cambridge University Press|isbn=978-1-139-49317-8|page=343}}</ref>

In Nepal, West Bengal, Odisha and Assam, animal sacrifices are performed at Shakti temples, particularly to mark the legend of goddess Durga slaying the buffalo demon. This involves slaying of a [[goat]] or a male [[water buffalo]]. Animal sacrifice is also an essential component as part of the [[Kaula (Hinduism)|Kaula]] [[tantra]] school of Shaktism. This practice is rare among Hindus, outside this region.<ref name="Fuller Christopher John 2004 83">{{cite book|last=Fuller Christopher John|title=The camphor flame: popular Hinduism and society in India|url=http://press.princeton.edu/titles/7823.html|edition=Revised and Expanded|year=2004|publisher=Princeton University Press|isbn=978-0-691-12048-5|page=83|chapter=4}}</ref>

In Bengal, animal sacrifice ritual follows the guidelines in texts such as Mahanirvana Tantra.These ritual includes selecting the animal, then a priest offers a prayer to the animal, then recites the [[Gayatri Mantra]] in its ear before killing it.<ref>{{cite book|last1=McDermott|first1=Rachel Fell|title=Revelry, rivalry, and longing for the Goddesses of Bengal: the fortunes of Hindu festivals|date=2011|publisher=Columbia University Press|location=New York, Chichester|isbn=978-0-231-12918-3|page=205|url=https://books.google.com/books?id=ggBeH_lmUu8C&pg=PR10 |access-date=17 December 2014}}</ref> The meat of the sacrificed animal is then cooked and eaten by the Shakta devotees.<ref name="Fuller Christopher John 2004 83"/>

In Nepal, animal sacrifice ''en masse'' occurs during the three-day-long [[Gadhimai festival]]. In 2009 it was speculated that more than 250,000 animals were sacrificed during this event.<ref>{{cite news|first=Olivia |last=Lang |url=https://www.theguardian.com/world/2009/nov/24/hindu-sacrifice-gadhimai-festival-nepal |title=Hindu sacrifice of 250,000 animals begins | World news | guardian.co.uk |publisher=Guardian |date= 2009-11-24|access-date=2012-08-13 |location=London}}</ref><ref>{{cite news|url=http://edition.cnn.com/2009/WORLD/asiapcf/11/24/nepal.animal.sacrifice/index.html |title=Ritual animal slaughter begins in Nepal - CNN.com |publisher=Edition.cnn.com |date=2009-11-24 |access-date=2012-08-13}}</ref>

In Odisha, during the [[Bali Jatra]], Shaktism devotees sacrifice male goats to the goddess [[Samaleswari]] in her temple in [[Sambalpur]], Orissa.<ref>{{cite book|first1= Georg |last1= Pfeffer |first2= Deepak Kumar |last2= Behera|title= Contemporary Society: Developmental issues, transition, and change|url= https://books.google.com/books?id=TZOvYPBrxl0C&pg=PA312 |publisher= Concept Publishing Company|page= 312|year= 1997|isbn= 9788170226420}}</ref><ref>{{cite web|url=http://orissa.gov.in/e-magazine/Orissareview/2010/October/engpdf/18-27.pdf |title=Bali Jatra of Sonepur |publisher=Orissa.gov.in |access-date=18 February 2015}}</ref>

The [[Rajput]] of [[Rajasthan]] worship their weapons and horses on [[Navaratri|Navratri]], and formerly offered a sacrifice of a goat to a goddess revered as Kuldevi – a practice that continues in some places.<ref>{{cite book|last1=Harlan|first1=Lindsey|title=The goddesses' henchmen gender in Indian hero worship|date=2003|publisher=Oxford University Press|location=Oxford [u.a.]|isbn=978-0195154269|pages=45 with footnote 55, 58–59}}</ref><ref name="Goat sacrifice to Shilamata">{{cite book|last1=Hiltebeitel|first1=Alf|author-link1=Alf Hiltebeitel|last2=Erndl|first2=Kathleen M.|title=Is the Goddess a Feminist?: the Politics of South Asian Goddesses|date=2000|publisher=Sheffield Academic Press|location=Sheffield, England|isbn=9780814736197|page=77}}</ref> The ritual requires slaying of the animal with a single stroke. In the past this ritual was considered a rite of passage into manhood and readiness as a warrior. The ritual is directed by a priest.<ref>{{cite book|last1=Harlan|first1=Lindsey|title=Religion and Rajput Women|year=1992|publisher=University of California Press|location=Berkeley, California|isbn=0-520-07339-8|pages=61, 88}}</ref> The ''Kuldevi'' among these Rajput communities is a warrior-pativrata guardian goddess, with local legends tracing reverence for her during Rajput-Muslim wars.<ref>{{cite book|last1=Harlan|first1=Lindsey|title=Religion and Rajput Women|year=1992|publisher=University of California Press|location=Berkeley, California|isbn=0-520-07339-8|pages=107–108}}</ref>

Animal Sacrifice of a buffalo or goat, particularly during smallpox epidemics, has been practiced in parts of South India. The sacrificed animal is dedicated to a goddess, and is probably related to the myth of goddess Kali in Andhra Pradesh, but in Karnataka, the typical goddess is [[Renuka]]. According to [[Alf Hiltebeitel]] – a professor of Religions, History and Human Sciences, these ritual animal sacrifices, with some differences, mirrors goddess - related ritual animal sacrifice found in [[Gilgamesh]] epic and in texts of Egyptian, Minoan and Greek sources.<ref name="Buffalo sacrifice">{{cite journal|last1=Hiltebeitel|first1=Alf|author-link=Alf Hiltebeitel|title=Rāma and Gilgamesh: the sacrifices of the water buffalo and the bull of heaven|journal=History of Religions|date=February 1980|volume=19|issue=3|pages=187–195, 211–214|jstor=1062467 |doi=10.1086/462845|s2cid=162925746}}</ref>

In the 19th century through the early 20th century, Indian laborers were shipped by the [[British Empire]] into colonial mining and plantations operations in the Indian ocean and the Caribbean regions. These included significant number of Shakta devotees. While instances of Shakta animal sacrifice during Kali puja in the Caribbean islands were recorded between 1850s to 1920s, these were relatively uncommon when compared to other rituals such as temple prayers, community dancing and fire walking.<ref>{{cite book|first1=Patrick|last1=Taylor|first2=Frederick|last2=Case|title=The Encyclopedia of Caribbean Religions: Volume 1: A - L|url=https://books.google.com/books?id=XOyYCgAAQBAJ&pg=PA285 |year=2013|publisher=University of Illinois Press|isbn=978-0-252-09433-0|pages=285–288}}</ref>

==Shaktism versus other Hindu traditions==
[[File:1849 engraving of "the Hindoo Goddess Karle".JPG|thumb|upright|"The Hindoo Goddess Kali", an illustration from ''Dr. Scudder's Tales for Little Readers About the Heathen'', by Dr. John Scudder (London, 1849).]]
Shaktism has at times been dismissed as a superstitious, black magic-infested practice that hardly qualifies as a true religion at all.{{sfn|Urban|2003}} {{page needed|date=October 2016}}{{sfn|White|2003}} {{page needed|date=October 2016}} A representative criticism of this sort issued from an Indian scholar in the 1920s:

{{Blockquote|The Tantras are the Bible of Shaktism, identifying all Force with the female principle in nature and teaching an undue adoration of the wives of Shiva and Vishnu to the neglect of their male counterparts. It is certain that a vast number of the inhabitants of India are guided in their daily life by Tantrik [sic] teaching, and are in bondage to the gross superstitions inculcated in these writings. And indeed it can scarcely be doubted that Shaktism is Hinduism arrived at its worst and most corrupt stage of development.{{sfn|Kapoor|2002|page=157}} }}

The tantra practices are secretive, subject to speculations and criticism. Scholars variously attribute such criticism to ignorance, misunderstanding or sectarian bias on the part of some observers, as well as unscrupulous practices by some Shaktas. These are some of the reasons many Hindus question the relevance and historicity of Tantra to their tradition.{{sfn|White|2003|page=262}}<ref name=hughurban>Hugh Urban (1997), Elitism and Esotericism: Strategies of Secrecy and Power in South Indian Tantra and French Freemasonry, Journal: Numen, Volume 44, Issue 1, pages 1 – 38</ref>

Beyond tantra, the Shakta sub-traditions subscribe to various philosophies, are similar in some aspects and differ in others. These traditions compare with Vaishnavism, Shaivism and [[Smarta tradition|Smartism]] as follows:

{| class="wikitable sortable"
|+Comparison of Shaktism with other traditions
|-
! !! [[Vaishnavism|Vaishnava Traditions]] !! [[Shaivism|Shaiva Tradition]]s !! style="background:#fc9;"|Shakta Traditions !! [[Smarta tradition|Smarta Traditions]] || References
|-
|Scriptural authority || Vedas and Upanishads || Vedas and Upanishads || Vedas, Upanishads and Tantras||Vedas and Upanishads ||<ref name=ryanjonesavatar>{{cite book|first1=Constance |last1=Jones |first2=James D. |last2=Ryan |title=Encyclopedia of Hinduism |year=2006|publisher=Infobase |isbn=978-0-8160-7564-5 |page=474 }}</ref><ref name="Dhavamony1999p33">{{cite book|first=Mariasusai |last=Dhavamony |title=Hindu Spirituality |date=1999 |publisher=Gregorian Press |isbn=978-88-7652-818-7 |pages=32–34 }}</ref>
|-
|Supreme deity || God Vishnu || God Shiva || Goddess Devi || None ||<ref name="JanGondaVandS">{{cite book|first=Jan|last=Gonda|title=Visnuism and Sivaism: A Comparison|year=1970|publisher=Bloomsbury Academic|isbn=978-1-4742-8080-8}}</ref><ref>{{cite book|first=Christopher |last=Partridge |title=Introduction to World Religions |year=2013|publisher=Fortress Press|isbn=978-0-8006-9970-3 |page=182 }}</ref>
|-
|Creator || Vishnu || Shiva || Devi || Brahman principle ||<ref name="JanGondaVandS"/><ref>{{cite book|first=Sanjukta|last=Gupta|title=Advaita Vedanta and Vaisnavism: The Philosophy of Madhusudana Sarasvati |date=1 February 2013|publisher=Routledge|isbn=978-1-134-15774-7|pages=65–71}}</ref>
|-
|[[Avatar]] || Key concept || Minor || Significant || Minor ||<ref name="ryanjonesavatar"/><ref name=laiengavatar>{{cite book|first=Lai Ah |last=Eng |title=Religious Diversity in Singapore |year=2008|publisher=Institute of Southeast Asian Studies, Singapore|isbn=978-981-230-754-5|page=221 }}</ref><ref name="Dhavamony2002p63">{{cite book|first=Mariasusai |last=Dhavamony |title=Hindu-Christian Dialogue: Theological Soundings and Perspectives |year=2002|publisher=Rodopi |isbn=90-420-1510-1 |page=63 }}</ref>
|-
|[[Sannyasa|Monastic]] life || Accepts || Recommends || Accepts || Recommends ||<ref name=ryanjonesavatar/><ref>Stephen H Phillips (1995), Classical Indian Metaphysics, Columbia University Press, {{ISBN|978-0812692983}}, page 332 with note 68</ref><ref>{{cite book|first=Patrick| last=Olivelle|year=1992|title= The Samnyasa Upanisads|publisher= Oxford University Press|isbn= 978-0195070453| pages=4–18}}</ref>
|-
|Rituals, [[Bhakti]] || Affirms || Affirms<ref name = anin/><ref>{{cite web|title=Shaivas|url=http://www.philtar.ac.uk/encyclopedia/hindu/devot/shaiv.html|website=Overview Of World Religions|publisher=Philtar|access-date=13 December 2017}}</ref><ref>{{cite book|last1=Munavalli|first1=Somashekar|title=Lingayat Dharma (Veerashaiva Religion)|date=2007|publisher=Veerashaiva Samaja of North America|page=83|url=http://www.vsna.org/images/publications/lingayat-dharma-april-2007.pdf}}</ref> || Affirms || Optional<ref>{{cite book|first=Prem|last=Prakash|title=The Yoga of Spiritual Devotion: A Modern Translation of the Narada Bhakti Sutras|year=1998|publisher=Inner Traditions|isbn=978-0-89281-664-4|pages=56–57}}</ref> ||<ref>{{cite journal | last=Frazier | first=J. | title=Bhakti in Hindu Cultures | journal=The Journal of Hindu Studies | publisher=Oxford University Press | volume=6 | issue=2 | year=2013 | pages=101–113 | doi=10.1093/jhs/hit028}}</ref>
|-
|[[Ahimsa]] and Vegetarianism || Affirms || Recommends,<ref name = anin>Gavin Flood (1996), An Introduction to Hinduism, Cambridge University Press, {{ISBN|978-0-521-43878-0}}, pages 162–167</ref> Optional || Optional || Recommends, recommends Optional || <ref>{{cite book|first1=Lisa |last1=Kemmerer |first2=Anthony J. |last2=Nocella |title=Call to Compassion: Reflections on Animal Advocacy from the World's Religions |year=2011|publisher=Lantern |isbn=978-1-59056-281-9|pages=27–36}}</ref><ref>{{cite book|first=Frederick J. |last=Simoons |title=Plants of Life, Plants of Death |year=1998|publisher= University of Wisconsin Press |isbn= 978-0-299-15904-7 |pages=182–183 }}</ref>
|-
|[[Free will]], [[Maya (illusion)|Maya]], [[Karma]] || Affirms || Affirms || Affirms || Affirms ||<ref name="JanGondaVandS"/>
|-
|Metaphysics || [[Brahman]] (Vishnu) and [[Atman (Hinduism)|Atman]] (Soul, Self) || Brahman (Shiva), Atman || Brahman (Devi), Atman || Brahman, Atman ||<ref name="JanGondaVandS"/>
|-
|[[Epistemology]] ([[Pramana]]) || 1. Perception 2. Inference 3. Reliable testimony || 1. Perception 2. Inference 3. Reliable testimony 4. Self-evident<ref>{{cite book|first=K. |last=Sivaraman |title=Śaivism in Philosophical Perspective |year=1973|publisher=Motilal Banarsidass|isbn=978-81-208-1771-5 |pages=336–340}}</ref> || 1. Perception 2. Inference 3. Reliable testimony || 1. Perception 2. Inference 3. Comparison and analogy 4. Postulation, derivation 5. Negative/cognitive proof 6. Reliable testimony ||<ref>John A. Grimes, A Concise Dictionary of Indian Philosophy: Sanskrit Terms Defined in English, State University of New York Press, {{ISBN|978-0791430675}}, page 238</ref>{{Sfn|Flood|1996|p=225}}<ref>Eliott Deutsche (2000), in Philosophy of Religion : Indian Philosophy Vol 4 (Editor: Roy Perrett), Routledge, {{ISBN|978-0815336112}}, pages 245-248</ref>
|-
|Philosophy||Dvaita, qualified advaita, advaita, Visishtadvaita|| Dvaita, qualified advaita, advaita || Shakti-advaita, [[Samkhya]] || Advaita ||{{sfn|McDaniel|2004|pp=177–225}}
|-
|Salvation ([[Soteriology]])|| Videhamukti, Yoga, champions householder life || Jivanmukta, [[Karma|Charya]]-[[Kriyā]]-[[Yoga]]-[[Jnana]]<ref>{{cite book|last1=Hurley|first1=Leigh|last2=Hurley|first2=Phillip|title=Tantra, Yoga of Ecstasy: the Sadhaka's Guide to Kundalinin and the Left-Hand Path|date=2012|publisher=Maithuna Publications|isbn=9780983784722|page=5 }}</ref> || Bhakti, Tantra, Yoga || Jivanmukta, Advaita, Yoga, champions monastic life ||<ref name="Kim Skoog 1996 63–84, 236–239">{{cite book|first=Kim |last=Skoog |editor1=Andrew O. Fort |editor2=Patricia Y. Mumme |title=Living Liberation in Hindu Thought |date= 1996 |publisher=SUNY Press |isbn= 978-0-7914-2706-4|pages= 63–84, 236–239 }}</ref><ref>{{cite book|first=Rajendra |last=Prasad |title=A Conceptual-analytic Study of Classical Indian Philosophy of Morals |year=2008|publisher=Concept |isbn=978-81-8069-544-5 |page=375 }}</ref>
|}

==Demography==
There is no census data available on demographic history or trends for Shaktism or other traditions within Hinduism.<ref>[http://www.pewforum.org/2012/12/18/global-religious-landscape-hindu/ The global religious landscape: Hindus], Pew Research (2012)</ref> Estimates vary on the relative number of adherents in Shaktism compared to other traditions of Hinduism. According to a 2010 estimate by Johnson and Grim, the Shaktism tradition is the smaller group with about 30 million or 3.2% of Hindus.<ref>{{cite book |last1=Johnson |first1=Todd M. |last2=Grim |first2=Brian J. |title=The World's Religions in Figures: An Introduction to International Religious Demography |year=2013 |publisher=John Wiley & Sons |isbn=9781118323038 |page=400}}</ref> Large shakta communities are particularly found in eastern states, such as [[West Bengal]], [[Assam]], [[Bihar]], [[Odisha]], [[Jharkhand]] and [[Tripura]] with substantial communities also existing in [[Punjab]], [[Jammu]], [[Himachal Pradesh]], [[Gujarat]] and Central India.<ref name=britannicashakti /><ref>{{cite web |url=https://www.historyofodisha.in/history-of-sakti-cult-in-odisha/ |title=History of Sakti Cult in Odisha |date=March 11, 2018 |publisher=History Of Odisha}}</ref> In West Bengal Shaktas belong to the upper [[caste]]s as well as lowest castes and tribes, while the lower middle castes are [[Vaishnava]]s.{{sfn|McDermott|2005|p=826}} In contrast, Galvin Flood states that Shaivism and Shaktism traditions are difficult to separate, as many Shaiva Hindus revere the goddess Shakti regularly.<ref>{{cite book|first=Gavin|last=Flood|title=The Blackwell Companion to Hinduism |year=2008|publisher=John Wiley & Sons|isbn=978-0-470-99868-7|page=200}}, Quote: "it is often impossible to meaningfully distinguish between Saiva and Sakta traditions".</ref> The denominations of Hinduism, states Julius Lipner, are unlike those found in major religions of the world, because Hindu denominations are fuzzy with individuals revering gods and goddesses [[henotheism|henotheistically]], with many Shaiva and Vaishnava adherents recognizing Sri (Lakshmi), Parvati, Saraswati and other aspects of the goddess Devi. Similarly, Shakta Hindus revere Shiva and goddesses such as Parvati (such as Durga, [[Radha]], [[Sita]] and others) and Saraswati important in Shaiva and Vaishnava traditions.<ref>[[Julius J. Lipner]] (2009), Hindus: Their Religious Beliefs and Practices, 2nd Edition, Routledge, {{ISBN|978-0-415-45677-7}}, pages 371-375</ref>

==Temples and influence==
{{Further-text|[[:Category:Shakti temples|List of Shakti Temples]] and [[Shakti Peethas]]}}
{{Shakti Peethas Map}}
Shakta temples are found all over South Asia. Many towns, villages and geographic landmarks are named for various forms of the Devi.{{sfn|Pattanaik|2000|pages=110-114}} Major pilgrimage sites of Shaktism are called "[[Shakti Peethas]]", literally "Seats of the Devi". These vary from four to fifty one.{{sfn|Bhattacharyya|1996|page=171}}

Some Shakta temples are also found in [[Southeast Asia]], the [[Americas]], [[Europe]], [[Australia]] and elsewhere.{{sfn|Fell McDermett|1998|pages=281-305}} Examples in the [[United States]] include the ''Kali Mandir'' in [[Laguna Beach, California]];<ref>[http://www.kalimandir.org Kali Mandir]</ref> and ''[[Sri Rajarajeswari Peetam]]'',<ref>[http://www.srividya.org Sri Rajarajeshwari Peetham]</ref> a ''[[Srividya]]'' temple in rural [[Rush, New York]].{{sfn|Dempsey|2006}}

Some [[Feminism|feminists]] and participants in [[New Age]] spirituality who are attracted to Goddess worship", suggest Shaktism is a "symbol of wholeness and healing, associated especially with repressed female power and sexuality."{{sfn|Fell McDermett|1998|pages=281-305}}

===Buddhism===
There has been a significant sharing of ideas, ritual grammar and concepts between Tantric Buddhism ([[Vajrayana]] tradition) found in Nepal and Tibet and the Tantric Shakta tradition of Hinduism.<ref>{{cite book|author1=J. Gordon Melton|first2=Martin|last2=Baumann|title=Religions of the World: A Comprehensive Encyclopedia of Beliefs and Practices, 2nd Edition |year=2010|publisher=ABC-CLIO|isbn=978-1-59884-204-3|page=2599 }}</ref><ref name=dalal332/> Both movements cherish female deities.<ref name="Keul2012p119"/> According to [[Miranda E. Shaw|Miranda Shaw]], "the confluence of Buddhism and Shaktism is such that Tantric Buddhism could properly be called Shakta Buddhism".<ref>{{cite book|author1=Mary McClintock Fulkerson|first2=Sheila|last2=Briggs|title=The Oxford Handbook of Feminist Theology |year=2012|publisher=Oxford University Press|isbn=978-0-19-927388-1|page=137}}</ref>

The Buddhist [[Aurangabad Caves]] about 100 kilometers from the [[Ajanta Caves]], dated to the 6th to 7th century CE, show Buddhist Matrikas (mother goddesses of Shaktism) next to the Buddha.<ref name= Brancaccio203/> Other goddesses in these caves include Durga. The goddess iconography in these Buddhist caves is close, but not identical to the Hindu Shakta tradition. The "seven Goddess mothers" are found in other Buddhist caves and literature, such as their discussion in the Buddhist text ''Manjusrimulakalpa'' and ''Vairocanabhisambodhi''.<ref name= Brancaccio203>{{cite book|first=Pia|last=Brancaccio|title=The Buddhist Caves at Aurangabad: Transformations in Art and Religion| url=https://books.google.com/books?id=m_4pXm7dD78C&pg=PA206 |year=2010| publisher=Brill Academic |isbn=978-90-04-18525-8|pages=21, 202–207}}, '''Quote:''' "To the right of the main Buddha image, carved out of the wall of the sanctum, is an ensemble of seven female images".</ref><ref>{{cite book|first1=David B.|last1=Gray|author2=Ryan Richard Overbey|title=Tantric Traditions in Transmission and Translation|url=https://books.google.com/books?id=OJWCCwAAQBAJ&pg=PA47 |year=2016|publisher=Oxford University Press|isbn=978-0-19-990952-0|pages=47–48}}</ref>

{{wide image|India settentrionale, saptamatrika, X sec.JPG|600px|''[[Matrika]]'' – mother goddesses – are found in both Shakta-Hinduism and Vajrayana-Buddhism.<ref name="Keul2012p119">{{cite book|first=István|last=Keul|title=Transformations and Transfer of Tantra in Asia and Beyond|url=https://books.google.com/books?id=38gxbEft3-4C&pg=PA119 |year=2012|publisher=Walter de Gruyter|isbn=978-3-11-025811-0|pages=119–123}}</ref><ref>{{cite book|first=Peter Alan |last=Roberts|title=Mahamudra and Related Instructions: Core Teachings of the Kagyu Schools|year=2011|publisher=Simon and Schuster|isbn=978-0-86171-444-5|page=715}}</ref>}}

===Jainism===
In [[Jainism]], ideas similar to Shaktism tradition are found, such as the Vidyadevis and the Shasanadevis.<ref name=dalal332>{{cite book|first=Roshen|last=Dalal|title=The Religions of India: A Concise Guide to Nine Major Faiths|url=https://books.google.com/books?id=pNmfdAKFpkQC&pg=PA332|year=2010|publisher=Penguin Books |isbn=978-0-14-341517-6|page=332}}</ref>

===Sikhism===
The secondary scripture of Sikhs, ''[[Dasam Granth]]'' attributed to [[Guru Gobind Singh]], includes numerous sections on Shakta goddesses, particularly [[Chandi]] – the fierce warrior form of the Hindu goddess.<ref name="Rinehart2011">{{cite book|first=Robin|last=Rinehart|title=Debating the Dasam Granth|year=2011|publisher=Oxford University Press|isbn=978-0-19-984247-6|pages=71, 107–110}}</ref> According to Nikky-Guninder Kaur Singh – a professor of Religious Studies, the stories about goddess Durga in the ''Dasam Granth'' are reworkings of ancient Shakti mythologies.<ref>{{cite book|first=Constance Waeber |last=Elsberg|title=Graceful Women: Gender and Identity in an American Sikh Community|url=https://books.google.com/books?id=bU8rmpdIwWYC&pg=PA37 |year=2003|publisher=University of Tennessee Press|isbn=978-1-57233-214-0|pages=37–38}}</ref> A significant part of this Sikh scripture is based on the teachings in the Shakta text ''Devi Mahatmya'' found in the ''[[Markandeya Purana]]'' of Hinduism.<ref>{{cite book|first1=Pashaura|last1=Singh|first2=Louis E.|last2=Fenech|title=The Oxford Handbook of Sikh Studies|url=https://books.google.com/books?id=8I0NAwAAQBAJ&pg=PA139|year=2014|publisher=Oxford University Press|isbn=978-0-19-969930-8|page=139}}</ref>

==See also==
* {{annotated link|Palden Lhamo}}
* {{annotated link|Tridevi}}

==References==
{{unclear citation style|date=March 2023}}

===Notes===
{{Notelist}}

===Citations===
{{Reflist|colwidth=30em}}

===Works cited===
{{Refbegin|2|indent=yes}}
*{{cite book |last=Bhattacharyya |first=N. N. |title=The Indian Mother Goddess |publisher=South Asia Books |location=New Delhi |orig-year=1970 |edition=2nd |year=1977}}
*{{cite book |last=Bhattacharyya |first=N. N. |title=History of the Sakta Religion |publisher=[[Munshiram Manoharlal Publishers]] |location=New Delhi |orig-year=1974 |edition=2nd |year=1996 }}
*{{cite book |last=Bolon |first=Carol Radcliffe |title=Forms of the Goddess Lajja Gauri in Indian Art |publisher=[[Penn State University Press]] |location=University Park, PA |year=1992}}
*{{cite book |last=Brooks |first=Douglas Renfrew |title=The Secret of the Three Cities: An Introduction to Hindu Shakta Tantrism |publisher=[[The University of Chicago Press]] |location=Chicago |year=1990 |isbn=978-0-226-07569-3 }}
*{{cite book |last=Brooks |first=Douglas Renfrew |title=Auspicious Wisdom: The Texts and Traditions of Srividya Shakta Tantrism in South India |publisher=[[State University of New York Press]] |location=Albany |year=1992 |isbn=978-0-7914-1146-9}}
*{{cite book |last=Brown |first=C. MacKenzie |title=The Triumph of the Goddess: The Canonical Models and Theological Issues of the Devi-Bhagavata Purana |publisher=State University of New York Press |series=SUNY Series in Hindu Studies |year=1991 |isbn=978-0-7914-0364-8}}
*{{cite book|first=Cheever Mackenzie |last=Brown|title=The Devi Gita: The Song of the Goddess: A Translation, Annotation, and Commentary| year=1998| publisher=State University of New York Press |location=Albany |isbn=978-0-7914-3939-5}}
*{{cite book|last=Coburn |first= Thomas B. |title= Encountering the Goddess: A translation of the Devi-Mahatmya and a Study of Its Interpretation| publisher= State University of New York Press | year= 1991 | isbn = 0791404463}}
*{{cite book|last=Coburn |first= Thomas B. |title=Devī Māhātmya, The Crystallization of the Goddess Tradition |publisher= South Asia Books |year=2002 |isbn =81-208-0557-7}}
*{{cite book|last= Dasgupta |first= S |title=Journal of the Indian Musicological Society |year=1996| volume= 27–28| publisher=Indian Musicological Society}}
*{{cite book |last=Dempsey |first=Corinne G. |title=The Goddess Lives in Upstate New York: Breaking Convention and Making Home at a North American Hindu Temple |url=https://archive.org/details/goddesslivesinup00cori |url-access=registration |publisher=[[Oxford University Press]] |location=New York |year=2006 }}
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*{{cite book |last=Erndl |first=Kathleen M. |title=Victory to the Mother: The Hindu Goddess of Northwest India in Myth, Ritual, and Symbol |url=https://archive.org/details/victorytomothert00ernd |url-access=registration |publisher=Oxford University Press |location=New York |year=1992}}
*{{cite book |last=Fell McDermott |first=Rachel |chapter=The Western Kali |editor1=Hawley, John |editor2=Wulff, Donna Marie |title=Devi: Goddesses of India |publisher=Motilal Banarsidass |year=1998 |isbn=978-81-208-1491-2}}
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*{{cite book |first1=Lynn |last1=Foulston |first2=Stuart|last2=Abbott| title=Hindu Goddesses: Beliefs and Practices| url=https://archive.org/details/hindugoddessesbe0000foul|url-access=registration | year=2009| publisher=Sussex Academic Press| isbn=978-1-902210-43-8}}
*{{cite book |last=Hawley |first=John Stratton |chapter=The Goddess in India |editor1=Hawley, John |editor2=Wulff, Donna Marie |title=Devi: Goddesses of India |publisher=Motilal Banarsidass |year=1998 |isbn=978-81-208-1491-2 }}
*{{cite book|last1=Hiltebeitel| first1=Alf |first2=Kathleen M. |last2=Erndl |title=Is the Goddess a Feminist?: The Politics of South Asian Goddesses |year = 2000|publisher=New York University Press|isbn=978-0-8147-3619-7}}
*{{cite book|first=Linda|last= Johnsen|title=The Living Goddess: Reclaiming the Tradition of the Mother of the Universe|year=2002|publisher=Yes International|isbn=978-0-936663-28-9}}
*{{cite book |last=Joshi |first=L. M. |title=Lalita Sahasranama: A Comprehensive Study of the One Thousand Names of Lalita Maha-tripurasundari |publisher=D.K. Printworld (P) Ltd |location=New Delhi |year=1998}}
*{{cite book |last=Joshi |first=M. C. |chapter=Historical and Iconographical Aspects of Shakta Tantrism |editor1=Harper, Katherine |editor2=Brown, Robert L. |title=The Roots of Tantra |publisher=State University of New York Press |location=Albany |year=2002 |isbn=978-0-7914-5305-6 }}
*{{cite book |last=Kali |first=Davadatta |title=In Praise of the Goddess: The Devimahatmya and Its Meaning |publisher=Nicolas-Hays |location=Berwick, ME |year=2003 |isbn=8120829530}}
*{{cite book |last=Kapoor |first=Subodh |title=A Short Introduction to Sakta Philosophy |publisher=Indigo Books |location=New Delhi |year=2002 |orig-year=1925 }}
*{{cite book |last=Kinsley |first=David |title=Hindu Goddesses: Visions of the Divine Feminine in the Hindu Religious Tradition |publisher=Motilal Banarsidass |year=1987 |isbn=978-81-208-0394-7 }}
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*{{cite book|last=McDaniel |first= June |title=Offering Flowers, Feeding Skulls | year =2004| publisher=Oxford University Press| isbn=978-0-19-534713-5}}
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*{{cite book |last=Nikhilananda |first=Swami (trans.) |title=[[The Gospel of Sri Ramakrishna]] |publisher=Ramakrishna-Vivekananda Center |location=New York |orig-year=1942 |edition=9th |year=2000 }}
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*{{cite book |editor-last=Pechilis |editor-first=Karen |title=The Graceful Guru: Hindu Female Gurus in India and the United States |publisher=Oxford University Press |location=New York |year=2004 }}
*{{cite book| first=Tracy| last=Pintchman| title=Guests at God's Wedding: Celebrating Kartik among the Women of Benares | year=2005|publisher=State University of New York Press|isbn=978-0-7914-6595-0}}
*{{cite book|first=Tracy|last=Pintchman| title=Seeking Mahadevi: Constructing the Identities of the Hindu Great Goddess |year=2014| publisher=State University of New York Press| isbn=978-0-7914-9049-5}}
*{{cite book| first=Tracy| last=Pintchman|title=The Rise of the Goddess in the Hindu Tradition| year=2015| publisher=State University of New York Press|isbn=978-1-4384-1618-2 }}
*{{Cite book|first=Ludo |last=Rocher| year= 1986| author-link= Ludo Rocher| title= The Puranas| publisher= Otto Harrassowitz Verlag| isbn= 978-3447025225}}
*{{cite book |last=Sarma |first=S. A. |title=Kena Upanisad: A Study From Sakta Perspective |publisher=[[Bharatiya Vidya Bhavan]] |location=Mumbai |year=2001}}
*{{cite book |last=Shankarnarayanan |first=S. |title=Sri Chakra |publisher=Samata Books |location=Chennai |orig-year=1971 |edition=4th |year=2002b}}
*{{cite book |last=Smith |first=Frederick M. |year=2006 |title=The Self Possessed: Deity and Spirit Possession in South Asian Literature |publisher=[[Columbia University Press]] |isbn=0-231-13748-6}}
*{{cite book |last=Subramuniyaswami |first=Satguru Sivaya |title=Merging with Siva: Hinduism's Contemporary Metaphysics |publisher=Himalayan Academy |location=Hawaii |orig-year=1999 |edition=2nd |year=2002 |isbn=978-0-945497-99-8 }}
*{{cite book |last=Suryanarayana Murthy |first=C. |title=Sri Lalita Sahasranama with Introduction and Commentary |publisher=Bharatiya Vidya Bhavan |location=Mumbai |year=2000 |orig-year=1962}}
*{{cite book |last=Urban |first=Hugh B. |title=Tantra: Sex, Secrecy, Politics and Power in the Study of Religion |publisher=University of California Press |location=Berkeley |year=2003 |isbn=978-0-520-93689-8 }}
*{{cite book |last=White |first=David Gordon |title=Kiss of the Yogini: "Tantric Sex" in its South Asian Contexts |publisher=University of Chicago Press |location=Chicago |year=2003 |isbn=978-0-226-89483-6 }}
*{{cite book |last=Winternitz |first=M. |title=History of Indian Literature |location=New Delhi |orig-year=1927 |year=1973}}
*{{cite book |last=Woodroffe |first=Sir John |title=Sakti and Sakta: Essays and Addresses on the Shâkta Tantrashâstra|publisher=Ganesh & Company |year=1951 |orig-year=1927 |isbn=978-1-60620-145-9 }}
*{{cite book |last=Yadav |first=Neeta |title=Ardhanārīśvara in Art and Literature |publisher=D. K. Printworld (P) Ltd. |location=New Delhi |year=2001}}
{{Refend}}

==Further reading==
*{{cite journal |last=Chatterji |first=Usha |title=Shakta and Shakti |journal=Studies in Comparative Religion |volume=2 |number=4 |year=1968 |url=http://www.studiesincomparativereligion.com/uploads/ArticlePDFs/74.pdf}}
*{{cite journal |last=Kinsley |first=David |url=https://www.jstor.org/stable/1463045 |title=The Portrait of the Goddess in the Devī-māhātmya |journal=Journal of the American Academy of Religion |volume=XLVI |number=4 |year=1978 |pages=489–506|doi=10.1093/jaarel/XLVI.4.489 |jstor=1463045 }}
*{{cite journal |last=Koester |first=Hans |url=http://ccbs.ntu.edu.tw/FULLTEXT/JR-JSS/shakti.htm |title=The Indian Religion of the Goddess Shakti |journal=Journal of the Siam Society |volume=23 |number=1 |year=1929 |pages=1–18}}

==External links==
{{Commons category}}

* [http://saktatraditions.org/ Śākta Traditions]
* [https://wrldrels.org/2020/06/24/women-in-hindu-shakta-tantra/ Women in Hindu Shakta Tantra]

{{Shaktism}}
{{Hindudharma}}
{{Authority control}}

[[Category:Shaktism| ]]
[[Category:Hindu denominations]]

Jaguar I-Pace

2023-01-24T18:09:49Z

173.165.237.1: /* Specifications */ Changed language with unclear meanings and updated specifications based on later models.

{{Use dmy dates|date=November 2020}}
{{Use British English|date=January 2018}}
{{Infobox automobile
| name = Jaguar I-Pace
| image = 2018 Jaguar I-Pace EV400 AWD Front.jpg
| caption =
| manufacturer = [[Jaguar Land Rover]]
| aka =
| production = 2018–present
| model_years =
| assembly = Austria: Graz ([[Magna Steyr]])
| designer = [[Ian Callum]]
| class = [[Compact executive car|Compact luxury]] [[Crossover (automobile)|crossover SUV]]
| body_style = 5-door [[coupé SUV]]
| layout = Dual-motor, [[all-wheel-drive]]
| platform = [[Jaguar Land Rover car platforms#D7e|JLR D7e]]
| related =
| motor = [[Permanent magnet synchronous motor]] x2 {{convert|200|PS|kW|abbr=on}} {{convert|348|Nm|abbr=on}} (total {{convert|400|PS|kW|abbr=on}} {{convert|696|Nm|abbr=on}})
| transmission = 1-speed direct-drive reduction
| drivetrain =
| battery = 90 [[kW·h]] [[Lithium-ion battery|lithium ion]]
| electric_range = [[Environmental Protection Agency|EPA]]: {{convert|246|mi|km|abbr=out}} [[Worldwide harmonized Light vehicles Test Procedure|WLTP]]: {{convert|292|mi|km|0|abbr=out}}
| charging = {{ubl|11kW AC (7.4kW "1-phase/32A only" AC 2018–2020)| 100 kW DC}}
| wheelbase = {{convert|2990|mm|in|1|abbr=on}}
| length = {{convert|4682|mm|in|1|abbr=on}}
| width = {{ubl
|{{convert|1895|mm|in|1|abbr=on}} (body)
|{{convert|2011|mm|in|1|abbr=on}} (mirrors folded)
|{{convert|2139|mm|in|1|abbr=on}} (mirrors unfolded)
}}
| height = {{convert|1565|mm|in|1|abbr=on}}
| weight = {{convert|2133|kg|lb|0|abbr=on}}
| successor =
| sp = uk
}}

The '''Jaguar I-Pace''' (stylised as '''I-PACE''') is a [[Battery electric vehicle|battery-electric]] [[Crossover (automobile)|crossover SUV]] produced by [[Jaguar Land Rover]] (JLR) under their [[Jaguar Cars|Jaguar]] marque. The I-Pace was announced in March 2018, European deliveries began in June 2018 and North American deliveries started in October 2018.

==Development==
[[File:Jaguar I-Pace IMG 0491.jpg|thumb|left|The production car is 12{{nbsp}}mm narrower and 12{{nbsp}}mm lower than the concept (pictured).]]

The Jaguar I-Pace was designed by [[Ian Callum]].<ref name=Davies>{{cite web|url= https://www.slashgear.com/jaguar-i-pace-concept-previews-model-x-rivaling-ev-for-2018-14463885/ |title=Jaguar I-Pace Concept previews Model X rivaling EV for 2018 |first=Chris |last=Davies |date=2016-11-14 |work=slashgear.com |access-date= 16 June 2017 |quote=Callum and his team}}</ref> The [[concept car|concept]] version of the car, described as a five-seater sports car, was unveiled by JLR at the [[LA Auto Show|2016 Los Angeles Motor Show]] and shown on-road in London in March 2017.<ref name="AC_20161116">{{Cite magazine |last=Burgess |first=Rachel |date=2016-11-16 |title=Jaguar Guns for Tesla with Radical New Electric SUV |magazine=Autocar |edition=6229 |publisher=Haymarket Consumer Media |volume=290 |issue=7 |pages=10–15}}</ref><ref name="JLR_I-Pace">{{cite web |url=http://www.jaguar.co.uk/jaguar-range/i-pace-concept-car/index.html |title=I-Pace Concept |publisher=Jaguar Land Rover}}</ref>

The I-Pace is built by contract manufacturer [[Magna Steyr]] in [[Graz]], Austria,<ref>{{cite web |url=http://www.autonews.com/article/20170613/BLOG06/170619897/jaguar-ramps-up-fine-tunes-i-pace-to-outduel-tesla |title=Jaguar ramps up, fine-tunes I-Pace to outduel Tesla |date=2017-06-13 |access-date=2017-06-17 |archive-url=https://web.archive.org/web/20170614230413/http://www.autonews.com/article/20170613/BLOG06/170619897/jaguar-ramps-up-fine-tunes-i-pace-to-outduel-tesla |archive-date=2017-06-14 |url-status=live }}</ref><ref name=Schmitt4>{{cite web|url= https://www.forbes.com/sites/bertelschmitt/2017/06/16/the-road-from-high-octane-to-high-tech-is-dangerous-father-of-tesla-beater-jaguar-says-why/4/ |title=The Road From High-Octane To High-Tech Is Dangerous. Father Of 'Tesla-Beater' Jaguar Says Why, page 4|magazine=Forbes |date= 16 June 2017 |access-date= 2017-06-16 }}</ref> and the production version of the I-Pace was revealed in Graz on 1 March 2018.<ref>{{cite news|last1=McIlroy|first1=John|title=New 2018 Jaguar I-Pace revealed: specs, prices and pics|url=http://www.autoexpress.co.uk/jaguar/i-pace/97706/new-2018-jaguar-i-pace-revealed-specs-prices-and-pics|access-date=2 March 2018|work=Auto Express|publisher=DEnnis Publishing|date=1 March 2018}}</ref>

Some of the electric drive technology{{which|date=March 2020}} has come out of the [[Jaguar Racing|Jaguar I-Type]] electric [[Formula E]] racing car programme,<ref>{{cite news |url= http://www.motorauthority.com/news/1104588_2019-jaguar-i-pace-spy-shots |title= 2019 Jaguar I-Pace spy shots |first= Viknesh |last= Vijayenthiran |date= 20 November 2016 |publisher= Motor Authority }}</ref> and the concentric motors were developed by JLR engineer Dr. Alex Michaelides.<ref name=Schmitt2>{{cite web|url= https://www.forbes.com/sites/bertelschmitt/2017/06/16/the-road-from-high-octane-to-high-tech-is-dangerous-father-of-tesla-beater-jaguar-says-why/2/ |title=The Road From High-Octane To High-Tech Is Dangerous. Father Of 'Tesla-Beater' Jaguar Says Why, page 2|magazine=Forbes |date= 16 June 2017 |access-date= 2017-06-16 }}</ref>
{{clr|left}}

==Specifications==
<gallery mode="nolines" widths="220">
File:2018 Jaguar I-Pace EV400 AWD Side.jpg|Side
File:2018 Jaguar I-Pace EV400 AWD Rear.jpg|Rear
File:Jaguar I-Pace intérieur.jpg|Interior
</gallery>

The Jaguar I-Pace launched with a [[Worldwide harmonized Light vehicles Test Procedure|WLTP]]-rated range of {{convert|292|mi|0|abbr=out}}<ref name="website">{{cite web |url=https://www.jaguar.com/jaguar-range/i-pace/index.html |website=Jaguar I-Pace |title=Jaguar I-Pace |publisher=Jaguar |access-date=1 September 2018}}</ref> and an [[Environmental Protection Agency|EPA]]-rated range of {{convert|234|mi|abbr=out}}. In December 2019, software enhancements were released to increase range to an [[Environmental Protection Agency|EPA]]-rated range of {{convert|246|mi|abbr=out}}.<ref>{{cite web|url=https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=40986|title=Fueleconomy.gov|website=Fueleconomy.gov|access-date=5 November 2018}}</ref><ref>{{cite web|last=Dubey|first=Yetnesh|title=Jaguar IPace Electric Car Gets Range Boost, Porsche Taycan Disappoints|url=https://fossbytes.com/jaguar-ipace-electric-car-range-boost-porsche-taycan-disappoints/|website=fossbytes.com|date=13 December 2019|access-date=13 December 2019}}</ref> The car has a wade depth{{clarify|date=March 2020}} of {{convert|500|mm|in|abbr=on}}.<ref>{{cite news|url= https://jalopnik.com/the-electric-le2019-jaguar-i-pace-can-wade-through-19-i-1824271097 |website=Jalopnik |publisher=[[Gizmodo Media Group]] |title= The Electric 2019 Jaguar I-Pace Can Wade Through 19 Inches Of Water, Which Is A Lot |first= Justin T. |last= Westbrook |date= 3 April 2018 |access-date= 2018-06-30}}</ref> The rear boot holds {{convert|23.17|cuft|L|order=flip|adj=ri0}},<ref>{{Cite web|url=https://www.jaguar.com/jaguar-range/i-pace/features/practicality.html|title=Jaguar I-PACE | Electric Car Practicality | Jaguar}}</ref> along with {{convert|1|cuft|L|order=flip}} of front boot space. The [[drag coefficient]] is 0.29.<ref name=Davies/>

The car has all-wheel drive via two motors powered by a 90{{nbsp}}kWh [[LG Chem]]<ref name=Davies/> lithium-ion battery with a [[battery management system]] developed by JLR.<ref name=Schmitt2/> Each motor delivers {{cvt|197|HP}} and {{cvt|258|lb·ft}} of torque, for a total power of {{cvt|395|HP}} and total torque of {{cvt|516|lb·ft}}.<ref name=Davies/> The 0{{ndash}}62{{nbsp}}mph (0{{ndash}}100{{nbsp}}km/h) time is 4.8 seconds,<ref name="website"/> and the top speed is electronically limited to 124{{nbsp}}mph (200{{nbsp}}km/h).<ref name=express>{{cite web|url=https://www.express.co.uk/life-style/cars/925870/Jaguar-I-Pace-2018-price-electric-range-launch-UK|title=New Jaguar I-Pace 2018 REVEALED and it's got its sight set on the Tesla Model X|first=Luke John|last=Smith|date=2 March 2018|website=Express.co.uk|access-date=19 December 2018}}</ref>

The battery contains 432 pouch cells.<ref>{{cite web|first=Sophie|last=Vorrath|url=http://reneweconomy.com.au/jaguar-unveils-its-tesla-killer-and-the-ev-race-is-on-78908/ |title=Jaguar unveils its "Tesla killer", and the EV race is on |publisher=RenewEconomy |date=2 March 2018 |access-date=2018-10-21}}</ref> It can charge from 0 to 80 percent in 85 minutes using 50{{nbsp}}kW DC charging, or 45 minutes using a 100{{nbsp}}kW charger. Home charging with an AC wall box (7{{nbsp}}kW) achieves the same state of charge in 10 hours.<ref name=express/> As the I-Pace was initially released with a single-phase 7{{nbsp}}kW AC charger, a one-hour charge, would add around {{convert|30|km|abbr=in}} of range.<ref>{{cite magazine |title=Jaguar I-Pace |language=fi |magazine=Moottori |date=13 January 2019}}</ref>. Later models had 11{{nbsp}}kW AC charging, at single-phase or three-phase, depending on market.

The car comes with a smartphone app which can locate the car, report on its locking, alarming, and charging status, and start its battery preconditioning and/or cabin heating/cooling.<ref>{{cite magazine |title=Jaguar I-Pace |language=fi |magazine=Moottori |date=13 January 2019 }}</ref>

== Awards ==
[[File:Ian Callum, COTY 2019, Le Grand-Saconnex (GIMS9894).jpg|thumb|upright|Jaguar Chief of Design [[Ian Callum]] holds 2019 European Car of the Year trophy for the Jaguar I-Pace]]
The I-Pace has won 62<ref>{{cite web|date=8 May 2019|title=Three Times a Winner|url=https://www.euroweeklynews.com/2019/05/08/three-times-a-winner/#.XNP_YaZ7mRs|access-date=9 May 2019|website=EuroWeeklyNews.com}}</ref> international awards. In March 2019, it won the [[European Car of the Year]] award, the first Jaguar to win the award.<ref>{{cite web|date=4 March 2019|title=European Car of the Year 2019: Jaguar's all electric I-Pace model wins prestigious prize|url=https://www.euronews.com/2019/03/04/european-car-of-the-year-2019-jaguar-s-all-electric-i-pace-model-wins-prestigious-prize|access-date=4 March 2019|website=European Car News}}</ref> In April 2019, it became the 2019 [[World Car of the Year]], and won Best Design and Best Green Car awards.<ref name="cnbc.com">{{cite web|date=17 April 2019|title=Jaguar I-Pace electric SUV sweeps awards at New York auto show|url=https://www.cnbc.com/2019/04/17/jaguar-i-pace-electric-suv-sweeps-awards-at-new-york-auto-show.html|access-date=17 April 2019|website=CNBC}}</ref>

==Safety==
In December 2018,<ref>{{cite web|url=https://electrek.co/2018/12/07/jaguar-i-pace-safety-rating-crash-test/|title=Jaguar I-Pace Achieves 5-Star Safety Rating|date=7 December 2018|website=electrotek|access-date=7 December 2018}}</ref> the European New Car Assessment Programme (NCAP) awarded the Jaguar I-Pace a 5-star safety rating.
{{Euro NCAP |year=2018 |overall_stars=5 |description=Jaguar I-Pace |reference={{cite web|url=https://www.euroncap.com/en/results/jaguar/i-pace/34193|title=Official Jaguar I-Pace safety rating|access-date=27 February 2019}} |adult_points=34.8 |adult_percent=91 |child_points=40.0 |child_percent=81 |pedestrian_points=35.3 |pedestrian_percent=73 |safety_points=10.6 |safety_percent=81 }}

==Racing==

=== Jaguar I-Pace eTrophy (Racecar) ===
{{Main|Jaguar I-Pace eTrophy (racecar)}}

The Jaguar I-Pace has a race-prepped version called the I-Pace eTrophy, a development of the I-Pace by Jaguar Special Vehicle Operations.

=== Series ===
In September 2017,<ref>{{cite web|url=https://media.jaguar.com/en-gb/news/2017/09/jaguar-charges-i-pace-all-electric-race-series|title=Jaguar Charges Up I-Pace With All-Electric Race Series|date=12 September 2017|website=media.jaguar.com|access-date=5 January 2019}}</ref> Jaguar announced their single-make racing series for the I-Pace, called [[Jaguar I-Pace eTrophy|eTrophy]], after the racecar of the same name.

On 24 August 2018,<ref>{{cite web|url=http://www.thedrive.com/news/23121/jaguar-i-pace-sets-a-laguna-seca-electric-car-lap-record|title=Jaguar I-Pace Sets a Laguna Seca Electric Lap Record|date=24 August 2018|website=TheDrive.com|access-date=24 August 2018}}</ref> the Jaguar I-Pace set a new EV lap record at Laguna Seca Racetrack in California.

==Sales==
{| class="wikitable" style="float:center; clear:center; margin:0 0 1em 1em; text-align:center;"
|-
! Year !! Europe<ref>"Jaguar I-Pace Europe Sales Figures" | https://carsalesbase.com/europe-jaguar-i-pace/</ref> !! United States<ref>"Jaguar I-Pace U.S Sales Figures" | https://carsalesbase.com/us-jaguar-i-pace/</ref>
|-
| 2018 || 6,490 || 393
|-
| 2019 || 12,232 || 2,594
|-
| 2020 || 13,444 || 1,546
|-
| 2021 || 8,079 || 1,409
|-
| '''Total''' || '''40,245''' || '''5,942'''
|}

==Partnership for autonomous ride service==
In 2018, [[Waymo]] selected the Jaguar I-Pace for use in its autonomous ride-hailing service, placing an order for 20,000 vehicles.<ref>{{cite news |last=Stumpf|first=Rob|title=Waymo Using 20,000 Jaguar I-Pace SUVs for Driverless Car Service |url=http://www.thedrive.com/tech/19769/waymo-using-20000-jaguar-i-pace-suvs-for-driverless-car-service |date=30 March 2018|access-date=25 May 2020}}</ref>

==Wireless charging project==
In June 2020, [[Jaguar Cars|Jaguar]] announced its support for a wirelessly-charged [[taxicab|taxi]] project in [[Oslo]], [[Norway]]. [[Jaguar Cars|Jaguar]] will give 25 I-Pace vehicles to taxi company Cabonline, which will use the vehicles to test the charging infrastructure on taxis in the Norwegian capital. [[Ralf Speth]], [[Jaguar Land Rover|Jaguar Land Rover’s]] chief executive said "The taxi industry is the ideal test bed for wireless charging, and indeed for high-mileage electric mobility across the board"{{Dubious|date=January 2022}}.<ref>{{cite news |last=Fossdyke|first=James |title=Jaguar launches wireless charging I-Pace taxi project in Norway |url=https://uk.motor1.com/news/430787/jaguar-ipace-wireless-taxi-oslo/ |date=26 June 2020 |access-date=12 July 2020}}</ref>

==References==

{{Reflist|}}

==External links==
{{Commons category}}
*{{Official website|https://www.jaguar.com/jaguar-range/i-pace}}

{{Jaguar Land Rover}}
{{Jaguar modern timeline}}

[[Category:Jaguar vehicles|I-Pace]]
[[Category:Cars introduced in 2018]]
[[Category:2020s cars]]
[[Category:Compact sport utility vehicles]]
[[Category:Luxury crossover sport utility vehicles]]
[[Category:All-wheel-drive vehicles]]
[[Category:Euro NCAP executive cars]]
[[Category:Production electric cars]]

Sulfuric acid

2022-03-04T19:33:44Z

173.165.237.1:

{{Short description|Chemical compound}}
{{redirect|Oil of vitriol|sweet oil of vitriol|Diethyl ether}}
{{Use dmy dates|date=November 2019}}
{{Use American English|date=April 2021}}
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 477003658
| ImageFileL1 = Sulfuric-acid-Givan-et-al-1999-3D-vdW.png
| ImageCaptionL1 = Space-filling model
| ImageFileR1 = Sulfuric-acid-Givan-et-al-1999-3D-balls.png
| ImageCaptionR1 = Ball-and-stick model
length = 142.2 pm, S-O bond length = 157.4 pm, O-H bond length = 97 pm
| ImageSize2 = 150
| ImageFile3 = Sulphuric acid 96 percent extra pure.jpg
| ImageSize3 = 140px
| IUPACName = Sulfuric acid
| OtherNames = Oil of vitriol 
Hydrogen sulfate
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 1086
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = O40UQP6WCF
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = D05963
| InChI = 1/H2O4S/c1-5(2,3)4/h(H2,1,2,3,4)
| InChIKey = QAOWNCQODCNURD-UHFFFAOYAC
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 26836
| SMILES = OS(=O)(=O)O
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 572964
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/H2O4S/c1-5(2,3)4/h(H2,1,2,3,4)
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = QAOWNCQODCNURD-UHFFFAOYSA-N
| CASNo = 7664-93-9
| CASNo_Ref = {{cascite|correct|CAS}}
| RTECS = WS5600000
| EINECS = 231-639-5
| UNNumber = 1830
| Gmelin = 2122
| PubChem = 1118
}}
|Section2={{Chembox Properties
| Formula = {{chem2|H2SO4}}
| MolarMass = 98.079 g/mol
| Appearance = Colorless liquid
| Odor = Odorless
| Density = 1.8302 g/cm3, liquid<ref name="CRCHCP" />
| Solubility = miscible, exothermic
| MeltingPtC = 10.31<ref name="CRCHCP">{{cite book |last1=Haynes |first1=William M. |title=CRC Handbook of Chemistry and Physics |date=2014 |publisher=CRC Press |isbn=9781482208689 |pages=4–92 |edition=95 |url=https://books.google.com/books?id=bNDMBQAAQBAJ |access-date=18 November 2018 |language=en}}</ref>
| BoilingPtC = 337<ref name="CRCHCP" />
| BoilingPt_notes = When sulfuric acid is above 300 °C (572 °F; 573 K), it gradually decomposes to {{chem2|SO3 + H2O}}
| Viscosity = 26.7 [[poise (unit)|cP]] (20 °C)
| pKa = -2.8, 1.99
| ConjugateBase = [[Bisulfate]]
| VaporPressure = 0.001 mmHg (20 °C)<ref name=PGCH/>
}}
| Section3 = {{Chembox Structure
| Structure_ref =<ref name="kemnitz">{{cite journal |last1=Kemnitz |first1=E. |last2=Werner |first2=C. |last3=Trojanov |first3=S. |title=Reinvestigation of Crystalline Sulfuric Acid and Oxonium Hydrogensulfate |journal=Acta Crystallographica Section C Crystal Structure Communications |date=15 November 1996 |volume=52 |issue=11 |pages=2665–2668 |doi=10.1107/S0108270196006749 }}</ref>
| CrystalStruct = monoclinic
| SpaceGroup = C2/c
| PointGroup =
| LattConst_a = 818.1(2) pm
| LattConst_b = 469.60(10) pm
| LattConst_c = 856.3(2) pm
| LattConst_alpha =
| LattConst_beta = 111.39(3) pm
| LattConst_gamma =
| LattConst_ref =
| LattConst_Comment =
| UnitCellVolume =
| UnitCellFormulas = 4
| Coordination =
| MolShape =
| OrbitalHybridisation =
| Dipole =
}}
|Section4={{Chembox Thermochemistry
| DeltaHf = −814 kJ·mol−1<ref name=b1>{{cite book |author= Zumdahl, Steven S. |title= Chemical Principles 6th Ed. |publisher= Houghton Mifflin Company |year= 2009 |isbn= 978-0-618-94690-7|page=A23}}</ref>
| Entropy = 157 J·mol−1·K−1<ref name=b1/>
}}
|Section7={{Chembox Hazards
| ExternalSDS = [https://web.archive.org/web/20181106185657/http://www.sciencelab.com/msds.php?msdsId=9925146 External MSDS]
| FlashPt = Non-flammable
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R = 2
| NFPA-S = W+OX
| GHSPictograms = {{GHS corrosion}} {{GHS skull and crossbones}}
| GHSSignalWord = '''Danger'''
| HPhrases = {{H-phrases|314}}
| PPhrases = {{P-phrases|260|264|280|301+330+331|303+361+353|363|304+340|305+351+338|310|321|405|501}}
| TLV-TWA = 1 mg/m3
| TLV-STEL = 2 mg/m3
| TLV = 15 mg/m3 (IDLH)
| PEL = TWA 1 mg/m3<ref name=PGCH>{{PGCH|0577}}</ref>
| IDLH = 15 mg/m3<ref name=PGCH/>
| REL = TWA 1 mg/m3<ref name=PGCH/>
| LD50 = 2140 mg/kg (rat, oral)<ref name=IDLH>{{IDLH|7664939|Sulfuric acid}}</ref>
| LC50 = 50 mg/m3 (guinea pig, 8 hr) 510 mg/m3 (rat, 2 hr) 320 mg/m3 (mouse, 2 hr) 18 mg/m3 (guinea pig)<ref name=IDLH/>
| LCLo = 87 mg/m3 (guinea pig, 2.75 hr)<ref name=IDLH/>
}}
|Section8={{Chembox Related
| OtherFunction_label = [[strong acid]]s
| OtherFunction = [[Selenic acid]] [[Hydrochloric acid]] [[Nitric acid]] [[Chromic acid]]
| OtherCompounds = [[Sulfurous acid]] [[Peroxymonosulfuric acid]] [[Sulfur trioxide]] [[Oleum]]
}}
}}

'''Sulfuric acid''' ([[American spelling]] and the [[preferred IUPAC name]]) or '''sulphuric acid''' ([[English in the Commonwealth of Nations|Commonwealth spelling]]), known in antiquity as '''oil of vitriol''', is a [[mineral acid]] composed of the elements [[sulfur]], [[oxygen]] and [[hydrogen]], with the [[molecular formula]] {{chem2|[[hydrogen|H2]][[sulfate|SO4]]}}. It is a colorless, odorless and [[Viscosity|viscous]] liquid that is [[Miscibility|miscible]] with water.<ref name="ds">{{cite web|url=http://www.arkema-inc.com/msds/01641.pdf|work=arkema-inc.com|title=Sulfuric acid safety data sheet|quote=Clear to turbid oily odorless liquid, colorless to slightly yellow.|url-status=dead|archive-url=https://web.archive.org/web/20120617181442/http://www.arkema-inc.com/msds/01641.pdf|archive-date=17 June 2012}}</ref>

Pure sulfuric acid does not exist naturally on Earth due to its [[Dehydration reaction|strong affinity to water vapor]]; for this reason, it is [[hygroscopic]] and readily absorbs [[water vapor]] from the [[air]].<ref name="ds"/> Concentrated sulfuric acid is highly corrosive towards other materials, from rocks to metals, since it is an oxidant with powerful dehydrating properties. [[Phosphorus pentoxide]] is a notable exception in that it is not dehydrated by sulfuric acid, but to the contrary dehydrates sulfuric acid to [[sulfur trioxide]]. Upon addition of sulfuric acid to water, a considerable amount of heat is released; thus the reverse procedure of adding water to the acid should not be performed since the heat released may boil the solution, spraying droplets of hot acid during the process. Upon contact with body tissue, sulfuric acid can cause severe [[strong acids|acidic]] [[chemical burn]]s and even secondary [[Thermal burn|thermal]] [[Burn|burns]] due to dehydration.<ref name="OA"/><ref name=TB>{{cite web|url=https://collaboration.basf.com/portal/load/fid1032678/E015%20Sulfuric%20acid%20C.pdf|archive-url=https://web.archive.org/web/20190614101454/https://collaboration.basf.com/portal/load/fid1032678/E015%20Sulfuric%20acid%20C.pdf|url-status=dead|archive-date=2019-06-14|title=BASF Chemical Emergency Medical Guidelines – Sulfuric acid (H2SO4)|publisher=BASF Chemical Company|date=2012|access-date=18 December 2014}}</ref> Dilute sulfuric acid is substantially less hazardous without the oxidative and dehydrating properties; however, it should still be handled with care for its acidity.

Sulfuric acid is a very important commodity chemical, and a nation's sulfuric acid production is a good indicator of its industrial strength.<ref name="Chenier 1987 45–57">{{cite book |last=Chenier |first=Philip J. |title=Survey of Industrial Chemistry |pages=[https://archive.org/details/surveyofindustri0000chen/page/45 45–57] |publisher=John Wiley & Sons |location=New York |year=1987 |isbn=978-0-471-01077-7 |url=https://archive.org/details/surveyofindustri0000chen/page/45 }}</ref> It is widely produced with different methods, such as [[contact process]], [[wet sulfuric acid process]], [[lead chamber process]] and some other methods.<ref>Hermann Müller "Sulfuric Acid and Sulfur Trioxide" in ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim. 2000 {{doi|10.1002/14356007.a25_635}}</ref> Sulfuric acid is also a key substance in the [[chemical industry]]. It is most commonly used in [[fertilizer]] manufacture,<ref>{{cite web |url=http://essentialchemicalindustry.org/chemicals/sulfuric-acid.html|title=Sulfuric acid}}</ref> but is also important in [[mineral processing]], [[oil refinery|oil refining]], [[wastewater processing]], and [[chemical synthesis]]. It has a wide range of end applications including in [[drain cleaner|domestic acidic drain cleaners]],<ref name="dc"/> as an [[electrolyte]] in [[lead–acid battery|lead-acid batteries]], in dehydrating a compound, and in various [[cleaning agent]]s.
Sulfuric acid can be obtained by dissolving [[sulfur trioxide]] in water.

==Physical properties==

===Grades of sulfuric acid===
Although nearly 100% sulfuric acid solutions can be made, the subsequent loss of {{chem2|[[sulfur trioxide|SO3]]}} at the boiling point brings the concentration to 98.3% acid. The 98.3% grade is more stable in storage, and is the usual form of what is described as "concentrated sulfuric acid". Other concentrations are used for different purposes. Some common concentrations are:<ref name="Columbia">{{cite book |chapter=Sulfuric Acid|chapter-url=http://www.encyclopedia.com/topic/sulfuric_acid.aspx|title=The Columbia Encyclopedia |edition=6th |year=2009 |access-date=16 March 2010}}</ref><ref name="EB11">{{cite book|chapter=Sulphuric acid|title=Encyclopædia Britannica|edition=11th|year=1910–1911|volume=26|pages=65–69|title-link=Encyclopædia Britannica Eleventh Edition}} Please note, no EB1911 wikilink is available to this article</ref>
{| class="wikitable"
|-
! Mass fraction {{chem2|H2SO4}}
! Density (kg/L)
! Concentration (mol/L)
! Common name
|-
| <29% || 1.00-1.25 || align=center| <4.2 || diluted sulfuric acid
|-
| 29–32% || 1.25–1.28 || align=center| 4.2–5.0 || battery acid (used in [[lead–acid batteries]])
|-
| 62–70% || 1.52–1.60 || align=center| 9.6–11.5 || chamber acid fertilizer acid
|-
| 78–80% || 1.70–1.73 || align=center| 13.5–14.0 || tower acid Glover acid
|-
| 93.2% || 1.83 || align=center| 17.4 || 66 [[Baumé scale|°Bé]] ("66-degree Baumé") acid
|-
| 98.3% || 1.84 || align=center| 18.4 || concentrated sulfuric acid
|}

"Chamber acid" and "tower acid" were the two concentrations of sulfuric acid produced by the [[lead chamber process]], chamber acid being the acid produced in the lead chamber itself (<70% to avoid contamination with [[nitrosylsulfuric acid]]) and tower acid being the acid recovered from the bottom of the Glover tower.<ref name="Columbia"/><ref name="EB11"/> They are now obsolete as commercial concentrations of sulfuric acid, although they may be prepared in the laboratory from concentrated sulfuric acid if needed. In particular, "10M" sulfuric acid (the modern equivalent of chamber acid, used in many [[titration]]s), is prepared by slowly adding 98% sulfuric acid to an equal volume of water, with good stirring: the temperature of the mixture can rise to 80 °C (176 °F) or higher.<ref name="EB11"/>

====Pure sulfuric acid====
Pure sulfuric acid is a colorless oily liquid, and has a vapor pressure of <0.001 mmHg at 25 °C and 1 mmHg at 145.8 °C,<ref name="OEHHA">{{cite book |chapter=Sulfuric acid|chapter-url=http://oehha.ca.gov/air/chronic_rels/pdf/sulfuric.pdf|title=Determination of Noncancer Chronic Reference Exposure Levels Batch 2B December 2001|year=2001|archive-url=https://web.archive.org/web/20030522222447/http://oehha.ca.gov/air/chronic_rels/pdf/sulfuric.pdf|access-date=1 October 2012|archive-date=22 May 2003}}</ref> and 98% sulfuric acid has a <1 mmHg vapor pressure at 40 °C.<ref name="Rhodia">{{cite web|url=http://www.rhodia.com/our_company/businesses/documents/Sulfuric_Acid_98.pdf|archive-url=https://web.archive.org/web/20110107022427/http://www.rhodia.com/our_company/businesses/documents/Sulfuric_Acid_98.pdf|url-status=dead|archive-date=7 January 2011|title=Sulfuric Acid 98%|year=2009|access-date=2 July 2014|publisher=rhodia.com}}</ref>

In the solid state, sulfuric acid is a molecular solid that forms [[monoclinic]] crystals with nearly [[trigonal]] lattice parameters. The structure consists of layers parallel to the (010) plane, in which each molecule is connected by [[hydrogen bond]]s to two others.<ref name="kemnitz"/> [[Hydrate]]s {{chem2|H2SO4*''n''H2O}} are known for ''n'' = 1, 2, 3, 4, 6.5, and 8, although most intermediate hydrates are stable against [[disproportionation]].<ref>{{cite journal |last1=Giauque |first1=W. F. |last2=Hornung |first2=E. W. |last3=Kunzler |first3=J. E. |last4=Rubin |first4=T. R. |title=The Thermodynamic Properties of Aqueous Sulfuric Acid Solutions and Hydrates from 15 to 300°K. 1 |journal=Journal of the American Chemical Society |date=January 1960 |volume=82 |issue=1 |pages=62–70 |doi=10.1021/ja01486a014}}</ref>

===Polarity and conductivity===
{| class="wikitable sortable floatright"
|+colspan=2|Equilibrium of anhydrous sulfuric acid<ref name="greenwood"/>
!Species
!mMol/kg
|-
|{{chem2|HSO4(-)}}
| 15.0
|-
|{{chem2|H3SO4(+)}}
| 11.3
|-
|{{chem2|H3O(+)}}
| 8.0
|-
|{{chem2|HS2O7(-)}}
| 4.4
|-
|{{chem2|H2S2O7}}
| 3.6
|-
|{{chem2|H2O}}
| 0.1
|}
[[Anhydrous]] {{chem2|H2SO4}} is a very [[chemical polarity|polar]] liquid, having a [[dielectric constant]] of around 100. It has a high [[electrical conductivity]], caused by dissociation through [[protonation|protonating]] itself, a process known as [[autoprotolysis]].<ref name=greenwood>{{Greenwood&Earnshaw2nd}}</ref>
:2 {{chem|H|2|SO|4}} {{eqm}} {{chem|H|3|SO|4|+}} + {{chem|HSO|4|-}}
The [[equilibrium constant]] for the autoprotolysis is<ref name=greenwood/>
:''K''ap (25 °C) = [{{chem|H|3|SO|4|+}}][{{chem|HSO|4|-}}] = {{val|2.7|e=-4}}

The comparable [[Self-ionization of water|equilibrium constant for water]], ''K''w is 10−14, a factor of 1010 (10 billion) smaller.

In spite of the viscosity of the acid, the effective [[molar conductivity|conductivities]] of the {{chem|H|3|SO|4|+}} and {{chem|HSO|4|-}} ions are high due to an intramolecular proton-switch mechanism (analogous to the [[Grotthuss mechanism]] in water), making sulfuric acid a good conductor of electricity. It is also an excellent solvent for many reactions.

==Chemical properties==

===Reaction with water and [[Dehydration reaction|dehydrating]] property===
[[File:Sulphuric acid on a piece of towel.JPG|thumb|right|Drops of concentrated sulfuric acid rapidly decompose a piece of cotton towel by dehydration.]]
[[File:07. Дехидратациони својства на концентрирана сулфурна киселина.webm|thumb|upright=1.2|An experiment that demonstrates the dehydration properties of concentrated sulfuric acid. When concentrated sulfuric acid comes into contact with [[sucrose]], slow carbonification of the sucrose takes place. The reaction is accompanied by the evolution of gaseous products that contribute to the formation of the foamy carbon pillar that rises above the beaker.]]
Because the [[hydration reaction]] of sulfuric acid is highly [[exothermic reaction|exothermic]], dilution should always be performed by adding the acid to the [[properties of water|water]] rather than the water to the acid.<ref>{{cite web |url = http://www.cleapss.org.uk/attachments/article/0/SSS22.pdf?Secondary/Science/Student%20Safety%20Sheets/ |title = Consortium of Local Education Authorities for the Provision of Science Equipment -STUDENT SAFETY SHEETS 22 Sulfuric(VI) acid |archive-url=https://web.archive.org/web/20130331050001/http://www.cleapss.org.uk/attachments/article/0/SSS22.pdf?Secondary/Science/Student%20Safety%20Sheets/ |archive-date=31 March 2013 |url-status=dead}}</ref> Because the reaction is in an equilibrium that favors the rapid protonation of water, addition of acid to the water ensures that the ''acid'' is the limiting reagent. This reaction is best thought of as the formation of [[hydronium]] ions:

:{{chem|H|2|SO|4}} + {{chem|H|2|O}} → {{chem|H|3|O|+}} + {{chem|HSO|4|-}} {{pad|2em}} ''K''a1 ≈ 103 (strong acid)
:{{chem|HSO|4|-}} + {{chem|H|2|O}} → {{chem|H|3|O|+}} + {{chem|SO|4|2-}} {{pad|2em}} ''K''a2 = {{val|1.0e-2}} <ref>{{cite web|url=http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/acidity.htm |title=Ionization Constants of Inorganic Acids |publisher=.chemistry.msu.edu |access-date=30 May 2011}}</ref>

{{chem|HSO|4|-}} is the ''[[bisulfate]]'' anion and {{chem|SO|4|2-}} is the ''[[sulfate]]'' anion. ''K''a1 and ''K''a2 are the [[acid dissociation constant]]s.

Because the hydration of sulfuric acid is [[thermodynamic]]ally favorable, its affinity for [[water (molecule)|water]] is quite strong; therefore, sulfuric acid is an excellent dehydrating agent. Concentrated sulfuric acid has a very powerful [[dehydration reaction|dehydrating]] property, removing water ([[water|H2O]]) from other [[chemical compound]]s including [[sugar]] and other [[carbohydrate]]s and producing [[carbon]], [[heat]], and [[steam]].

In the [[laboratory]], this is often demonstrated by mixing [[table sugar]] (sucrose) into sulfuric acid. The sugar changes from white to dark brown and then to black as carbon is formed. A rigid column of black, porous carbon will emerge as well. The carbon will smell strongly of [[caramel (aroma)|caramel]] due to the heat generated.<ref>[https://www.youtube.com/watch?v=UcpodCsTxtc sulfuric acid on sugar cubes chemistry experiment 8. Old Version]. YouTube. Retrieved on 18 July 2011.</ref>

:<math chem>\overbrace{\ce{C12H22O11}}^\text{sucrose}\ \ce{->[\ce{H2SO4}]}\ \underset{\text{(black graphitic foam)}}{\ce{12C}} + \ce{11H2O}_\text{(g,l)}</math>

Similarly, mixing [[starch]] into concentrated sulfuric acid will give elemental [[carbon]] and water as absorbed by the sulfuric acid (which becomes slightly diluted). The effect of this can be seen when concentrated sulfuric acid is spilled on paper, which is composed of [[cellulose]]; the cellulose reacts to give a [[combustion|burnt]] appearance, the [[carbon]] appears much as soot would in a fire.
Although less dramatic, the action of the acid on [[cotton]], even in diluted form, will destroy the fabric.

:<math chem>\overbrace{\ce{(C6H10O5)_\mathit{n}}}^\text{polysaccharide}\ \ce{->[\ce{H2SO4}]}\ 6n\ce{C} + 5n\ce{H2O}</math>

The reaction with [[copper(II) sulfate]] can also demonstrate the dehydration property of sulfuric acid. The blue crystal is changed into white powder as water is removed.
:<math chem>\overbrace{\underset{\text{(blue crystal)}}{\ce{CuSO4.5H2O}}}^\text{copper(II) sulfate hydrate}
\ \ce{->[\ce{H2SO4}]}
\ \overbrace{\underset{\text{(white powder)}}{\ce{CuSO4}}}^\text{Anhydrous copper(II) sulfate} + \ce{5H2O}</math>

===Acid-base properties===
As an acid, sulfuric acid reacts with most [[base (chemistry)|bases]] to give the corresponding sulfate. For example, the blue [[copper]] salt [[copper(II) sulfate]], commonly used for [[electroplating]] and as a [[fungicide]], is prepared by the reaction of [[copper(II) oxide]] with sulfuric acid:
:CuO (s) + {{chem|H|2|SO|4}} (aq) → {{chem|CuSO|4}} (aq) + {{chem|H|2|O}} (l)

Sulfuric acid can also be used to displace weaker acids from their salts. Reaction with [[sodium acetate]], for example, displaces [[acetic acid]], {{chem|CH|3|COOH}}, and forms [[sodium bisulfate]]:
:{{chem|H|2|SO|4}} + {{chem|CH|3|COONa}} → {{chem|NaHSO|4}} + {{chem|CH|3|COOH}}

Similarly, reacting sulfuric acid with [[potassium nitrate]] can be used to produce [[nitric acid]] and a precipitate of [[potassium bisulfate]]. When combined with [[nitric acid]], sulfuric acid acts both as an acid and a dehydrating agent, forming the [[nitronium ion]] {{chem|NO|2|+}}, which is important in [[nitration]] reactions involving [[electrophilic aromatic substitution]]. This type of reaction, where protonation occurs on an [[oxygen]] atom, is important in many [[organic chemistry]] reactions, such as [[Fischer esterification]] and dehydration of alcohols.

[[File:Structure of protonated sulfuric acid.png|thumb|Solid state structure of the [D3SO4]+ ion present in [D3SO4]+[SbF6]−, synthesized by using [[deuterium|D]]F in place of HF. (see text)]]

When allowed to react with [[superacid]]s, sulfuric acid can act as a base and be protonated, forming the [H3SO4]+ ion. Salts of [H3SO4]+ have been prepared using the following reaction in liquid [[hydrogen fluoride|HF]]:
:((CH3)3SiO)2SO2 + 3 HF + SbF5 → [H3SO4]+[SbF6]− + 2 (CH3)3SiF

The above reaction is thermodynamically favored due to the high [[bond enthalpy]] of the Si–F bond in the side product. Protonation using simply [[fluoroantimonic acid|HF/SbF5]], however, has met with failure, as pure sulfuric acid undergoes [[molecular autoionization|self-ionization]] to give [H3O]+ ions
:2 H2SO4 {{eqm}} [H3O]+ + [HS2O7]−
:which prevents the conversion of H2SO4 to [H3SO4]+ by the HF/SbF5 system.<ref name="InorgChem">{{cite book|author1=Housecroft, Catherine E.|title=Inorganic Chemistry, 3rd Edition|author2=Sharpe, Alan G.|publisher=Pearson|year=2008|isbn=978-0-13-175553-6|page=523|chapter=Chapter 16: The group 16 elements}}</ref>

=== Reactions with metals ===
Even dilute sulfuric acid reacts with many metals via a single displacement reaction, like other typical [[acid]]s, producing [[hydrogen]] gas and [[Salt (chemistry)|salt]]s (the metal sulfate). It attacks reactive metals (metals at positions above [[copper]] in the [[reactivity series]]) such as [[iron]], [[aluminium]], [[zinc]], [[manganese]], [[magnesium]], and [[nickel]].
:Fe + {{chem|H|2|SO|4}} → {{chem|H|2}} + {{chem|FeSO|4}}

Concentrated sulfuric acid can serve as an [[oxidizing agent]], releasing sulfur dioxide:<ref name="OA">{{cite web|url=http://www.dynamicscience.com.au/tester/solutions/chemistry/sulfuricacid1.html|title=Sulfuric acid – uses|work=dynamicscience.com.au|url-status=dead|archive-url=https://web.archive.org/web/20130509024826/http://www.dynamicscience.com.au/tester/solutions/chemistry/sulfuricacid1.html|archive-date=9 May 2013}}</ref>
:Cu + 2 H2SO4 → SO2 + 2 H2O + {{chem|SO|4|2-}} + Cu2+

[[Lead]] and [[tungsten]], however, are resistant to sulfuric acid.

===Reactions with carbon===
Hot concentrated sulfuric acid oxidizes [[carbon]]<ref>{{cite book|author1=Kinney, Corliss Robert |author2=Grey, V. E. |title=Reactions of a Bituminous Coal with Sulfuric Acid|year=1959|publisher=Pennsylvania State University|url=https://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/03_2_BOSTON_04-59_0169.pdf |archive-url=https://web.archive.org/web/20170428004603/https://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/03_2_BOSTON_04-59_0169.pdf |url-status=dead |archive-date=2017-04-28 }}</ref> (as bituminous coal) and [[sulfur]]:
:C + 2 H2SO4 → CO2 + 2 SO2 + 2 H2O
:S + 2 H2SO4 → 3 SO2 + 2 H2O

===Reaction with sodium chloride===
It reacts with [[sodium chloride]], and gives [[hydrogen chloride]] [[gas]] and [[sodium bisulfate]]:
:NaCl + H2SO4 → NaHSO4 + HCl

===Electrophilic aromatic substitution===
Benzene undergoes [[electrophilic aromatic substitution]] with sulfuric acid to give the corresponding [[sulfonic acid]]s:<ref>{{cite web|url=http://www.chem.ucalgary.ca/courses/351/Carey/Ch12/ch12-4.html |title=Reactions of Arenes. Electrophilic Aromatic Substitution |author=Carey, F. A. |work=On-Line Learning Center for Organic Chemistry |publisher=[[University of Calgary]] |access-date=27 January 2008 |url-status=unfit |archive-url=https://web.archive.org/web/20080706063639/http://www.chem.ucalgary.ca/courses/351/Carey/Ch12/ch12-4.html |archive-date=6 July 2008}}</ref>
:[[File:BenzeneSulfonation.png|250px]]

==Occurrence==
[[File:Rio tinto river CarolStoker NASA Ames Research Center.jpg|thumb|[[Rio Tinto (river)|Rio Tinto]] with its highly acidic water]]

Pure sulfuric acid is not encountered naturally on Earth in anhydrous form, due to its great [[hygroscopy|affinity for water]]. Dilute sulfuric acid is a constituent of [[acid rain]], which is formed by atmospheric [[redox|oxidation]] of [[sulfur dioxide]] in the presence of [[water (molecule)|water]] – i.e., oxidation of [[sulfurous acid]]. When sulfur-containing fuels such as coal or oil are burned, sulfur dioxide is the main byproduct (besides the chief products carbon oxides and water).

Sulfuric acid is formed naturally by the oxidation of sulfide minerals, such as iron sulfide. The resulting water can be highly acidic and is called [[acid mine drainage]] (AMD) or acid rock drainage (ARD). This acidic water is capable of dissolving metals present in sulfide ores, which results in brightly colored, toxic solutions. The oxidation of [[pyrite]] (iron sulfide) by molecular oxygen produces iron(II), or {{chem|Fe|2+}}:
:2 {{chem|FeS|2}} (s) + 7 {{chem|O|2}} + 2 {{H2O}} → 2 {{chem|Fe|2+}} + 4 {{chem|SO|4|2-}} + 4 {{chem|H|+}}

The {{chem|Fe|2+}} can be further oxidized to {{chem|Fe|3+}}:
:4 {{chem|Fe|2+}} + {{chem|O|2}} + 4 {{chem|H|+}} → 4 {{chem|Fe|3+}} + 2 {{H2O}}

The {{chem|Fe|3+}} produced can be precipitated as the [[hydroxide]] or [[hydrous iron oxide]]:
:{{chem|Fe|3+}} + 3 {{H2O}} → {{chem|Fe|(OH)|3}}↓ + 3 {{chem|H|+}}

The iron(III) ion ("ferric iron") can also oxidize pyrite:
:{{chem|FeS|2}}(s) + 14 {{chem|Fe|3+}} + 8 {{H2O}} → 15 {{chem|Fe|2+}} + 2 {{chem|SO|4|2-}} + 16 {{chem|H|+}}

When iron(III) oxidation of pyrite occurs, the process can become rapid. [[pH]] values below zero have been measured in ARD produced by this process.

ARD can also produce sulfuric acid at a slower rate, so that the [[acid neutralizing capacity]] (ANC) of the aquifer can neutralize the produced acid. In such cases, the [[total dissolved solids]] (TDS) concentration of the water can be increased from the dissolution of minerals from the acid-neutralization reaction with the minerals.

Sulfuric acid is used as a defense by certain marine species, for example, the phaeophyte alga ''Desmarestia munda'' (order [[Desmarestiales]]) concentrates sulfuric acid in cell vacuoles.<ref name='Pelletreau'>{{cite journal|first= K.|last= Pelletreau|author2=Muller-Parker, G. |journal= Marine Biology|year= 2002|volume= 141|issue=1|pages=1–9|doi=10.1007/s00227-002-0809-6|title= Sulfuric acid in the phaeophyte alga Desmarestia munda deters feeding by the sea urchin Strongylocentrotus droebachiensis|s2cid= 83697676}}</ref>

===Stratospheric aerosol===

In the [[stratosphere]], the atmosphere's second layer that is generally between 10 and 50 km above Earth's surface, sulfuric acid is formed by the oxidation of volcanic sulfur dioxide by the [[hydroxyl radical]]:<ref name='Kremser'>{{cite journal|first= S.|last= Kremser|author2= Thomson, L.W.|journal= Reviews of Geophysics|year= 2016|volume= 54|issue= 2|pages=278–335|doi=10.1002/2015RG000511|title= Stratospheric aerosol—Observations, processes, and impact on climate|bibcode= 2016RvGeo..54..278K|url= http://eprints.whiterose.ac.uk/97280/7/Kremser_et_al-2016-Reviews_of_Geophysics.pdf|doi-access= free}}</ref>
:{{chem|SO|2}} + HO• → {{chem|HSO|3}}
:{{chem|HSO|3}} + {{chem|O|2}} → {{chem|SO|3}} + {{chem|HO|2|}}
:{{chem|SO|3}} + {{H2O}} → {{chem|H|2|SO|4}}

Because sulfuric acid reaches [[supersaturation]] in the stratosphere, it can nucleate aerosol particles and provide a surface for aerosol growth via condensation and coagulation with other water-sulfuric acid aerosols. This results in the [[stratospheric aerosol layer]].<ref name='Kremser' />

===Extraterrestrial sulfuric acid===
The permanent [[Venus]]ian clouds produce a concentrated acid rain, as the clouds in the atmosphere of Earth produce water rain.<ref>{{cite journal |title=Chemical composition of Venus atmosphere and clouds: Some unsolved problems |first=Vladimir A. |last=Krasnopolsky |date=2006 |journal=[[Planetary and Space Science]] |volume=54 |issue=13–14 |pages=1352–1359 |doi=10.1016/j.pss.2006.04.019 |bibcode=2006P&SS...54.1352K}}</ref> [[Jupiter]]'s moon [[Europa (moon)|Europa]] is also thought to have an atmosphere containing sulfuric acid hydrates.<ref>{{cite journal |first1=T. M. |last1=Orlando |first2=T. B. |last2=McCord |first3=G. A. |last3=Grieves |title=The chemical nature of Europa surface material and the relation to a subsurface ocean |journal=[[Icarus (journal)|Icarus]] |volume=177 |year=2005 |issue=2 |pages=528–533 |doi=10.1016/j.icarus.2005.05.009 |bibcode=2005Icar..177..528O}}</ref>

==Manufacture==
{{Main|Contact process|Wet sulfuric acid process|Lead chamber process}}

Sulfuric acid is produced from [[sulfur]], oxygen and water via the conventional [[contact process]] (DCDA) or the [[wet sulfuric acid process]] (WSA).

===Contact process===
{{Main|Contact process}}
In the first step, sulfur is burned to produce sulfur dioxide.
:S (s) + {{chem|O|2}} → {{chem|SO|2}}

The sulfur dioxide is oxidized to sulfur trioxide by oxygen in the presence of a [[vanadium(V) oxide]] [[catalyst]]. This reaction is reversible and the formation of the sulfur trioxide is exothermic.
:2 {{chem|SO|2}} + {{chem|O|2}} {{eqm}} 2 {{chem|SO|3}}

The sulfur trioxide is absorbed into 97–98% {{chem|H|2|SO|4}} to form [[oleum]] ({{chem|H|2|S|2|O|7}}), also known as fuming sulfuric acid and pyrosulphuric acid. The oleum is then diluted with water to form concentrated sulfuric acid.

:{{chem|H|2|SO|4}} + {{chem|SO|3}} → {{chem|H|2|S|2|O|7}}
:{{chem|H|2|S|2|O|7}} + {{chem|H|2|O}} → 2 {{chem|H|2|SO|4}}

Directly dissolving {{chem|SO|3}} in water is not practiced.

===Wet sulfuric acid process===
{{Main|Wet sulfuric acid process}}
In the first step, sulfur is burned to produce sulfur dioxide:
:S + {{chem|O|2}} → {{chem|SO|2}} (−297 kJ/mol)

or, alternatively, [[hydrogen sulfide]] ({{chem|H|2|S}}) gas is incinerated to {{chem|SO|2}} gas:
:2 {{chem|H|2|S}} + 3 {{chem|O|2}} → 2 {{chem|H|2|O}} + 2 {{chem|SO|2}} (−1036 kJ/mol)
The sulfur dioxide then oxidized to sulfur trioxide using oxygen with [[vanadium(V) oxide]] as [[catalyst]].
:2 {{chem|SO|2}} + {{chem|O|2}} {{eqm}} 2 {{chem|SO|3}} (−198 kJ/mol) (reaction is reversible)

The sulfur trioxide is hydrated into sulfuric acid {{chem|H|2|SO|4}}:
:{{chem|SO|3}} + {{chem|H|2|O}} → {{chem|H|2|SO|4}}(g) (−101 kJ/mol)

The last step is the condensation of the sulfuric acid to liquid 97–98% {{chem|H|2|SO|4}}:
:{{chem|H|2|SO|4}}(g) → {{chem|H|2|SO|4}}(l) (−69 kJ/mol)

===Other methods===
A method that is the less well-known is the metabisulfite method, in which [[metabisulfite]] is placed at the bottom of a beaker and 12.6 molar concentration [[hydrochloric acid]] is added. The resulting gas is bubbled through [[nitric acid]], which will release brown/red vapors of nitrogen dioxide as the reaction proceeds. The completion of the reaction is indicated by the ceasing of the fumes. This method does not produce an inseparable mist, which is quite convenient.
:3 SO2 + 2 HNO3 + 2 H2O → 3 H2SO4 + 2 NO
Burning [[sulfur]] together with saltpeter ([[potassium nitrate]], {{chem|KNO|3}}), in the presence of steam, has been used historically. As saltpeter decomposes, it oxidizes the sulfur to {{chem|SO|3}}, which combines with water to produce sulfuric acid.

Alternatively, dissolving sulfur dioxide in an aqueous solution of an oxidizing metal salt such as copper (II) or iron (III) chloride:
:2 FeCl3 + 2 H2O + SO2 → 2 FeCl2 + H2SO4 + 2 HCl
:2 CuCl2 + 2 H2O + SO2 → 2 CuCl + H2SO4 + 2 HCl

Two less well-known laboratory methods of producing sulfuric acid, albeit in dilute form and requiring some extra effort in purification. A solution of [[copper (II) sulfate]] can be electrolyzed with a copper cathode and platinum/graphite anode to give spongy [[copper]] at cathode and evolution of oxygen gas at the anode, the solution of dilute sulfuric acid indicates completion of the reaction when it turns from blue to clear (production of hydrogen at cathode is another sign):

:2 CuSO4 + 2 H2O → 2 Cu + 2 H2SO4 + O2

More costly, dangerous, and troublesome yet novel is the electrobromine method, which employs a mixture of [[sulfur]], water, and [[hydrobromic acid]] as the electrolytic solution. The sulfur is pushed to bottom of container under the acid solution. Then the copper cathode and platinum/graphite anode are used with the cathode near the surface and the anode is positioned at the bottom of the electrolyte to apply the current. This may take longer and emits toxic [[bromine]]/sulfur bromide vapors, but the reactant acid is recyclable. Overall, only the sulfur and water are converted to sulfuric acid (omitting losses of acid as vapors):

:2 HBr → H2 + Br2 (electrolysis of aqueous hydrogen bromide)
:Br2 + Br− ↔ Br3− (initial [[tribromide]] production, eventually reverses as Br− depletes)
:2 S + Br2 → S2Br2 (bromine reacts with sulfur to form [[disulfur dibromide]])
:S2Br2 + 8 H2O + 5 Br2 → 2 H2SO4 + 12 HBr (oxidation and hydration of disulfur dibromide)

Prior to 1900, most sulfuric acid was manufactured by the [[lead chamber process]].<ref>{{cite journal |first=Edward M. |last=Jones |title=Chamber Process Manufacture of Sulfuric Acid |journal=Industrial and Engineering Chemistry |year=1950 |volume=42 |issue=11 |pages=2208–2210 |doi=10.1021/ie50491a016}}</ref> As late as 1940, up to 50% of sulfuric acid manufactured in the United States was produced by chamber process plants.

In the early to mid 19th century "vitriol" plants existed, among other places, in [[Prestonpans]] in Scotland, [[Shropshire]] and the [[Lagan Valley]] in County Antrim Ireland, where it was used as a bleach for linen. Early bleaching of linen was done using lactic acid from sour milk but this was a slow process and the use of vitriol sped up the bleaching process.<ref>{{cite book|title=A history of lactic acid making: a chapter in the history of biotechnology|last=(Harm)|first=Benninga, H.|date=1990|publisher=Kluwer Academic Publishers|isbn=9780792306252|location=Dordrecht [Netherland]|oclc=20852966|page=4}}</ref>

==Uses==
[[File:Sulfuric acid 2000.png|thumb|upright=1.35|Sulfuric acid production in 2000]]
Sulfuric acid is a very important commodity chemical, and indeed, a nation's sulfuric acid production is a good indicator of its industrial strength.<ref name="Chenier 1987 45–57"/> World production in the year 2004 was about 180 million [[tonne]]s, with the following geographic distribution: Asia 35%, North America (including Mexico) 24%, Africa 11%, Western Europe 10%, Eastern Europe and Russia 10%, Australia and Oceania 7%, South America 7%.<ref>{{cite book|author1=Davenport, William George |author2=King, Matthew J. |name-list-style=amp |title=Sulfuric acid manufacture: analysis, control and optimization|url=https://books.google.com/books?id=tRAb2CniRG4C|access-date=23 December 2011|year=2006|publisher=Elsevier|isbn=978-0-08-044428-4|pages=8, 13}}</ref> Most of this amount (≈60%) is consumed for fertilizers, particularly superphosphates, ammonium phosphate and ammonium sulfates. About 20% is used in chemical industry for production of detergents, synthetic resins, dyestuffs, pharmaceuticals, petroleum catalysts, insecticides and [[antifreeze]], as well as in various processes such as oil well acidicizing, aluminium reduction, paper sizing, and water treatment. About 6% of uses are related to [[pigment]]s and include paints, [[enamel paint|enamels]], printing inks, coated fabrics and paper, while the rest is dispersed into a multitude of applications such as production of explosives, [[cellophane]], acetate and viscose textiles, lubricants, non-ferrous metals, and batteries.<ref>{{Greenwood&Earnshaw2nd|page=653}}</ref>

===Industrial production of chemicals===
The major use for sulfuric acid is in the "wet method" for the production of [[phosphoric acid]], used for manufacture of [[phosphate]] [[fertilizer]]s. In this method, phosphate rock is used, and more than 100 million tonnes are processed annually. This raw material is shown below as [[fluorapatite]], though the exact composition may vary. This is treated with 93% sulfuric acid to produce [[calcium sulfate]], [[hydrogen fluoride]] (HF) and [[phosphoric acid]]. The HF is removed as [[hydrofluoric acid]]. The overall process can be represented as:
:<chem>\overset{fluorapatite}{Ca5F(PO4)3} + {5H2SO4} + 10H2O -> \overset{calcium~sulfate}{5CaSO4.2H2O} + {HF} + 3H3PO4</chem>

[[Ammonium sulfate]], an important nitrogen fertilizer, is most commonly produced as a byproduct from [[Coke (fuel)|coking plants]] supplying the iron and steel making plants. Reacting the [[ammonia]] produced in the thermal decomposition of [[coal]] with waste sulfuric acid allows the ammonia to be crystallized out as a salt (often brown because of iron contamination) and sold into the agro-chemicals industry.

Another important use for sulfuric acid is for the manufacture of [[aluminium sulfate]], also known as paper maker's alum. This can react with small amounts of soap on [[paper pulp]] fibers to give gelatinous aluminium [[carboxylate]]s, which help to coagulate the pulp fibers into a hard paper surface. It is also used for making [[aluminium hydroxide]], which is used at [[water treatment]] plants to [[filter (water)|filter]] out impurities, as well as to improve the taste of the [[water]]. [[Aluminium sulfate]] is made by reacting [[bauxite]] with sulfuric acid:
:2 {{chem|Al|O|(OH)}} + 3 {{chem|H|2|SO|4}} → {{chem|Al|2|(SO|4|)|3}} + 4 {{chem|H|2|O}}

Sulfuric acid is also important in the manufacture of [[dye]]stuffs solutions.

===Sulfur–iodine cycle===
The [[sulfur–iodine cycle]] is a series of thermo-chemical processes possibly usable to produce [[hydrogen]] from [[water]]. It consists of three chemical reactions whose net reactant is water and whose net products are hydrogen and [[oxygen]].

:{|
|-
| 2 {{chem|I|2}} + 2 {{chem|SO|2}} + 4 '''{{chem|H|2|O}}''' → 4 HI + 2 {{chem|H|2|SO|4}} ||     || (120 °C, [[Bunsen reaction]])
|-
| 2 {{chem|H|2|SO|4}} → 2 {{chem|SO|2}} + 2 '''{{chem|H|2|O}}''' + '''{{chem|O|2}}''' ||     || (830 °C)
|-
| 4 HI → 2 {{chem|I|2}} + 2 '''{{chem|H|2}}''' ||     || (320 °C)
|}

The compounds of sulfur and [[iodine]] are recovered and reused, hence the consideration of the process as a cycle. This process is [[endothermic]] and must occur at high temperatures, so energy in the form of heat has to be supplied.

The sulfur–iodine cycle has been proposed as a way to supply hydrogen for a [[hydrogen economy|hydrogen-based economy]]. It is an alternative to [[Electrolysis of water|electrolysis]], and does not require [[hydrocarbon]]s like current methods of [[steam reforming]]. But note that all of the available energy in the hydrogen so produced is supplied by the heat used to make it.

The sulfur–iodine cycle is currently being researched as a feasible method of obtaining hydrogen, but the concentrated, corrosive acid at high temperatures poses currently insurmountable safety hazards if the process were built on a large scale.<ref>{{cite book |url=https://books.google.com/books?id=D-yPCwAAQBAJ&q=oxygen+from+sulfur-iodine+cycle+danger|title=Our Energy Future: Resources, Alternatives and the Environment|last1=Ngo|first1=Christian|last2=Natowitz|first2=Joseph|publisher=John Wiley & Sons|year=2016|isbn=9781119213369|pages=418–419}}</ref><ref>{{cite web |url=https://www.hydrogen.energy.gov/pdfs/review05/pd27_pickard.pdf |title=2005 DOE Hydrogen Program Review: Sulfur-Iodine Thermochemical Cycle |last=Pickard |first=Paul |publisher=Sandia National Labs |date=25 May 2005 |access-date=8 October 2021 |url-status=live}}</ref>

===Hybrid sulfur cycle===
The [[hybrid sulfur cycle]] (HyS) is a two-step [[water splitting]] process intended to be used for hydrogen production. Based on sulfur oxidation and reduction, it is classified as a hybrid thermochemical cycle because it uses an electrochemical (instead of a thermochemical) reaction for one of the two steps. The remaining thermochemical step is shared with the sulfur-iodine cycle.

===Industrial cleaning agent===
{{Main|Cleaning agent}}
Sulfuric acid is used in large quantities by the [[iron]] and [[steelmaking]] [[steel industry|industry]] to [[pickling (metal)|remove]] oxidation, [[rust]], and [[fouling|scaling]] from rolled sheet and billets prior to sale to the [[automobile]] and [[major appliances]] industry.{{citation needed|date=September 2011}} Used acid is often recycled using a spent acid regeneration (SAR) plant. These plants combust spent acid{{clarify|reason="What is it, exactly? Is it still the same acid, dirty, reacted, or what?"|date=February 2015}} with natural gas, refinery gas, fuel oil or other fuel sources. This combustion process produces gaseous [[sulfur dioxide]] ({{chem|SO|2}}) and [[sulfur trioxide]] ({{chem|SO|3}}) which are then used to manufacture "new" sulfuric acid. SAR plants are common additions to metal smelting plants, oil refineries, and other industries where sulfuric acid is consumed in bulk, as operating a SAR plant is much cheaper than the recurring costs of spent acid disposal and new acid purchases.

[[Hydrogen peroxide]] ({{chem|H|2|O|2}}) can be added to sulfuric acid to produce [[piranha solution]], a powerful but very toxic cleaning solution with which substrate surfaces can be cleaned. Piranha solution is typically used in the microelectronics industry, and also in laboratory settings to clean glassware.

===Catalyst===
Sulfuric acid is used for a variety of other purposes in the chemical industry. For example, it is the usual acid catalyst for the conversion of [[cyclohexanone oxime]] to [[caprolactam]], used for making [[nylon]]. It is used for making [[hydrochloric acid]] from [[salt]] via the [[Mannheim process]]. Much {{chem|H|2|SO|4}} is used in [[petroleum]] refining, for example as a catalyst for the reaction of [[isobutane]] with [[isobutylene]] to give [[isooctane]], a compound that raises the [[octane rating]] of [[gasoline]] (petrol). Sulfuric acid is also often used as a dehydrating or oxidizing agent in industrial reactions, such as the dehydration of various sugars to form solid carbon.

===Electrolyte===
[[File:Acidic drain cleaner containing sulfuric acid (sulphuric acid).jpg|thumb|Acidic [[drain cleaner]]s usually contain sulfuric acid at a high concentration which turns a piece of [[pH paper]] red and chars it instantly, demonstrating both the strong acidic nature and dehydrating property.]]

Sulfuric acid acts as the electrolyte in [[lead–acid battery|lead–acid batteries]] (lead-acid accumulator):

At [[anode]]:
:{{chem|Pb}} + {{chem|SO|4}}2− ⇌ {{chem|PbSO|4}} + 2 e−

At [[cathode]]:
:{{chem|PbO|2}} + 4 H+ + {{chem|SO|4}}2− + 2 e− ⇌ {{chem|PbSO|4}} + 2 H2O

[[File:Acidic drain opener.JPG|thumb|An acidic [[drain cleaner]] can be used to dissolve grease, hair and even tissue paper inside water pipes.]]

Overall:
:{{chem|Pb}} + {{chem|PbO|2}} + 4 H+ + 2 {{chem|SO|4}}2− ⇌ 2 {{chem|PbSO|4}} + 2 H2O

===Domestic uses===
Sulfuric acid at high concentrations is frequently the major ingredient in [[drain cleaner#Acidic drain openers|acidic drain cleaners]]<ref name="dc">{{cite web|url=http://www.staplesdisposables.com/uploads/products/B470FF98A27F414881DB3FE1A1116C93.pdf|title=Sulphuric acid drain cleaner|publisher=herchem.com|url-status=dead|archive-url=https://web.archive.org/web/20131029192755/http://www.staplesdisposables.com/uploads/products/B470FF98A27F414881DB3FE1A1116C93.pdf|archive-date=29 October 2013}}</ref> which are used to remove [[lipids|grease]], [[hair]], [[tissue paper]], etc. Similar to their [[drain opener|alkaline versions]], such drain openers can dissolve fats and proteins via [[hydrolysis]]. Moreover, as concentrated sulfuric acid has a strong dehydrating property, it can remove tissue paper via dehydrating process as well. Since the acid may react with water vigorously, such acidic drain openers should be added slowly into the pipe to be cleaned.

==History==
[[File:Dalton's-sulphuric-acid.jpg|left|thumb|[[John Dalton]]'s 1808 sulfuric acid molecule shows a central [[sulfur]] atom bonded to three oxygen atoms, or [[sulfur trioxide]], the [[anhydride]] of sulfuric acid.]]
The study of [[vitriol]], a category of glassy minerals from which the acid can be derived, began in [[classical antiquity|ancient times]]. [[Sumer]]ians had a list of types of vitriol that they classified according to the substances' color. Some of the earliest discussions on the origin and properties of vitriol is in the works of the Greek physician [[Dioscorides]] (first century AD) and the Roman naturalist [[Pliny the Elder]] (23–79 AD). [[Galen]] also discussed its medical use. Metallurgical uses for vitriolic substances were recorded in the Hellenistic alchemical works of [[Zosimos of Panopolis]], in the treatise ''Phisica et Mystica'', and the [[Leyden papyrus X]].<ref>{{Cite journal|last1=Karpenko|first1=Vladimír|last2=Norris|first2=John A.|year=2002|title=Vitriol in the History of Chemistry|journal=Chemické listy|volume=96|issue=12|pages=997–1005|url=http://www.chemicke-listy.cz/ojs3/index.php/chemicke-listy/article/view/2266}}</ref>

[[Alchemy and chemistry in medieval Islam|Medieval Islamic chemists]] like [[Jabir ibn Hayyan|Jābir ibn Ḥayyān]] (died c. 806 – c. 816 AD, known in Latin as Geber), [[Muhammad ibn Zakariya al-Razi|Abū Bakr al-Rāzī]] (865 – 925 AD, known in Latin as Rhazes), [[Ibn Sina]] (980 – 1037 AD, known in Latin as Avicenna), and [[Muḥammad ibn Ibrāhīm al-Watwat]] (1234 – 1318 AD) included vitriol in their mineral classification lists.<ref>{{harvnb|Karpenko|Norris|2002|pp=999–1000}}.</ref>

Sulfuric acid was called "oil of vitriol" by medieval European alchemists because it was prepared by roasting "green vitriol" ([[iron(II) sulfate]]) in an iron [[retort]]. The first vague allusions to it appear in the works of [[Vincent of Beauvais]], in the ''Compositum de Compositis'' ascribed to Saint [[Albertus Magnus]], and in [[pseudo-Geber]]'s ''Summa perfectionis'' (all thirteenth century AD).<ref>{{harvnb|Karpenko|Norris|2002|pp=1002–1004}}.</ref>

In the seventeenth century, the German-Dutch chemist [[Johann Glauber]] prepared sulfuric acid by burning [[sulfur]] together with saltpeter ([[potassium nitrate]], {{chem|KNO|3}}), in the presence of steam. As saltpeter decomposes, it oxidizes the sulfur to {{chem|SO|3}}, which combines with water to produce sulfuric acid. In 1736, [[Joshua Ward]], a London pharmacist, used this method to begin the first large-scale production of sulfuric acid.

In 1746 in Birmingham, [[John Roebuck]] adapted this method to produce sulfuric acid in [[lead]]-lined chambers, which were stronger, less expensive, and could be made larger than the previously used glass containers. This process allowed the effective industrialization of sulfuric acid production. After several refinements, this method, called the [[lead chamber process]] or "chamber process", remained the standard for sulfuric acid production for almost two centuries.<ref name=b1/>

Sulfuric acid created by John Roebuck's process approached a 65% concentration. Later refinements to the lead chamber process by French chemist [[Joseph Louis Gay-Lussac]] and British chemist John Glover improved concentration to 78%. However, the manufacture of some [[dye]]s and other chemical processes require a more concentrated product. Throughout the 18th century, this could only be made by [[dry distillation|dry distilling]] minerals in a technique similar to the original [[alchemy|alchemical]] processes. [[Pyrite]] (iron disulfide, {{chem|FeS|2}}) was heated in air to yield iron(II) sulfate, {{chem|FeSO|4}}, which was oxidized by further heating in air to form [[iron(III) sulfate]], Fe2(SO4)3, which, when heated to 480 °C, decomposed to [[iron(III) oxide]] and sulfur trioxide, which could be passed through water to yield sulfuric acid in any concentration. However, the expense of this process prevented the large-scale use of concentrated sulfuric acid.<ref name=b1/>

In 1831, British [[vinegar]] merchant Peregrine Phillips patented the [[contact process]], which was a far more economical process for producing sulfur trioxide and concentrated sulfuric acid. Today, nearly all of the world's sulfuric acid is produced using this method.<ref name=z1>{{cite book|author=Philip J. Chenier|title=Survey of industrial chemistry|url=https://books.google.com/books?id=KlziQA-yx3gC&pg=PA28|access-date=23 December 2011|date=1 April 2002|publisher=Springer|isbn=978-0-306-47246-6|pages=28–}}</ref>

==Safety==

===Laboratory hazards===
[[File:Sulfuric acid burning tissue paper.jpg|thumb|left|Drops of 98% sulfuric acid char a piece of tissue paper instantly. Carbon is left after the dehydration reaction staining the paper black.]]
[[File:Sulfuric acid 98% chemical burn.jpg|thumb|left|Superficial chemical burn caused by two 98% sulfuric acid splashes (forearm skin)]]
Sulfuric acid is capable of causing very severe burns, especially when it is at high [[concentration]]s. In common with other corrosive [[acids]] and [[alkali]], it readily decomposes [[proteins]] and [[lipids]] through [[amide hydrolysis|amide]] and [[ester hydrolysis]] upon contact with [[Tissue (biology)|living tissues]], such as [[skin]] and [[flesh]]. In addition, it exhibits a strong [[Dehydration reaction|dehydrating property]] on [[carbohydrates]], liberating extra [[heat]] and causing [[burn#By depth|secondary thermal burns]].<ref name="OA"/><ref name=TB/> Accordingly, it rapidly attacks the [[cornea]] and can induce [[blindness|permanent blindness]] if splashed onto [[eye]]s. If ingested, it damages [[internal organs]] irreversibly and may even be fatal.<ref name="ds"/> [[Protective equipment]] should hence always be used when handling it. Moreover, its [[oxidizing|strong oxidizing property]] makes it highly corrosive to many [[metal]]s and may extend its destruction on other materials.<ref name="OA"/> Because of such reasons, damage posed by sulfuric acid is potentially more severe than that by other comparable [[strong acids]], such as [[hydrochloric acid]] and [[nitric acid]].
<div style="float: right; margin-left: 1.0 em">[[File:Hazard C.svg|70px]] [[File:Dangclass8.png|70px]]</div>

Sulfuric acid must be stored carefully in containers made of nonreactive material (such as glass). Solutions equal to or stronger than 1.5 M are labeled "CORROSIVE", while solutions greater than 0.5 M but less than 1.5 M are labeled "IRRITANT". However, even the normal laboratory "dilute" grade (approximately 1 M, 10%) will char paper if left in contact for a sufficient time.

The standard first aid treatment for acid spills on the skin is, as for other [[corrosive|corrosive agents]], irrigation with large quantities of water. Washing is continued for at least ten to fifteen minutes to cool the tissue surrounding the acid burn and to prevent secondary damage. Contaminated clothing is removed immediately and the underlying skin washed thoroughly.

===Dilution hazards===
Preparation of the diluted acid can be dangerous due to the heat released in the dilution process. To avoid splattering, the concentrated acid is usually added to water and not the other way around. A saying used to remember this is "Do like you oughta, add the acid to the water".<ref>{{Cite web|last=Snyder|first=Lucy A.|date=2005-11-04|title=Do like you oughta, add acid to water|url=https://www.lucysnyder.com/index.php/do-like-you-oughta-add-acid-to-water/|access-date=2022-01-23|website=Lucy A. Snyder|language=en-US}}</ref>{{Better source needed|reason=The current source is insufficiently reliable ([[WP:NOTRS]]).|date=January 2022}} Water has a higher heat capacity than the acid, and so a vessel of cold water will absorb heat as acid is added.

{| class="wikitable floatleft"
|+Comparison of sulfuric acid and water
|-
! Physical property
! H2SO4
! Water
! Units
|- 
![[Density]]
| 1.84
| 1.0
| kg/L
|- 
![[Volumetric heat capacity]]
| 2.54
| 4.18
| kJ/L
|-
![[Boiling point]]
| 337
| 100
| °C
|}

Also, because the acid is denser than water, it sinks to the bottom. Heat is generated at the interface between acid and water, which is at the bottom of the vessel. Acid will not boil, because of its higher boiling point. Warm water near the interface rises due to [[convection]], which cools the interface, and prevents boiling of either acid or water.

In contrast, addition of water to concentrated sulfuric acid results in a thin layer of water on top of the acid. Heat generated in this thin layer of water can boil, leading to the dispersal of a sulfuric acid [[aerosol]] or worse, an [[explosion]].

Preparation of solutions greater than 6 M (35%) in concentration is most dangerous, because the heat produced may be sufficient to boil the diluted acid: efficient mechanical stirring and external cooling (such as an ice bath) are essential.

Reaction rates double for about every 10-degree Celsius [[Arrhenius equation|increase in temperature]].<ref>[[Linus Carl Pauling|Pauling, L.C.]] (1988) ''General Chemistry'', Dover Publications</ref> Therefore, the reaction will become more violent as dilution proceeds, unless the mixture is given time to cool. Adding acid to warm water will cause a violent reaction.

On a laboratory scale, sulfuric acid can be diluted by pouring concentrated acid onto crushed ice made from de-ionized water. The ice melts in an endothermic process while dissolving the acid. The amount of heat needed to melt the ice in this process is greater than the amount of heat evolved by dissolving the acid so the solution remains cold. After all the ice has melted, further dilution can take place using water.

===Industrial hazards===
Sulfuric acid is non-flammable.

The main occupational risks posed by this acid are skin contact leading to burns (see above) and the inhalation of aerosols. Exposure to aerosols at high concentrations leads to immediate and severe irritation of the eyes, respiratory tract and mucous membranes: this ceases rapidly after exposure, although there is a risk of subsequent [[pulmonary edema]] if tissue damage has been more severe. At lower concentrations, the most commonly reported symptom of chronic exposure to sulfuric acid aerosols is erosion of the teeth, found in virtually all studies: indications of possible chronic damage to the [[respiratory tract]] are inconclusive as of 1997. Repeated occupational exposure to sulfuric acid mists may increase the chance of lung cancer by up to 64 percent.<ref>{{cite journal |pmid= 3479642 |volume=79 |issue=5 |title=Lung cancer mortality in workers exposed to sulfuric acid mist and other acid mists |journal=J Natl Cancer Inst |pages=911–21 |last1= Beaumont |first1= JJ |last2= Leveton |first2= J |last3= Knox |first3= K |last4= Bloom |first4= T |last5= McQuiston |first5= T |last6= Young |first6= M |last7= Goldsmith |first7= R |last8= Steenland |first8= NK |last9= Brown |first9= DP |last10= Halperin |first10= WE |year=1987 |doi=10.1093/jnci/79.5.911}}</ref> In the United States, the [[permissible exposure limit]] (PEL) for sulfuric acid is fixed at 1 mg/m3: limits in other countries are similar. There have been reports of sulfuric acid ingestion leading to [[vitamin B12 deficiency]] with subacute combined degeneration. The spinal cord is most often affected in such cases, but the optic nerves may show [[demyelination]], loss of [[axon]]s and [[gliosis]].

==Legal restrictions==
International commerce of sulfuric acid is controlled under the [[United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances|United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances, 1988]], which lists sulfuric acid under Table II of the convention as a chemical frequently used in the illicit manufacture of narcotic drugs or psychotropic substances.<ref name=incb>[https://web.archive.org/web/20080227224025/http://www.incb.org/pdf/e/list/red.pdf Annex to Form D ("Red List")], 11th Edition, January 2007 (p. 4). [[International Narcotics Control Board]]. [[Vienna, Austria]].</ref>

==See also==
*[[Aqua regia]]
*[[Diethyl ether]] – also known as "sweet oil of vitriol"
*[[Piranha solution]]
*[[Sulfur oxoacid]]
*[[Sulfuric acid poisoning]]

==References==
{{reflist}}

==External links==
{{Commons category|Sulfuric acid}}
*{{ICSC|0362|03}}
*[http://www.periodicvideos.com/videos/mv_sulfuric_acid.htm Sulfuric acid] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
*[https://www.cdc.gov/niosh/npg/npgd0577.html NIOSH Pocket Guide to Chemical Hazards]
*[https://www.cdc.gov/niosh/topics/sulfuric-acid/ CDC – Sulfuric Acid – NIOSH Workplace Safety and Health Topic]
*[http://ptcl.chem.ox.ac.uk/MSDS/SU/sulfuric_acid_concentrated.html External Material Safety Data Sheet]
*Calculators: [http://www.aim.env.uea.ac.uk/aim/surftens/surftens.php surface tensions], and [http://www.aim.env.uea.ac.uk/aim/density/density_electrolyte.php densities, molarities and molalities] of aqueous sulfuric acid
*[http://www2.iq.usp.br/docente/gutz/Curtipot_.html Sulfuric acid analysis – titration freeware]
*Process flowsheet of sulfuric acid manufacturing by [http://www.inclusive-science-engineering.com/manufacture-of-h2so4-by-chamber-process/manufacture-of-h2so4-by-chamber-process-2/ lead chamber process]

{{Hydrogen compounds}}
{{Sulfur compounds}}
{{Sulfates}}

{{Authority control}}

[[Category:Sulfuric acid| ]]
[[Category:Acid catalysts]]
[[Category:Alchemical substances]]
[[Category:Dehydrating agents]]
[[Category:Equilibrium chemistry]]
[[Category:Hydrogen compounds]]
[[Category:Inorganic solvents]]
[[Category:Mineral acids]]
[[Category:Oxidizing acids]]
[[Category:Oxidizing agents]]
[[Category:Photographic chemicals]]
[[Category:Sulfates]]
[[Category:Sulfur oxoacids]]
[[Category:Sulfur]]
[[Category:E-number additives]]

Sodium chloride

2022-03-04T19:23:57Z

173.165.237.1: /* Aqueous solutions */

{{short description|Chemical compound with formula NaCl}}
{{About|the chemical|its familiar form, common table salt|Salt|the medical solutions|Saline (medicine)|the mineral|Halite}}
{{Redirect|NaCl}}
{{Use dmy dates|date=November 2016}}
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 477002432
| Name =
| ImageFile = Halit-Kristalle.jpg
| ImageCaption = Sodium chloride as the mineral [[halite]]
| ImageFile1 = NaCl bonds.svg
| ImageCaption1 = Crystal structure with sodium in purple and chloride in green<ref>{{cite web|url=https://physicsopenlab.org/2018/01/22/sodium-chloride-nacl-crystal/|title=Sodium Chloride (NaCl) Crystal|publisher=PhysicsOpenLab|access-date=23 August 2021}}</ref>
| IUPACName = Sodium chloride
| OtherNames = {{unbulleted list
| Common salt
| halite
| rock salt
| saline
| table salt
| regular salt
| sea salt
}}
| SystematicName =
| Section1 = {{Chembox Identifiers
| CASNo = 7647-14-5
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 5234
| UNII = 451W47IQ8X
| UNII_Ref = {{fdacite|correct|FDA}}
| EINECS = 231-598-3
| KEGG = D02056
| KEGG_Ref = {{keggcite|correct|kegg}}
| MeSHName = Sodium+chloride
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 26710
| ChEMBL = 1200574
| ChEMBL_Ref = {{ebicite|changed|EBI}}
| RTECS = VZ4725000
| Beilstein = 3534976
| Gmelin = 13673
| SMILES = [Na+].[Cl-]
| StdInChI = 1S/ClH.Na/h1H;/q;+1/p-1
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| InChI = 1/ClH.Na/h1H;/q;+1/p-1
| StdInChIKey = FAPWRFPIFSIZLT-UHFFFAOYSA-M
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| InChIKey = FAPWRFPIFSIZLT-REWHXWOFAE
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 5044
}}
| Section2 = {{Chembox Properties
| Formula = NaCl
| MolarMass = 58.443 g/mol<ref name="crc">Haynes, 4.89</ref>
| Appearance = Colorless cubic crystals<ref name=crc/>
| Odor = Odorless
| Density = 2.17 g/cm3<ref name=crc/>
| MeltingPtC = 800.7
| MeltingPt_ref=<ref name=crc/>
| BoilingPtC = 1465
| BoilingPt_ref=<ref name=crc/>
| Solubility = 360 g/1000 g pure water at T = 25 °C<ref name="crc" />
| Solvent1 = ammonia
| Solubility1 = 21.5 g/L at T = ?{{Clarify|date = June 2021}}
| Solvent2 = methanol
| Solubility2 = 14.9 g/L at T = ?{{Clarify|date = June 2021}}
| RefractIndex = 1.5441 (at 589 nm)<ref>Haynes, 10.241</ref>
| MagSus = −30.2·10−6 cm3/mol<ref>Haynes, 4.135</ref>
}}
| Section3 = {{Chembox Structure
| Structure_ref =<ref>Haynes, 4.148</ref>
| CrystalStruct = Face-centered cubic (''see text''), [[Pearson symbol|cF8]]
| SpaceGroup = Fm{{overline|3}}m (No. 225)
| LattConst_a = 564.02 pm
| UnitCellFormulas = 4
| Coordination = octahedral at Na+ octahedral at Cl−
}}
| Section4 =
| Section5 = {{Chembox Thermochemistry
| Thermochemistry_ref =<ref>Haynes, 5.8</ref>
| DeltaHf = −411.120 kJ/mol
| Entropy = 72.10 J/(K·mol)
| HeatCapacity = 50.5 J/(K·mol)
}}
| Section6 = {{Chembox Pharmacology
| ATCCode_prefix = A12
| ATCCode_suffix = CA01
| ATC_Supplemental = {{ATC|B05|CB01}}, {{ATC|B05|XA03}}, {{ATC|S01|XA03}}
}}
| Section7 = {{Chembox Hazards
| NFPA-H = 0
| NFPA-F = 0
| NFPA-R = 0
| LD50 = 3 g/kg (oral, rats)<ref>[http://chem.sis.nlm.nih.gov/chemidplus/rn/7647-14-5 Sodium chloride]. nlm.nih.gov.</ref>
}}
| Section8 = {{Chembox Related
| OtherAnions = [[Sodium fluoride]] [[Sodium bromide]] [[Sodium iodide]] [[Sodium astatide]]
| OtherCations = [[Lithium chloride]] [[Potassium chloride]] [[Rubidium chloride]] [[Caesium chloride]] [[Francium chloride]]
}}
}}

'''Sodium chloride''' {{IPAc-en|ˌ|s|oʊ|d|i|ə|m|_|ˈ|k|l|ɔr|aɪ|d}},<ref>{{Citation |last=Wells |first=John C. |title=Longman Pronunciation Dictionary |pages=143 and 755 |year=2008 |edition=3rd |publisher=Longman |isbn=9781405881180}}</ref> commonly known as '''salt''' (although [[sea salt]] also contains other chemical [[salt (chemistry)|salt]]s), is an [[ionic compound]] with the [[chemical formula]] '''NaCl''', representing a 1:1 ratio of [[sodium]] and [[chloride]] ions. With [[molar mass]]es of 22.99 and 35.45 g/mol respectively, 100 g of NaCl contains 39.34 g Na and 60.66 g Cl. Sodium chloride is the [[salt (chemistry)|salt]] most responsible for the [[salinity]] of [[seawater]] and of the [[extracellular fluid]] of many [[multicellular organism]]s. In its edible form of [[salt|table salt]], it is commonly used as a [[condiment]] and [[Curing (food preservation)|food preservative]]. Large quantities of sodium chloride are used in many industrial processes, and it is a major source of sodium and [[chlorine]] compounds used as [[feedstock]]s for further [[Chemical synthesis|chemical syntheses]]. A second major application of sodium chloride is de-icing of roadways in sub-freezing weather.
{{TOC limit}}

==Uses==
In addition to the familiar domestic uses of salt, more dominant applications of the approximately 250 million tonnes per year production (2008 data) include chemicals and de-icing.<ref name="Ullmann">Westphal, Gisbert ''et al.'' (2002) "Sodium Chloride" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim {{DOI|10.1002/14356007.a24_317.pub4}}.</ref>

===Chemicals production===
Salt is used, directly or indirectly, in the production of many chemicals, which consume most of the world's production.<ref name=usgs/>

====Chlor-alkali industry====
{{See also|Chloralkali process}}
It is the starting point for the [[chloralkali process]], the industrial process to produce [[chlorine]] and [[sodium hydroxide]], according to the [[chemical equation]]
:2 NaCl + 2 H2O → Cl2 + H2 + 2 NaOH

This electrolysis is conducted in either a mercury cell, a diaphragm cell, or a membrane cell. Each of those uses a different method to separate the chlorine from the sodium hydroxide. Other technologies are under development due to the high energy consumption of the electrolysis, whereby small improvements in the efficiency can have large economic paybacks. Some applications of chlorine include [[PVC]], disinfectants, and solvents. Sodium hydroxide enables industries that produce paper, soap, and aluminium.

===Soda-ash industry===
Sodium chloride is used in the [[Solvay process]] to produce [[sodium carbonate]] and [[calcium chloride]]. Sodium carbonate, in turn, is used to produce [[glass]], [[sodium bicarbonate]], and [[dye]]s, as well as a myriad of other chemicals. In the [[Mannheim process]] and in the [[Hargreaves process]], sodium chloride is used for the production of [[sodium sulfate]] and [[hydrochloric acid]].

===Standard===
Sodium chloride has an international standard that is created by [[ASTM International]]. The standard is named '''ASTM E534-13''' and is the standard test methods for chemical analysis of sodium chloride. These methods listed provide procedures for analyzing sodium chloride to determine whether it is suitable for its intended use and application.

===Miscellaneous industrial uses===
Sodium chloride is heavily used, so even relatively minor applications can consume massive quantities. In oil and gas exploration, salt is an important component of drilling fluids in well drilling. It is used to [[Flocculation|flocculate]] and increase the density of the drilling fluid to overcome high downwell gas pressures. Whenever a drill hits a salt formation, salt is added to the drilling fluid to saturate the solution in order to minimize the dissolution within the salt stratum.<ref name=Ullmann/> Salt is also used to increase the curing of concrete in cemented casings.<ref name=usgs/>

In textiles and dyeing, salt is used as a brine rinse to separate organic contaminants, to promote "salting out" of dyestuff precipitates, and to blend with concentrated dyes to standardize{{clarify|date=October 2016}} them. One of its main roles is to provide the positive ion charge to promote the absorption of negatively charged ions of dyes.<ref name=usgs/>

It is also used in processing [[aluminium]], [[beryllium]], [[copper]], [[steel]] and [[vanadium]]. In the [[pulp and paper industry]], salt is used to bleach wood pulp. It also is used to make [[sodium chlorate]], which is added along with [[sulfuric acid]] and water to manufacture [[chlorine dioxide]], an excellent oxygen-based [[bleach]]ing chemical. The chlorine dioxide process, which originated in Germany after World War I, is becoming more popular because of environmental pressures to reduce or eliminate chlorinated bleaching compounds. In tanning and leather treatment, salt is added to animal [[Hide (skin)|hides]] to inhibit microbial activity on the underside of the hides and to attract moisture back into the hides.<ref name=usgs/>

In rubber manufacture, salt is used to make [[Synthetic rubber|buna]], [[neoprene]] and white rubber types. Salt brine and sulfuric acid are used to coagulate an emulsified [[latex]] made from chlorinated [[butadiene]].<ref name=usgs/><ref name=Ullmann/>

Salt also is added to secure the soil and to provide firmness to the foundation on which highways are built. The salt acts to minimize the effects of shifting caused in the subsurface by changes in humidity and traffic load.<ref name=usgs/>

Sodium chloride is sometimes used as a cheap and safe [[desiccant]] because of its [[hygroscopic]] properties, making [[Salting (food)|salting]] an effective method of [[food preservation]] historically; the salt draws water out of bacteria through [[osmotic pressure]], keeping it from reproducing, a major source of food spoilage. Even though more effective desiccants are available, few are safe for humans to ingest.

===Water softening===
[[Hard water]] contains calcium and magnesium ions that interfere with action of [[soap]] and contribute to the buildup of a scale or film of alkaline mineral deposits in household and industrial equipment and pipes. Commercial and residential water-softening units use [[ion-exchange resin]]s to remove the offending ions that cause the hardness. These resins are generated and regenerated using sodium chloride.<ref name=usgs/><ref name=Ullmann/>

===Road salt===
[[File:WatNaCl.png|thumb|left|upright=1.15|Phase diagram of water–NaCl mixture]]
The second major application of salt is for [[de-icing]] and anti-icing of roads, both in [[grit bin]]s and spread by [[winter service vehicle]]s. In anticipation of snowfall, roads are optimally "anti-iced" with brine (concentrated [[Solution (chemistry)|solution]] of salt in water), which prevents bonding between the snow-ice and the road surface. This procedure obviates the heavy use of salt after the snowfall. For de-icing, mixtures of brine and salt are used, sometimes with additional agents such as [[calcium chloride]] and/or [[magnesium chloride]]. The use of salt or brine becomes ineffective below {{convert|−10|°C|0}}.
[[File:Winter road salt.jpg|thumbnail|left|upright=1.15|Mounds of road salt for use in winter]]
Salt for de-icing in the United Kingdom predominantly comes from a single mine in [[Winsford]] in [[Salt in Cheshire|Cheshire]]. Prior to distribution it is mixed with <100 ppm of [[sodium ferrocyanide]] as an anti-caking agent, which enables rock salt to flow freely out of the gritting vehicles despite being stockpiled prior to use. In recent years this additive has also been used in table salt. Other additives had been used in road salt to reduce the total costs. For example, in the US, a byproduct carbohydrate solution from sugar-beet processing was mixed with rock salt and adhered to road surfaces about 40% better than loose rock salt alone. Because it stayed on the road longer, the treatment did not have to be repeated several times, saving time and money.<ref name=usgs/>

In the technical terms of physical chemistry, the minimum freezing point of a water-salt mixture is {{convert|−21.12|C|F}} for 23.31 wt% of salt. Freezing near this concentration is however so slow that the [[eutectic point]] of {{convert|−22.4|C|F}} can be reached with about 25 wt% of salt.<ref name="u1" />

====Environmental effects====
Road salt ends up in fresh-water bodies and could harm aquatic plants and animals by disrupting their [[osmoregulation]] ability.<ref>Rastogi, Nina (16 February 2010) [http://www.slate.com/id/2244156 Does road salt harm the environment?] slate.com.</ref> The omnipresence of salt poses a problem in any coastal coating application, as trapped salts cause great problems in adhesion. Naval authorities and ship builders monitor the salt concentrations on surfaces during construction. Maximal salt concentrations on surfaces are dependent on the authority and application. The [[International Maritime Organization|IMO]] regulation is mostly used and sets salt levels to a maximum of 50 mg/m2 soluble salts measured as sodium chloride. These measurements are done by means of a [[Bresle test]]. Salinization (increasing salinity, aka ''[[freshwater salinization]] syndrome'') and subsequent increased metal leaching is an ongoing problem throughout North America and European fresh waterways.<ref>{{Cite web |url=https://phys.org/news/2018-12-saltier-waterways-dangerous-chemical-cocktails.html |title=Saltier waterways are creating dangerous 'chemical cocktails' |website=phys.org}}</ref>

In highway de-icing, salt has been associated with [[corrosion]] of bridge decks, motor vehicles, reinforcement bar and wire, and unprotected steel structures used in road construction. Surface runoff, vehicle spraying, and windblown actions also affect soil, roadside vegetation, and local surface water and groundwater supplies. Although evidence of environmental loading of salt has been found during peak usage, the spring rains and thaws usually dilute the concentrations of sodium in the area where salt was applied.<ref name=usgs/> A 2009 study found that approximately 70% of the road salt being applied in the [[Minneapolis-St Paul]] metro area is retained in the local watershed.<ref>{{Cite web |url=https://www.sciencedaily.com/releases/2009/02/090210125424.htm |title=Most Road Salt Is Making It into Lakes And Rivers |date=20 February 2009 |website=www.sciencedaily.com |publisher=University of Minnesota |access-date=27 September 2015}}</ref>

====Substitution====
Some agencies are substituting beer, molasses, and beet juice instead of road salt.<ref>{{Cite web |url=https://phys.org/news/2018-01-salt-solution-winter-dangers-threatens.html|author=Casey, Michael |title=Turning to beet juice and beer to address road salt danger |website=phys.org}}</ref> Airlines utilize more [[glycol]] and [[sugar]] rather than salt based solutions for [[de-icing]].<ref>{{Cite web |url=https://www.mro-network.com/maintenance-repair-overhaul/easa-cautions-organic-salt-deicing-fluid |title=EASA Cautions on Organic Salt Deicing Fluid |date=9 December 2016 |website=MRO Network}}</ref>

===Food industry and agriculture===
{{main|Salt}}
Many [[microorganism]]s cannot live in a salty environment: water is drawn out of their [[cell (biology)|cells]] by [[osmosis]]. For this reason salt is used to [[Food preservation|preserve]] some foods, such as bacon, fish, or cabbage.

Salt is added to food, either by the food producer or by the consumer, as a flavor enhancer, preservative, binder, [[fermentation (food)|fermentation]]-control additive, texture-control agent and color developer. The salt consumption in the food industry is subdivided, in descending order of consumption, into other food processing, meat packers, [[canning]], baking, dairy and grain mill products. Salt is added to promote color development in bacon, ham and other processed meat products. As a preservative, salt inhibits the growth of bacteria. Salt acts as a binder in [[sausage]]s to form a binding gel made up of meat, fat, and moisture. Salt also acts as a flavor enhancer and as a [[tenderizer]].<ref name=usgs/>

In many dairy industries, salt is added to cheese as a color-, fermentation-, and texture-control agent. The dairy subsector includes companies that manufacture creamery butter, condensed and evaporated milk, frozen desserts, ice cream, natural and processed cheese, and specialty dairy products. In canning, salt is primarily added as a flavor enhancer and [[preservative]]. It also is used as a carrier for other ingredients, dehydrating agent, enzyme inhibitor and tenderizer. In baking, salt is added to control the rate of fermentation in bread dough. It also is used to strengthen the [[gluten]] (the elastic protein-water complex in certain doughs) and as a flavor enhancer, such as a topping on baked goods. The food-processing category also contains grain mill products. These products consist of milling flour and rice and manufacturing cereal breakfast food and blended or prepared flour. Salt is also used a seasoning agent, e.g. in potato chips, [[pretzel]]s, cat and dog food.<ref name=usgs/>

Sodium chloride is used in veterinary medicine as [[emesis]]-causing agent. It is given as warm saturated solution. Emesis can also be caused by [[pharynx|pharyngeal]] placement of small amount of plain salt or salt crystals.

===Medicine===

{{Main|Saline (medicine)}}
Sodium chloride is used together with water as one of the primary solutions for [[intravenous therapy]]. [[Nasal spray]] often contains a [[Saline (medicine)|saline]] solution.

===Firefighting===
[[File:Metlx.jpg|thumb|upright|A class-D fire extinguisher for various metals]]
Sodium chloride is the principal extinguishing agent in fire extinguishers (Met-L-X, Super D) used on combustible metal fires such as magnesium, potassium, sodium, and NaK alloys (Class D). [[Thermoplastic]] powder is added to the mixture, along with waterproofing (metal stearates) and anti-caking materials (tricalcium phosphate) to form the extinguishing agent. When it is applied to the fire, the salt acts like a heat sink, dissipating heat from the fire, and also forms an oxygen-excluding crust to smother the fire. The plastic additive melts and helps the crust maintain its integrity until the burning metal cools below its ignition temperature. This type of extinguisher was invented in the late 1940s as a cartridge-operated unit, although stored pressure versions are now popular. Common sizes are {{convert|30|lb|kg}} portable and {{convert|350|lb|kg}} wheeled.{{citation needed|date=August 2020}}

===Cleanser===
Since at least [[medieval]] times, people have used salt as a cleansing agent rubbed on household surfaces. It is also used in many brands of [[shampoo]], toothpaste and popularly to de-ice driveways and patches of ice.

===Optical usage===
Defect-free NaCl crystals have an optical transmittance of about 90% for infrared light, specifically between 200 [[Nanometer|nm]] and 20 [[µm]]. They were therefore used in optical components (windows and prisms) operating in that spectral range, where few non-absorbing alternatives exist and where requirements for absence of microscopic inhomogeneities are less strict than in the visible range. While inexpensive, NaCl crystals are soft and [[Hygroscopy|hygroscopic]] – when exposed to the ambient air, they gradually cover with "frost". This limits application of NaCl to dry environments, vacuum sealed assembly areas or for short-term uses such as prototyping. Nowadays materials like [[zinc selenide]] (ZnSe), which are stronger mechanically and are less sensitive to moisture, are used instead of NaCl for the infrared spectral range.

==Chemistry==

===Solid sodium chloride===
{{See also|Cubic crystal system}}
[[File:Natrium chloride kristal under microscope.jpg|thumb|Sodium chloride crystal under microscope.]]
[[File:NaCl octahedra.svg|thumb|NaCl octahedra. The yellow stipples represent the electrostatic force between the ions of opposite charge]]
In solid sodium chloride, each ion is surrounded by six ions of the opposite charge as expected on electrostatic grounds. The surrounding ions are located at the vertices of a regular [[octahedron]]. In the language of [[close-packing]], the larger [[Chlorine|chloride]] [[ion]]s (167 pm in size<ref name="Shannon">{{cite journal|doi=10.1107/S0567739476001551|title=Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides|author=R. D. Shannon|journal=Acta Crystallogr A|volume=32|issue=5|year=1976|pages=751–767|bibcode = 1976AcCrA..32..751S |doi-access=free}}</ref>) are arranged in a cubic array whereas the smaller [[sodium]] ions (116 pm<ref name=Shannon />) fill all the cubic gaps (octahedral voids) between them. This same basic structure is found in many other [[Chemical compound|compounds]] and is commonly known as the [[halite]] or rock-salt crystal structure. It can be represented as a [[Cubic crystal system|face-centered cubic]] (fcc) lattice with a two-atom basis or as two interpenetrating face centered cubic lattices. The first atom is located at each lattice point, and the second atom is located halfway between lattice points along the fcc unit cell edge.

Solid sodium chloride has a melting point of 801 °C. [[Thermal conductivity]] of sodium chloride as a function of temperature has a maximum of 2.03 W/(cm K) at {{convert|8|K}} and decreases to 0.069 at {{convert|314|K}}. It also decreases with [[Doping (semiconductor)|doping]].<ref>{{Cite book |last1=Sirdeshmukh |first1=Dinker B. |url=https://books.google.com/books?id=X-yL7EgMK6wC&pg=PA68 |title=Alkali halides: a handbook of physical properties |last2=Sirdeshmukh, Lalitha |last3=Subhadra, K. G. |publisher=Springer |year=2001 |isbn=978-3-540-42180-1 |pages=65, 68 |name-list-style=amp}}</ref>

Atomic-resolution real-time video imaging allows visualization of the initial stage of crystal nucleation of sodium chloride.<ref>{{cite journal |last1=Nakamuro |first1=Takayuki |last2=Sakakibara |first2=Masaya |last3=Nada |first3=Hiroki |last4=Harano |first4=Koji |last5=Nakamura |first5=Eiichi |title=Capturing the Moment of Emergence of Crystal Nucleus from Disorder |journal=Journal of the American Chemical Society |year=2021 |volume=143 |issue=4 |pages=1763–1767 |doi=10.1021/jacs.0c12100 |pmid=33475359 |doi-access=free }}</ref>

===Aqueous solutions===
{| class="wikitable" style="float:right; margin-left:1em;"
! {{Chemical datatable header}}|Solubility of NaCl (g NaCl / 1 kg of solvent at {{convert|25|C|F}})<ref>{{Cite book |last=Burgess |first=J |title=Metal Ions in Solution |publisher=Ellis Horwood |year=1978 |isbn=978-0-85312-027-8 |location=New York}}</ref>
|-
| [[Water (molecule)|Water]] || 360
|-
| [[Formamide]] || 94
|-
| [[Glycerin]] || 83
|-
| [[Propylene glycol]] || 71
|-
| [[Formic acid]] || 52
|-
| [[Ammonia|Liquid ammonia]] || 30.2
|-
| [[Methanol]] || 14
|-
| [[Ethanol]] || 0.65
|-
| [[Dimethylformamide]] || 0.4
|-
| [[1-Propanol]] || 0.124
|-
| [[Sulfolane]] || 0.05
|-
| [[1-Butanol]] || 0.05
|-
| [[2-Propanol]] || 0.03
|-
| [[1-Pentanol]] || 0.018
|-
| [[Acetonitrile]] || 0.003
|-
| [[Acetone]] || 0.00042
|}
The attraction between the Na+ and Cl− ions in the solid is so strong that only highly polar solvents like water dissolve NaCl well.
[[File:NaCl(H2O)2slab.png|thumb|left|upright=1.25|View of one slab of NaCl(H2O)2 (red = O, white = H, green = Cl, purple = Na).<ref>{{Cite journal |last1=Klewe |first1=B |last2=Pedersen |year=1974 |title=The crystal structure of sodium chloride dihydrate |journal=Acta Crystallogr. |volume=B30 |issue=10 |pages=2363–2371 |doi=10.1107/S0567740874007138 |doi-access=free}}</ref>]]
When dissolved in water, the sodium chloride framework disintegrates as the Na+ and Cl− ions become surrounded by polar water molecules. These solutions consist of [[metal aquo complex]] with the formula [Na(H2O)8]+, with the Na–O distance of 250 [[picometer|pm]]. The chloride ions are also strongly solvated, each being surrounded by an average of six molecules of water.<ref name="Lincoln">Lincoln, S. F.; Richens, D. T. and Sykes, A. G. (2003) "Metal Aqua Ions" Comprehensive Coordination Chemistry II Volume 1, pp. 515–555. {{DOI|10.1016/B0-08-043748-6/01055-0}}.</ref> Solutions of sodium chloride have very different properties from pure water. The [[freezing point]] is {{convert|−21.12|C|F}} for 23.31% [[Mass fraction (chemistry)#Mass percentage|mass fraction]] of salt, and the boiling point of saturated salt solution is near {{convert|108.7|C|F}}.<ref name="u1">Elvers, B. ''et al.'' (ed.) (1991) ''Ullmann's Encyclopedia of Industrial Chemistry'', 5th ed. Vol. A24, Wiley, p. 319, {{ISBN|978-3-527-20124-2}}.</ref> From cold solutions, salt crystallises as the [[water of hydration|dihydrate]] NaCl·2H2O.{{citation needed|date=March 2021}}

===pH of sodium chloride solutions===
The pH of a sodium chloride solution remains ≈7 due to the extremely weak basicity of the Cl− ion, which is the conjugate base of the strong acid HCl. In other words, NaCl has no effect on system pH<ref>{{Cite web |url=https://www.flinnsci.com/api/library/Download/1f87f104ec4b4492a621f480797fbab1 |title=Acidic, Basic, and Neutral Salts |date=2016 |website=Flinn Scientific Chem Fax |access-date=18 September 2018 |quote=Neutralization of a strong acid and a strong base gives a neutral salt.}}</ref> in diluted solutions where the effects of ionic strength and activity coefficients are negligible.

===Unexpected stable stoichiometric variants===
Common salt has a 1:1 molar ratio of sodium and chlorine. In 2013, compounds of sodium and chloride of different [[stoichiometry|stoichiometries]] have been discovered; five new compounds were predicted (e.g., Na3Cl, Na2Cl, Na3Cl2, NaCl3, and NaCl7). The existence of some of them has been experimentally confirmed at high pressures: cubic and orthorhombic NaCl3 and two-dimensional metallic tetragonal Na3Cl. This indicates that compounds violating chemical intuition are possible, in simple systems under nonambient conditions.<ref>{{Cite journal |last1=Zhang |first1=W. |last2=Oganov |first2=A. R. |last3=Goncharov |first3=A. F. |last4=Zhu |first4=Q. |last5=Boulfelfel |first5=S. E. |last6=Lyakhov |first6=A. O. |last7=Stavrou |first7=E. |last8=Somayazulu |first8=M. |last9=Prakapenka |first9=V. B. |last10=Konôpková |first10=Z. |year=2013 |title=Unexpected Stable Stoichiometries of Sodium Chlorides |journal=Science |volume=342 |issue=6165 |pages=1502–1505 |arxiv=1310.7674 |bibcode=2013Sci...342.1502Z |doi=10.1126/science.1244989 |pmid=24357316|s2cid=15298372 }}</ref>

==Occurrence==
Small particles of [[sea salt]] are the dominant [[cloud condensation nuclei]] far out at sea, which allow the formation of [[cloud]]s in otherwise [[pollution|non-polluted]] [[air]].<ref>{{Cite journal |last=Mason |first=B. J. |date=2006 |title=The role of sea-salt particles as cloud condensation nuclei over the remote oceans |journal=Quarterly Journal of the Royal Meteorological Society |volume=127 |issue=576 |pages=2023–32 |bibcode=2001QJRMS.127.2023M |doi=10.1002/qj.49712757609}}</ref>

==Production==
Salt is currently [[Mass production|mass-produced]] by [[evaporation]] of [[seawater]] or [[brine]] from [[brine well]]s and [[salt lake (geography)|salt lakes]]. [[Salt mine|Mining]] of rock salt is also a major source. China is the world's main supplier of salt.<ref name="usgs">Kostick, Dennis S. (October 2010) [http://minerals.usgs.gov/minerals/pubs/commodity/salt/myb1-2008-salt.pdf "Salt"] in ''U.S. Geological Survey, 2008 Minerals Yearbook''</ref> In 2017, world production was estimated at 280 million [[tonne]]s, the top five producers (in million tonnes) being China (68.0), United States (43.0), India (26.0), Germany (13.0), and Canada (13.0).<ref>[https://minerals.usgs.gov/minerals/pubs/commodity/salt/mcs-2018-salt.pdf Salt], U.S. Geological Survey</ref> Salt is also a byproduct of [[potassium]] mining.

<gallery mode="packed">
File:Salt mine 0096.jpg|Modern rock salt mine near [[Mount Morris (town), New York|Mount Morris]], [[New York (state)|New York]], [[United States]]
File:Dead-Sea---Salt-Evaporation-Ponds.jpg|[[Jordan]]ian and [[Israel]]i salt evaporation ponds at the south end of the [[Dead Sea]].
File:Piles of Salt Salar de Uyuni Bolivia Luca Galuzzi 2006 a.jpg|Mounds of salt, [[Salar de Uyuni]], [[Bolivia]].
</gallery>

==See also==
{{Portal|Chemistry}}
{{colbegin}}
* [[Biosalinity]]
* [[Salt|Edible salt (table salt)]]
* [[Halite]], the mineral form of sodium chloride
* [[Health effects of salt]]
* [[Salinity]]
* [[Salting the earth]]
* [[Salt poisoning]]
{{colend}}

==References==
{{reflist}}
* {{USGS|title=Salt|url=http://minerals.usgs.gov/minerals/pubs/commodity/salt/myb1-2008-salt.pdf}}

==Cited sources==
* {{Cite book |title=CRC Handbook of Chemistry and Physics |title-link=CRC Handbook of Chemistry and Physics |publisher=[[CRC Press]] |year=2011 |isbn=978-1439855119 |editor-last=Haynes |editor-first=William M. |edition=92nd}}

==External links==
{{Commons|NaCl}}
{{Cookbook|Salt}}
* [http://minerals.usgs.gov/minerals/pubs/commodity/salt/ Salt] [[United States Geological Survey]] Statistics and Information
* {{Cite journal |date=December 1997 |title=Using Salt and Sand for Winter Road Maintenance |url=http://www.usroads.com/journals/p/rmj/9712/rm971202.htm |url-status=dead |journal=Road Management Journal |archive-url=https://web.archive.org/web/20160921160156/http://www.usroads.com/journals/p/rmj/9712/rm971202.htm |archive-date=21 September 2016 |access-date=13 February 2007}}
* Calculators: [http://www.aim.env.uea.ac.uk/aim/surftens/surftens.php surface tensions], and [http://www.aim.env.uea.ac.uk/aim/density/density_electrolyte.php densities, molarities and molalities] of aqueous NaCl (and other salts)
* [http://hazard.com/msds/mf/baker/baker/files/s3338.htm JtBaker MSDS]

{{Sodium compounds}}
{{Chlorides}}
{{Molecules detected in outer space}}
{{Authority control}}

{{DEFAULTSORT:Sodium Chloride}}
[[Category:Alkali metal chlorides]]
[[Category:Chlorides]]
[[Category:Household chemicals]]
[[Category:Metal halides]]
[[Category:Sodium compounds]]
[[Category:Sodium minerals]]
[[Category:Rock salt crystal structure]]

Sodium chloride

2022-03-04T19:23:05Z

173.165.237.1: /* Aqueous solutions */

{{short description|Chemical compound with formula NaCl}}
{{About|the chemical|its familiar form, common table salt|Salt|the medical solutions|Saline (medicine)|the mineral|Halite}}
{{Redirect|NaCl}}
{{Use dmy dates|date=November 2016}}
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 477002432
| Name =
| ImageFile = Halit-Kristalle.jpg
| ImageCaption = Sodium chloride as the mineral [[halite]]
| ImageFile1 = NaCl bonds.svg
| ImageCaption1 = Crystal structure with sodium in purple and chloride in green<ref>{{cite web|url=https://physicsopenlab.org/2018/01/22/sodium-chloride-nacl-crystal/|title=Sodium Chloride (NaCl) Crystal|publisher=PhysicsOpenLab|access-date=23 August 2021}}</ref>
| IUPACName = Sodium chloride
| OtherNames = {{unbulleted list
| Common salt
| halite
| rock salt
| saline
| table salt
| regular salt
| sea salt
}}
| SystematicName =
| Section1 = {{Chembox Identifiers
| CASNo = 7647-14-5
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 5234
| UNII = 451W47IQ8X
| UNII_Ref = {{fdacite|correct|FDA}}
| EINECS = 231-598-3
| KEGG = D02056
| KEGG_Ref = {{keggcite|correct|kegg}}
| MeSHName = Sodium+chloride
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 26710
| ChEMBL = 1200574
| ChEMBL_Ref = {{ebicite|changed|EBI}}
| RTECS = VZ4725000
| Beilstein = 3534976
| Gmelin = 13673
| SMILES = [Na+].[Cl-]
| StdInChI = 1S/ClH.Na/h1H;/q;+1/p-1
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| InChI = 1/ClH.Na/h1H;/q;+1/p-1
| StdInChIKey = FAPWRFPIFSIZLT-UHFFFAOYSA-M
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| InChIKey = FAPWRFPIFSIZLT-REWHXWOFAE
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 5044
}}
| Section2 = {{Chembox Properties
| Formula = NaCl
| MolarMass = 58.443 g/mol<ref name="crc">Haynes, 4.89</ref>
| Appearance = Colorless cubic crystals<ref name=crc/>
| Odor = Odorless
| Density = 2.17 g/cm3<ref name=crc/>
| MeltingPtC = 800.7
| MeltingPt_ref=<ref name=crc/>
| BoilingPtC = 1465
| BoilingPt_ref=<ref name=crc/>
| Solubility = 360 g/1000 g pure water at T = 25 °C<ref name="crc" />
| Solvent1 = ammonia
| Solubility1 = 21.5 g/L at T = ?{{Clarify|date = June 2021}}
| Solvent2 = methanol
| Solubility2 = 14.9 g/L at T = ?{{Clarify|date = June 2021}}
| RefractIndex = 1.5441 (at 589 nm)<ref>Haynes, 10.241</ref>
| MagSus = −30.2·10−6 cm3/mol<ref>Haynes, 4.135</ref>
}}
| Section3 = {{Chembox Structure
| Structure_ref =<ref>Haynes, 4.148</ref>
| CrystalStruct = Face-centered cubic (''see text''), [[Pearson symbol|cF8]]
| SpaceGroup = Fm{{overline|3}}m (No. 225)
| LattConst_a = 564.02 pm
| UnitCellFormulas = 4
| Coordination = octahedral at Na+ octahedral at Cl−
}}
| Section4 =
| Section5 = {{Chembox Thermochemistry
| Thermochemistry_ref =<ref>Haynes, 5.8</ref>
| DeltaHf = −411.120 kJ/mol
| Entropy = 72.10 J/(K·mol)
| HeatCapacity = 50.5 J/(K·mol)
}}
| Section6 = {{Chembox Pharmacology
| ATCCode_prefix = A12
| ATCCode_suffix = CA01
| ATC_Supplemental = {{ATC|B05|CB01}}, {{ATC|B05|XA03}}, {{ATC|S01|XA03}}
}}
| Section7 = {{Chembox Hazards
| NFPA-H = 0
| NFPA-F = 0
| NFPA-R = 0
| LD50 = 3 g/kg (oral, rats)<ref>[http://chem.sis.nlm.nih.gov/chemidplus/rn/7647-14-5 Sodium chloride]. nlm.nih.gov.</ref>
}}
| Section8 = {{Chembox Related
| OtherAnions = [[Sodium fluoride]] [[Sodium bromide]] [[Sodium iodide]] [[Sodium astatide]]
| OtherCations = [[Lithium chloride]] [[Potassium chloride]] [[Rubidium chloride]] [[Caesium chloride]] [[Francium chloride]]
}}
}}

'''Sodium chloride''' {{IPAc-en|ˌ|s|oʊ|d|i|ə|m|_|ˈ|k|l|ɔr|aɪ|d}},<ref>{{Citation |last=Wells |first=John C. |title=Longman Pronunciation Dictionary |pages=143 and 755 |year=2008 |edition=3rd |publisher=Longman |isbn=9781405881180}}</ref> commonly known as '''salt''' (although [[sea salt]] also contains other chemical [[salt (chemistry)|salt]]s), is an [[ionic compound]] with the [[chemical formula]] '''NaCl''', representing a 1:1 ratio of [[sodium]] and [[chloride]] ions. With [[molar mass]]es of 22.99 and 35.45 g/mol respectively, 100 g of NaCl contains 39.34 g Na and 60.66 g Cl. Sodium chloride is the [[salt (chemistry)|salt]] most responsible for the [[salinity]] of [[seawater]] and of the [[extracellular fluid]] of many [[multicellular organism]]s. In its edible form of [[salt|table salt]], it is commonly used as a [[condiment]] and [[Curing (food preservation)|food preservative]]. Large quantities of sodium chloride are used in many industrial processes, and it is a major source of sodium and [[chlorine]] compounds used as [[feedstock]]s for further [[Chemical synthesis|chemical syntheses]]. A second major application of sodium chloride is de-icing of roadways in sub-freezing weather.
{{TOC limit}}

==Uses==
In addition to the familiar domestic uses of salt, more dominant applications of the approximately 250 million tonnes per year production (2008 data) include chemicals and de-icing.<ref name="Ullmann">Westphal, Gisbert ''et al.'' (2002) "Sodium Chloride" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim {{DOI|10.1002/14356007.a24_317.pub4}}.</ref>

===Chemicals production===
Salt is used, directly or indirectly, in the production of many chemicals, which consume most of the world's production.<ref name=usgs/>

====Chlor-alkali industry====
{{See also|Chloralkali process}}
It is the starting point for the [[chloralkali process]], the industrial process to produce [[chlorine]] and [[sodium hydroxide]], according to the [[chemical equation]]
:2 NaCl + 2 H2O → Cl2 + H2 + 2 NaOH

This electrolysis is conducted in either a mercury cell, a diaphragm cell, or a membrane cell. Each of those uses a different method to separate the chlorine from the sodium hydroxide. Other technologies are under development due to the high energy consumption of the electrolysis, whereby small improvements in the efficiency can have large economic paybacks. Some applications of chlorine include [[PVC]], disinfectants, and solvents. Sodium hydroxide enables industries that produce paper, soap, and aluminium.

===Soda-ash industry===
Sodium chloride is used in the [[Solvay process]] to produce [[sodium carbonate]] and [[calcium chloride]]. Sodium carbonate, in turn, is used to produce [[glass]], [[sodium bicarbonate]], and [[dye]]s, as well as a myriad of other chemicals. In the [[Mannheim process]] and in the [[Hargreaves process]], sodium chloride is used for the production of [[sodium sulfate]] and [[hydrochloric acid]].

===Standard===
Sodium chloride has an international standard that is created by [[ASTM International]]. The standard is named '''ASTM E534-13''' and is the standard test methods for chemical analysis of sodium chloride. These methods listed provide procedures for analyzing sodium chloride to determine whether it is suitable for its intended use and application.

===Miscellaneous industrial uses===
Sodium chloride is heavily used, so even relatively minor applications can consume massive quantities. In oil and gas exploration, salt is an important component of drilling fluids in well drilling. It is used to [[Flocculation|flocculate]] and increase the density of the drilling fluid to overcome high downwell gas pressures. Whenever a drill hits a salt formation, salt is added to the drilling fluid to saturate the solution in order to minimize the dissolution within the salt stratum.<ref name=Ullmann/> Salt is also used to increase the curing of concrete in cemented casings.<ref name=usgs/>

In textiles and dyeing, salt is used as a brine rinse to separate organic contaminants, to promote "salting out" of dyestuff precipitates, and to blend with concentrated dyes to standardize{{clarify|date=October 2016}} them. One of its main roles is to provide the positive ion charge to promote the absorption of negatively charged ions of dyes.<ref name=usgs/>

It is also used in processing [[aluminium]], [[beryllium]], [[copper]], [[steel]] and [[vanadium]]. In the [[pulp and paper industry]], salt is used to bleach wood pulp. It also is used to make [[sodium chlorate]], which is added along with [[sulfuric acid]] and water to manufacture [[chlorine dioxide]], an excellent oxygen-based [[bleach]]ing chemical. The chlorine dioxide process, which originated in Germany after World War I, is becoming more popular because of environmental pressures to reduce or eliminate chlorinated bleaching compounds. In tanning and leather treatment, salt is added to animal [[Hide (skin)|hides]] to inhibit microbial activity on the underside of the hides and to attract moisture back into the hides.<ref name=usgs/>

In rubber manufacture, salt is used to make [[Synthetic rubber|buna]], [[neoprene]] and white rubber types. Salt brine and sulfuric acid are used to coagulate an emulsified [[latex]] made from chlorinated [[butadiene]].<ref name=usgs/><ref name=Ullmann/>

Salt also is added to secure the soil and to provide firmness to the foundation on which highways are built. The salt acts to minimize the effects of shifting caused in the subsurface by changes in humidity and traffic load.<ref name=usgs/>

Sodium chloride is sometimes used as a cheap and safe [[desiccant]] because of its [[hygroscopic]] properties, making [[Salting (food)|salting]] an effective method of [[food preservation]] historically; the salt draws water out of bacteria through [[osmotic pressure]], keeping it from reproducing, a major source of food spoilage. Even though more effective desiccants are available, few are safe for humans to ingest.

===Water softening===
[[Hard water]] contains calcium and magnesium ions that interfere with action of [[soap]] and contribute to the buildup of a scale or film of alkaline mineral deposits in household and industrial equipment and pipes. Commercial and residential water-softening units use [[ion-exchange resin]]s to remove the offending ions that cause the hardness. These resins are generated and regenerated using sodium chloride.<ref name=usgs/><ref name=Ullmann/>

===Road salt===
[[File:WatNaCl.png|thumb|left|upright=1.15|Phase diagram of water–NaCl mixture]]
The second major application of salt is for [[de-icing]] and anti-icing of roads, both in [[grit bin]]s and spread by [[winter service vehicle]]s. In anticipation of snowfall, roads are optimally "anti-iced" with brine (concentrated [[Solution (chemistry)|solution]] of salt in water), which prevents bonding between the snow-ice and the road surface. This procedure obviates the heavy use of salt after the snowfall. For de-icing, mixtures of brine and salt are used, sometimes with additional agents such as [[calcium chloride]] and/or [[magnesium chloride]]. The use of salt or brine becomes ineffective below {{convert|−10|°C|0}}.
[[File:Winter road salt.jpg|thumbnail|left|upright=1.15|Mounds of road salt for use in winter]]
Salt for de-icing in the United Kingdom predominantly comes from a single mine in [[Winsford]] in [[Salt in Cheshire|Cheshire]]. Prior to distribution it is mixed with <100 ppm of [[sodium ferrocyanide]] as an anti-caking agent, which enables rock salt to flow freely out of the gritting vehicles despite being stockpiled prior to use. In recent years this additive has also been used in table salt. Other additives had been used in road salt to reduce the total costs. For example, in the US, a byproduct carbohydrate solution from sugar-beet processing was mixed with rock salt and adhered to road surfaces about 40% better than loose rock salt alone. Because it stayed on the road longer, the treatment did not have to be repeated several times, saving time and money.<ref name=usgs/>

In the technical terms of physical chemistry, the minimum freezing point of a water-salt mixture is {{convert|−21.12|C|F}} for 23.31 wt% of salt. Freezing near this concentration is however so slow that the [[eutectic point]] of {{convert|−22.4|C|F}} can be reached with about 25 wt% of salt.<ref name="u1" />

====Environmental effects====
Road salt ends up in fresh-water bodies and could harm aquatic plants and animals by disrupting their [[osmoregulation]] ability.<ref>Rastogi, Nina (16 February 2010) [http://www.slate.com/id/2244156 Does road salt harm the environment?] slate.com.</ref> The omnipresence of salt poses a problem in any coastal coating application, as trapped salts cause great problems in adhesion. Naval authorities and ship builders monitor the salt concentrations on surfaces during construction. Maximal salt concentrations on surfaces are dependent on the authority and application. The [[International Maritime Organization|IMO]] regulation is mostly used and sets salt levels to a maximum of 50 mg/m2 soluble salts measured as sodium chloride. These measurements are done by means of a [[Bresle test]]. Salinization (increasing salinity, aka ''[[freshwater salinization]] syndrome'') and subsequent increased metal leaching is an ongoing problem throughout North America and European fresh waterways.<ref>{{Cite web |url=https://phys.org/news/2018-12-saltier-waterways-dangerous-chemical-cocktails.html |title=Saltier waterways are creating dangerous 'chemical cocktails' |website=phys.org}}</ref>

In highway de-icing, salt has been associated with [[corrosion]] of bridge decks, motor vehicles, reinforcement bar and wire, and unprotected steel structures used in road construction. Surface runoff, vehicle spraying, and windblown actions also affect soil, roadside vegetation, and local surface water and groundwater supplies. Although evidence of environmental loading of salt has been found during peak usage, the spring rains and thaws usually dilute the concentrations of sodium in the area where salt was applied.<ref name=usgs/> A 2009 study found that approximately 70% of the road salt being applied in the [[Minneapolis-St Paul]] metro area is retained in the local watershed.<ref>{{Cite web |url=https://www.sciencedaily.com/releases/2009/02/090210125424.htm |title=Most Road Salt Is Making It into Lakes And Rivers |date=20 February 2009 |website=www.sciencedaily.com |publisher=University of Minnesota |access-date=27 September 2015}}</ref>

====Substitution====
Some agencies are substituting beer, molasses, and beet juice instead of road salt.<ref>{{Cite web |url=https://phys.org/news/2018-01-salt-solution-winter-dangers-threatens.html|author=Casey, Michael |title=Turning to beet juice and beer to address road salt danger |website=phys.org}}</ref> Airlines utilize more [[glycol]] and [[sugar]] rather than salt based solutions for [[de-icing]].<ref>{{Cite web |url=https://www.mro-network.com/maintenance-repair-overhaul/easa-cautions-organic-salt-deicing-fluid |title=EASA Cautions on Organic Salt Deicing Fluid |date=9 December 2016 |website=MRO Network}}</ref>

===Food industry and agriculture===
{{main|Salt}}
Many [[microorganism]]s cannot live in a salty environment: water is drawn out of their [[cell (biology)|cells]] by [[osmosis]]. For this reason salt is used to [[Food preservation|preserve]] some foods, such as bacon, fish, or cabbage.

Salt is added to food, either by the food producer or by the consumer, as a flavor enhancer, preservative, binder, [[fermentation (food)|fermentation]]-control additive, texture-control agent and color developer. The salt consumption in the food industry is subdivided, in descending order of consumption, into other food processing, meat packers, [[canning]], baking, dairy and grain mill products. Salt is added to promote color development in bacon, ham and other processed meat products. As a preservative, salt inhibits the growth of bacteria. Salt acts as a binder in [[sausage]]s to form a binding gel made up of meat, fat, and moisture. Salt also acts as a flavor enhancer and as a [[tenderizer]].<ref name=usgs/>

In many dairy industries, salt is added to cheese as a color-, fermentation-, and texture-control agent. The dairy subsector includes companies that manufacture creamery butter, condensed and evaporated milk, frozen desserts, ice cream, natural and processed cheese, and specialty dairy products. In canning, salt is primarily added as a flavor enhancer and [[preservative]]. It also is used as a carrier for other ingredients, dehydrating agent, enzyme inhibitor and tenderizer. In baking, salt is added to control the rate of fermentation in bread dough. It also is used to strengthen the [[gluten]] (the elastic protein-water complex in certain doughs) and as a flavor enhancer, such as a topping on baked goods. The food-processing category also contains grain mill products. These products consist of milling flour and rice and manufacturing cereal breakfast food and blended or prepared flour. Salt is also used a seasoning agent, e.g. in potato chips, [[pretzel]]s, cat and dog food.<ref name=usgs/>

Sodium chloride is used in veterinary medicine as [[emesis]]-causing agent. It is given as warm saturated solution. Emesis can also be caused by [[pharynx|pharyngeal]] placement of small amount of plain salt or salt crystals.

===Medicine===

{{Main|Saline (medicine)}}
Sodium chloride is used together with water as one of the primary solutions for [[intravenous therapy]]. [[Nasal spray]] often contains a [[Saline (medicine)|saline]] solution.

===Firefighting===
[[File:Metlx.jpg|thumb|upright|A class-D fire extinguisher for various metals]]
Sodium chloride is the principal extinguishing agent in fire extinguishers (Met-L-X, Super D) used on combustible metal fires such as magnesium, potassium, sodium, and NaK alloys (Class D). [[Thermoplastic]] powder is added to the mixture, along with waterproofing (metal stearates) and anti-caking materials (tricalcium phosphate) to form the extinguishing agent. When it is applied to the fire, the salt acts like a heat sink, dissipating heat from the fire, and also forms an oxygen-excluding crust to smother the fire. The plastic additive melts and helps the crust maintain its integrity until the burning metal cools below its ignition temperature. This type of extinguisher was invented in the late 1940s as a cartridge-operated unit, although stored pressure versions are now popular. Common sizes are {{convert|30|lb|kg}} portable and {{convert|350|lb|kg}} wheeled.{{citation needed|date=August 2020}}

===Cleanser===
Since at least [[medieval]] times, people have used salt as a cleansing agent rubbed on household surfaces. It is also used in many brands of [[shampoo]], toothpaste and popularly to de-ice driveways and patches of ice.

===Optical usage===
Defect-free NaCl crystals have an optical transmittance of about 90% for infrared light, specifically between 200 [[Nanometer|nm]] and 20 [[µm]]. They were therefore used in optical components (windows and prisms) operating in that spectral range, where few non-absorbing alternatives exist and where requirements for absence of microscopic inhomogeneities are less strict than in the visible range. While inexpensive, NaCl crystals are soft and [[Hygroscopy|hygroscopic]] – when exposed to the ambient air, they gradually cover with "frost". This limits application of NaCl to dry environments, vacuum sealed assembly areas or for short-term uses such as prototyping. Nowadays materials like [[zinc selenide]] (ZnSe), which are stronger mechanically and are less sensitive to moisture, are used instead of NaCl for the infrared spectral range.

==Chemistry==

===Solid sodium chloride===
{{See also|Cubic crystal system}}
[[File:Natrium chloride kristal under microscope.jpg|thumb|Sodium chloride crystal under microscope.]]
[[File:NaCl octahedra.svg|thumb|NaCl octahedra. The yellow stipples represent the electrostatic force between the ions of opposite charge]]
In solid sodium chloride, each ion is surrounded by six ions of the opposite charge as expected on electrostatic grounds. The surrounding ions are located at the vertices of a regular [[octahedron]]. In the language of [[close-packing]], the larger [[Chlorine|chloride]] [[ion]]s (167 pm in size<ref name="Shannon">{{cite journal|doi=10.1107/S0567739476001551|title=Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides|author=R. D. Shannon|journal=Acta Crystallogr A|volume=32|issue=5|year=1976|pages=751–767|bibcode = 1976AcCrA..32..751S |doi-access=free}}</ref>) are arranged in a cubic array whereas the smaller [[sodium]] ions (116 pm<ref name=Shannon />) fill all the cubic gaps (octahedral voids) between them. This same basic structure is found in many other [[Chemical compound|compounds]] and is commonly known as the [[halite]] or rock-salt crystal structure. It can be represented as a [[Cubic crystal system|face-centered cubic]] (fcc) lattice with a two-atom basis or as two interpenetrating face centered cubic lattices. The first atom is located at each lattice point, and the second atom is located halfway between lattice points along the fcc unit cell edge.

Solid sodium chloride has a melting point of 801 °C. [[Thermal conductivity]] of sodium chloride as a function of temperature has a maximum of 2.03 W/(cm K) at {{convert|8|K}} and decreases to 0.069 at {{convert|314|K}}. It also decreases with [[Doping (semiconductor)|doping]].<ref>{{Cite book |last1=Sirdeshmukh |first1=Dinker B. |url=https://books.google.com/books?id=X-yL7EgMK6wC&pg=PA68 |title=Alkali halides: a handbook of physical properties |last2=Sirdeshmukh, Lalitha |last3=Subhadra, K. G. |publisher=Springer |year=2001 |isbn=978-3-540-42180-1 |pages=65, 68 |name-list-style=amp}}</ref>

Atomic-resolution real-time video imaging allows visualization of the initial stage of crystal nucleation of sodium chloride.<ref>{{cite journal |last1=Nakamuro |first1=Takayuki |last2=Sakakibara |first2=Masaya |last3=Nada |first3=Hiroki |last4=Harano |first4=Koji |last5=Nakamura |first5=Eiichi |title=Capturing the Moment of Emergence of Crystal Nucleus from Disorder |journal=Journal of the American Chemical Society |year=2021 |volume=143 |issue=4 |pages=1763–1767 |doi=10.1021/jacs.0c12100 |pmid=33475359 |doi-access=free }}</ref>

===Aqueous solutions===
{| class="wikitable" style="float:right; margin-left:1em;"
! {{Chemical datatable header}}|Solubility of NaCl (g NaCl / 1 kg of solvent at {{convert|25|C|F}})<ref>{{Cite book |last=Burgess |first=J |title=Metal Ions in Solution |publisher=Ellis Horwood |year=1978 |isbn=978-0-85312-027-8 |location=New York}}</ref>
|-
| [[Water (molecule)|Water]] || 360
|-
| [[Formamide]] || 94
|-
| [[Glycerin]] || 83
|-
| [[Propylene glycol]] || 71
|-
| [[Formic acid]] || 52
|-
| [[Ammonia|Liquid ammonia]] || 30.2
|-
| [[Methanol]] || 14
|-
| [[Ethanol]] || 0.65
|-
| [[Dimethylformamide]] || 0.4
|-
| [[1-Propanol]] || 0.124
|-
| [[Sulfolane]] || 0.05
|-
| [[1-Butanol]] || 0.05
|-
| [[2-Propanol]] || 0.03
|-
| [[1-Pentanol]] || 0.018
|-
| [[Acetonitrile]] || 0.003
|-
| [[Acetone]] || 0.00042
|}
The attraction between the Na+ and Cl− ions in the solid is so strong that only highly polar solvents like water dissolve NaCl well.
[[File:NaCl(H2O)2slab.png|thumb|left|upright=1.25|View of one slab of NaCl(H2O)2 (red = O, white = H, green = Cl, purple = Na).<ref>{{Cite journal |last1=Klewe |first1=B |last2=Pedersen |year=1974 |title=The crystal structure of sodium chloride dihydrate |journal=Acta Crystallogr. |volume=B30 |issue=10 |pages=2363–2371 |doi=10.1107/S0567740874007138 |doi-access=free}}</ref>]]
When dissolved in water, the sodium chloride framework disintegrates as the Na+ and Cl− ions become surrounded by polar water molecules. These solutions consist of [[metal aquo complex]] with the formula [Na(H2O)8]+, with the Na–O distance of 250 [[picometer|pm]]. The chloride ions are also strongly solvated, each being surrounded by an average of 6 molecules of water.<ref name="Lincoln">Lincoln, S. F.; Richens, D. T. and Sykes, A. G. (2003) "Metal Aqua Ions" Comprehensive Coordination Chemistry II Volume 1, pp. 515–555. {{DOI|10.1016/B0-08-043748-6/01055-0}}.</ref> Solutions of sodium chloride have very different properties from pure water. The [[freezing point]] is {{convert|−21.12|C|F}} for 23.31% [[Mass fraction (chemistry)#Mass percentage|mass fraction]] of salt, and the boiling point of saturated salt solution is near {{convert|108.7|C|F}}.<ref name="u1">Elvers, B. ''et al.'' (ed.) (1991) ''Ullmann's Encyclopedia of Industrial Chemistry'', 5th ed. Vol. A24, Wiley, p. 319, {{ISBN|978-3-527-20124-2}}.</ref> From cold solutions, salt crystallises as the [[water of hydration|dihydrate]] NaCl·2H2O.{{citation needed|date=March 2021}}

===pH of sodium chloride solutions===
The pH of a sodium chloride solution remains ≈7 due to the extremely weak basicity of the Cl− ion, which is the conjugate base of the strong acid HCl. In other words, NaCl has no effect on system pH<ref>{{Cite web |url=https://www.flinnsci.com/api/library/Download/1f87f104ec4b4492a621f480797fbab1 |title=Acidic, Basic, and Neutral Salts |date=2016 |website=Flinn Scientific Chem Fax |access-date=18 September 2018 |quote=Neutralization of a strong acid and a strong base gives a neutral salt.}}</ref> in diluted solutions where the effects of ionic strength and activity coefficients are negligible.

===Unexpected stable stoichiometric variants===
Common salt has a 1:1 molar ratio of sodium and chlorine. In 2013, compounds of sodium and chloride of different [[stoichiometry|stoichiometries]] have been discovered; five new compounds were predicted (e.g., Na3Cl, Na2Cl, Na3Cl2, NaCl3, and NaCl7). The existence of some of them has been experimentally confirmed at high pressures: cubic and orthorhombic NaCl3 and two-dimensional metallic tetragonal Na3Cl. This indicates that compounds violating chemical intuition are possible, in simple systems under nonambient conditions.<ref>{{Cite journal |last1=Zhang |first1=W. |last2=Oganov |first2=A. R. |last3=Goncharov |first3=A. F. |last4=Zhu |first4=Q. |last5=Boulfelfel |first5=S. E. |last6=Lyakhov |first6=A. O. |last7=Stavrou |first7=E. |last8=Somayazulu |first8=M. |last9=Prakapenka |first9=V. B. |last10=Konôpková |first10=Z. |year=2013 |title=Unexpected Stable Stoichiometries of Sodium Chlorides |journal=Science |volume=342 |issue=6165 |pages=1502–1505 |arxiv=1310.7674 |bibcode=2013Sci...342.1502Z |doi=10.1126/science.1244989 |pmid=24357316|s2cid=15298372 }}</ref>

==Occurrence==
Small particles of [[sea salt]] are the dominant [[cloud condensation nuclei]] far out at sea, which allow the formation of [[cloud]]s in otherwise [[pollution|non-polluted]] [[air]].<ref>{{Cite journal |last=Mason |first=B. J. |date=2006 |title=The role of sea-salt particles as cloud condensation nuclei over the remote oceans |journal=Quarterly Journal of the Royal Meteorological Society |volume=127 |issue=576 |pages=2023–32 |bibcode=2001QJRMS.127.2023M |doi=10.1002/qj.49712757609}}</ref>

==Production==
Salt is currently [[Mass production|mass-produced]] by [[evaporation]] of [[seawater]] or [[brine]] from [[brine well]]s and [[salt lake (geography)|salt lakes]]. [[Salt mine|Mining]] of rock salt is also a major source. China is the world's main supplier of salt.<ref name="usgs">Kostick, Dennis S. (October 2010) [http://minerals.usgs.gov/minerals/pubs/commodity/salt/myb1-2008-salt.pdf "Salt"] in ''U.S. Geological Survey, 2008 Minerals Yearbook''</ref> In 2017, world production was estimated at 280 million [[tonne]]s, the top five producers (in million tonnes) being China (68.0), United States (43.0), India (26.0), Germany (13.0), and Canada (13.0).<ref>[https://minerals.usgs.gov/minerals/pubs/commodity/salt/mcs-2018-salt.pdf Salt], U.S. Geological Survey</ref> Salt is also a byproduct of [[potassium]] mining.

<gallery mode="packed">
File:Salt mine 0096.jpg|Modern rock salt mine near [[Mount Morris (town), New York|Mount Morris]], [[New York (state)|New York]], [[United States]]
File:Dead-Sea---Salt-Evaporation-Ponds.jpg|[[Jordan]]ian and [[Israel]]i salt evaporation ponds at the south end of the [[Dead Sea]].
File:Piles of Salt Salar de Uyuni Bolivia Luca Galuzzi 2006 a.jpg|Mounds of salt, [[Salar de Uyuni]], [[Bolivia]].
</gallery>

==See also==
{{Portal|Chemistry}}
{{colbegin}}
* [[Biosalinity]]
* [[Salt|Edible salt (table salt)]]
* [[Halite]], the mineral form of sodium chloride
* [[Health effects of salt]]
* [[Salinity]]
* [[Salting the earth]]
* [[Salt poisoning]]
{{colend}}

==References==
{{reflist}}
* {{USGS|title=Salt|url=http://minerals.usgs.gov/minerals/pubs/commodity/salt/myb1-2008-salt.pdf}}

==Cited sources==
* {{Cite book |title=CRC Handbook of Chemistry and Physics |title-link=CRC Handbook of Chemistry and Physics |publisher=[[CRC Press]] |year=2011 |isbn=978-1439855119 |editor-last=Haynes |editor-first=William M. |edition=92nd}}

==External links==
{{Commons|NaCl}}
{{Cookbook|Salt}}
* [http://minerals.usgs.gov/minerals/pubs/commodity/salt/ Salt] [[United States Geological Survey]] Statistics and Information
* {{Cite journal |date=December 1997 |title=Using Salt and Sand for Winter Road Maintenance |url=http://www.usroads.com/journals/p/rmj/9712/rm971202.htm |url-status=dead |journal=Road Management Journal |archive-url=https://web.archive.org/web/20160921160156/http://www.usroads.com/journals/p/rmj/9712/rm971202.htm |archive-date=21 September 2016 |access-date=13 February 2007}}
* Calculators: [http://www.aim.env.uea.ac.uk/aim/surftens/surftens.php surface tensions], and [http://www.aim.env.uea.ac.uk/aim/density/density_electrolyte.php densities, molarities and molalities] of aqueous NaCl (and other salts)
* [http://hazard.com/msds/mf/baker/baker/files/s3338.htm JtBaker MSDS]

{{Sodium compounds}}
{{Chlorides}}
{{Molecules detected in outer space}}
{{Authority control}}

{{DEFAULTSORT:Sodium Chloride}}
[[Category:Alkali metal chlorides]]
[[Category:Chlorides]]
[[Category:Household chemicals]]
[[Category:Metal halides]]
[[Category:Sodium compounds]]
[[Category:Sodium minerals]]
[[Category:Rock salt crystal structure]]

Coordination complex

2022-03-04T19:18:35Z

173.165.237.1: /* Reactivity */

{{Short description|Molecule or ion containing ligands datively bonded to a central metallic atom}}
[[File:Cisplatin-3D-balls.png|thumb|upright=1.2|[[Cisplatin]], PtCl2(NH3)2, is a coordination complex of platinum(II) with two chloride and two ammonia [[ligand]]s. It is one of the most successful anticancer drugs.]]

A '''coordination complex''' consists of a central [[atom]] or [[ion]], which is usually [[metal]]lic and is called the ''coordination centre'', and a surrounding array of [[chemical bond|bound]] [[molecules]] or ions, that are in turn known as ''[[ligand]]s'' or complexing agents.<ref>{{cite book |title= Introduction to Coordination Chemistry |first= Geoffrey A. |last= Lawrance |year= 2010 |publisher= Wiley |isbn= 9780470687123 |doi= 10.1002/9780470687123}}</ref><ref>{{GoldBookRef | title = complex | file = C01203}}</ref><ref>{{GoldBookRef | file = C01330 | title = coordination entity}}</ref> Many metal-containing [[chemical compound|compounds]], especially those that include [[transition metal]]s (elements like [[titanium]] that belong to the [[Block (periodic table)|Periodic Table's d-block]]), are coordination complexes.<ref>{{Greenwood&Earnshaw2nd}}</ref>

==Nomenclature and terminology==
Coordination complexes are so pervasive that their structures and reactions are described in many ways, sometimes confusingly. The atom within a ligand that is bonded to the central metal atom or ion is called the '''donor atom'''. In a typical complex, a metal ion is bonded to several donor atoms, which can be the same or different. A [[Ligand#Polydentate and polyhapto ligand motifs and nomenclature|polydentate]] (multiple bonded) ligand is a molecule or ion that bonds to the central atom through several of the ligand's atoms; ligands with 2, 3, 4 or even 6 bonds to the central atom are common. These complexes are called [[chelate complex]]es; the formation of such complexes is called chelation, complexation, and coordination.

The central atom or ion, together with all ligands, comprise the [[coordination sphere]].<ref>{{cite web |url= http://www.chemistry-dictionary.com/definition/coordination+sphere.php |title= Definition of coordination sphere |publisher= chemistry-dictionary.com }}</ref><ref>{{cite web |url= http://www.chem.purdue.edu/gchelp/cchem/whatis.html |title= What Is A Coordination Compound? |publisher= Purdue University Department of Chemistry }}</ref> The central atoms or ion and the donor atoms comprise the first coordination sphere.

'''Coordination''' refers to the "coordinate covalent bonds" ([[dipolar bond]]s) between the ligands and the central atom. Originally, a complex implied a reversible association of [[molecule]]s, [[atom]]s, or [[ion]]s through such weak [[chemical bond]]s. As applied to coordination chemistry, this meaning has evolved. Some metal complexes are formed virtually irreversibly and many are bound together by bonds that are quite strong.<ref>{{Cite book|isbn=978-0-471-19957-1 |page=1355|last=Cotton|first=Frank Albert|author2=Geoffrey Wilkinson |author3=Carlos A. Murillo |title=Advanced Inorganic Chemistry|year=1999}}</ref><ref>{{Cite book|isbn=978-0-13-841891-5 |page=642|last=Miessler|first=Gary L.|author2=Donald Arthur Tarr|title=Inorganic Chemistry|year=1999}}</ref>

The number of donor atoms attached to the central atom or ion is called the [[coordination number]]. The most common coordination numbers are 2, 4, and especially 6. A hydrated ion is one kind of a complex ion (or simply a complex), a species formed between a central metal ion and one or more surrounding ligands, molecules or ions that contain at least one lone pair of electrons.

If all the ligands are [[Denticity|monodentate]], then the number of donor atoms equals the number of ligands. For example, the cobalt(II) hexahydrate ion or the hexaaquacobalt(II) ion [Co(H2O)6]2+ is a hydrated-complex ion that consists of six water molecules attached to a metal ion Co. The oxidation state and the coordination number reflect the number of bonds formed between the metal ion and the ligands in the complex ion. However, the coordination number of Pt([[Ethylenediamine|en]]){{su|b=2|p=2+}} is 4 (rather than 2) since it has two bidentate ligands, which contain four donor atoms in total.

Any donor atom will give a pair of electrons. There are some donor atoms or groups which can offer more than one pair of electrons. Such are called bidentate (offers two pairs of electrons) or polydentate (offers more than two pairs of electrons). In some cases an atom or a group offers a pair of electrons to two similar or different central metal atoms or acceptors—by division of the electron pair—into a [[three-center two-electron bond]]. These are called bridging ligands.

==History==
[[File:Alfred Werner ETH-Bib Portr 09965.jpg|thumb|upright|[[Alfred Werner]]]]
Coordination complexes have been known since the beginning of modern chemistry. Early well-known coordination complexes include dyes such as [[Prussian blue]]. Their properties were first well understood in the late 1800s, following the 1869 work of [[Christian Wilhelm Blomstrand]]. Blomstrand developed what has come to be known as the ''complex ion chain theory.'' In considering metal amine complexes, he theorized that the ammonia molecules compensated for the charge of the ion by forming chains of the type [(NH3)X]X+, where X is the coordination number of the metal ion. He compared his theoretical ammonia chains to hydrocarbons of the form (CH2)X.<ref>{{Cite web|title=Coordination compound - History of coordination compounds|url=https://www.britannica.com/science/coordination-compound|access-date=2021-07-07|website=Encyclopedia Britannica|language=en}}</ref>

Following this theory, Danish scientist [[Sophus Mads Jørgensen]] made improvements to it. In his version of the theory, Jørgensen claimed that when a molecule dissociates in a solution there were two possible outcomes: the ions would bind via the ammonia chains Blomstrand had described or the ions would bind directly to the metal.

It was not until 1893 that the most widely accepted version of the theory today was published by [[Alfred Werner]]. Werner's work included two important changes to the Blomstrand theory. The first was that Werner described the two possibilities in terms of location in the coordination sphere. He claimed that if the ions were to form a chain, this would occur outside of the coordination sphere while the ions that bound directly to the metal would do so within the coordination sphere.<ref>{{Cite web|url = http://www.britannica.com/EBchecked/topic/136410/coordination-compound|title = Coordination Compound}}</ref> In one of his most important discoveries however Werner disproved the majority of the chain theory. Werner discovered the spatial arrangements of the ligands that were involved in the formation of the complex hexacoordinate cobalt. His theory allows one to understand the difference between a coordinated ligand and a charge balancing ion in a compound, for example the chloride ion in the cobaltammine chlorides and to explain many of the previously inexplicable isomers.

In 1911, Werner first resolved the coordination complex [[hexol]] into [[Enantiomer|optical isomers]], overthrowing the theory that only carbon compounds could possess [[Chirality (chemistry)|chirality]].<ref>{{Cite journal|last=Werner|first=A.|date=May 1911|title=Zur Kenntnis des asymmetrischen Kobaltatoms. I|url=http://doi.wiley.com/10.1002/cber.19110440297|journal=Berichte der Deutschen Chemischen Gesellschaft|language=de|volume=44|issue=2|pages=1887–1898|doi=10.1002/cber.19110440297}}</ref>

==Structures==
[[File:Hexol-2D-wedged.png|thumb|Structure of hexol]]
The ions or molecules surrounding the central atom are called [[ligand]]s. Ligands are classified as [[ligand#Classification of ligands as L and X|L or X]] (or a combination thereof), depending on how many electrons they provide for the bond between ligand and central atom. L ligands provide two electrons from a [[lone pair|lone electron pair]], resulting in a [[coordinate covalent bond]]. X ligands provide one electron, with the central atom providing the other electron, thus forming a regular [[covalent bond]]. The ligands are said to be '''coordinated''' to the atom. For [[alkene]]s, the [[pi bond]]s can coordinate to metal atoms. An example is [[ethylene]] in the complex [[Zeise's salt|[PtCl3(C2H4)]−]].

===Geometry===
In coordination chemistry, a structure is first described by its [[coordination number]], the number of ligands attached to the metal (more specifically, the number of donor atoms). Usually one can count the ligands attached , but sometimes even the counting can become ambiguous. Coordination numbers are normally between two and nine, but large numbers of ligands are not uncommon for the lanthanides and actinides. The number of bonds depends on the size, charge, and [[electron configuration]] of the metal ion and the ligands. Metal ions may have more than one coordination number.

Typically the chemistry of transition metal complexes is dominated by interactions between s and p [[molecular orbital]]s of the donor-atoms in the ligands and the d orbitals of the metal ions. The s, p, and d orbitals of the metal can accommodate 18 electrons (see [[18-Electron rule]]). The maximum coordination number for a certain metal is thus related to the electronic configuration of the metal ion (to be more specific, the number of empty orbitals) and to the ratio of the size of the ligands and the metal ion. Large metals and small ligands lead to high coordination numbers, e.g. [Mo(CN)8]4−. Small metals with large ligands lead to low coordination numbers, e.g. Pt[P(CMe3)]2. Due to their large size, [[lanthanide]]s, [[actinide]]s, and early transition metals tend to have high coordination numbers.

Most structures follow the points-on-a-sphere pattern (or, as if the central atom were in the middle of a [[polyhedron]] where the corners of that shape are the locations of the ligands), where orbital overlap (between ligand and metal orbitals) and ligand-ligand repulsions tend to lead to certain regular geometries. The most observed geometries are listed below, but there are many cases that deviate from a regular geometry, e.g. due to the use of ligands of diverse types (which results in irregular bond lengths; the coordination atoms do not follow a points-on-a-sphere pattern), due to the size of ligands, or due to [[electronic effect]]s (see, e.g., [[Jahn–Teller distortion]]):

*[[Linear molecular geometry|Linear]] for two-coordination
*[[Trigonal planar molecular geometry|Trigonal planar]] for three-coordination
*[[Tetrahedral molecular geometry|Tetrahedral]] or [[square planar molecular geometry|square planar]] for four-coordination
*[[Trigonal bipyramid molecular geometry|Trigonal bipyramidal]] for five-coordination
*[[Octahedral molecular geometry|Octahedral]] for six-coordination
*[[Pentagonal bipyramidal molecular geometry|Pentagonal bipyramidal]] for seven-coordination
*[[Square antiprismatic molecular geometry|Square antiprismatic]] for eight-coordination
*[[Tricapped trigonal prismatic molecular geometry|Tricapped trigonal prismatic]] for nine-coordination

The idealized descriptions of 5-, 7-, 8-, and 9- coordination are often indistinct geometrically from alternative structures with slightly differing L-M-L (ligand-metal-ligand) angles, e.g. the difference between square pyramidal and trigonal bipyramidal structures.<ref>Wells A.F. (1984) ''Structural Inorganic Chemistry'' 5th edition Oxford Science Publications {{ISBN|0-19-855370-6}}</ref>

*[[Square pyramidal molecular geometry|Square pyramidal]] for five-coordination<ref>{{cite journal
| title = Transition metal pentacoordination
|author1=Angelo R. Rossi |author2=Roald. Hoffmann | journal = [[Inorganic Chemistry (journal)|Inorganic Chemistry]]
| year = 1975
| volume = 14
| issue = 2
| pages = 365–374
| doi = 10.1021/ic50144a032
}}</ref>
* [[Capped octahedral molecular geometry|Capped octahedral]] or [[Capped trigonal prismatic molecular geometry|capped trigonal prismatic]] for seven-coordination<ref>{{cite journal
| title = Seven-coordination. A molecular orbital exploration of structure, stereochemistry, and reaction dynamics
|author1=Roald. Hoffmann |author2=Barbara F. Beier |author3=Earl L. Muetterties |author4=Angelo R. Rossi | journal = [[Inorganic Chemistry (journal)|Inorganic Chemistry]]
| year = 1977
| volume = 16
| issue = 3
| pages = 511–522
| doi = 10.1021/ic50169a002
}}</ref>
* [[Dodecahedral molecular geometry|Dodecahedral]] or [[Bicapped trigonal prismatic molecular geometry|bicapped trigonal prismatic]] for eight-coordination<ref>{{cite journal
| title = Eight-Coordination
| author1 = Jeremy K. Burdett
| author2 = Roald Hoffmann
| author3 = Robert C. Fay
| journal = [[Inorganic Chemistry (journal)|Inorganic Chemistry]]
| year = 1978
| volume = 17
| issue = 9
| pages = 2553–2568
| doi = 10.1021/ic50187a041
}}</ref>
*[[Capped square antiprismatic molecular geometry|Capped square antiprismatic]] for nine-coordination

To distinguish between the alternative coordinations for five-coordinated complexes, the [[Geometry index|τ geometry index]] was invented by Addison et al.<ref>{{cite journal |last1 = Addison |first1 = A. W. |last2 = Rao |first2 = N. T. |last3 = Reedijk |first3 = J. |last4 = van Rijn |first4 = J. |last5 = Verschoor |first5 = G. C. |year = 1984 |title = Synthesis, structure, and spectroscopic properties of copper(II) compounds containing nitrogen–sulphur donor ligands; the crystal and molecular structure of aqua[1,7-bis(''N''-methylbenzimidazol-2′-yl)-2,6-dithiaheptane]copper(II) perchlorate |journal = J. Chem. Soc., Dalton Trans. |issue = 7 |pages = 1349–1356 |doi = 10.1039/dt9840001349}}</ref> This index depends on angles by the coordination center and changes between 0 for the square pyramidal to 1 for trigonal bipyramidal structures, allowing to classify the cases in between. This system was later extended to four-coordinated complexes by Houser et al.<ref>{{cite journal |last1 = Yang |first1 = L. |last2 = Powell |first2 = D. R. |last3 = Houser |first3 = R. P. |year = 2007 |title = Structural variation in copper(I) complexes with pyridylmethylamide ligands: structural analysis with a new four-coordinate geometry index, {{math|''τ''4}} |journal = Dalton Trans. |issue = 9 |pages = 955–64 |doi = 10.1039/b617136b|pmid = 17308676 }}</ref> and also Okuniewski et al.<ref>{{cite journal |last1 = Okuniewski |first1 = A. |last2 = Rosiak |first2 = D. |last3 = Chojnacki |first3 = J. |last4 = Becker |first4 = B. |year = 2015 |title = Coordination polymers and molecular structures among complexes of mercury(II) halides with selected 1-benzoylthioureas |journal = Polyhedron |volume = 90 |pages = 47–57 |doi = 10.1016/j.poly.2015.01.035}}</ref>

In systems with low [[d electron count]], due to special electronic effects such as (second-order) [[Jahn–Teller effect|Jahn–Teller]] stabilization,<ref>{{cite journal | title = "Non-VSEPR" Structures and Bonding in d0 Systems | first = Martin | last = Kaupp | journal = [[Angewandte Chemie|Angew. Chem. Int. Ed. Engl.]] | year = 2001 | volume = 40 | issue = 1 | pages = 3534–3565 | doi = 10.1002/1521-3773(20011001)40:19<3534::AID-ANIE3534>3.0.CO;2-#}}</ref> certain geometries (in which the coordination atoms do not follow a points-on-a-sphere pattern) are stabilized relative to the other possibilities, e.g. for some compounds the trigonal prismatic geometry is stabilized relative to octahedral structures for six-coordination.

*[[Bent molecular geometry|Bent]] for two-coordination
*[[Trigonal pyramidal molecular geometry|Trigonal pyramidal]] for three-coordination
*[[Trigonal prismatic molecular geometry|Trigonal prismatic]] for six-coordination

===Isomerism===
The arrangement of the ligands is fixed for a given complex, but in some cases it is mutable by a reaction that forms another stable [[isomer]].

There exist many kinds of [[isomerism]] in coordination complexes, just as in many other compounds.

====Stereoisomerism====
[[Stereoisomerism]] occurs with the same bonds in distinct orientations. Stereoisomerism can be further classified into:<ref>von Zelewsky, A. "Stereochemistry of Coordination Compounds" John Wiley: Chichester, 1995. {{ISBN|0-471-95599-X}}.</ref>

=====Cis–trans isomerism and facial–meridional isomerism=====
[[Cis–trans isomerism]] occurs in octahedral and [[square planar]] complexes (but not tetrahedral). When two ligands are adjacent they are said to be '''cis''', when
opposite each other, '''trans'''. When three identical ligands occupy one face of an octahedron, the isomer is said to be facial, or '''fac'''. In a ''fac'' isomer, any two identical ligands are adjacent or ''cis'' to each other. If these three ligands and the metal ion are in one plane, the isomer is said to be meridional, or '''mer'''. A ''mer'' isomer can be considered as a combination of a ''trans'' and a ''cis'', since it contains both trans and cis pairs of identical ligands.

<div align="center">
<gallery>
Image:Cis-dichlorotetraamminecobalt(III).png|''cis''-[CoCl2(NH3)4]+
Image:Trans-dichlorotetraamminecobalt(III).png|''trans''-[CoCl2(NH3)4]+
Image:Fac-trichlorotriamminecobalt(III).png|''fac''-[CoCl3(NH3)3]
Image:Mer-trichlorotriamminecobalt(III).png|''mer''-[CoCl3(NH3)3]
</gallery>
</div>

=====Optical isomerism=====
[[Optical isomerism]] occurs when a complex is not superimposable with its mirror image. It is so called because the two isomers are each [[optically active]], that is, they rotate the plane of [[polarized light]] in opposite directions. In the first molecule shown, the symbol Λ (''[[lambda]]'') is used as a prefix to describe the left-handed propeller twist formed by three bidentate ligands. The second molecule is the mirror image of the first, with the symbol Δ (''[[delta (letter)|delta]]'') as a prefix for the right-handed propeller twist. The third and fourth molecules are a similar pair of Λ and Δ isomers, in this case with two bidentate ligands and two identical monodentate ligands.<ref>{{Cite book|isbn=978-0-13-841891-5 |last=Miessler|first=Gary L.|author2=Donald Arthur Tarr|title=Inorganic Chemistry|year=1999|pages=315, 316|chapter=9}}</ref>

<div align="center">
<gallery>
Image:Delta-tris(oxalato)ferrate(III)-3D-balls.png|[[Potassium ferrioxalate|Λ-[Fe(ox)3]3−]]
Image:Lambda-tris(oxalato)ferrate(III)-3D-balls.png|Δ-[Fe(ox)3]3−
Image:Delta-cis-dichlorobis(ethylenediamine)cobalt(III).png|[[cis-Dichlorobis(ethylenediamine)cobalt(III) chloride|Λ-''cis''-[CoCl2(en)2]+]]
Image:Lambda-cis-dichlorobis(ethylenediamine)cobalt(III).png|Δ-''cis''-[CoCl2(en)2]+
</gallery>
</div>

====Structural isomerism====
[[Structural isomerism]] occurs when the bonds are themselves different. Four types of structural isomerism are recognized: ionisation isomerism, solvate or hydrate isomerism, linkage isomerism and coordination isomerism.
# '''Ionisation isomerism''' – the isomers give different ions in solution although they have the same composition. This type of isomerism occurs when the counter ion of the complex is also a potential ligand. For example, pentaamminebromocobalt(III) sulphate [Co(NH3)5Br]SO4 is red violet and in solution gives a precipitate with barium chloride, confirming the presence of sulphate ion, while pentaamminesulphatecobalt(III) bromide [Co(NH3)5SO4]Br is red and tests negative for sulphate ion in solution, but instead gives a precipitate of AgBr with silver nitrate.<ref name=Huheey>Huheey, James E., ''Inorganic Chemistry'' (3rd ed., Harper & Row 1983), p.524–5 {{ISBN|0-06-042987-9}}</ref>
# '''Solvate or hydrate isomerism''' – the isomers have the same composition but differ with respect to the number of molecules of solvent that serve as ligand vs simply occupying sites in the crystal. Examples: [Cr(H2O)6]Cl3 is violet colored, [CrCl(H2O)5]Cl2·H2O is blue-green, and [CrCl2(H2O)4]Cl·2H2O is dark green. See [[water of crystallization]].<ref name=Huheey/>
# '''[[Linkage isomerism]]''' occurs with ligands with more than one type{{clarify|reason=underlying WP articles seem to focus on different elements but somewhat allude to non-equivalent atoms of same element. Need to avoid implying too specific a meaning (may also need to adjust related articles).|date=February 2021}} of donor atom, known as [[ambidentate ligand]]s.<ref name=Jolly>{{cite book |last1=Jolly |first1=William L. |title=Modern Inorganic Chemistry |date=1984 |publisher=McGraw-Hill |isbn=0-07-032760-2 |pages=357–9}}</ref> For example, [[nitrite]] can coordinate through O or N.<ref>Huheey, James E., ''Inorganic Chemistry'' (3rd ed., Harper & Row 1983), p.513–24 {{ISBN|0-06-042987-9}}</ref> One pair of nitrite linkage isomers have structures (NH3)5CoNO22+ (nitro isomer) and (NH3)5CoONO2+ (nitrito isomer).<ref name=Jolly/>
# '''Coordination isomerism''' – this occurs when both positive and negative ions of a salt are complex ions and the two isomers differ in the distribution of ligands between the cation and the anion. For example, [Co(NH3)6][Cr(CN)6] and [Cr(NH3)6][Co(CN)6].<ref name=Huheey/>

==Electronic properties==
Many of the properties of transition metal complexes are dictated by their electronic structures. The electronic structure can be described by a relatively ionic model that ascribes formal charges to the metals and ligands. This approach is the essence of [[crystal field theory]] (CFT). Crystal field theory, introduced by [[Hans Bethe]] in 1929, gives a [[quantum mechanics|quantum mechanically]] based attempt at understanding complexes. But crystal field theory treats all interactions in a complex as ionic and assumes that the ligands can be approximated by negative point charges.

More sophisticated models embrace covalency, and this approach is described by [[ligand field theory]] (LFT) and [[Molecular orbital theory]] (MO). Ligand field theory, introduced in 1935 and built from molecular orbital theory, can handle a broader range of complexes and can explain complexes in which the interactions are [[covalent]]. The chemical applications of [[group theory]] can aid in the understanding of crystal or ligand field theory, by allowing simple, symmetry based solutions to the formal equations.

Chemists tend to employ the simplest model required to predict the properties of interest; for this reason, CFT has been a favorite for the discussions when possible. MO and LF theories are more complicated, but provide a more realistic perspective.

The electronic configuration of the complexes gives them some important properties:

[[File:Copper complex.jpg|thumb|Synthesis of copper(II)-tetraphenylporphyrin, a metal complex, from [[tetraphenylporphyrin]] and [[copper(II) acetate monohydrate]].]]

===Color of transition metal complexes===
Transition metal complexes often have spectacular colors caused by electronic transitions by the absorption of light. For this reason they are often applied as [[Pigment#Physical basis|pigments]]. Most transitions that are related to colored metal complexes are either d–d transitions or [[charge transfer band]]s. In a d–d transition, an electron in a d orbital on the metal is excited by a photon to another d orbital of higher energy, therefore d–d transitions occur only for partially-filled d-orbital complexes (d1–9). For complexes having d0 or d10 configuration, charge transfer is still possible even though d–d transitions are not. A charge transfer band entails promotion of an electron from a metal-based orbital into an empty ligand-based orbital ([[Charge transfer complex|metal-to-ligand charge transfer]] or MLCT). The converse also occurs: excitation of an electron in a ligand-based orbital into an empty metal-based orbital ([[Charge transfer complex|ligand-to-metal charge transfer]] or LMCT). These phenomena can be observed with the aid of electronic spectroscopy; also known as [[UV-Vis]].<ref>{{cite book |last1= Harris |first1= D. |last2= Bertolucci |first2= M. |title= Symmetry and Spectroscopy |year= 1989 |publisher= Dover Publications | isbn= 9780486661445 }}</ref> For simple compounds with high symmetry, the d–d transitions can be assigned using [[Tanabe–Sugano diagram]]s. These assignments are gaining increased support with [[computational chemistry]].

{| class="wikitable"
|+ Colours of Various Example Coordination Complexes
|-
!  
! Fe2+
! Fe3+
! Co2+
! Cu2+
! Al3+
! Cr3+
|-
! [[Metal ions in aqueous solution|Hydrated Ion]]
| style="background: #CBE9AD;" | {{H:title|Hexaaquairon(2+) cation|[Fe(H2O)6]2+|dotted=no}} Pale green {{H:title|Suspended in solution|Solution|dotted=no}}
| style="background: #EAD558;" | {{H:title|Hexaaquairon(3+) cation|[Fe(H2O)6]3+|dotted=no}} Yellow/brown {{H:title|Suspended in solution|Solution|dotted=no}}
| style="background: #FF99CB;" | {{H:title|Hexaaquacobalt(2+) cation|[Co(H2O)6]2+|dotted=no}} Pink {{H:title|Suspended in solution|Solution|dotted=no}}
| style="background: #C7D9F1;" | {{H:title|Hexaaquacopper(2+) cation|[Cu(H2O)6]2+|dotted=no}} Blue {{H:title|Suspended in solution|Solution|dotted=no}}
| style="background: #F2F2F2;" | {{H:title|Hexaaquaaluminium(3+) cation|[Al(H2O)6]3+|dotted=no}} Colourless {{H:title|Suspended in solution|Solution|dotted=no}}
| style="background: #D7E3BD;" | {{H:title|Hexaaquachromium(3+) cation|[Cr(H2O)6]3+|dotted=no}} Green {{H:title|Suspended in solution|Solution|dotted=no}}
|-
! (OH)−, dilute
| style="background: #92D14F;" | {{H:title|Tetraaquadihydroxidoiron|[Fe(H2O)4(OH)2]|dotted=no}} Dark green {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #9B752A;" | {{H:title|Triaquatrihydroxidoiron|[Fe(H2O)3(OH)3]|dotted=no}} Brown {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #8AE5D6;" | {{H:title|Tetraaquadihydroxidocobalt|[Co(H2O)4(OH)2]|dotted=no}} Blue/green {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #8EB2E2;" | {{H:title|Tetraaquadihydroxidocopper|[Cu(H2O)4(OH)2]|dotted=no}} Blue {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #FFFFFF;" | {{H:title|Triaquatrihydroxidoaluminium|[Al(H2O)3(OH)3]|dotted=no}} White {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #76923D;" | {{H:title|Triaquatrihydroxidochromium|[Cr(H2O)3(OH)3]|dotted=no}} Green {{H:title|Precipitates from solution|Precipitate|dotted=no}}
|-
! (OH)−, concentrated
| style="background: #92D14F;" | {{H:title|Tetraaquadihydroxidoiron|[Fe(H2O)4(OH)2]|dotted=no}} Dark green {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #9B752A;" | {{H:title|Triaquatrihydroxidoiron|[Fe(H2O)3(OH)3]|dotted=no}} Brown {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #8AE5D6;" | {{H:title|Tetraaquadihydroxidocobalt|[Co(H2O)4(OH)2]|dotted=no}} Blue/green {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #8EB2E2;" | {{H:title|Tetraaquadihydroxidocopper|[Cu(H2O)4(OH)2]|dotted=no}} Blue {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #FFFFFF;" | {{H:title|Tetrahydroxidoaluminium|[Al(OH)4]−|dotted=no}} Colourless Solution
| style="background: #C3D59B;" | {{H:title|Hexahydroxidochromate(3−) anion|[Cr(OH)6]3−|dotted=no}} Green {{H:title|Suspended in solution|Solution|dotted=no}}
|-
! NH3, dilute
| style="background: #92D14F;" | {{H:title|Hexaammineiron|[Fe(NH3)6]2+|dotted=no}} Dark green {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #9B752A;" | {{H:title|Hexaammineiron|[Fe(NH3)6]3+|dotted=no}} Brown {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #D3D359;" | {{H:title|Hexaamminecobalt(2+) cation|[Co(NH3)6]2+|dotted=no}} Straw coloured {{H:title|Suspended in solution|Solution|dotted=no}}
| style="background: #548DD4;" | {{H:title|Tetraamminediaquacopper(2+) cation|[Cu(NH3)4(H2O)2]2+|dotted=no}} Deep blue {{H:title|Suspended in solution|Solution|dotted=no}}
| style="background: #FFFFFF;" | {{H:title|Triamminealuminium|[Al(NH3)3]3+|dotted=no}} White {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #CC0099;" | {{H:title|hexaamminechromium(3+) cation|[Cr(NH3)6]3+|dotted=no}} Purple {{H:title|Suspended in solution|Solution|dotted=no}}
|-
! NH3, concentrated
| style="background: #92D14F;" | {{H:title|Hexaammineiron|[Fe(NH3)6]2+|dotted=no}} Dark green {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #9B752A;" | {{H:title|Hexaammineiron|[Fe(NH3)6]3+|dotted=no}} Brown {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #D3D359;" | {{H:title|Hexaamminecobalt(2+) cation|[Co(NH3)6]2+|dotted=no}} Straw coloured {{H:title|Suspended in solution|Solution|dotted=no}}
| style="background: #548DD4;" | {{H:title|Tetraamminediaquacopper(2+) cation|[Cu(NH3)4(H2O)2]2+|dotted=no}} Deep blue {{H:title|Suspended in solution|Solution|dotted=no}}
| style="background: #FFFFFF;" | {{H:title|Triamminealuminium|[Al(NH3)3]3+|dotted=no}} White {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #CC0099;" | {{H:title|hexaamminechromium(3+) cation|[Cr(NH3)6]3+|dotted=no}} Purple {{H:title|Suspended in solution|Solution|dotted=no}}
|-
! (CO3)2-
| style="background: #92D14F;" | {{H:title|Iron(II) carbonate|FeCO3|dotted=no}} Dark green {{H:title|Precipitates from solution|Precipitate|dotted=no}}
| style="background: #9B752A;" | {{H:title|Iron(III) carbonate|Fe2(CO3)3|dotted=no}} Brown {{H:title|Precipitates from solution|Precipitate+bubbles|dotted=no}}
| style="background: #FF99CB;"| {{H:title|Cobalt(II) carbonate|CoCO3|dotted=no}} Pink {{H:title|Precipitates from solution with an effervescence of Carbon Dioxide|Precipitate|dotted=no}}
| style="background: #8AE5D6;" | {{H:title|Copper(II) carbonate|CuCO3|dotted=no}} Blue/green {{H:title|Precipitates from solution|Precipitate|dotted=no}}
|}

===Colors of lanthanide complexes===
Superficially [[lanthanide]] complexes are similar to those of the transition metals in that some are colored. However, for the common Ln3+ ions (Ln = lanthanide) the colors are all pale, and hardly influenced by the nature of the ligand. The colors are due to 4f electron transitions. As the 4f orbitals in lanthanides are "buried" in the xenon core and shielded from the ligand by the 5s and 5p orbitals they are therefore not influenced by the ligands to any great extent leading to a much smaller [[Crystal field theory|crystal field]] splitting than in the transition metals. The absorption spectra of an Ln3+ ion approximates to that of the free ion where the electronic states are described by [[Angular momentum coupling#Spin-orbit coupling|spin-orbit coupling]]. This contrasts to the transition metals where the ground state is split by the crystal field. Absorptions for Ln3+ are weak as electric dipole transitions are parity forbidden ([[Laporte rule|Laporte forbidden]]) but can gain intensity due to the effect of a low-symmetry ligand field or mixing with higher electronic states (''e.g.'' d orbitals). f-f absorption bands are extremely sharp which contrasts with those observed for transition metals which generally have broad bands.<ref name = "C&W6th">{{Cotton&Wilkinson6th}}</ref><ref name=CottonSA2006>{{cite book |last=Cotton |first=Simon |year=2006 |title=Lanthanide and Actinide Chemistry|publisher= John Wiley & Sons Ltd}}</ref> This can lead to extremely unusual effects, such as significant color changes under different forms of lighting.

===Magnetism===
{{main|magnetochemistry}}
Metal complexes that have unpaired electrons are [[magnetic]]. Considering only monometallic complexes, unpaired electrons arise because the complex has an odd number of electrons or because electron pairing is destabilized. Thus, monomeric Ti(III) species have one "d-electron" and must be [[paramagnetism|(para)magnetic]], regardless of the geometry or the nature of the ligands. Ti(II), with two d-electrons, forms some complexes that have two unpaired electrons and others with none. This effect is illustrated by the compounds TiX2[(CH3)2PCH2CH2P(CH3)2]2: when X = [[Chlorine|Cl]], the complex is paramagnetic ([[high spin|high-spin]] configuration), whereas when X = [[methyl group|CH3]], it is diamagnetic ([[low spin|low-spin]] configuration). It is important to realize that ligands provide an important means of adjusting the [[ground state]] properties.

In bi- and polymetallic complexes, in which the individual centres have an odd number of electrons or that are high-spin, the situation is more complicated. If there is interaction (either direct or through ligand) between the two (or more) metal centres, the electrons may couple ([[Antiferromagnetism|antiferromagnetic coupling]], resulting in a diamagnetic compound), or they may enhance each other ([[Ferromagnetism|ferromagnetic coupling]]). When there is no interaction, the two (or more) individual metal centers behave as if in two separate molecules.

===Reactivity===
Complexes show a variety of possible reactivities:<ref>R. G. Wilkins Kinetics and Mechanism of Reactions of Transition Metal Complexes, 2nd Edition, VCH, Weinheim, 1991. {{ISBN|1-56081-125-0}}</ref>

*Electron transfers
*:[[Electron transfer]] (ET) between metal ions can occur via two distinct mechanisms, [[Inner sphere electron transfer|inner]] and [[outer sphere electron transfer]]s. In an inner sphere reaction, a [[bridging ligand]] serves as a conduit for ET.
*(Degenerate) [[ligand exchange]]
*:One important indicator of reactivity is the rate of degenerate exchange of ligands. For example, the rate of interchange of coordinate water in [M(H2O)6]''n''+ complexes varies over 20 orders of magnitude. Complexes where the ligands are released and rebound rapidly are classified as labile. Such labile complexes can be quite stable thermodynamically. Typical labile metal complexes either have low-charge (Na+), electrons in d-orbitals that are [[antibonding]] with respect to the ligands (Zn2+), or lack covalency (Ln3+, where Ln is any lanthanide). The lability of a metal complex also depends on the high-spin vs. low-spin configurations when such is possible. Thus, high-spin Fe(II) and Co(III) form labile complexes, whereas low-spin analogues are inert. Cr(III) can exist only in the low-spin state (quartet), which is inert because of its high formal oxidation state, absence of electrons in orbitals that are M–L antibonding, plus some "ligand field stabilization" associated with the d3 configuration.
* Associative processes
*:Complexes that have unfilled or half-filled orbitals are often capable of reacting with substrates. Most substrates have a singlet ground-state; that is, they have lone electron pairs (e.g., water, amines, ethers), so these substrates need an empty orbital to be able to react with a metal centre. Some substrates (e.g., molecular oxygen) [[triplet oxygen|have a triplet ground state]], which results that metals with half-filled orbitals have a tendency to react with such substrates (it must be said that the [[dioxygen]] molecule also has lone pairs, so it is also capable to react as a 'normal' Lewis base).

If the ligands around the metal are carefully chosen, the metal can aid in ([[stoichiometric]] or [[catalytic]]) transformations of molecules or be used as a sensor.

==Classification==
Metal complexes, also known as coordination compounds, include virtually all metal compounds.<ref>Exception: metal vapors, [[plasma (physics)|plasma]]s, and [[alloy]]s.</ref> The study of "coordination chemistry" is the study of "inorganic chemistry" of all [[alkali metal|alkali]] and [[alkaline earth metal]]s, [[transition metal]]s, [[lanthanide]]s, [[actinides]], and [[metalloid]]s. Thus, coordination chemistry is the chemistry of the majority of the periodic table. Metals and metal ions exist, in the condensed phases at least, only surrounded by ligands.

The areas of coordination chemistry can be classified according to the nature of the ligands, in broad terms:
*Classical (or "[[Alfred Werner|Werner]] Complexes"): Ligands in classical coordination chemistry bind to metals, almost exclusively, via their [[lone pair]]s of electrons residing on the main-group atoms of the ligand. Typical ligands are H2O, NH3, [[chloride|Cl−]], [[Cyanide|CN−]], [[ethylenediamine|en]]. Some of the simplest members of such complexes are described in [[metal aquo complex]]es, [[metal ammine complex]]es,
:Examples: [Co([[EDTA]])]−, [[Cobalt(III) hexammine chloride|[Co(NH3)6]3+]], [[Potassium ferrioxalate|[Fe(C2O4)3]3-]]
*Organometallic Chemistry: Ligands are organic (alkenes, alkynes, alkyls) as well as "organic-like" ligands such as phosphines, hydride, and CO.
:Example: [[Cyclopentadienyliron dicarbonyl dimer|(C5H5)Fe(CO)2CH3]]
*Bioinorganic Chemistry: Ligands are those provided by nature, especially including the side chains of amino acids, and many [[cofactor (biochemistry)|cofactor]]s such as [[porphyrin]]s.
:Example: [[hemoglobin]] contains [[heme]], a porphyrin complex of iron
:Example: [[chlorophyll]] contains a porphyrin complex of magnesium
:Many natural ligands are "classical" especially including water.
*Cluster Chemistry: Ligands include all of the above as well as other metal ions or atoms as well.
: Example Ru3(CO)12

*In some cases there are combinations of different fields:
:Example: [[Iron-sulfur protein|[Fe4S4(Scysteinyl)4]2−]], in which a cluster is embedded in a biologically active species.

[[Mineralogy]], [[materials science]], and [[solid state chemistry]] – as they apply to metal ions – are subsets of coordination chemistry in the sense that the metals are surrounded by ligands. In many cases these ligands are oxides or sulfides, but the metals are coordinated nonetheless, and the principles and guidelines discussed below apply. In [[water of crystallization|hydrate]]s, at least some of the ligands are water molecules. It is true that the focus of mineralogy, materials science, and solid state chemistry differs from the usual focus of coordination or inorganic chemistry. The former are concerned primarily with polymeric structures, properties arising from a collective effects of many highly interconnected metals. In contrast, coordination chemistry focuses on reactivity and properties of complexes containing individual metal atoms or small ensembles of metal atoms.

==Nomenclature of coordination complexes==
The basic procedure for naming a complex is:
# When naming a complex ion, the ligands are named before the metal ion.
# The ligands' names are given in alphabetical order. Numerical prefixes do not affect the order.
#* Multiple occurring monodentate ligands receive a prefix according to the number of occurrences: ''di-'', ''tri-'', ''tetra-'', ''penta-'', or ''hexa-''.
#* Multiple occurring polydentate ligands (e.g., ethylenediamine, oxalate) receive ''bis-'', ''tris-'', ''tetrakis-'', etc.
#* Anions end in ''o''. This replaces the final 'e' when the anion ends with '-ide', '-ate' or '-ite', e.g. ''chloride'' becomes ''chlorido'' and ''sulfate'' becomes ''sulfato''. Formerly, '-ide' was changed to '-o' (e.g. ''chloro'' and ''cyano''), but this rule has been modified in the 2005 IUPAC recommendations and the correct forms for these ligands are now ''chlorido'' and ''cyanido''.<ref>{{cite web |url= http://www.iupac.org/fileadmin/user_upload/databases/Red_Book_2005.pdf |title= Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005 |at= section 1.6.4 (p. 10-11) |publisher= [[IUPAC]] |access-date= 2016-03-06 |archive-url= https://web.archive.org/web/20141222172055/http://www.iupac.org/fileadmin/user_upload/databases/Red_Book_2005.pdf |archive-date= 2014-12-22 |url-status= dead }}</ref>
#* Neutral ligands are given their usual name, with some exceptions: NH3 becomes ''[[ammine]]''; H2O becomes ''aqua'' or ''aquo''; CO becomes ''carbonyl''; NO becomes ''nitrosyl''.
# Write the name of the central atom/ion. If the complex is an anion, the central atom's name will end in ''-ate'', and its Latin name will be used if available (except for mercury).
# The oxidation state of the central atom is to be specified (when it is one of several possible, or zero), and should be written as a Roman numeral (or 0) enclosed in parentheses.
# Name of the cation should be preceded by the name of anion. (if applicable, as in last example)

Examples:
{|class="wikitable"
!metal
!changed to
|-
|cobalt
|cobaltate
|-
|aluminium
|aluminate
|-
|chromium
|chromate
|-
|vanadium
|vanadate
|-
|copper
|cuprate
|-
|iron
|ferrate
|}

: [Cd(CN)2(en)2] → dicyanidobis(ethylenediamine)cadmium(II)
: [CoCl(NH3)5]SO4 → pentaamminechloridocobalt(III) sulfate
: [Cu(H2O)6] 2+ → hexaaquacopper(II) ion
: [CuCl5NH3]3− → amminepentachloridocuprate(II) ion
: K4[Fe(CN)6] → potassium hexacyanidoferrate(II)
: [NiCl4]2− → tetrachloridonickelate(II) ion (The use of chloro- was removed from IUPAC naming convention)<ref>{{cite web |url= http://www.iupac.org/fileadmin/user_upload/databases/Red_Book_2005.pdf |title= Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005 |at= section 1.6.4 (p. 10-11) |publisher= [[IUPAC]] |access-date= 2016-03-06 |archive-url= https://web.archive.org/web/20141222172055/http://www.iupac.org/fileadmin/user_upload/databases/Red_Book_2005.pdf |archive-date= 2014-12-22 |url-status= dead }}</ref>

The coordination number of ligands attached to more than one metal (bridging ligands) is indicated by a subscript to the Greek symbol [[mu (letter)|μ]] placed before the ligand name. Thus the [[Dimer (chemistry)|dimer]] of [[aluminium trichloride]] is described by Al2Cl4(μ2-Cl)2.

Any anionic group can be electronically stabilized by any cation. An anionic complex can be stabilised by a hydrogen cation, becoming an acidic complex which can dissociate to release the cationic hydrogen. This kind of complex compound has a name with "ic" added after the central metal. For example, H2[Pt(CN)4] has the name tetracyanoplatinic (II) acid.

== Stability constant ==
{{Main|Stability constants of complexes}}

The affinity of metal ions for ligands is described by a stability constant, also called the formation constant, and is represented by the symbol Kf. It is the [[equilibrium constant]] for its assembly from the constituent metal and ligands, and can be calculated accordingly, as in the following example for a simple case:

:xM (aq) + yL (aq) {{eqm}} zZ (aq)

:<math>K_f = \frac{[\text{Z}]^z}{[\text{M}]^x[\text{L}]^y}</math>

where : x, y, and z are the [[stoichiometric]] coefficients of each species. M stands for metal / metal ion , the L for Lewis bases , and finally Z for complex ions. Formation constants vary widely. Large values indicate that the metal has high affinity for the ligand, provided the system is at equilibrium.<ref>{{Cite web|url = http://www2.ucdsb.on.ca/tiss/stretton/CHEM2/solubil8.htm|title = Complex Ion Equilibria}}</ref>

Sometimes the stability constant will be in a different form known as the constant of destability. This constant is expressed as the inverse of the constant of formation and is denoted as Kd = 1/Kf .<ref>{{Cite web|url = http://www2.bakersfieldcollege.edu/wcooper/Chem%20B1B%20Notes%20Fall_09/Chap_17_Solubility_Equilibrium_Notes.pdf|title = Solubility and Complex-ion Equilibria|last = Stretton|first = Tom}}</ref> This constant represents the reverse reaction for the decomposition of a complex ion into its individual metal and ligand components. When comparing the values for Kd, the larger the value, the more unstable the complex ion is.

As a result of these complex ions forming in solutions they also can play a key role in solubility of other compounds. When a complex ion is formed it can alter the concentrations of its components in the solution. For example:

:Ag{{su|p=+|b=(aq)}} + 2NH4OH(aq) {{eqm}} Ag(NH3){{su|b=2|p=+}} + H2O

:AgCl(s) + H2O(l) {{eqm}} Ag{{su|b=(aq)|p=+}} + Cl{{su|b=(aq)|p=−}}

If these reactions both occurred in the same reaction vessel, the solubility of the silver chloride would be increased by the presence of NH4OH because formation of the Diammine argentum(I) complex consumes a significant portion of the free silver ions from the solution. By [[Le Chatelier's principle]], this causes the equilibrium reaction for the dissolving of the silver chloride, which has silver ion as a product, to shift to the right.

This new solubility can be calculated given the values of Kf and Ksp for the original reactions. The solubility is found essentially by combining the two separate equilibria into one combined equilibrium reaction and this combined reaction is the one that determines the new solubility. So Kc, the new solubility constant, is denoted by:
:<math>K_c = K_{sp} K_f</math>


==Application of coordination compounds==
Metals only exist in solution as coordination complexes, it follows then that this class of compounds is useful in a wide variety of ways.

===Bioinorganic chemistry===
In [[bioinorganic chemistry]] and [[bioorganometallic chemistry]], coordination complexes serve either structural or catalytic functions. An estimated 30% of proteins contain metal ions. Examples include the intensely colored [[Vitamin B12|vitamin B12]], the [[Heme|heme group]] in [[hemoglobin]], the [[cytochrome]]s, the [[Chlorin|chlorin group]] in [[chlorophyll]], and [[carboxypeptidase]], a hydrolytic enzyme important in digestion. Another complex ion enzyme is [[catalase]], which decomposes the cell's waste [[hydrogen peroxide]]. Synthetic coordination compounds are also used to bind to proteins and especially nucleic acids (e.g. anticancer drug [[cisplatin]]).

===Industry===
[[Homogeneous catalysis]] is a major application of coordination compounds for the production of organic substances. Processes include [[hydrogenation]], [[hydroformylation]], [[oxidation]]. In one example, a combination of titanium trichloride and triethylaluminium gives rise to [[Ziegler–Natta catalyst]]s, used for the [[polymerization]] of ethylene and propylene to give polymers of great commercial importance as fibers, films, and plastics.

Nickel, cobalt, and copper can be extracted using [[hydrometallurgy|hydrometallurgical processes]] involving complex ions. They are extracted from their ores as [[Metal ammine complex|ammine]] complexes. Metals can also be separated using the selective precipitation and solubility of complex ions. Cyanide is used chiefly for extraction of gold and silver from their ores.

[[Phthalocyanine]] complexes are an important class of pigments.

===Analysis===
At one time, coordination compounds were used to identify the presence of metals in a sample. [[Qualitative inorganic analysis]] has largely been superseded by instrumental methods of analysis such as [[atomic absorption spectroscopy]] (AAS), [[inductively coupled plasma atomic emission spectroscopy]] (ICP-AES) and [[inductively coupled plasma mass spectrometry]] (ICP-MS).

==See also==
{{commons category|Coordination compounds}}
*[[Activated complex]]
*[[IUPAC nomenclature of inorganic chemistry]]
*[[Coordination cage]]
*[[Coordination geometry]]
*[[Coordination isomerism]]
*[[Coordination polymers]], in which coordination complexes are the repeating units.
*[[Inclusion compound]]s
*[[Organometallic chemistry]] deals with a special class of coordination compounds where organic fragments are bonded to a metal at least through one C atom.

==References==
{{reflist|33em}}

==Further reading==
* De Vito, D.; Weber, J. ; Merbach, A. E. “Calculated Volume and Energy Profiles for Water Exchange on t2g 6 Rhodium(III) and Iridium(III) Hexaaquaions: Conclusive Evidence for an Ia Mechanism” Inorganic Chemistry, 2004, Volume 43, pages 858–863. {{doi|10.1021/ic035096n}}
* Zumdahl, Steven S. Chemical Principles, Fifth Edition. New York: Houghton Mifflin, 2005. 943–946, 957. {{OCLC|77760970}}
* Harris, D., Bertolucci, M., ''Symmetry and Spectroscopy''. 1989 New York, Dover Publications

==External links==
{{Wikibooks|A-level Chemistry/OCR (Salters)|Complexes}}
*[http://www.chemistry.wustl.edu/~edudev/LabTutorials/naming_coord_comp.html Naming Coordination Compounds]
*[http://www.wou.edu/las/physci/ch462/tmcolors.htm Transition Metal Complex Colors]

{{Coordination complexes}}
{{BranchesofChemistry}}
{{Authority control}}

{{DEFAULTSORT:Coordination Complex}}
[[Category:Coordination complexes| ]]
[[Category:Inorganic chemistry]]
[[Category:Transition metals]]
[[Category:Coordination chemistry]]

Kia Niro

2020-06-15T19:41:52Z

173.165.237.1: /* Kia Niro EV (electric version) */

{{short description|Hybrid subcompact crossover}}
{{update|date=October 2018}}
{{Infobox automobile
| name = Kia Niro (DE) (MY)
| image = 2017 Kia Niro 3 S-A 1.6.jpg
| caption =
| manufacturer = [[Kia Motors]]
| aka =
| production = 2016–present
| model_years = 2017–present
| assembly = South Korea: [[Hwaseong, Gyeonggi]] ([[List of Kia design and manufacturing facilities#Hwaseong Plant|Hwaseong Plant]])<ref>{{Cite web |url=http://pr.kia.com/en/now/tour/global-plant/hwaseong-plant.do |access-date=2017-02-06 }}{{dead link|date=March 2020|bot=medic}}{{cbignore|bot=medic}}</ref>
| designer = [[Peter Schreyer]]
| class = [[Subcompact car|Subcompact]] [[Crossover (automobile)|crossover SUV]]
| body_style = 5-door [[Sport utility vehicle|SUV]]
| layout = [[Front-engine, front-wheel-drive layout|Front-engine, front-wheel-drive]]
| platform =
| related = [[Kia KX3]] [[Hyundai Ioniq]]
| engine = 1.6 L ''[[Hyundai_Kappa_engine#Kappa_II_GDi|Kappa II]] '' [[Inline-four engine|I4]] (104 hp)
| motor = 43 hp HEV / 60 PHEV / 201 EV
| transmission = 6-speed [[Dual-clutch transmission|dual-clutch]]
| wheelbase = {{convert|2700|mm|in|1|abbr=on}}
| length = {{convert|4355|mm|in|1|abbr=on}}
| width = {{convert|1805|mm|in|1|abbr=on}}
| height = {{convert|1545|mm|in|1|abbr=on}}
| weight = {{convert|1,409–1,434|kg|lb|abbr=on}}
| predecessor =
| successor =
| sp = us
}}

The '''Kia Niro''' is a [[Hybrid vehicle|hybrid]] [[subcompact]] [[Crossover (automobile)|crossover]] manufactured by [[Kia Motors]] since 2016. A plug in version was launched in the [[United Kingdom]] in the end of 2017, and in the [[United States]] in the beginning of 2018,<ref>{{Cite news|url=https://www.greencarreports.com/news/1112520_2018-kia-niro-plug-in-hybrid-goes-on-sale-in-uk|title=2018 Kia Niro Plug-In Hybrid goes on sale in UK|last=Szymkowski|first=Sean|work=Green Car Reports|date=2017-09-07|access-date=2018-03-16|language=en}}</ref><ref>{{Cite news|url=http://www.theadvocate.com/baton_rouge/entertainment_life/cars/article_cb275ee8-1751-11e8-b9e5-6f7aa1a13719.html|title=2018 Kia Niro|last=Wheeler|first=Steve|work=The Advocate|date=2018-02-23|access-date=2018-03-16|language=en}}</ref> with an electric version launched in 2018.<ref>{{Cite news|url=http://www.caradvice.com.au/599202/2018-kia-niro-ev-spied/|title=2018 Kia Niro EV spied {{!}} CarAdvice|work=CarAdvice.com|access-date=2017-11-11|language=en-GB}}</ref><ref>{{Cite news|url=https://www.greencarreports.com/news/1113677_electric-hyundai-kona-kia-niro-production-to-rise-again-report|title=Electric Hyundai Kona, Kia Niro production to rise again: report|work=Green Car Reports|access-date=2017-11-11|language=en}}</ref>

== Development ==

=== Concept (2013) ===
[[File:Festival automobile international 2018 - Kia Niro concept - 004.jpg|thumb|left|Kia Niro Concept at ''Festival Automobile International'' 2018 in Paris]]

The '''Kia Niro''' concept debuted at the [[Frankfurt Auto Show#2013|2013 Frankfurt Auto Show]]. The car, designed almost entirely by [[Peter Schreyer]] at Kia's [[List of Kia design and manufacturing facilities#Kia Design Center Europe|Frankfurt studio]], is a sporty three door subcompact crossover, with [[butterfly doors]] that open into the roof panel.<ref>{{cite web|url=http://www.caranddriver.com/news/kia-niro-concept-photos-and-info-news|title=Kia Niro Concept|last=Meiners|first=Jens|work=[[Car and Driver]]|date=August 29, 2013|accessdate=February 14, 2016}}</ref>

The front wheels are powered by the 1.6 litre ''[[Hyundai Gamma engine#1.6 Gamma T-GDI (G4FJ)|Gamma]]'' [[Inline-four engine|inline-4]] producing {{Convert|160|hp|0|abbr=on}} mated with a seven speed [[Sequential manual transmission|rotary-shifted]] [[dual-clutch transmission]], while a 45 hp electric hybrid system powers the rear wheels when driving in rougher road conditions.<ref>{{cite web|url=http://www.topspeed.com/cars/kia/2013-kia-niro-concept-ar159991.html|title=2013 Kia Niro Concept|last=Cupler|first=Justin|work=Top Speed|date=August 9, 2013|accessdate=February 14, 2016}}</ref><ref name="kia">{{cite web|url=http://www.kia.com/eu/future/kia-urban-concept/|title=2013 Niro Concept|work=[[Kia Motors|Kia]]|accessdate=February 14, 2016}}</ref>

=== KX–3 Concept ===
The '''Kia KX–3''' concept followed at the November 2014 [[Auto Guangzhou|Guangzhou Auto Show]]. Inspired by the earlier Niro concept, it has grown larger in size into a compact SUV, measuring {{convert|167.71|in|mm}} long and {{convert|69.48|in|mm}} wide. A [[turbocharger|turbocharged]] 1.6 litre engine delivers power to all four wheels via a seven speed dual clutch transmission.<ref>{{cite web|url=http://www.topspeed.com/cars/kia/2014-kia-kx3-concept-ar166345.html|title=2014 Kia KX3 Concept|last=Garlitos|first=Kirby|work=Top Speed|date=November 21, 2014|accessdate=February 14, 2016}}</ref>

== Production version ==
The 2017 Kia Niro was unveiled at the [[Chicago Auto Show#2016|2016 Chicago Auto Show]]. A subcompact hybrid utility vehicle, the model's exterior design is marketed as "un hybrid",<ref>{{cite web|url=http://www.autoblog.com/2016/02/11/kia-niro-crossover-chicago-2016/|title=Kia Niro crossover is the company's first dedicated hybrid|last=Joseph|first=Noah|work=Autoblog|date=February 11, 2014|accessdate=February 14, 2016}}</ref> saying it is more conventional than other hybrid cars.<ref>{{cite web|url=https://www.forbes.com/sites/johnmccormick/2016/02/11/green-rules-with-kia-niro-optima-plug-in-hybrid/|title=Green Day For Kia Niro, Optima Plug-In Hybrid|last=McCormick|first=John|work=[[Forbes]]|date=February 11, 2014|accessdate=February 14, 2016}}</ref>

The Niro uses a hybrid powertrain producing altogether 139 hp, and returns a fuel economy of {{convert|43|to|50|mpgus|L/100 km}} by also using lightweight materials, including high strength steel and aluminium.<ref>{{cite web|url=http://www.caranddriver.com/news/2017-kia-niro-hybrid-photos-and-info-news|title=2017 Kia Niro Hybrid Debuts, Spearheading New Green Lineup|last=Wendler|first=Andrew|work=[[Car and Driver]]|date=February 11, 2016|accessdate=February 14, 2016}}</ref><ref>{{cite web|url=http://www.automoblog.net/2017/02/23/2017-kia-niro-hybrid-touring-review/|title=2017 Kia Niro Hybrid Touring Review|work=Automoblog.net|date=February 23, 2017|accessdate=March 2, 2017}}</ref> Its battery has a capacity of 1.56 kWh, and a weight of 33 kg.

A plug in version is offered as well since September 2018, featuring an 8.9 kWh battery.<ref name="Halvorson">{{cite web |last1=Halvorson |first1=Bengt |title=2018 Kia Niro Plug-In Hybrid |url=https://www.caranddriver.com/reviews/2018-kia-niro-plug-in-hybrid-first-drive-review |website=Car and Driver |accessdate=14 September 2018 |language=en}}</ref><ref>{{cite web|url=http://www.topspeed.com/cars/kia/2017-kia-niro-ar169443.html|title=2017 Kia Niro|last=Florea|first=Ciprian|work=Top Speed|date=February 11, 2016|accessdate=February 14, 2016}}</ref> The Kia Niro and Niro Plug in Hybrid form part of Kia hybrid range, that also includes the [[Kia Optima#Plug-in hybrid|Optima Plug-in Hybrid]] and Optima Sportswagon Plug-in Hybrid.<ref>{{Cite web|url=https://www.brayleys.co.uk/kia/new-cars/hybrid|title=Kia Hybrid Cars {{!}} Optima & Niro PHEV|website=www.brayleys.co.uk|language=en-gb|access-date=2017-08-14}}</ref> The Kia Niro went on sale in South Korea on 31 March 2016.<ref>{{Cite web|url=http://www.niroforums.co.uk/viewtopic.php?f=8&t=94|title=Kia Niro Officially Launched in Korea - Kia Niro Forums|website=www.niroforums.co.uk|access-date=2016-06-02}}</ref> In its first month on sale, the Niro hit an all time sales record in the green car market in South Korea, even beating the [[Hyundai Ioniq]].<ref>{{Cite web|url=http://pulsenews.co.kr/view.php?year=2016&no=329865|title=Kia Motors’ Niro hits record high in monthly sales - Pulse by Maeil Business News Korea|last=Park|first=Chang-young|website=pulsenews.co.kr|language=en|date=2016-05-09|access-date=2018-03-16}}</ref>
<gallery widths="200" heights="150">
File:2017 Kia Niro First Edition S-A 1.6 Rear.jpg|MY17–19 (rear view)
File:2019 Kia Niro.jpg|MY20 Facelift (Asia and Europe ver.)
File:2018 Kia Niro 3 PHEV S-A 1.6.jpg|MY18 front view Plug in Hybrid (PHEV)
File:Kia Niro PHEV Back IMG 0274.jpg|MY18 view Plug in Hybrid (PHEV)
</gallery>

=== Engine ===
{| class="wikitable sortable collapsible"
|+Gasoline/Hybrid Engine
!Engine Name!!Trim!!Displacement (bore x stroke)!!Power@rpm, Torque@rpm!!Compression ratio (:1)
|-
|rowspan=3|[[Hyundai_Kappa_engine#Kappa_II_GDi|Kappa II GDi HEV]]||rowspan=3|FE, LX, EX, Touring||{{convert|1579|cc|abbr=on}} ({{convert|72.0|x|97.0|mm|abbr=on}})|| {{convert|104|hp|kW PS|abbr=on}}@5700, {{convert|109|lbft|Nm|0|abbr=on}}@4000||13:1
|-
|electric motor||{{convert|43|hp|kW PS|abbr=on}}1850–2500, {{convert|125|lbft|Nm|0|abbr=on}}@0–1800||na
|-
|combined||{{convert|139|hp|kW PS|abbr=on}}@5700, {{convert|195|lbft|Nm|0|abbr=on}}@4000||13:1
|}

== Kia Niro EV ([[electric car|electric]] version) ==

{{Infobox electric vehicle
| image = File:2019 Kia Niro EV First Edition.jpg
| caption =
| name = Kia Niro EV
| manufacturer = [[Kia Motors]]
| parent_company =
| aka =
| production = 2018–present
| model_years = 2018–present
| assembly =
| designer =
| class = [[Compact car]]
| body_style = 5-door [[hatchback]]
| layout =
| platform =
| related = [[Hyundai Ionic]] EV; [[Hyundai Kona Electric]]; [[Kia Soul EV]]
| motor = {{convert|100|kW|abbr=on}} (39.2kWh) {{convert|150|kW|abbr=on}} (64kWh)
| transmission = direct drive reduction gear
| drivetrain = [[front-wheel drive]]
| battery = 64 [[kWh]] / 39.2 [[kWh]] [[lithium-ion polymer battery]] (Kona Electric) 1.56 [[kWh]] [[lithium-ion polymer battery]] (Niro EV)
| electric_range = {{convert|288|km|abbr=on}} (39.2kWh) {{convert|455|km|abbr=on}} (64kWh)
| wheelbase = {{cvt|2700|mm|in|1}}
| length = {{cvt|4375|mm|in|1}}
| width = {{cvt|1805|mm|in|1}}
| height = {{cvt|1560|mm|in|1}}
| weight = {{cvt|1748|kg|lbs|1}}
| predecessor =
| successor =
}}

An all electric version of the Niro was launched in 2018 at International Electric Vehicle Expo in Korea, named Niro EV in Asia and North America and e-Niro in Europe.{{cn|date=March 2020}}

It shares powertrain and battery configuration with the [[Hyundai Kona|Hyundai Kona Electric.]] Niro EV is available in two battery versions: 39,2 kWh and 64 kWh. The batteries are [[Liquid cooling|liquid-cooled]] lithium ion polymer. Batteries are manufactured/supplied by SK Innovation, which is different than the Kona Electric.{{cn|date=March 2020}}

The 39,2 kWh version is propelled by 100 kW (134 hp) [[Electric motor|permanent-magnet electric motor]] with 395 Nm (291 lb-ft) of torque and can travel up to 288 km (179 mi) on one charge according to [[Worldwide harmonized light vehicles test procedure|WLTP]], while the 64 kWh version offers 455 km (283 mi) of WLTP range and has a more powerful 150 kW (201 hp) motor producing the same amount of torque.<ref>{{Cite web|url=https://evcompare.io//cars/kia/kia_niro_ev_long-range_2018/|title=Kia Niro EV Long-range specs, photos, price, offers and incentives|website=EV Compare.io|language=en|access-date=2019-04-22|archive-url=https://web.archive.org/web/20190418155443/https://evcompare.io/cars/kia/kia_niro_ev_long-range_2018/|archive-date=2019-04-18|url-status=dead}}</ref> Both cars are [[front-wheel drive]]. In the US, the Niro EV has an official EPA range of 239 miles on a full charge.

Both versions have a [[Combined Charging System|CCS]] charge port which enables DC fast charging at up to 100 kW. The on board charger power is 7.2 kW or optionally 11 kW.{{cn|date=March 2020}}

<gallery widths="200" heights="150">
File:Kia Niro EV, Paris Motor Show 2018, IMG 0289.jpg|alt=Kia Niro EV rear view photo|Kia Niro EV rear
</gallery>

=== Safety ===
;Euro NCAP
[[Euro NCAP]] test results for a LHD variant on a registration from 2016:<ref>{{cite web|url=https://www.euroncap.com/en/results/kia/niro/25041 |title=Kia Niro |publisher=Euro NCAP |date= |accessdate=August 11, 2017}}</ref>
{| class="wikitable"
|-
|'''Test'''
|'''Score'''
|'''Points'''
|-
|Overall:
|{{rating|4|5}}
| style="text-align:center;"|
|-
|Adult occupant:
| style="text-align:center;"|83%
| style="text-align:center;"|31.8
|-
|Child occupant:
| style="text-align:center;"|80%
| style="text-align:center;"|39.6
|-
|Pedestrian:
| style="text-align:center;"|57%
| style="text-align:center;"|24.3
|-
|Safety assist:
| style="text-align:center;"|59%
| style="text-align:center;"|7.1
|}

===2016 Guinness World Record===
In December 2016, the Niro officially received a [[Guinness World Records]] title for the lowest fuel consumption by a hybrid vehicle, as it traveled from [[Los Angeles]] to [[New York City]] with a fuel consumption record of 76.6 mpg.<ref>{{cite web |url=http://thekoreancarblog.com/2016/12/21/2017-kia-niro-sets-guinness-world-records-title-lowest-fuel-consumption-hybrid-vehicle/ |title=2017 Kia Niro Sets Guinness World Records' Title for Lowest Fuel Consumption by a Hybrid Vehicle |author=Uceda, Erick |publisher=The Korean Car Blog |date=December 21, 2016 |accessdate=December 22, 2016}}</ref> This record had last been held by the [[Kia Optima#Hybrid version|Kia Optima Hybrid]] in 2011, with a fuel consumption average of 64.55 mpg.<ref>{{cite web |url=https://www.autotrader.com/car-news/volkswagen-passat-tdi-sets-world-record-for-fuel-economy-210689 |title=Volkswagen Passat TDI Sets World Record for Fuel Economy |author=Palermo, Nick |publisher=[[Autotrader.com|Autotrader]] |date=July 2013 |accessdate=September 28, 2017}}</ref>

===Reception===
''[[Popular Mechanics]]'' named the 2019 Kia Niro EV as its 2019 Car of the Year, praising it for its normal looks, 239 miles range, and that it can use [[Volkswagen Group of America]]'s [[Electrify America]] chargers to allow the car to be used on long car trips.<ref>{{Cite web|url=https://www.popularmechanics.com/cars/a27006058/automotive-excellence-2019/|title=The 2019 Popular Mechanics Automotive Excellence Awards|first=Ezra|last=Dyer|date=April 16, 2019|website=Popular Mechanics}}</ref>

== Sales ==
{|class="wikitable"
|-
! Calendar year
! United States<ref>https://www.kiamedia.com/us/en/sales</ref>
|-
| 2017
| 27,237
|-
| 2018
| 28,232
|-
|2019
|24,467
|}

== References ==
{{reflist|30em}}

== External links ==
* {{Official website|http://www.kia.com/worldwide/vehicles/niro.do}}

{{Kia Motors}}
{{Kia North America}}
{{Kia}}

[[Category:Kia vehicles|Niro]]
[[Category:Kia concept vehicles|Niro]]
[[Category:Mini sport utility vehicles]]
[[Category:Crossover sport utility vehicles]]
[[Category:Front-wheel-drive vehicles]]
[[Category:Hybrid vehicles]]
[[Category:2010s cars]]
[[Category:Cars introduced in 2016]]

Kia Niro

2020-06-15T19:36:24Z

173.165.237.1: /* Kia Niro EV (electric version) */

{{short description|Hybrid subcompact crossover}}
{{update|date=October 2018}}
{{Infobox automobile
| name = Kia Niro (DE) (MY)
| image = 2017 Kia Niro 3 S-A 1.6.jpg
| caption =
| manufacturer = [[Kia Motors]]
| aka =
| production = 2016–present
| model_years = 2017–present
| assembly = South Korea: [[Hwaseong, Gyeonggi]] ([[List of Kia design and manufacturing facilities#Hwaseong Plant|Hwaseong Plant]])<ref>{{Cite web |url=http://pr.kia.com/en/now/tour/global-plant/hwaseong-plant.do |access-date=2017-02-06 }}{{dead link|date=March 2020|bot=medic}}{{cbignore|bot=medic}}</ref>
| designer = [[Peter Schreyer]]
| class = [[Subcompact car|Subcompact]] [[Crossover (automobile)|crossover SUV]]
| body_style = 5-door [[Sport utility vehicle|SUV]]
| layout = [[Front-engine, front-wheel-drive layout|Front-engine, front-wheel-drive]]
| platform =
| related = [[Kia KX3]] [[Hyundai Ioniq]]
| engine = 1.6 L ''[[Hyundai_Kappa_engine#Kappa_II_GDi|Kappa II]] '' [[Inline-four engine|I4]] (104 hp)
| motor = 43 hp HEV / 60 PHEV / 201 EV
| transmission = 6-speed [[Dual-clutch transmission|dual-clutch]]
| wheelbase = {{convert|2700|mm|in|1|abbr=on}}
| length = {{convert|4355|mm|in|1|abbr=on}}
| width = {{convert|1805|mm|in|1|abbr=on}}
| height = {{convert|1545|mm|in|1|abbr=on}}
| weight = {{convert|1,409–1,434|kg|lb|abbr=on}}
| predecessor =
| successor =
| sp = us
}}

The '''Kia Niro''' is a [[Hybrid vehicle|hybrid]] [[subcompact]] [[Crossover (automobile)|crossover]] manufactured by [[Kia Motors]] since 2016. A plug in version was launched in the [[United Kingdom]] in the end of 2017, and in the [[United States]] in the beginning of 2018,<ref>{{Cite news|url=https://www.greencarreports.com/news/1112520_2018-kia-niro-plug-in-hybrid-goes-on-sale-in-uk|title=2018 Kia Niro Plug-In Hybrid goes on sale in UK|last=Szymkowski|first=Sean|work=Green Car Reports|date=2017-09-07|access-date=2018-03-16|language=en}}</ref><ref>{{Cite news|url=http://www.theadvocate.com/baton_rouge/entertainment_life/cars/article_cb275ee8-1751-11e8-b9e5-6f7aa1a13719.html|title=2018 Kia Niro|last=Wheeler|first=Steve|work=The Advocate|date=2018-02-23|access-date=2018-03-16|language=en}}</ref> with an electric version launched in 2018.<ref>{{Cite news|url=http://www.caradvice.com.au/599202/2018-kia-niro-ev-spied/|title=2018 Kia Niro EV spied {{!}} CarAdvice|work=CarAdvice.com|access-date=2017-11-11|language=en-GB}}</ref><ref>{{Cite news|url=https://www.greencarreports.com/news/1113677_electric-hyundai-kona-kia-niro-production-to-rise-again-report|title=Electric Hyundai Kona, Kia Niro production to rise again: report|work=Green Car Reports|access-date=2017-11-11|language=en}}</ref>

== Development ==

=== Concept (2013) ===
[[File:Festival automobile international 2018 - Kia Niro concept - 004.jpg|thumb|left|Kia Niro Concept at ''Festival Automobile International'' 2018 in Paris]]

The '''Kia Niro''' concept debuted at the [[Frankfurt Auto Show#2013|2013 Frankfurt Auto Show]]. The car, designed almost entirely by [[Peter Schreyer]] at Kia's [[List of Kia design and manufacturing facilities#Kia Design Center Europe|Frankfurt studio]], is a sporty three door subcompact crossover, with [[butterfly doors]] that open into the roof panel.<ref>{{cite web|url=http://www.caranddriver.com/news/kia-niro-concept-photos-and-info-news|title=Kia Niro Concept|last=Meiners|first=Jens|work=[[Car and Driver]]|date=August 29, 2013|accessdate=February 14, 2016}}</ref>

The front wheels are powered by the 1.6 litre ''[[Hyundai Gamma engine#1.6 Gamma T-GDI (G4FJ)|Gamma]]'' [[Inline-four engine|inline-4]] producing {{Convert|160|hp|0|abbr=on}} mated with a seven speed [[Sequential manual transmission|rotary-shifted]] [[dual-clutch transmission]], while a 45 hp electric hybrid system powers the rear wheels when driving in rougher road conditions.<ref>{{cite web|url=http://www.topspeed.com/cars/kia/2013-kia-niro-concept-ar159991.html|title=2013 Kia Niro Concept|last=Cupler|first=Justin|work=Top Speed|date=August 9, 2013|accessdate=February 14, 2016}}</ref><ref name="kia">{{cite web|url=http://www.kia.com/eu/future/kia-urban-concept/|title=2013 Niro Concept|work=[[Kia Motors|Kia]]|accessdate=February 14, 2016}}</ref>

=== KX–3 Concept ===
The '''Kia KX–3''' concept followed at the November 2014 [[Auto Guangzhou|Guangzhou Auto Show]]. Inspired by the earlier Niro concept, it has grown larger in size into a compact SUV, measuring {{convert|167.71|in|mm}} long and {{convert|69.48|in|mm}} wide. A [[turbocharger|turbocharged]] 1.6 litre engine delivers power to all four wheels via a seven speed dual clutch transmission.<ref>{{cite web|url=http://www.topspeed.com/cars/kia/2014-kia-kx3-concept-ar166345.html|title=2014 Kia KX3 Concept|last=Garlitos|first=Kirby|work=Top Speed|date=November 21, 2014|accessdate=February 14, 2016}}</ref>

== Production version ==
The 2017 Kia Niro was unveiled at the [[Chicago Auto Show#2016|2016 Chicago Auto Show]]. A subcompact hybrid utility vehicle, the model's exterior design is marketed as "un hybrid",<ref>{{cite web|url=http://www.autoblog.com/2016/02/11/kia-niro-crossover-chicago-2016/|title=Kia Niro crossover is the company's first dedicated hybrid|last=Joseph|first=Noah|work=Autoblog|date=February 11, 2014|accessdate=February 14, 2016}}</ref> saying it is more conventional than other hybrid cars.<ref>{{cite web|url=https://www.forbes.com/sites/johnmccormick/2016/02/11/green-rules-with-kia-niro-optima-plug-in-hybrid/|title=Green Day For Kia Niro, Optima Plug-In Hybrid|last=McCormick|first=John|work=[[Forbes]]|date=February 11, 2014|accessdate=February 14, 2016}}</ref>

The Niro uses a hybrid powertrain producing altogether 139 hp, and returns a fuel economy of {{convert|43|to|50|mpgus|L/100 km}} by also using lightweight materials, including high strength steel and aluminium.<ref>{{cite web|url=http://www.caranddriver.com/news/2017-kia-niro-hybrid-photos-and-info-news|title=2017 Kia Niro Hybrid Debuts, Spearheading New Green Lineup|last=Wendler|first=Andrew|work=[[Car and Driver]]|date=February 11, 2016|accessdate=February 14, 2016}}</ref><ref>{{cite web|url=http://www.automoblog.net/2017/02/23/2017-kia-niro-hybrid-touring-review/|title=2017 Kia Niro Hybrid Touring Review|work=Automoblog.net|date=February 23, 2017|accessdate=March 2, 2017}}</ref> Its battery has a capacity of 1.56 kWh, and a weight of 33 kg.

A plug in version is offered as well since September 2018, featuring an 8.9 kWh battery.<ref name="Halvorson">{{cite web |last1=Halvorson |first1=Bengt |title=2018 Kia Niro Plug-In Hybrid |url=https://www.caranddriver.com/reviews/2018-kia-niro-plug-in-hybrid-first-drive-review |website=Car and Driver |accessdate=14 September 2018 |language=en}}</ref><ref>{{cite web|url=http://www.topspeed.com/cars/kia/2017-kia-niro-ar169443.html|title=2017 Kia Niro|last=Florea|first=Ciprian|work=Top Speed|date=February 11, 2016|accessdate=February 14, 2016}}</ref> The Kia Niro and Niro Plug in Hybrid form part of Kia hybrid range, that also includes the [[Kia Optima#Plug-in hybrid|Optima Plug-in Hybrid]] and Optima Sportswagon Plug-in Hybrid.<ref>{{Cite web|url=https://www.brayleys.co.uk/kia/new-cars/hybrid|title=Kia Hybrid Cars {{!}} Optima & Niro PHEV|website=www.brayleys.co.uk|language=en-gb|access-date=2017-08-14}}</ref> The Kia Niro went on sale in South Korea on 31 March 2016.<ref>{{Cite web|url=http://www.niroforums.co.uk/viewtopic.php?f=8&t=94|title=Kia Niro Officially Launched in Korea - Kia Niro Forums|website=www.niroforums.co.uk|access-date=2016-06-02}}</ref> In its first month on sale, the Niro hit an all time sales record in the green car market in South Korea, even beating the [[Hyundai Ioniq]].<ref>{{Cite web|url=http://pulsenews.co.kr/view.php?year=2016&no=329865|title=Kia Motors’ Niro hits record high in monthly sales - Pulse by Maeil Business News Korea|last=Park|first=Chang-young|website=pulsenews.co.kr|language=en|date=2016-05-09|access-date=2018-03-16}}</ref>
<gallery widths="200" heights="150">
File:2017 Kia Niro First Edition S-A 1.6 Rear.jpg|MY17–19 (rear view)
File:2019 Kia Niro.jpg|MY20 Facelift (Asia and Europe ver.)
File:2018 Kia Niro 3 PHEV S-A 1.6.jpg|MY18 front view Plug in Hybrid (PHEV)
File:Kia Niro PHEV Back IMG 0274.jpg|MY18 view Plug in Hybrid (PHEV)
</gallery>

=== Engine ===
{| class="wikitable sortable collapsible"
|+Gasoline/Hybrid Engine
!Engine Name!!Trim!!Displacement (bore x stroke)!!Power@rpm, Torque@rpm!!Compression ratio (:1)
|-
|rowspan=3|[[Hyundai_Kappa_engine#Kappa_II_GDi|Kappa II GDi HEV]]||rowspan=3|FE, LX, EX, Touring||{{convert|1579|cc|abbr=on}} ({{convert|72.0|x|97.0|mm|abbr=on}})|| {{convert|104|hp|kW PS|abbr=on}}@5700, {{convert|109|lbft|Nm|0|abbr=on}}@4000||13:1
|-
|electric motor||{{convert|43|hp|kW PS|abbr=on}}1850–2500, {{convert|125|lbft|Nm|0|abbr=on}}@0–1800||na
|-
|combined||{{convert|139|hp|kW PS|abbr=on}}@5700, {{convert|195|lbft|Nm|0|abbr=on}}@4000||13:1
|}

== Kia Niro EV ([[electric car|electric]] version) ==

{{Infobox electric vehicle
| image = File:2019 Kia Niro EV First Edition.jpg
| caption =
| name = Kia Niro EV
| manufacturer = [[Kia Motors]]
| parent_company =
| aka =
| production = 2018–present
| model_years = 2018–present
| assembly =
| designer =
| class = [[Plug-in hybrid]] [[Compact car]]
| body_style = 5-door [[hatchback]]
| layout =
| platform =
| related =
| motor = {{convert|100|kW|abbr=on}} (39.2kWh) {{convert|150|kW|abbr=on}} (64kWh)
| engine = 1.6-L GDI four-cylinder [[Hyundai Kappa engine|Kappa engine]]
| transmission =
| drivetrain =
| battery = 64 [[kWh]] / 39.2 [[kWh]] [[lithium-ion polymer battery]] (Kona Electric) 1.56 [[kWh]] [[lithium-ion polymer battery]] (Niro EV)
| fuel_capacity =
| range =
| electric_range = {{convert|288|km|abbr=on}} (39.2kWh) {{convert|455|km|abbr=on}} (64kWh)
| wheelbase = {{cvt|2700|mm|in|1}}
| length = {{cvt|4375|mm|in|1}}
| width = {{cvt|1805|mm|in|1}}
| height = {{cvt|1560|mm|in|1}}
| weight = {{cvt|1748|kg|lbs|1}}
| predecessor =
| successor =
}}

An all electric version of the Niro was launched in 2018 at International Electric Vehicle Expo in Korea, named Niro EV in Asia and e-Niro in Europe.{{cn|date=March 2020}}

It shares powertrain and battery configuration with the [[Hyundai Kona|Hyundai Kona Electric.]] Niro EV is available in two battery versions: 39,2 kWh and 64 kWh. The batteries are [[Liquid cooling|liquid-cooled]] lithium ion polymer. Batteries are manufactured/supplied by SK Innovation, which is different than the Kona Electric.{{cn|date=March 2020}}

The 39,2 kWh version is propelled by 100 kW (134 hp) [[Electric motor|permanent-magnet electric motor]] with 395 Nm (291 lb-ft) of torque and can travel up to 288 km (179 mi) on one charge according to [[Worldwide harmonized light vehicles test procedure|WLTP]], while the 64 kWh version offers 455 km (283 mi) of WLTP range and has a more powerful 150 kW (201 hp) motor producing the same amount of torque.<ref>{{Cite web|url=https://evcompare.io//cars/kia/kia_niro_ev_long-range_2018/|title=Kia Niro EV Long-range specs, photos, price, offers and incentives|website=EV Compare.io|language=en|access-date=2019-04-22|archive-url=https://web.archive.org/web/20190418155443/https://evcompare.io/cars/kia/kia_niro_ev_long-range_2018/|archive-date=2019-04-18|url-status=dead}}</ref> Both cars are [[front-wheel drive]]. In the US, the Niro EV has an official EPA range of 239 miles on a full charge.

Both versions have a [[Combined Charging System|CCS]] charge port which enables DC fast charging at up to 100 kW. The on board charger power is 7.2 kW or optionally 11 kW.{{cn|date=March 2020}}

<gallery widths="200" heights="150">
File:Kia Niro EV, Paris Motor Show 2018, IMG 0289.jpg|alt=Kia Niro EV rear view photo|Kia Niro EV rear
</gallery>

=== Safety ===
;Euro NCAP
[[Euro NCAP]] test results for a LHD variant on a registration from 2016:<ref>{{cite web|url=https://www.euroncap.com/en/results/kia/niro/25041 |title=Kia Niro |publisher=Euro NCAP |date= |accessdate=August 11, 2017}}</ref>
{| class="wikitable"
|-
|'''Test'''
|'''Score'''
|'''Points'''
|-
|Overall:
|{{rating|4|5}}
| style="text-align:center;"|
|-
|Adult occupant:
| style="text-align:center;"|83%
| style="text-align:center;"|31.8
|-
|Child occupant:
| style="text-align:center;"|80%
| style="text-align:center;"|39.6
|-
|Pedestrian:
| style="text-align:center;"|57%
| style="text-align:center;"|24.3
|-
|Safety assist:
| style="text-align:center;"|59%
| style="text-align:center;"|7.1
|}

===2016 Guinness World Record===
In December 2016, the Niro officially received a [[Guinness World Records]] title for the lowest fuel consumption by a hybrid vehicle, as it traveled from [[Los Angeles]] to [[New York City]] with a fuel consumption record of 76.6 mpg.<ref>{{cite web |url=http://thekoreancarblog.com/2016/12/21/2017-kia-niro-sets-guinness-world-records-title-lowest-fuel-consumption-hybrid-vehicle/ |title=2017 Kia Niro Sets Guinness World Records' Title for Lowest Fuel Consumption by a Hybrid Vehicle |author=Uceda, Erick |publisher=The Korean Car Blog |date=December 21, 2016 |accessdate=December 22, 2016}}</ref> This record had last been held by the [[Kia Optima#Hybrid version|Kia Optima Hybrid]] in 2011, with a fuel consumption average of 64.55 mpg.<ref>{{cite web |url=https://www.autotrader.com/car-news/volkswagen-passat-tdi-sets-world-record-for-fuel-economy-210689 |title=Volkswagen Passat TDI Sets World Record for Fuel Economy |author=Palermo, Nick |publisher=[[Autotrader.com|Autotrader]] |date=July 2013 |accessdate=September 28, 2017}}</ref>

===Reception===
''[[Popular Mechanics]]'' named the 2019 Kia Niro EV as its 2019 Car of the Year, praising it for its normal looks, 239 miles range, and that it can use [[Volkswagen Group of America]]'s [[Electrify America]] chargers to allow the car to be used on long car trips.<ref>{{Cite web|url=https://www.popularmechanics.com/cars/a27006058/automotive-excellence-2019/|title=The 2019 Popular Mechanics Automotive Excellence Awards|first=Ezra|last=Dyer|date=April 16, 2019|website=Popular Mechanics}}</ref>

== Sales ==
{|class="wikitable"
|-
! Calendar year
! United States<ref>https://www.kiamedia.com/us/en/sales</ref>
|-
| 2017
| 27,237
|-
| 2018
| 28,232
|-
|2019
|24,467
|}

== References ==
{{reflist|30em}}

== External links ==
* {{Official website|http://www.kia.com/worldwide/vehicles/niro.do}}

{{Kia Motors}}
{{Kia North America}}
{{Kia}}

[[Category:Kia vehicles|Niro]]
[[Category:Kia concept vehicles|Niro]]
[[Category:Mini sport utility vehicles]]
[[Category:Crossover sport utility vehicles]]
[[Category:Front-wheel-drive vehicles]]
[[Category:Hybrid vehicles]]
[[Category:2010s cars]]
[[Category:Cars introduced in 2016]]

Copper(II) hydroxide

2020-02-12T19:05:50Z

173.165.237.1: /* Mineral */

{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 451965851
| Name = Copper(II) hydroxide
| ImageFile = Copper(II) hydroxide.JPG
| ImageName = Copper(II) hydroxide
| ImageFile2 =Kristallstruktur Kupfer(II)-hydroxid.png
| IUPACName = Copper(II) hydroxide
| OtherNames = Cupric hydroxide
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 144498
| InChI = 1/Cu.2H2O/h;2*1H2/q+2;;/p-2
| SMILES = [Cu+2].[OH-].[OH-]
| InChIKey = JJLJMEJHUUYSSY-NUQVWONBAH
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/Cu.2H2O/h;2*1H2/q+2;;/p-2
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = JJLJMEJHUUYSSY-UHFFFAOYSA-L
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 20427-59-2
| UNII_Ref = {{fdacite|changed|FDA}}
| UNII = 3314XO9W9A
| PubChem = 164826
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = C18712
}}
|Section2={{Chembox Properties
| Formula = Cu(OH)2
| MolarMass = 97.561 g/mol
| Appearance = Blue or blue-green solid
| Density = 3.368 g/cm3, solid
| Solubility = negligible
| SolubleOther = insoluble in [[ethanol]]; soluble in [[ammonium hydroxide|NH4OH]], [[potassium cyanide|KCN]]
| SolubilityProduct = 2.20 x 10−20<ref>Pradyot Patnaik. ''Handbook of Inorganic Chemicals''. McGraw-Hill, 2002, {{ISBN|0-07-049439-8}}</ref>
| MeltingPtC = 80
| MeltingPt_notes = (decomposes into [[Copper(II) oxide|CuO]])
| BoilingPt =
| MagSus = +1170.0·10−6 cm3/mol
}}
|Section4={{Chembox Thermochemistry
| DeltaHf = −450 kJ·mol−1
| Entropy = 108 J·mol−1·K−1
}}
|Section7={{Chembox Hazards
| ExternalSDS = http://www.sciencelab.com/xMSDS-Cupric_Hydroxide-9923594
| MainHazards = Skin, Eye, & Respiratory Irritant
| NFPA-H = 2
| NFPA-F = 0
| NFPA-R = 0
| FlashPt = Non-flammable
| RPhrases =
| SPhrases =
| LD50 = 1000 mg/kg (oral, rat)
| PEL = TWA 1 mg/m3 (as Cu)<ref name=PGCH>{{PGCH|0150}}</ref>
| REL = TWA 1 mg/m3 (as Cu)<ref name=PGCH/>
| IDLH = TWA 100 mg/m3 (as Cu)<ref name=PGCH/>
}}
|Section8={{Chembox Related
| OtherAnions = [[Copper(II) oxide]] [[Copper(II) carbonate]] [[Copper(II) sulfate]] [[Copper(II) chloride]]
| OtherCations = [[Nickel(II) hydroxide]] [[Zinc hydroxide]] [[Iron(II) hydroxide]] [[Cobalt hydroxide]]
| OtherCompounds = [[Copper(I) oxide]] [[Copper(I) chloride]]
}}
}}

'''Copper(II) hydroxide''' is the [[hydroxide]] of [[copper]] with the [[chemical formula]] of Cu(OH)2. It is a pale greenish blue or bluish green solid. Some forms of copper(II) hydroxide are sold as "stabilized" copper hydroxide, although they likely consist of a mixture of [[copper(II) carbonate]] and hydroxide. Copper hydroxide is a weak base.

==Occurrence==
Copper(II) hydroxide has been known since [[Smelting#Copper and bronze|copper smelting]] began around 5000 BC although the [[alchemy|alchemists]] were probably the first to manufacture it by mixing solutions of [[lye]] (sodium or potassium hydroxide) and [[blue vitriol]] (copper(II) sulfate).<ref>Richard Cowen, [http://www.geology.ucdavis.edu/~cowen/~GEL115/115CH3.html ''Essays on Geology, History, and People'', Chapter 3: "Fire and Metals: Copper"].</ref> Sources of both compounds were available in antiquity.

It was produced on an industrial scale during the 17th and 18th centuries for use in [[pigments]] such as [[blue verditer]] and [[Bremen green]].<ref>Tony Johansen, [http://www.paintmaking.com/historic_pigments.htm ''Historic Artist's Pigments''] {{Webarchive|url=https://web.archive.org/web/20090609114501/http://www.paintmaking.com/historic_pigments.htm |date=2009-06-09 }}. PaintMaking.com. 2006.</ref> These pigments were used in [[ceramics (art)|ceramics]] and [[painting]].<ref>[http://www.naturalpigments.com/detail.asp?PRODUCT_ID=417-11B ''Blue verditer''] {{webarchive|url=https://web.archive.org/web/20070927005127/http://www.naturalpigments.com/detail.asp?PRODUCT_ID=417-11B |date=2007-09-27 }}. Natural Pigments. 2007.</ref>

===Laboratory synthesis===
Copper(II) hydroxide can be produced by adding a [[sodium hydroxide]] to a dilute solution of [[copper(II) sulfate]] (CuSO4·5H2O).<ref name=brauer>O. Glemser and H. Sauer "Copper(II) Hydroxide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1013.</ref> The precipitate produced in this manner, however, often contains water and an appreciable amount of sodium hydroxide impurity. A purer product can be attained if [[ammonium chloride]] is added to the solution beforehand.<ref>{{cite journal|author = Y. Cudennec, A. Lecerf|title = The transformation of Cu(OH)2 into CuO, revisited|journal = Solid State Sciences|volume = 5 |pages = 1471–1474|year = 2003|doi = 10.1016/j.solidstatesciences.2003.09.009}}</ref> Alternatively, copper hydroxide is readily made by [[electrolysis of water]] (containing a little [[electrolyte]] such as [[sodium sulfate]], or [[magnesium sulfate]]) with a copper [[anode]].

===Mineral===
The mineral of the formula Cu(OH)2 is called [[spertiniite]]. Copper(II) hydroxide is rarely found as an uncombined [[mineral]] because it slowly reacts with [[carbon dioxide]] from the atmosphere to form a [[basic copper carbonate|basic copper(II) carbonate]]. Thus copper slowly acquires a dull green coating in moist air by the reaction:
:2 Cu(OH)2 + CO2 → Cu2CO3(OH)2 + H2O
The green material is in principle a 1:1 mole mixture of Cu(OH)2 and CuCO3.<ref>Masterson, W. L., & Hurley, C. N. (2004). ''Chemistry: Principles and Reactions, 5th Ed''. Thomson Learning, Inc. (p 331)"</ref> This [[patina]] forms on [[bronze]] and other copper [[alloy]] statues such as the [[Statue of Liberty]].

==Structure==
The structure of Cu(OH)2 has been determined by [[X-ray crystallography]] The copper center is square pyramidal. Four Cu-O distances in the plane range are 1.96 Å, and the axial Cu-O distance is 2.36 Å. The hydroxide ligands in the plane are either doubly [[bridging ligand|bridging]] or triply bridging.<ref>{{cite journal|journal=Acta Crystallogr.|year=1990|volume=C46|pages=2279–2284|title=Structure of Copper(II) Hydroxide, Cu(OH)2|authors=H. R. Oswald, A. Reller, H. W. Schmalle, E. Dubler|doi=10.1107/S0108270190006230}}</ref>

==Reactions==
It is stable to about 100 °C.<ref name=brauer/>

Copper(II) hydroxide reacts with a solution of [[ammonia]] to form a deep blue solution of [[Metal ammine complex|tetramminecopper]] [Cu(NH3)4]2+ [[complex (chemistry)|complex ion]]. It catalyzes the oxidation of ammonia solutions in presence of dioxygen, giving rise to copper ammine nitrites, such as Cu(NO2)2( NH3)n.<ref>{{cite journal|author = Y. Cudennec|title = Etude cinétique de l'oxydation de l'ammoniac en présence d'ions cuivriques|journal = Comptes Rendus de l'Académie des Sciences, Série IIB |volume = 320 | issue = 6 |pages = 309–316|year = 1995|display-authors=etal}}</ref><ref>{{cite journal|author = Y. Cudennec|title = Synthesis and study of Cu(NO2)2(NH3)4 and Cu(NO2)2(NH3)2|journal = European Journal of Solid State and Inorganic Chemistry|volume = 30 |issue = 1–2 |pages = 77–85|year = 1993|display-authors=etal}}</ref>

Copper(II) hydroxide is mildly [[amphoterism|amphoteric]]. It dissolves slightly in concentrated [[alkali]], forming [Cu(OH)4]2−.<ref>Pauling, Linus (1970). ''General Chemistry''. Dover Publications, Inc. (p 702).</ref><ref name=brauer/>

===Reagent for organic chemistry===
Copper(II) hydroxide has a rather specialized role in [[organic synthesis]]. Often, when it is utilized for this purpose, it is prepared [[In situ#Chemistry and chemical engineering|in situ]] by mixing a soluble copper(II) salt and [[potassium hydroxide]].

It is sometimes used in the synthesis of [[aryl]] [[amine]]s. For example, copper(II) hydroxide catalyzes the reaction of [[ethylenediamine]] with 1-bromoanthraquinone or 1-amino-4-bromoanthraquinone to form 1-((2-aminoethyl)amino)anthraquinone or 1-amino-4-((2-aminoethyl)amino)anthraquinone, respectively:<ref name=Tsuda>{{cite journal|doi=10.1002/047084289X.rc228|author1= Tsuda, T.|title=Copper(II) Hydroxide|journal=Encyclopedia of Reagents for Organic Synthesis|year=2001}}</ref>

:[[File:Ullmann redrawn.tif|600px|center]]

Copper(II) hydroxide also converts acid [[hydrazide]]s to [[carboxylic acids]] at room temperature. This conversion is useful in the synthesis of carboxylic acids in the presence of other fragile [[functional groups]]. The yields are generally excellent as is the case with the production of [[benzoic acid]] and [[octanoic acid]]:<ref name=Tsuda/>

:[[File:Carboxylic acid synthesis .tif|600px|center]]

==Uses==
Copper(II) hydroxide in ammonia solution, known as [[Schweizer's reagent]], possesses the interesting ability to dissolve [[cellulose]]. This property led to it being used in the production of [[rayon]], a [[cellulose fiber]].

It is also used widely in the aquarium industry for its ability to destroy external parasites in fish, including flukes, marine ich, brook and marine velvet, without killing the fish. Although other water-soluble copper compounds can be effective in this role, they generally result in high fish mortality.

Copper(II) hydroxide has been used as an alternative to the [[Bordeaux mixture]], a [[fungicide]] and [[nematicide]].<ref>[http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7481.html ''Bordeaux Mixture'']. UC [[Integrated Pest Management|IPM]] online. 2007.</ref> Such products include Kocide 3000, produced by Kocide L.L.C. Copper(II) hydroxide is also occasionally used as [[ceramic colorants|ceramic colorant]].

Copper(II) hydroxide has been combined with latex paint, making a product designed to control root growth in potted plants. Secondary and lateral roots thrive and expand, resulting in a dense and healthy root system. It was sold under the name Spin Out, which was first introduced by Griffin L.L.C. The rights are now owned by SePRO Corp.<ref>[http://www.sepro.com/default.php "SePRO Corporation"].</ref> It is now sold as Microkote either in a solution you apply yourself, or as treated pots.

==Other copper(II) hydroxides==
[[File:Azurite crystal structure.jpg|thumb|Chemical structure of [[azurite]], one of many copper(II) hydroxides (color code: red = O, green = Cu, gray = C, white = H).<ref>{{cite journal|title=Verfeinerung der Struktur von Azurit, Cu3(OH)2(CO3)2, durch Neutronenbeugung|author1=Zigan, F.|author2=Schuster, H.D.|journal=Zeitschrift für Kristallographie, Kristallgeometrie, Kristallphysik, Kristallchemie|year=1972|volume=135|pages=416–436}}</ref>]]

Together with other components, copper(II) hydroxides are numerous. Several copper(II)-containing [[minerals]] contain hydroxide. Notable examples include [[azurite]], [[malachite]], [[antlerite]], and [[brochantite]]. Azurite (2CuCO3·Cu(OH)2) and malachite (CuCO3·Cu(OH)2) are hydroxy-[[carbonates]], whereas [[antlerite]] (CuSO4·2Cu(OH)2) and [[brochantite]] (CuSO4·3Cu(OH)2) are hydroxy-[[sulfates]].

Many synthetic copper(II) hydroxide derivatives have been investigated.<ref>{{cite journal|author1=Kondinski, A.|author2=Monakhov, K.|year=2017|title=Breaking the Gordian Knot in the Structural Chemistry of Polyoxometalates: Copper(II)–Oxo/Hydroxo Clusters|doi=10.1002/chem.201605876|journal=Chemistry: A European Journal|pmid=28083988|volume=23|pages=7841–7852}}</ref>

==References==
{{Reflist}}

==External links==
{{Commons category|Copper(II) hydroxide}}
*[https://web.archive.org/web/20160303215243/http://www.sciencelab.com/msds.php?msdsId=9923594 Material Safety Data Sheet]

{{Copper compounds}}
{{Hydroxides}}

[[Category:Copper(II) compounds]]
[[Category:Hydroxides]]
[[Category:Oxidizing agents]]
[[Category:Catalysts]]

Ammonium phosphate

2020-02-03T19:19:15Z

173.165.237.1:

{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 428203184
| ImageFile = Ammonium phosphate.png
| ImageFile1 = Triammonium-phosphate-3D-balls.png
| ImageSize1 = 240px
| ImageName1 = Ball-and-stick model of three ammonium cations and one phosphate anion
| Reference = <ref name="hand">
{{cite book | last = Lide | first = David R. | year = 1998
| title = Handbook of Chemistry and Physics
| edition = 87 | volume =
| location = Boca Raton, Florida
| publisher = CRC Press
| isbn = 978-0-8493-0594-8 | pages = 4–42, 5–19}}</ref>
| IUPACName = ammonium phosphate
| OtherNames = triammonium phosphate
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 140090
| InChI = 1/3H3N.H3O4P/c;;;1-5(2,3)4/h3*1H3;(H3,1,2,3,4)
| InChIKey = ZRIUUUJAJJNDSS-UHFFFAOYAA
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/3H3N.H3O4P/c;;;1-5(2,3)4/h3*1H3;(H3,1,2,3,4)
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = ZRIUUUJAJJNDSS-UHFFFAOYSA-N
| CASNo_Comment = {{cascite|correct|CAS}}
| CASNo = 10361-65-6
| EC_number = 269-789-9
| UNII_Ref = {{fdacite|changed|FDA}}
| UNII = 2ZJF06M0I9
| PubChem = 159282
| SMILES = [O-]P([O-])([O-])=O.[NH4+].[NH4+].[NH4+]
}}
|Section2={{Chembox Properties
| Formula = (NH4)3PO4
| Appearance = White, [[tetrahedral]] crystals
| Density =
| MeltingPt =
| BoilingPt =
| Solubility = 58.0 g/100 mL (25 °C)
| MolarMass=149.09 g/mol}}
|Section3={{Chembox Hazards
| GHSPictograms = {{GHS07}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|302|319}}
| PPhrases = {{P-phrases|264|270|280|301+312|305+351+338|330|337+313|501}}
| NFPA-H = 2
| NFPA-F = 0
| NFPA-R = 0
| MainHazards =
| FlashPt =
| AutoignitionPt = }}
|Section4={{Chembox Thermochemistry
| DeltaHf = −1671.9 kJ/mol
| DeltaHc =
| Entropy =
| HeatCapacity = }}
|Section8={{Chembox Related
| OtherCations = [[Trisodium phosphate]] [[Tripotassium phosphate]]
| OtherCompounds = [[Diammonium phosphate]] [[Monoammonium phosphate]]
}}
}}

'''Ammonium phosphate''' is an ammonium [[salt (chemistry)|salt]] of orthophosphoric acid. It is a highly unstable compound with the [[formula]] (NH4)3PO4. Because of its instability, it is elusive and of no commercial value. A related "double salt", (NH4)3PO4.(NH4)2HPO4 is also recognized but is too unstable for practical use. Both triammonium salts evolve ammonia. In contrast to the unstable nature of the triammonium salts, the [[diammonium phosphate]] (NH4)2HPO4 monoammonium salt (NH4)H2PO4, are stable materials that are commonly used as fertilizers to provide plants with fixed nitrogen and phosphorus.<ref name=Ullmann>{{Ullmann|first1=Klaus|last1=Schrödter|first2=Gerhard|last2=Bettermann|first3=Thomas |last3=Staffel|first4=Friedrich|last4=Wahl|first5=Thomas|last5=Klein||first6=Thomas|last6=Hofmann|title=Phosphoric Acid and Phosphates|year=2008|doi=10.1002/14356007.a19_465.pub3}}</ref>

==Preparation of triammonium phosphate==
Triammonium phosphate can be prepared in the laboratory by treating 85% phosphoric acid with 30% ammonia solution:{{cn|date=April 2019}}

:H3PO4 + 3 NH3 → (NH4)3PO4

(NH4)3PO4 is a colorless, crystalline solid. The solid, which has the odor of ammonia, is readily soluble in water. The salt converts to diammonium hydrogen phosphate (NH4)2HPO4.

==See also==
* [[Ammonium polyphosphate]]
* [[Ammonium dihydrogen phosphate|Monoammonium phosphate]]
* [[Diammonium phosphate]]

==References==
{{Reflist}}

[[Category:Phosphates]]
[[Category:Ammonium compounds]]
[[Category:Inorganic fertilizers]]

{{inorganic-compound-stub}}
{{Phosphates}}

Bayer process

2019-12-27T14:58:02Z

173.165.237.1: /* Waste */

The '''Bayer process''' is the principal industrial means of refining [[bauxite]] to produce [[alumina]] (aluminium oxide) and was developed by [[Carl Josef Bayer]]. Bauxite, the most important ore of [[aluminium]], contains only 30–60% [[aluminium oxide]] (Al2O3), the rest being a mixture of [[silica]], various [[iron oxide]]s, and [[titanium dioxide]].<ref>{{cite book |author=Harris, Chris |author2=McLachlan, R. (Rosalie) |author3=Clark, Colin |title=Micro reform – impacts on firms: aluminium case study |publisher=Industry Commission |location=Melbourne |year=1998 |pages= |isbn=978-0-646-33550-6 |oclc= |doi= |accessdate=}}</ref> The aluminium oxide must be purified before it can be refined to aluminium metal.

==Process==
[[File:Bayer-process-en.svg|thumb|right|500 px|The '''Bayer process''']]
Bauxite ore is a mixture of hydrated aluminium oxides and compounds of other elements such as iron. The aluminium compounds in the bauxite may be present as [[gibbsite]] 2(Al(OH)3), [[boehmite]] (γ-AlO(OH)) or [[diaspore]] (α-AlO(OH)); the different forms of the aluminium component and the impurities dictate the extraction conditions. Aluminum oxides and hydroxides are [[amphoteric]], meaning that they are both acidic and basic. The solubility of Al(III) in water is very low but increases substantially at either high or low pH. In the Bayer process, bauxite ore is heated in a [[pressure vessel]] along with a [[sodium hydroxide]] solution (caustic soda) at a temperature of 150 to 200 °C. At these temperatures, the [[aluminium]] is dissolved as [[sodium aluminate]] (primarily [Al(OH)4]−) in an extraction process. After separation of the residue by filtering, gibbsite is precipitated when the liquid is cooled and then [[Seed crystal|seeded]] with fine-grained aluminum hydroxide crystals from previous extractions. The precipitation may take several days without addition of seed crystals.<ref name="Grocott99">{{cite journal |last1=Hind |first1=Andrew R. |last2=Bhargava |first2=Suresh K. |last3=Grocott |first3=Stephen C. |title=The surface chemistry of Bayer process solids: a review |journal=Colloids and Surfaces A: Physicochemical and Engineering Aspects |date=January 1999 |volume=146 |issue=1–3 |pages=359–374 |doi=10.1016/S0927-7757(98)00798-5}}</ref>

The extraction process converts the aluminium oxide in the ore to soluble sodium aluminate, 2NaAlO2, according to the [[chemical equation]]:

:Al2O3 + 2 NaOH → 2 NaAlO2 + H2O

This treatment also dissolves silica, but the other components of bauxite do not dissolve. Sometimes{{when|date=October 2019}} [[lime (material)|lime]] is added at this stage to precipitate the silica as [[calcium silicate]]. The solution is clarified by filtering off the solid impurities, commonly with a rotary sand trap and with the aid of a [[flocculant]] such as [[starch]], to remove the fine particles. The undissolved waste after the aluminium compounds are extracted, [[bauxite tailings]], contains [[iron oxides]], [[silica]], [[calcia]], [[Titanium dioxide|titania]] and some unreacted alumina. The original process was that the [[alkali]]ne solution was cooled and treated by bubbling carbon dioxide through it, a method by which aluminium hydroxide [[precipitation (chemistry)|precipitates]]:

:2 NaAlO2 + 3 H2O + CO2 → 2 Al(OH)3 + [[sodium carbonate|Na2CO3]]

But later, this gave way to seeding the supersaturated solution with high-purity aluminium hydroxide (Al(OH)3) crystal, which eliminated the need for cooling the liquid and was more economically feasible:

:2 H2O + NaAlO2 → Al(OH)3 + NaOH

Some of the aluminium hydroxide produced is used in the manufacture of water treatment chemicals such as [[aluminium sulfate]], PAC ([[Aluminium chlorohydrate|Polyaluminium chloride]]) or sodium aluminate; a significant amount is also used as a filler in rubber and plastics as a fire retardant. Some 90% of the gibbsite produced is converted into [[aluminium oxide]], Al2O3, by heating in [[rotary kiln]]s or fluid flash [[calciner]]s to a temperature in excess of 1000 °C.

:2 [[Aluminium hydroxide|Al(OH)3]] → [[alumina|Al2O3]] + 3 [[water|H2O]]

The left-over, 'spent' sodium aluminate solution is then recycled. Apart from improving the economy of the process, recycling accumulates [[gallium]] and [[vanadium]] impurities in the liquors, so that they can be extracted profitably.

Organic impurities that accumulate during the precipitation of gibbsite may cause various problems, for example high levels of undesirable materials in the gibbsite, discoloration of the liquor and of the gibbsite, losses of the caustic material, and increased viscosity and density of the working fluid.

For bauxites having more than 10% silica, the Bayer process becomes uneconomic because of the formation of insoluble [[sodium aluminium silicate]], which reduces yield, so another process must be chosen.

1.9-3.6 tons of bauxite is required to produce 1 ton of aluminum oxide. This is due to a majority of the aluminum in the ore is dissolved in the process.<ref name="Grocott99" /> Over 90% (95-96%) of the aluminium oxide produced is used in the [[Hall–Héroult process]] to produce aluminium.<ref>{{cite web|title=The Aluminum Smelting Process|url=http://www.aluminum-production.com/important_figures.html|website=Aluminum Production|publisher=aluminumproduction.com|accessdate=12 April 2018}}</ref>

== Waste ==
[[Red mud]] is the waste product that is produced in the digestion of bauxite with sodium hydroxide. It has high calcium and sodium hydroxide content with a complex chemical composition, and accordingly is very caustic and a potential source of pollution. The amount of red mud produced is considerable, and this has led scientists and refiners to seek uses for it. One such use is in ceramic production.
Red mud dries into a fine powder that contains iron, aluminum, calcium and sodium. It becomes a health risk when some plants use the waste to produce aluminum oxides.<ref>{{cite journal|title=The Surface Chemistry of Bayer Process Solids: A Review|journal=Colloids and Surfaces A: Physicochemical and Engineering Aspects|volume=146|issue=1–3|pages=359–374|doi=10.1016/S0927-7757(98)00798-5|year=1999|last1=Hind|first1=Andrew R.|last2=Bhargava|first2=Suresh K.|last3=Grocott|first3=Stephen C.}}</ref>

In the United States, the waste is disposed in large [[Reservoir|impoundments]], a sort of reservoir created by a dam. The impoundments are typically lined with clay or synthetic liners. The US does not approve of the use of the waste due to the dangers it risks to the environment. The EPA identified high levels of arsenic and chromium in some red mud samples.<ref>{{cite web|title=TENORM: Bauxite and Alumina Production Wastes|url=https://www.epa.gov/radiation/tenorm-bauxite-and-alumina-production-wastes|website=www.epa.gov|publisher=United States Environmental Protection Agency|accessdate=12 April 2018|date=2015-04-22}}</ref>

=== Ajka alumina plant accident ===
On October 4, 2010, the Ajka alumina plant in Hungary had an [[Ajka alumina plant accident|incident]] where the western dam of its red mud reservoir collapsed. The reservoir was filled with 700,000 m3 of a mixture of red mud and water with a pH of 12. The mixture was released into the valley of Torna river and flooded parts of the city of Devecser and the villages of Kolontár and Somlóvásárhely. The incident resulted in 10 deaths, more than a hundred injuries, and contamination in lakes and rivers.<ref>{{cite journal|last1=Ruyters|first1=Stefan|last2=Mertens|first2=Jelle|last3=Vassilieva|first3=Elvira|last4=Dehandschutter|first4=Boris|last5=Poffijin|first5=Andre|last6=Smolders|first6=Erik|title=The Red Mud Accident in Ajka (Hungary): Plant Toxicity and Trace Metal Bioavailability in Red Mud Contaminated Soil|journal=Environmental Science & Technology|volume=45|issue=4|pages=1616–1622|doi=10.1021/es104000m|pmid=21204523|year=2011}}</ref>

==History of the Bayer process==
The Bayer process was invented in 1888 by [[Carl Josef Bayer]].<ref name=":0" /> Working in Saint Petersburg, Russia to develop a method for supplying alumina to the textile industry (it was used as a [[mordant]] in dyeing cotton), Bayer discovered in 1887 that the aluminium hydroxide that precipitated from alkaline solution was crystalline and could be easily filtered and washed, while that precipitated from acid medium by neutralization was gelatinous and difficult to wash.<ref name=":0" /> The industrial success of this process caused it to replace the Le Chatelier process which was used to produce alumina from bauxite.<ref name=":0" />

The engineering aspects of the process were improved upon to decrease the cost starting in 1967 in [[Germany]] and [[Czechoslovakia]].<ref name=":0" /> This was done by increasing the heat recovery and using large [[autoclaves]] and precipitation tanks.<ref name=":0" /> To more effectively use energy, [[heat exchangers]] and flash tanks were used and larger reactors decreased the amount of heat lost.<ref name=":0" /> Efficiency was increased by connecting the autoclaves to make operation more efficient.<ref name=":0">{{cite web|title=Bayer's Process for Alumina Production: A Historical Production|url=http://www.scs.illinois.edu/~mainzv/HIST/bulletin_open_access/num17-18/num17-18%20p15-19.pdf|website=scs.illinois.edu|publisher=Fathi Habashi, Laval University|accessdate=6 April 2018}}</ref>

A few years earlier, [[Henri Étienne Sainte-Claire Deville]] in France developed a method for making alumina by heating bauxite in sodium carbonate, Na2CO3, at 1200 °C, leaching the sodium aluminate formed with water, then precipitating aluminium hydroxide by [[carbon dioxide]], CO2, which was then filtered and dried. This process (known as the [[Deville process]]) was abandoned in favor of the Bayer process.

The process began to gain importance in metallurgy together with the invention of the Hall–Héroult electrolytic aluminium process, invented just one year earlier in 1886. Together with the [[Gold cyanidation|cyanidation process]] invented in 1887, the Bayer process marks the birth of the modern field of [[hydrometallurgy]].

Today, the process produces nearly all the world's alumina supply as an intermediate step in aluminium production.

==See also==
{{Wikipedia books|Aluminium}}
*[[Ajka alumina plant accident]]
*[[Deville process]]
*[[Hall–Héroult process]]
*[[History of aluminium]]
{{Clear}}

==References==
<references/>
* {{cite journal | author = Habashi, F. | title = A short history of hydrometallurgy | journal = [[Hydrometallurgy (journal)|Hydrometallurgy]] | volume = 79 | issue = 1–2 | pages = 15–22 | year = 2005 | doi = 10.1016/j.hydromet.2004.01.008}}

{{Extractive metallurgy}}

[[Category:Chemical processes]]
[[Category:Aluminium industry]]
[[Category:Metallurgical processes]]

Insulated-gate bipolar transistor

2019-06-03T14:59:03Z

173.165.237.1: /* History */ Patent formatting. Please note that 419977 is the incorrect patent number as well.

[[Image:IGBT symbol.gif|right|thumb|300px|IGBT schematic symbol]]
An '''insulated-gate bipolar transistor''' ('''IGBT''') is a three-terminal [[power semiconductor device]] primarily used as an electronic switch which, as it was developed, came to combine high efficiency and fast switching. It consists of four alternating layers (P-N-P-N) that are controlled by a metal-oxide-semiconductor (MOS) gate structure without regenerative action. Although the structure of the IGBT is topologically the same as a [[thyristor]] with a 'MOS' gate (MOS gate thyristor), the thyristor action is completely suppressed and only the [[transistor]] action is permitted in the entire device operation range.
It switches electric power in many applications: [[variable-frequency drive]]s (VFDs), [[electric car]]s, trains, variable speed refrigerators, lamp ballasts, air-conditioners and even stereo systems with [[switching amplifier]]s.

Since it is designed to turn on and off rapidly, [[amplifier]]s that use it often synthesize complex waveforms with [[pulse-width modulation]] and [[low-pass filter]]s. In switching applications modern devices feature [[Pulse repetition frequency|pulse repetition rate]]s well into the ultrasonic range—frequencies which are at least ten times the highest audio frequency handled by the device when used as an analog audio amplifier.

{|class="wikitable" style="float:right; margin:0 0 1em 1em;"
|+
!colspan="4" style="background:#ffdead;"|IGBT comparison table <ref>[http://www.electronics-tutorials.ws/power/insulated-gate-bipolar-transistor.html Basic Electronics Tutorials.]</ref>
|+
|- style="font-size:12pt" valign="bottom"
! width="155" height="16" | Device characteristic
! width="135" | Power bipolar
! width="135" | Power MOSFET
! width="135" | IGBT

|- style="font-size:12pt" valign="bottom"
| height="16" | Voltage rating
| High <1kV
| High <1kV
| Very high >1kV

|- style="font-size:12pt" valign="bottom"
| height="16" | Current rating
| High <500A
|High > 500A
| High >500A

|- style="font-size:12pt" valign="bottom"
| height="19" | Input drive
| Current ratio hFE 20-200
| Voltage VGS 3-10 V
| Voltage VGE 4-8 V

|- style="font-size:12pt" valign="bottom"
| height="16" | Input impedance
| Low
| High
| High

|- style="font-size:12pt" valign="bottom"
| height="16" | Output impedance
| Low
| Medium
| Low

|- style="font-size:12pt" valign="bottom"
| height="16" | Switching speed
| Slow (µs)
| Fast (ns)
| Medium

|- style="font-size:12pt" valign="bottom"
| height="16" | Cost
| Low
| Medium
| High

|}

==Device structure==

[[Image:IGBT Cross Section.jpg|right|thumb|Cross-section of a typical IGBT showing internal connection of MOSFET and bipolar device]]

An IGBT cell is constructed similarly to a n-channel vertical-construction [[power MOSFET]], except the n+ drain is replaced with a p+ collector layer, thus forming a vertical PNP [[bipolar junction transistor]].
This additional p+ region creates a cascade connection of a PNP bipolar junction transistor with the surface n-channel [[MOSFET]].

==History==

The first-generation IGBTs of the 1980s and early 1990s were prone to failure through effects such as [[latchup]] (in which the device will not turn off as long as current is flowing) and [[secondary breakdown]] (in which a localized hotspot in the device goes into [[thermal runaway]] and burns the device out at high currents). Second-generation devices were much improved. The current third-generation IGBTs are even better, with speed rivaling MOSFETs, and excellent ruggedness and tolerance of overloads.<ref name="A.Nakagawa 1987">A. Nakagawa et al., "Safe operating area for 1200-V non-latch-up bipolar-mode MOSFETs", IEEE Trans. on Electron Devices, ED-34, pp. 351–355 (1987).</ref> Extremely high pulse ratings of second and third-generation devices also make them useful for generating large power pulses in areas including [[particle physics|particle]] and [[plasma physics]], where they are starting to supersede older devices such as [[thyratron]]s and [[triggered spark gap]]s. High pulse ratings and low prices on the surplus market also make them attractive to the high-voltage hobbyists for controlling large amounts of power to drive devices such as solid-state [[Tesla coil]]s and [[coilgun]]s.

[[Image:IvsV IGBT.png|thumb|right|300px|Static characteristic of an IGBT]]

IGBT mode of operation was first proposed by Yamagami in his Japanese patent S47-21739, which was filed in 1968. This mode of operation was first experimentally reported in the lateral four-layer device (SCR) by B. W. Scharf and J. D. Plummer in 1978.<ref>B. W. Scharf and J. D. Plummer, 1978 IEEE International Solid-State Circuits Conference, SESSION XVI FAM 16.6 "A MOS-Controlled Triac Devices".</ref> This mode of operation was also experimentally discovered in vertical device in 1979 by [[B. Jayant Baliga]].<ref>B. J. Baliga, "ENHANCEMENT- AND DEPLETION-MODE VERTICAL-CHANNEL M.O.S. GATED THYRISTORS" Electronics Letters p. 645 (1979).</ref> The device structure was referred to as a "V-groove MOSFET device with the drain region replaced by a p-type anode region" in this paper and subsequently as "the insulated-gate rectifier" (IGR),<ref name="J. Baliga, pp. 264–267">B. J. Baliga, et al., [http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1482803&tag=1 "The insulated gate rectifier (IGR): A new power switching device"], IEEE International Electron Devices Meeting, Abstract 10.6, pp. 264–267 (1982).</ref> the insulated-gate transistor (IGT),<ref name="J. Baliga, pp. 452–454">B. J. Baliga, [https://archive.is/20130415002638/http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1483543 "Fast-switching insulated gate transistors"], IEEE Electron Device Letters, Vol. EDL-4, pp. 452–454 (1983).</ref> the conductivity-modulated field-effect transistor (COMFET)<ref name=COMFET/> and "bipolar-mode MOSFET".<ref>A. Nakagawa et al., "High voltage bipolar-mode MOSFETs with high current capability", Ext. Abst. of SSDM, pp. 309–312 (1984).</ref>

Plummer filed a patent application for IGBT mode of operation in the four-layer device (SCR) in 1978. USP No. 4199774 was issued in 1980, and B1 Re33209<ref>[http://www.google.com/patents?id=I8EGAAAAEBAJ&dq=Re33209 B1 Re33209 is attached in the pdf file of Re 33209].</ref> was reissued in 1995 for the IGBT mode operation in the four-layer device (SCR).

The IGBT mode of operation in the four-layer device (SCR) switched to thyristor operation if the collector current exceeded the latch-up current, which is known as "holding current" in the well known theory of the thyristor. The development of IGBT was characterized by the efforts to completely suppress the thyristor operation or the latch-up in the four-layer device because the latch-up caused the fatal device failure. The technology of IGBT had, thus, been established when the complete suppression of the latch-up of the parasitic thyristor was achieved as described in the following.

Hans W. Becke and Carl F. Wheatley invented a similar device, for which they filed a patent application in 1980, and which they referred to as "power MOSFET with an anode region".<ref name="U. S. Patent No. 4,364,073">[http://www.google.com/patents?id=0ug5AAAAEBAJ&dq=4,364,073, U. S. Patent No. 4,364,073], Power MOSFET with an Anode Region, issued December 14, 1982 to Hans W. Becke and Carl F. Wheatley.</ref> This patent has been called "the seminal patent of the insulated gate bipolar transistor".<ref>{{cite web | url = http://www.eng.umd.edu/html/news/news_story.php?id=5778 | title = C. Frank Wheatley, Jr., BSEE | work = Innovation Hall of Fame at A. James Clark School of Engineering}}</ref> The patent claimed that "no thyristor action occurs under any device operating conditions". This substantially means that the device exhibits non-latch-up IGBT operation over the entire device operation range.

A. Nakagawa et. al. invented the device design concept of non-latch-up IGBTs in 1984.<ref>A. Nakagawa et al., "Non-latch-up 1200 V 75 A bipolar-mode MOSFET with large ASO", IEEE International Electron Devices Meeting Technical Digest, pp. 860–861 (1984).</ref> The invention<ref>A. Nakagawa, H. Ohashi, Y. Yamaguchi, K. Watanabe and T. Thukakoshi, "Conductivity modulated MOSFET" [http://www.google.com/patents?id=D68DAAAAEBAJ&dq=6025622 US Patent No. 6025622 (Feb. 15, 2000)], No. 5086323 (Feb. 4, 1992) and [http://www.google.com/patents?vid=USPAT4672407 No. 4672407 (Jun. 9, 1987)].</ref> is characterized by the device design setting the device saturation current below the latch-up current, which triggers the parasitic thyristor. This invention realized complete suppression of the parasitic thyristor action, for the first time, because the maximal collector current was limited by the saturation current and never exceeded the latch-up current. After the invention of the device design concept of non-latch-up IGBTs, IGBTs evolved rapidly, and the design of non-latch-up IGBTs became a de facto standard and the patent of non-latch-up IGBTs became the basic IGBT patent of actual devices.

There are two important device concepts concerning IGBTs. First one is the device concept discovered by J. D. Plummer in 1978. US Patent Re.33209 was issued for the device concept. The device proposed by J. D. Plummer is the same structure as a thyristor with a MOS gate. J. D. Plummer discovered and proposed that the device can be used as a transistor although the device operates as a thyristor in higher current density level. J. D. Plummer reported this fact in his technical paper: "A MOS-Controlled Triac Devices" B.W. Scharf and J.D. Plummer, 1978 IEEE International Solid-State Circuits Conference, SESSION XVI FAM 16.6.<ref>"A MOS-Controlled Triac Devices" B.W. Scharf and J.D. Plummer, 1978 IEEE International Solid-State Circuits Conference, SESSION XVI FAM 16.6</ref> The device proposed by J. D. Plummer is referred, here, as “Plummer’s device.” On the other hand, Hans W. Becke invented and proposed, in 1980, another new device in which the thyristor action is completely eliminated under any device operating conditions although the basic device structure is the same as that proposed by J. D. Plummer. The device invented by Hans W. Becke is referred, here, as “Becke’s device” and is described in US Patent 4364073. The difference between “Plummer’s device” and “Becke’s device” is that “Plummer’s device” has the mode of thyristor action in its operation range and “Becke’s device” never has the mode of thyristor action in its entire operation range. This is a critical point, because the thyristor action is the same as so-called “latch-up.” “Latch-up” is the main cause of fatal device failure. Thus, theoretically, “Plummer’s device” never realizes a rugged or strong power device which has a large safe operating area. The large safe operating area can be achieved only after “latch-up” is completely suppressed and eliminated in the entire device operation range. Hence, the invention of the device by Hans W. Becke is decisively more important. And, this is the real IGBT. However, the Becke's patent (US Patent 4364073) did not disclose any measures to realize actual devices.

In the early development stage of IGBT, all the researchers tried to increase the latch-up current itself in order to suppress the latch-up of the parasitic thyristor. However, all these efforts failed because IGBT could conduct enormously large current. Successful suppression of the latch-up was made possible by limiting the maximal collector current, which IGBT could conduct, below the latch-up current by controlling/reducing the saturation current of the inherent MOSFET. This was the concept of non-latch-up IGBT. “Becke’s device” was made possible by the non-latch-up IGBT.

The IGBT is characterized by its ability to simultaneously handle a high voltage and a large current. The product of the voltage and the current density that the IGBT can handle reached more than 5{{E|5}} W/cm2,<ref name="A.Nakagawa 1987"/><ref name="A. Nakagawa pp. 150–153"/> which far exceeded the value, 2{{E|5}} W/cm2, of existing power devices such as bipolar transistors and power MOSFETs. This is a consequence of the large [[safe operating area]] of the IGBT. The IGBT is the most rugged and the strongest power device that ever developed, thus, providing users with easy use of the device and displaced bipolar transistors and even GTOs.
This excellent feature of the IGBT had suddenly emerged when the non-latch-up IGBT was established in 1984 by solving the problem of so-called “latch-up,” which is the main cause of device destruction or device failure. Before that, the developed devices were very weak and were easy to be destroyed because of “latch-up.”

IGBT is defined as a transistor. Thus, the device, which operates in IGBT-mode and switches to thyristor operation in higher current, should not be called as IGBT. Thus, the invention of Plummer, US Pat. No. 419977, RE33209, which is cited above, is not IGBT. MOS gate thyristor is not IGBT, either. Even "IGT" is not actual IGBT, because the switching safe operation area is narrow and limited by latch-up and because the allowable maximal collector current could not be turned-off due to thyristor action of "latch-up." The detailed discussions will be necessary.

==Patent issues in the development of IGBT==

IGBT manufacturers paid the license fee of Becke’s patent.<ref name="U. S. Patent No. 4,364,073"/> Toshiba commercialized “non-latch-up IGBT” in 1985. Stanford University insisted in 1991 that Toshiba’s device infringed US Patent RE33209 of “Plummer’s device.” Toshiba answered that “non-latch-up IGBTs” never latched up in the entire device operation range and thus did not infringe US Patent RE33209 of “Plummer’s patent.” Stanford University never responded after Nov. 1992. Toshiba purchased the license of “Becke’s patent” but never paid any license fee for “Plummer’s device.” Other IGBT manufacturers also paid the license fee for Becke’s patent.

==Practical devices==

Practical devices capable of operating over an extended current range were first reported by Baliga et al. in 1982.<ref name="J. Baliga, pp. 264–267"/> A similar paper was also submitted by J. P. Russel et al. to IEEE Electron Device Letter in 1982.<ref name=COMFET>J.P. Russel et al., [https://archive.is/20130415035324/http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1483393 "The COMFET—A new high conductance MOS-gated device"], IEEE Electron Device Lett., vol. EDL-4, pp. 63–65, 1983</ref> The applications for the device were initially regarded by the [[power electronics]] community to be severely restricted by its slow switching speed and latch-up of the parasitic thyristor structure inherent within the device. However, it was demonstrated by Baliga and also by A. M. Goodman et al. in 1983 that the switching speed could be adjusted over a broad range by using electron irradiation.<ref name="J. Baliga, pp. 452–454"/><ref>A. M. Goodman et al., [https://archive.is/20130415010228/http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1483570 "Improved COMFETs with fast switching speed and high-current capability"], IEEE International Electron Devices Meeting Technical Digest, pp. 79–82,1983</ref> This was followed by demonstration of operation of the device at elevated temperatures by Baliga in 1985.<ref>B. J. Baliga, [http://www.sciencedirect.com/science/article/pii/0038110185900097 "Temperature behavior of insulated gate transistor characteristics"], Solid State Electronics, Vol. 28, pp. 289–297, 1985.</ref> Successful efforts to suppress the latch-up of the parasitic thyristor and the scaling of the voltage rating of the devices at GE allowed the introduction of commercial devices in 1983,<ref>Product of the Year Award: "Insulated Gate Transistor", General Electric Company, Electronics Products, 1983.</ref> which could be utilized for a wide variety of applications. The electrical characteristics of GE's device, IGT D94FQ/FR4, were reported in detail by Marvin W. Smith in the proceedings of PCI April 1984.<ref>Marvin W. Smith, "APPLICATIONS OF INSULATED GATE TRANSISTORS" PCI April 1984 PROCEEDINGS, pp. 121-131, 1984</ref> Marvin W. Smith showed in Fig.12 of the proceedings that turn-off above 10 amperes for gate resistance of 5kOhm and above 5 amperes for gate resistance of 1kOhm was limited by switching safe operating area although IGT D94FQ/FR4 was able to conduct 40 amperes of collector current. Marvin W. Smith also stated that the switching safe operating area was limited by the latch-up of the parasitic thyristor.

Complete suppression of the parasitic thyristor action and the resultant non-latch-up IGBT operation for the entire device operation range was achieved by A. Nakagawa et al. in 1984.<ref>A. Nakagawa et al., "Non-latch-up 1200 V 75 A bipolar-mode MOSFET with large ASO", IEEE International Electron Devices Meeting Technical Digest, pp.860-861,1984.</ref> The non-latch-up design concept was filed for US patents.<ref>A.Nakagawa, H. Ohashi, Y. Yamaguchi, K. Watanabe and T. Thukakoshi, "Conductivity modulated MOSFET" [http://www.google.com/patents?id=D68DAAAAEBAJ&dq=6025622 US Patent No.6025622(Feb.15, 2000)], No.5086323 (Feb.4, 1992) and [http://www.google.com/patents?vid=USPAT4672407 No.4672407(Jun.9, 1987)]</ref> To test the lack of latch-up, the prototype 1200 V IGBTs were directly connected without any loads across a 600 V constant voltage source and were switched on for 25 microseconds. The entire 600 V was dropped across the device and a large short circuit current flowed. The devices successfully withstood this severe condition. This was the first demonstration of so-called "short-circuit-withstanding-capability" in IGBTs. Non-latch-up IGBT operation was ensured, for the first time, for the entire device operation range.<ref name="A. Nakagawa pp. 150–153">A. Nakagawa et al., [https://archive.is/20130415041544/http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1485466 "Experimental and numerical study of non-latch-up bipolar-mode MOSFET characteristics"], IEEE International Electron Devices Meeting Technical Digest, pp. 150–153, 1985</ref> In this sense, the non-latch-up IGBT proposed by Hans W. Becke and Carl F. Wheatley was realized by A. Nakagawa et al. in 1984. Products of non-latch-up IGBTs were first commercialized by Toshiba in 1985. This was the real birth of the present IGBT.

Once the non-latch-up capability was achieved in IGBTs, it was found that IGBTs exhibited very rugged and a very large [[safe operating area]]. It was demonstrated that the product of the operating current density and the collector voltage exceeded the theoretical limit of bipolar transistors, 2{{E|5}} W/cm2, and reached 5{{E|5}} W/cm2.<ref name="A.Nakagawa 1987"/><ref name="A. Nakagawa pp. 150–153"/>

The insulating material is typically made of solid polymers which have issues with degradation. There are developments that use an [[ion gel]] to improve manufacturing and reduce the voltage required.<ref>{{cite web|url=http://www.license.umn.edu/Products/Ion-Gel-as-a-Gate-Insulator-in-Field-Effect-Transistors__Z07062.aspx |title=Ion Gel as a Gate Insulator in Field Effect Transistors |deadurl=yes |archiveurl=https://web.archive.org/web/20111114011218/http://www.license.umn.edu/Products/Ion-Gel-as-a-Gate-Insulator-in-Field-Effect-Transistors__Z07062.aspx |archivedate=2011-11-14 |df= }}</ref>

==Applications and advantages==
The IGBT combines the simple gate-drive characteristics of [[Power MOSFET|MOSFET]]s with the high-current and low-saturation-voltage capability of [[Bipolar junction transistor|bipolar transistor]]s. The IGBT combines an isolated-gate [[field-effect transistor|FET]] for the control input and a bipolar power [[transistor]] as a switch in a single device. The IGBT is used in medium- to high-power applications like [[switched-mode power supplies]], [[traction motor]] control and [[induction heating]]. Large IGBT modules typically consist of many devices in parallel and can have very high current-handling capabilities in the order of hundreds of [[ampere]]s with blocking voltages of {{nowrap|6500 [[volts|V]]}}. These IGBTs can control loads of hundreds of [[kilowatts]].

==Comparison with power MOSFETs==

An IGBT features a significantly lower forward voltage drop compared to a conventional MOSFET in higher blocking voltage rated devices, although, MOSFETS exhibit much lower forward voltage at lower current densities due to the absence of a diode Vf in the IGBT's output BJT. As the blocking voltage rating of both MOSFET and IGBT devices increases, the depth of the n- drift region must increase and the doping must decrease, resulting in roughly square relationship decrease in forward conduction versus blocking voltage capability of the device. By injecting minority carriers (holes) from the collector p+ region into the n- drift region during forward conduction, the resistance of the n- drift region is considerably reduced. However, this resultant reduction in on-state forward voltage comes with several penalties:

* The additional PN junction blocks reverse current flow. This means that unlike a MOSFET, IGBTs cannot conduct in the reverse direction. In bridge circuits, where reverse current flow is needed, an additional diode (called a [[flyback diode|freewheeling diode]]) is placed in parallel (actually [[Antiparallel (electronics)|anti-parallel]]) with the IGBT to conduct current in the opposite direction. The penalty isn't overly severe because at higher voltages, where IGBT usage dominates, discrete diodes have a significantly higher performance than the body diode of a MOSFET.
* The reverse bias rating of the N-drift region to collector P+ diode is usually only of tens of volts, so if the circuit application applies a reverse voltage to the IGBT, an additional series diode must be used.
* The minority carriers injected into the N-drift region take time to enter and exit or recombine at turn-on and turn-off. This results in longer switching times, and hence higher switching loss compared to a power MOSFET.
* The on-state forward voltage drop in IGBTs behaves very differently from power MOSFETS. The MOSFET voltage drop can be modeled as a resistance, with the voltage drop proportional to current. By contrast, the IGBT has a diode-like voltage drop (typically of the order of 2V) increasing only with the [[natural logarithm|log]] of the current. Additionally, MOSFET resistance is typically lower for smaller blocking voltages, so the choice between IGBTs and power MOSFETS will depend on both the blocking voltage and current involved in a particular application.

In general, high voltage, high current and low switching frequencies favor the IGBT while low voltage, low current and high switching frequencies are the domain of the MOSFET.

==IGBT models==
Circuits with IGBTs can be developed and [[computer modeling|modeled]] with various [[electronic circuit simulation|circuit simulating]] computer programs such as [[SPICE]], [[Saber (software)|Saber]], and other programs. To simulate an IGBT circuit, the device (and other devices in the circuit) must have a model which predicts or simulates the device's response to various voltages and currents on their electrical terminals. For more precise simulations the effect of temperature on various parts of the IGBT may be included with the simulation.
Two common methods of modeling are available: [[semiconductor device physics|device physics]]-based model, [[equivalent circuit]]s or macromodels. [[SPICE]] simulates IGBTs using a macromodel that combines an ensemble of components like [[field-effect transistor|FET]]s and [[bipolar junction transistor|BJT]]s in a [[Darlington transistor|Darlington configuration]].{{Citation needed|date=September 2007}} An alternative physics-based model is the Hefner model, introduced by Allen Hefner of the [[National Institute of Standards and Technology]]. Hefner's model is fairly complex that has shown very good results. Hefner's model is described in a 1988 paper and was later extended to a thermo-electrical model which include the IGBT's response to internal heating. This model has been added to a version of the [[Saber (software)|Saber]] simulation software.<ref>{{cite journal |last1= Hefner Jr. |first1 = Allen R Jr |last2= Diebolt |first2= DM |url= http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=321038 |title= An experimentally verified IGBT model implemented in the Saber circuit simulator |publisher= IEEE Transactions on Power Electronics |volume= 9 |issue= 5 |pages= 532–542 |year= 1994 |accessdate= January 2016}}</ref>

 
==IGBT failure mechanisms==
The failure mechanisms of IGBTs includes overstress (O) and wearout (W) separately.

The wearout failures mainly include bias temperature instability (BTI), hot carrier injection (HCI), time-dependent dielectric breakdown (TDDB), electromigration (ECM), solder fatigue, material reconstruction, corrosion. The overstress failure mainly include electrostatic discharge (ESD), latch-up, avalanche, secondary breakdown, wire-bond liftoff and burnout.<ref>{{Cite journal|last=Nishad Patil|first=Jose Celaya, Diganta Das, Kai Goebel, Michael Pecht|date=2009|title=Precursor parameter identification for insulated gate bipolar transistor (IGBT) prognostics|url=|journal=IEEE Transactions on Reliability|volume=58|pages=271-276|via=}}</ref>

== Usage ==

<center>
{| border=0
| valign=top | [[Image:IGBT 3300V 1200A Mitsubishi.jpg|thumb|IGBT module (IGBTs and [[flyback diode|freewheeling diodes]]) with a rated current of {{nowrap|1,200 A}} and a maximum voltage of {{nowrap|3,300 V}}]] || [[Image:IGBT 2441.JPG|thumb|Opened IGBT module with four IGBTs {{nobr|(half of [[H-bridge]])}} rated for {{nowrap|400 A}} {{nowrap|600 V}}]] || [[Image:igbt.jpg|thumb|Small IGBT module, rated up to {{nowrap|30 A}}, up to {{nowrap|900 V}}]] || [[File:CM600DU-24NFH.jpg|thumb|Mitsubishi Electric CM600DU-24NFH IGBT module rated for {{nowrap|600 A}} {{nowrap|1200 V}}, with the cover removed to show the IGBT dies and freewheeling diodes.]]
|}
</center>

==See also==
{{Portal|Electronics}}
* [[Bootstrapping (electronics)|Bootstrapping]]
* [[Current injection technique]]
* [[FGMOS]]
* [[Solar inverter]]

==References==
{{Reflist|30em}}

== Further reading==
* {{cite book |last1=Wintrich |first1= Arendt |last2= Nicolai |first2= Ulrich |last3= Tursky |first3= Werner |last4= Reimann |first4= Tobias |title= Application Manual Power Semiconductors |url= https://www.semikron.com/service-support/application-manual.html |format= PDF-Version |edition= 2nd Revised |year= 2015 |publisher=ISLE Verlag |location=Germany |isbn= 978-3-938843-83-3 |editor-last= Semikron |editor-link= Semikron |access-date= 2019-02-17}}

==External links==
{{Commons category|Insulated_gate_bipolar_transistors|IGBT}}
* [http://www.elec.gla.ac.uk/groups/dev_mod/papers/igbt/igbt.html Device physics information] from the [[University of Glasgow]]
* [http://www.intusoft.com/articles/Igbt.pdf Spice model for IGBT]
* [http://www.powerguru.org/igbt-driver-calculation/ IGBT driver calculation]

{{Electronic component}}
{{Authority control}}

[[Category:Transistor types]]
[[Category:Solid state switches]]
[[Category:Power electronics]]
[[Category:Bipolar transistors]]

Insulated-gate bipolar transistor

2019-06-03T14:52:43Z

173.165.237.1: /* Patent issues in the development of IGBT */ Patent formatting

[[Image:IGBT symbol.gif|right|thumb|300px|IGBT schematic symbol]]
An '''insulated-gate bipolar transistor''' ('''IGBT''') is a three-terminal [[power semiconductor device]] primarily used as an electronic switch which, as it was developed, came to combine high efficiency and fast switching. It consists of four alternating layers (P-N-P-N) that are controlled by a metal-oxide-semiconductor (MOS) gate structure without regenerative action. Although the structure of the IGBT is topologically the same as a [[thyristor]] with a 'MOS' gate (MOS gate thyristor), the thyristor action is completely suppressed and only the [[transistor]] action is permitted in the entire device operation range.
It switches electric power in many applications: [[variable-frequency drive]]s (VFDs), [[electric car]]s, trains, variable speed refrigerators, lamp ballasts, air-conditioners and even stereo systems with [[switching amplifier]]s.

Since it is designed to turn on and off rapidly, [[amplifier]]s that use it often synthesize complex waveforms with [[pulse-width modulation]] and [[low-pass filter]]s. In switching applications modern devices feature [[Pulse repetition frequency|pulse repetition rate]]s well into the ultrasonic range—frequencies which are at least ten times the highest audio frequency handled by the device when used as an analog audio amplifier.

{|class="wikitable" style="float:right; margin:0 0 1em 1em;"
|+
!colspan="4" style="background:#ffdead;"|IGBT comparison table <ref>[http://www.electronics-tutorials.ws/power/insulated-gate-bipolar-transistor.html Basic Electronics Tutorials.]</ref>
|+
|- style="font-size:12pt" valign="bottom"
! width="155" height="16" | Device characteristic
! width="135" | Power bipolar
! width="135" | Power MOSFET
! width="135" | IGBT

|- style="font-size:12pt" valign="bottom"
| height="16" | Voltage rating
| High <1kV
| High <1kV
| Very high >1kV

|- style="font-size:12pt" valign="bottom"
| height="16" | Current rating
| High <500A
|High > 500A
| High >500A

|- style="font-size:12pt" valign="bottom"
| height="19" | Input drive
| Current ratio hFE 20-200
| Voltage VGS 3-10 V
| Voltage VGE 4-8 V

|- style="font-size:12pt" valign="bottom"
| height="16" | Input impedance
| Low
| High
| High

|- style="font-size:12pt" valign="bottom"
| height="16" | Output impedance
| Low
| Medium
| Low

|- style="font-size:12pt" valign="bottom"
| height="16" | Switching speed
| Slow (µs)
| Fast (ns)
| Medium

|- style="font-size:12pt" valign="bottom"
| height="16" | Cost
| Low
| Medium
| High

|}

==Device structure==

[[Image:IGBT Cross Section.jpg|right|thumb|Cross-section of a typical IGBT showing internal connection of MOSFET and bipolar device]]

An IGBT cell is constructed similarly to a n-channel vertical-construction [[power MOSFET]], except the n+ drain is replaced with a p+ collector layer, thus forming a vertical PNP [[bipolar junction transistor]].
This additional p+ region creates a cascade connection of a PNP bipolar junction transistor with the surface n-channel [[MOSFET]].

==History==

The first-generation IGBTs of the 1980s and early 1990s were prone to failure through effects such as [[latchup]] (in which the device will not turn off as long as current is flowing) and [[secondary breakdown]] (in which a localized hotspot in the device goes into [[thermal runaway]] and burns the device out at high currents). Second-generation devices were much improved. The current third-generation IGBTs are even better, with speed rivaling MOSFETs, and excellent ruggedness and tolerance of overloads.<ref name="A.Nakagawa 1987">A. Nakagawa et al., "Safe operating area for 1200-V non-latch-up bipolar-mode MOSFETs", IEEE Trans. on Electron Devices, ED-34, pp. 351–355 (1987).</ref> Extremely high pulse ratings of second and third-generation devices also make them useful for generating large power pulses in areas including [[particle physics|particle]] and [[plasma physics]], where they are starting to supersede older devices such as [[thyratron]]s and [[triggered spark gap]]s. High pulse ratings and low prices on the surplus market also make them attractive to the high-voltage hobbyists for controlling large amounts of power to drive devices such as solid-state [[Tesla coil]]s and [[coilgun]]s.

[[Image:IvsV IGBT.png|thumb|right|300px|Static characteristic of an IGBT]]

IGBT mode of operation was first proposed by Yamagami in his Japanese patent S47-21739, which was filed in 1968. This mode of operation was first experimentally reported in the lateral four-layer device (SCR) by B. W. Scharf and J. D. Plummer in 1978.<ref>B. W. Scharf and J. D. Plummer, 1978 IEEE International Solid-State Circuits Conference, SESSION XVI FAM 16.6 "A MOS-Controlled Triac Devices".</ref> This mode of operation was also experimentally discovered in vertical device in 1979 by [[B. Jayant Baliga]].<ref>B. J. Baliga, "ENHANCEMENT- AND DEPLETION-MODE VERTICAL-CHANNEL M.O.S. GATED THYRISTORS" Electronics Letters p. 645 (1979).</ref> The device structure was referred to as a "V-groove MOSFET device with the drain region replaced by a p-type anode region" in this paper and subsequently as "the insulated-gate rectifier" (IGR),<ref name="J. Baliga, pp. 264–267">B. J. Baliga, et al., [http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1482803&tag=1 "The insulated gate rectifier (IGR): A new power switching device"], IEEE International Electron Devices Meeting, Abstract 10.6, pp. 264–267 (1982).</ref> the insulated-gate transistor (IGT),<ref name="J. Baliga, pp. 452–454">B. J. Baliga, [https://archive.is/20130415002638/http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1483543 "Fast-switching insulated gate transistors"], IEEE Electron Device Letters, Vol. EDL-4, pp. 452–454 (1983).</ref> the conductivity-modulated field-effect transistor (COMFET)<ref name=COMFET/> and "bipolar-mode MOSFET".<ref>A. Nakagawa et al., "High voltage bipolar-mode MOSFETs with high current capability", Ext. Abst. of SSDM, pp. 309–312 (1984).</ref>

Plummer filed a patent application for IGBT mode of operation in the four-layer device (SCR) in 1978. USP No. 4199774 was issued in 1980, and B1 Re33209<ref>[http://www.google.com/patents?id=I8EGAAAAEBAJ&dq=Re33209 B1 Re33209 is attached in the pdf file of Re 33209].</ref> was reissued in 1995 for the IGBT mode operation in the four-layer device (SCR).

The IGBT mode of operation in the four-layer device (SCR) switched to thyristor operation if the collector current exceeded the latch-up current, which is known as "holding current" in the well known theory of the thyristor. The development of IGBT was characterized by the efforts to completely suppress the thyristor operation or the latch-up in the four-layer device because the latch-up caused the fatal device failure. The technology of IGBT had, thus, been established when the complete suppression of the latch-up of the parasitic thyristor was achieved as described in the following.

Hans W. Becke and Carl F. Wheatley invented a similar device, for which they filed a patent application in 1980, and which they referred to as "power MOSFET with an anode region".<ref name="U. S. Patent No. 4,364,073">[http://www.google.com/patents?id=0ug5AAAAEBAJ&dq=4,364,073, U. S. Patent No. 4,364,073], Power MOSFET with an Anode Region, issued December 14, 1982 to Hans W. Becke and Carl F. Wheatley.</ref> This patent has been called "the seminal patent of the insulated gate bipolar transistor".<ref>{{cite web | url = http://www.eng.umd.edu/html/news/news_story.php?id=5778 | title = C. Frank Wheatley, Jr., BSEE | work = Innovation Hall of Fame at A. James Clark School of Engineering}}</ref> The patent claimed that "no thyristor action occurs under any device operating conditions". This substantially means that the device exhibits non-latch-up IGBT operation over the entire device operation range.

A. Nakagawa et. al. invented the device design concept of non-latch-up IGBTs in 1984.<ref>A. Nakagawa et al., "Non-latch-up 1200 V 75 A bipolar-mode MOSFET with large ASO", IEEE International Electron Devices Meeting Technical Digest, pp. 860–861 (1984).</ref> The invention<ref>A. Nakagawa, H. Ohashi, Y. Yamaguchi, K. Watanabe and T. Thukakoshi, "Conductivity modulated MOSFET" [http://www.google.com/patents?id=D68DAAAAEBAJ&dq=6025622 US Patent No. 6025622 (Feb. 15, 2000)], No. 5086323 (Feb. 4, 1992) and [http://www.google.com/patents?vid=USPAT4672407 No. 4672407 (Jun. 9, 1987)].</ref> is characterized by the device design setting the device saturation current below the latch-up current, which triggers the parasitic thyristor. This invention realized complete suppression of the parasitic thyristor action, for the first time, because the maximal collector current was limited by the saturation current and never exceeded the latch-up current. After the invention of the device design concept of non-latch-up IGBTs, IGBTs evolved rapidly, and the design of non-latch-up IGBTs became a de facto standard and the patent of non-latch-up IGBTs became the basic IGBT patent of actual devices.

There are two important device concepts concerning IGBTs. First one is the device concept discovered by J. D. Plummer in 1978. US Patent Re.33209 was issued for the device concept. The device proposed by J. D. Plummer is the same structure as a thyristor with a MOS gate. J. D. Plummer discovered and proposed that the device can be used as a transistor although the device operates as a thyristor in higher current density level. J. D. Plummer reported this fact in his technical paper: "A MOS-Controlled Triac Devices" B.W. Scharf and J.D. Plummer, 1978 IEEE International Solid-State Circuits Conference, SESSION XVI FAM 16.6.<ref>"A MOS-Controlled Triac Devices" B.W. Scharf and J.D. Plummer, 1978 IEEE International Solid-State Circuits Conference, SESSION XVI FAM 16.6</ref> The device proposed by J. D. Plummer is referred, here, as “Plummer’s device.” On the other hand, Hans W. Becke invented and proposed, in 1980, another new device in which the thyristor action is completely eliminated under any device operating conditions although the basic device structure is the same as that proposed by J. D. Plummer. The device invented by Hans W. Becke is referred, here, as “Becke’s device” and is described in US Patent 4364073. The difference between “Plummer’s device” and “Becke’s device” is that “Plummer’s device” has the mode of thyristor action in its operation range and “Becke’s device” never has the mode of thyristor action in its entire operation range. This is a critical point, because the thyristor action is the same as so-called “latch-up.” “Latch-up” is the main cause of fatal device failure. Thus, theoretically, “Plummer’s device” never realizes a rugged or strong power device which has a large safe operating area. The large safe operating area can be achieved only after “latch-up” is completely suppressed and eliminated in the entire device operation range. Hence, the invention of the device by Hans W. Becke is decisively more important. And, this is the real IGBT. However, the Becke's patent (US Patent 4364073) did not disclose any measures to realize actual devices.

In the early development stage of IGBT, all the researchers tried to increase the latch-up current itself in order to suppress the latch-up of the parasitic thyristor. However, all these efforts failed because IGBT could conduct enormously large current. Successful suppression of the latch-up was made possible by limiting the maximal collector current, which IGBT could conduct, below the latch-up current by controlling/reducing the saturation current of the inherent MOSFET. This was the concept of non-latch-up IGBT. “Becke’s device” was made possible by the non-latch-up IGBT.

The IGBT is characterized by its ability to simultaneously handle a high voltage and a large current. The product of the voltage and the current density that the IGBT can handle reached more than 5{{E|5}} W/cm2,<ref name="A.Nakagawa 1987"/><ref name="A. Nakagawa pp. 150–153"/> which far exceeded the value, 2{{E|5}} W/cm2, of existing power devices such as bipolar transistors and power MOSFETs. This is a consequence of the large [[safe operating area]] of the IGBT. The IGBT is the most rugged and the strongest power device that ever developed, thus, providing users with easy use of the device and displaced bipolar transistors and even GTOs.
This excellent feature of the IGBT had suddenly emerged when the non-latch-up IGBT was established in 1984 by solving the problem of so-called “latch-up,” which is the main cause of device destruction or device failure. Before that, the developed devices were very weak and were easy to be destroyed because of “latch-up.”

IGBT is defined as a transistor. Thus, the device, which operates in IGBT-mode and switches to thyristor operation in higher current, should not be called as IGBT. Thus, the invention of Plummer, USP No. 419977, Re33209, which is cited above, is not IGBT. MOS gate thyristor is not IGBT, either. Even "IGT" is not actual IGBT, because the switching safe operation area is narrow and limited by latch-up and because the allowable maximal collector current could not be turned-off due to thyristor action of "latch-up." The detailed discussions will be necessary.

==Patent issues in the development of IGBT==

IGBT manufacturers paid the license fee of Becke’s patent.<ref name="U. S. Patent No. 4,364,073"/> Toshiba commercialized “non-latch-up IGBT” in 1985. Stanford University insisted in 1991 that Toshiba’s device infringed US Patent RE33209 of “Plummer’s device.” Toshiba answered that “non-latch-up IGBTs” never latched up in the entire device operation range and thus did not infringe US Patent RE33209 of “Plummer’s patent.” Stanford University never responded after Nov. 1992. Toshiba purchased the license of “Becke’s patent” but never paid any license fee for “Plummer’s device.” Other IGBT manufacturers also paid the license fee for Becke’s patent.

==Practical devices==

Practical devices capable of operating over an extended current range were first reported by Baliga et al. in 1982.<ref name="J. Baliga, pp. 264–267"/> A similar paper was also submitted by J. P. Russel et al. to IEEE Electron Device Letter in 1982.<ref name=COMFET>J.P. Russel et al., [https://archive.is/20130415035324/http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1483393 "The COMFET—A new high conductance MOS-gated device"], IEEE Electron Device Lett., vol. EDL-4, pp. 63–65, 1983</ref> The applications for the device were initially regarded by the [[power electronics]] community to be severely restricted by its slow switching speed and latch-up of the parasitic thyristor structure inherent within the device. However, it was demonstrated by Baliga and also by A. M. Goodman et al. in 1983 that the switching speed could be adjusted over a broad range by using electron irradiation.<ref name="J. Baliga, pp. 452–454"/><ref>A. M. Goodman et al., [https://archive.is/20130415010228/http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1483570 "Improved COMFETs with fast switching speed and high-current capability"], IEEE International Electron Devices Meeting Technical Digest, pp. 79–82,1983</ref> This was followed by demonstration of operation of the device at elevated temperatures by Baliga in 1985.<ref>B. J. Baliga, [http://www.sciencedirect.com/science/article/pii/0038110185900097 "Temperature behavior of insulated gate transistor characteristics"], Solid State Electronics, Vol. 28, pp. 289–297, 1985.</ref> Successful efforts to suppress the latch-up of the parasitic thyristor and the scaling of the voltage rating of the devices at GE allowed the introduction of commercial devices in 1983,<ref>Product of the Year Award: "Insulated Gate Transistor", General Electric Company, Electronics Products, 1983.</ref> which could be utilized for a wide variety of applications. The electrical characteristics of GE's device, IGT D94FQ/FR4, were reported in detail by Marvin W. Smith in the proceedings of PCI April 1984.<ref>Marvin W. Smith, "APPLICATIONS OF INSULATED GATE TRANSISTORS" PCI April 1984 PROCEEDINGS, pp. 121-131, 1984</ref> Marvin W. Smith showed in Fig.12 of the proceedings that turn-off above 10 amperes for gate resistance of 5kOhm and above 5 amperes for gate resistance of 1kOhm was limited by switching safe operating area although IGT D94FQ/FR4 was able to conduct 40 amperes of collector current. Marvin W. Smith also stated that the switching safe operating area was limited by the latch-up of the parasitic thyristor.

Complete suppression of the parasitic thyristor action and the resultant non-latch-up IGBT operation for the entire device operation range was achieved by A. Nakagawa et al. in 1984.<ref>A. Nakagawa et al., "Non-latch-up 1200 V 75 A bipolar-mode MOSFET with large ASO", IEEE International Electron Devices Meeting Technical Digest, pp.860-861,1984.</ref> The non-latch-up design concept was filed for US patents.<ref>A.Nakagawa, H. Ohashi, Y. Yamaguchi, K. Watanabe and T. Thukakoshi, "Conductivity modulated MOSFET" [http://www.google.com/patents?id=D68DAAAAEBAJ&dq=6025622 US Patent No.6025622(Feb.15, 2000)], No.5086323 (Feb.4, 1992) and [http://www.google.com/patents?vid=USPAT4672407 No.4672407(Jun.9, 1987)]</ref> To test the lack of latch-up, the prototype 1200 V IGBTs were directly connected without any loads across a 600 V constant voltage source and were switched on for 25 microseconds. The entire 600 V was dropped across the device and a large short circuit current flowed. The devices successfully withstood this severe condition. This was the first demonstration of so-called "short-circuit-withstanding-capability" in IGBTs. Non-latch-up IGBT operation was ensured, for the first time, for the entire device operation range.<ref name="A. Nakagawa pp. 150–153">A. Nakagawa et al., [https://archive.is/20130415041544/http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1485466 "Experimental and numerical study of non-latch-up bipolar-mode MOSFET characteristics"], IEEE International Electron Devices Meeting Technical Digest, pp. 150–153, 1985</ref> In this sense, the non-latch-up IGBT proposed by Hans W. Becke and Carl F. Wheatley was realized by A. Nakagawa et al. in 1984. Products of non-latch-up IGBTs were first commercialized by Toshiba in 1985. This was the real birth of the present IGBT.

Once the non-latch-up capability was achieved in IGBTs, it was found that IGBTs exhibited very rugged and a very large [[safe operating area]]. It was demonstrated that the product of the operating current density and the collector voltage exceeded the theoretical limit of bipolar transistors, 2{{E|5}} W/cm2, and reached 5{{E|5}} W/cm2.<ref name="A.Nakagawa 1987"/><ref name="A. Nakagawa pp. 150–153"/>

The insulating material is typically made of solid polymers which have issues with degradation. There are developments that use an [[ion gel]] to improve manufacturing and reduce the voltage required.<ref>{{cite web|url=http://www.license.umn.edu/Products/Ion-Gel-as-a-Gate-Insulator-in-Field-Effect-Transistors__Z07062.aspx |title=Ion Gel as a Gate Insulator in Field Effect Transistors |deadurl=yes |archiveurl=https://web.archive.org/web/20111114011218/http://www.license.umn.edu/Products/Ion-Gel-as-a-Gate-Insulator-in-Field-Effect-Transistors__Z07062.aspx |archivedate=2011-11-14 |df= }}</ref>

==Applications and advantages==
The IGBT combines the simple gate-drive characteristics of [[Power MOSFET|MOSFET]]s with the high-current and low-saturation-voltage capability of [[Bipolar junction transistor|bipolar transistor]]s. The IGBT combines an isolated-gate [[field-effect transistor|FET]] for the control input and a bipolar power [[transistor]] as a switch in a single device. The IGBT is used in medium- to high-power applications like [[switched-mode power supplies]], [[traction motor]] control and [[induction heating]]. Large IGBT modules typically consist of many devices in parallel and can have very high current-handling capabilities in the order of hundreds of [[ampere]]s with blocking voltages of {{nowrap|6500 [[volts|V]]}}. These IGBTs can control loads of hundreds of [[kilowatts]].

==Comparison with power MOSFETs==

An IGBT features a significantly lower forward voltage drop compared to a conventional MOSFET in higher blocking voltage rated devices, although, MOSFETS exhibit much lower forward voltage at lower current densities due to the absence of a diode Vf in the IGBT's output BJT. As the blocking voltage rating of both MOSFET and IGBT devices increases, the depth of the n- drift region must increase and the doping must decrease, resulting in roughly square relationship decrease in forward conduction versus blocking voltage capability of the device. By injecting minority carriers (holes) from the collector p+ region into the n- drift region during forward conduction, the resistance of the n- drift region is considerably reduced. However, this resultant reduction in on-state forward voltage comes with several penalties:

* The additional PN junction blocks reverse current flow. This means that unlike a MOSFET, IGBTs cannot conduct in the reverse direction. In bridge circuits, where reverse current flow is needed, an additional diode (called a [[flyback diode|freewheeling diode]]) is placed in parallel (actually [[Antiparallel (electronics)|anti-parallel]]) with the IGBT to conduct current in the opposite direction. The penalty isn't overly severe because at higher voltages, where IGBT usage dominates, discrete diodes have a significantly higher performance than the body diode of a MOSFET.
* The reverse bias rating of the N-drift region to collector P+ diode is usually only of tens of volts, so if the circuit application applies a reverse voltage to the IGBT, an additional series diode must be used.
* The minority carriers injected into the N-drift region take time to enter and exit or recombine at turn-on and turn-off. This results in longer switching times, and hence higher switching loss compared to a power MOSFET.
* The on-state forward voltage drop in IGBTs behaves very differently from power MOSFETS. The MOSFET voltage drop can be modeled as a resistance, with the voltage drop proportional to current. By contrast, the IGBT has a diode-like voltage drop (typically of the order of 2V) increasing only with the [[natural logarithm|log]] of the current. Additionally, MOSFET resistance is typically lower for smaller blocking voltages, so the choice between IGBTs and power MOSFETS will depend on both the blocking voltage and current involved in a particular application.

In general, high voltage, high current and low switching frequencies favor the IGBT while low voltage, low current and high switching frequencies are the domain of the MOSFET.

==IGBT models==
Circuits with IGBTs can be developed and [[computer modeling|modeled]] with various [[electronic circuit simulation|circuit simulating]] computer programs such as [[SPICE]], [[Saber (software)|Saber]], and other programs. To simulate an IGBT circuit, the device (and other devices in the circuit) must have a model which predicts or simulates the device's response to various voltages and currents on their electrical terminals. For more precise simulations the effect of temperature on various parts of the IGBT may be included with the simulation.
Two common methods of modeling are available: [[semiconductor device physics|device physics]]-based model, [[equivalent circuit]]s or macromodels. [[SPICE]] simulates IGBTs using a macromodel that combines an ensemble of components like [[field-effect transistor|FET]]s and [[bipolar junction transistor|BJT]]s in a [[Darlington transistor|Darlington configuration]].{{Citation needed|date=September 2007}} An alternative physics-based model is the Hefner model, introduced by Allen Hefner of the [[National Institute of Standards and Technology]]. Hefner's model is fairly complex that has shown very good results. Hefner's model is described in a 1988 paper and was later extended to a thermo-electrical model which include the IGBT's response to internal heating. This model has been added to a version of the [[Saber (software)|Saber]] simulation software.<ref>{{cite journal |last1= Hefner Jr. |first1 = Allen R Jr |last2= Diebolt |first2= DM |url= http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=321038 |title= An experimentally verified IGBT model implemented in the Saber circuit simulator |publisher= IEEE Transactions on Power Electronics |volume= 9 |issue= 5 |pages= 532–542 |year= 1994 |accessdate= January 2016}}</ref>

 
==IGBT failure mechanisms==
The failure mechanisms of IGBTs includes overstress (O) and wearout (W) separately.

The wearout failures mainly include bias temperature instability (BTI), hot carrier injection (HCI), time-dependent dielectric breakdown (TDDB), electromigration (ECM), solder fatigue, material reconstruction, corrosion. The overstress failure mainly include electrostatic discharge (ESD), latch-up, avalanche, secondary breakdown, wire-bond liftoff and burnout.<ref>{{Cite journal|last=Nishad Patil|first=Jose Celaya, Diganta Das, Kai Goebel, Michael Pecht|date=2009|title=Precursor parameter identification for insulated gate bipolar transistor (IGBT) prognostics|url=|journal=IEEE Transactions on Reliability|volume=58|pages=271-276|via=}}</ref>

== Usage ==

<center>
{| border=0
| valign=top | [[Image:IGBT 3300V 1200A Mitsubishi.jpg|thumb|IGBT module (IGBTs and [[flyback diode|freewheeling diodes]]) with a rated current of {{nowrap|1,200 A}} and a maximum voltage of {{nowrap|3,300 V}}]] || [[Image:IGBT 2441.JPG|thumb|Opened IGBT module with four IGBTs {{nobr|(half of [[H-bridge]])}} rated for {{nowrap|400 A}} {{nowrap|600 V}}]] || [[Image:igbt.jpg|thumb|Small IGBT module, rated up to {{nowrap|30 A}}, up to {{nowrap|900 V}}]] || [[File:CM600DU-24NFH.jpg|thumb|Mitsubishi Electric CM600DU-24NFH IGBT module rated for {{nowrap|600 A}} {{nowrap|1200 V}}, with the cover removed to show the IGBT dies and freewheeling diodes.]]
|}
</center>

==See also==
{{Portal|Electronics}}
* [[Bootstrapping (electronics)|Bootstrapping]]
* [[Current injection technique]]
* [[FGMOS]]
* [[Solar inverter]]

==References==
{{Reflist|30em}}

== Further reading==
* {{cite book |last1=Wintrich |first1= Arendt |last2= Nicolai |first2= Ulrich |last3= Tursky |first3= Werner |last4= Reimann |first4= Tobias |title= Application Manual Power Semiconductors |url= https://www.semikron.com/service-support/application-manual.html |format= PDF-Version |edition= 2nd Revised |year= 2015 |publisher=ISLE Verlag |location=Germany |isbn= 978-3-938843-83-3 |editor-last= Semikron |editor-link= Semikron |access-date= 2019-02-17}}

==External links==
{{Commons category|Insulated_gate_bipolar_transistors|IGBT}}
* [http://www.elec.gla.ac.uk/groups/dev_mod/papers/igbt/igbt.html Device physics information] from the [[University of Glasgow]]
* [http://www.intusoft.com/articles/Igbt.pdf Spice model for IGBT]
* [http://www.powerguru.org/igbt-driver-calculation/ IGBT driver calculation]

{{Electronic component}}
{{Authority control}}

[[Category:Transistor types]]
[[Category:Solid state switches]]
[[Category:Power electronics]]
[[Category:Bipolar transistors]]

Latch-up

2019-06-03T14:39:04Z

173.165.237.1: /* Preventing latch-up */ Spell out SCR acronym

A '''latch-up''' is a type of [[short circuit]] which can occur in an [[integrated circuit]] (IC). More specifically it is the inadvertent creation of a low-[[Electrical impedance|impedance]] path between the power supply rails of a [[MOSFET]] circuit, triggering a [[parasitic structure]] which disrupts proper functioning of the part, possibly even leading to its destruction due to overcurrent. A [[Power cycling|power cycle]] is required to correct this situation.

A '''single event latch-up''' is a latch-up caused by a [[single event upset]], typically heavy ions or protons from cosmic rays or solar flares.<ref>
R. Koga, K.B. Crawford, S.J. Hansel,
B.M. Johnson, D.D. Lau, S.H. Penzin,
S.D. Pinkerton,
M.C. Maher.
[http://www.ti.com/lit/an/snoa256a/snoa256a.pdf "AN-932 SEU and Latch Up Tolerant Advanced CMOS Technology"].
1994.
</ref><ref>
[http://www.techbriefs.com/component/content/article/1836 "Single-event latch-up protection of integrated circuits"].
2002.
</ref>

The parasitic structure is usually equivalent to a [[thyristor]] (or [[Silicon-controlled rectifier|SCR]]), a [[P-n junction|PNPN]] structure which acts as a PNP and an NPN [[Bipolar junction transistor|transistor]] stacked next to each other. During a latch-up when one of the transistors is conducting, the other one begins conducting too. They both keep each other in saturation for as long as the structure is forward-biased and some current flows through it - which usually means until a power-down. The SCR parasitic structure is formed as a part of the totem-pole [[MOSFET|PMOS and NMOS transistor]] pair on the output drivers of the gates.

The latch-up does not have to happen between the power rails - it can happen at any place where the required parasitic structure exists. A common cause of latch-up is a positive or negative voltage spike on an input or output pin of a digital chip that exceeds the rail voltage by more than a diode drop. Another cause is the supply voltage exceeding the absolute maximum rating, often from a [[Transient (oscillation)|transient]] [[voltage spike|spike]] in the power supply. It leads to a [[avalanche diode|breakdown]] of an internal [[P-n junction|junction]]. This frequently happens in circuits which use multiple supply voltages that do not come up in the required sequence on power-up, leading to voltages on data lines exceeding the input rating of parts that have not yet reached a nominal supply voltage. Latch-ups can also be caused by an [[electrostatic discharge]] event.

[[File:latchup.png|right|thumb|400px|Intrinsic bipolar junction transistors in the CMOS technology]]

Another common cause of latch-ups is [[ionizing radiation]] which makes this a significant issue in electronic products designed for space (or very high-altitude) applications.

High-power microwave interference can also trigger latch ups.<ref>
H. Wang, J. Li, H. Li, K. Xiao and H. Chen.
[http://www.jpier.org/PIER/pier87/19.08100408.pdf "Experimental study and Spice simulation of CMOS inverters latch-up effects due to high power microwave interference"].
2008.
</ref>

Both CMOS integrated circuits and TTL integrated circuits are more susceptible to latch-up at higher temperatures.<ref>
Cooper, M.S.;
Retzler, J.P.
[https://dx.doi.org/10.1109/TNS.1978.4329568 "High Temperature Schottky TTL latch-up"].
doi: 10.1109/TNS.1978.4329568
1978.
</ref>

==CMOS latch-up==

[[File:latchup ckt.png|right|thumb|170px|Equivalent circuit of CMOS latch-up]]

All CMOS ICs have latch-up paths, but there are several design techniques that reduce susceptibility to latch-up.<ref>
[http://large.stanford.edu/courses/2015/ph241/clark2/docs/AN-600.pdf "Understanding Latch-Up in Advanced CMOS Logic"].
quote:
"structures used in all CMOS ICs ... have latch-up paths associated with them"
</ref><ref>
Jerry C. Whitaker.
[https://books.google.com/books?id=n-fh3wIPZbkC "Microelectronics 2nd Edition"].
2005.
p. 7-7 to 7-8.
quote:
"CMOS inverters and gates inherently have ...
parasitic bipolar transistors that form a silicon controlled rectifier (SCR).
Although ... latch-up cannot be avoided,
CMOS manufacturers design input and output circuits that are latch-up resistant"
</ref><ref>
Fairchild.
[https://www.fairchildsemi.com/application-notes/AN/AN-339.pdf "Fairchild's Process Enhancements Eliminate the CMOS SCR Latch-Up Problem In 74HC Logic"].
1998.
</ref>

In CMOS technology, there are a number of intrinsic bipolar junction transistors. In CMOS processes, these transistors can create problems when the combination of n-well/p-well and substrate results in the formation of parasitic n-p-n-p structures. Triggering these thyristor-like devices leads to a shorting of the Vdd and GND lines, usually resulting in destruction of the chip, or a system failure that can only be resolved by power-down. <ref>'''Jan M. Rabaey''', University of California,Berkeley;'''Anantha Chandrakasan''', Massachusetts Institute of Technology,Cambridge;'''Borivoje Nikolic''', University of California, Berkeley; Digital Integrated Circuits (2nd Edition) {{ISBN|978-0-13-090996-1}} </ref>

Consider the n-well structure in the first figure. The n-p-n-p structure is formed by the source of the NMOS, the p-substrate, the n-well and the source of the PMOS. A circuit equivalent is also shown. When one of the two bipolar transistors gets forward biased (due to current flowing through the well, or substrate), it feeds the base of the other transistor. This positive feedback increases the current until the circuit fails or burns out.

The invention of the now industry-standard technique to prevent CMOS latch-up was made by Hughes Aircraft company in 1977.<ref>
[http://www.google.com/patents/US4173767 "Hughes Aircraft Patent US4173767"].
</ref>

== Preventing latch-up ==
It is possible to design chips to be resistant to latch-up by adding a layer of insulating oxide (called a ''trench'') that surrounds both the NMOS and the PMOS transistors. This breaks the parasitic silicon-controlled rectifier (SCR) structure between these transistors. Such parts are important in the cases where the proper sequencing of power and signals cannot be guaranteed, such as [[hot swap]] devices.

Devices fabricated in lightly doped epitaxial layers grown on heavily doped substrates are also less susceptible to latch-up. The heavily doped layer acts as a current sink where excess minority carriers can quickly recombine.<ref>Stephen A. Campbell, The Science and Engineering of Microelectronic Fabrication, Oxford University Press (Indian Edition 2007) p.461 {{ISBN|978-0-19-568144-4}}</ref>

Most [[silicon on insulator|silicon-on-insulator]] devices are inherently latch-up-resistant. Latch-up is the low resistance connection between tub{{Clarify|date=November 2013}} and power supply rails.

Also to avoid the latch, a separate tap connection is put for each transistor. But this will increase the size of the device so fabs give a minimum space to put a tap, for example, 10 µm in 130 nm technology.{{Clarify|date=April 2013}}

== Testing for latch-up ==
* See [[Electronic Industries Alliance|EIA]]/[[JEDEC]] STANDARD '''IC Latch-Up Test''' EIA/JESD78. This standard is commonly referenced in IC [[wikt:qualification|qualification]] specifications.

==References==
{{Reflist}}

== External links ==
* [http://www.ece.drexel.edu/courses/ECE-E431/latch-up/latch-up.html Latch-up in CMOS designs]
* [http://www.analog.com/library/analogDialogue/archives/35-05/latchup/index.html Analog Devices: Winning the battle against latchup in CMOS analog devices]
* [http://www.maxwell.com/products/microelectronics/latchup-protection Maxwell Technologies Microelectronics: Latchup Protection Technology]
* [http://www.eevblog.com/2009/07/04/eevblog-16-all-about-cmos-scr-latchup/ SCR Latchup Video Tutorial]

[[Category:Integrated circuits]]
[[Category:Semiconductor device defects]]

Potassium

2019-04-30T16:35:31Z

173.165.237.1:

{{short description|Chemical element with atomic number 19}}
{{pp-move-indef}}
{{Infobox potassium}}
'''Potassium''' is a [[chemical element]] with symbol '''K''' (from [[New Latin|Neo-Latin]] ''[[wikt:kalium#Latin|kalium]]'') and [[atomic number]] 19. Potassium is a silvery-white metal that is soft enough to be cut with a knife, with little force. <ref>{{cite web |url=https://www.britannica.com/science/potassium |title=Potassium/ Chemical element |last=Augustyn |first=Adam |publisher=Encyclopedia Britannica |accessdate=2019-04-17 |quote=Potassium Physical properties }}</ref> Potassium metal reacts rapidly with atmospheric [[oxygen]] to form flaky white [[potassium peroxide]] in only seconds of exposure. It was first isolated from [[potash]], the ashes of plants, from which its name derives. In the [[periodic table]], potassium is one of the [[alkali metal]]s, all of which have a single outer-shell [[valence electron]] that is easily removed to create an ion with a positive charge, a [[cation]], that combines with [[anion]]s to form [[Salt (chemistry)|salts]]. Potassium in nature occurs only in ionic salts. Elemental potassium reacts vigorously with water, generating sufficient heat to ignite [[hydrogen]] emitted in the reaction, and burning with a [[lilac]]-[[flame color|colored flame]]. It is found dissolved in sea water (which is 0.04% potassium by weight<ref name="seawaterconcentration">{{cite journal |journal= [[The Journal of Experimental Biology]] |url= http://jeb.biologists.org/content/jexbio/16/2/178.full.pdf |title=The Sodium and Potassium Content of Sea Water |first=D. A. |last= Webb |page= 183 |date=April 1939 |issue=2}}</ref><ref>{{cite web |url= http://www.seafriends.org.nz/oceano/seawater.htm |title=Detailed composition of seawater at 3.5% salinity |first= J. |last= Anthoni |work=seafriends.org.nz |year=2006 |accessdate=2011-09-23}}</ref>), and occurs in many [[mineral]]s such as [[orthoclase]], a common constituent of [[granite]]s and other [[igneous rock]]s.

Potassium is chemically very similar to [[sodium]], the previous element in group 1 of the periodic table. They have a similar first [[ionization energy]], which allows for each atom to give up its sole outer electron. That they are different elements that combine with the same [[anion]]s to make similar salts was suspected in 1702,<ref name="1702Suspect" /> and was proven in 1807 using [[electrolysis]]. Naturally occurring potassium is composed of three [[isotope]]s, of which [[potassium-40|{{chem|40|K}}]] is [[radioactive]]. Traces of {{chem|40|K}} are found in all potassium, and it is the most common [[radioisotope]] in the human body.

Potassium ions are vital for the functioning of all living cells. The transfer of potassium ions across nerve cell membranes is necessary for normal nerve transmission; potassium deficiency and excess can each result in numerous signs and symptoms, including an abnormal heart rhythm and various [[Electrocardiography|electrocardiographic]] abnormalities. Fresh fruits and vegetables are good dietary sources of potassium. The body responds to the influx of dietary potassium, which raises [[serum (blood)|serum]] potassium levels, with a shift of potassium from outside to inside cells and an increase in potassium excretion by the kidneys.

Most industrial applications of potassium exploit the high [[solubility]] in water of potassium compounds, such as [[Saltwater soap|potassium]] [[soap]]s. Heavy crop production rapidly depletes the soil of potassium, and this can be remedied with agricultural fertilizers containing potassium, accounting for 95% of global potassium chemical production.<ref name="g73">[[#Greenwood|Greenwood]], p. 73</ref>
{{TOC limit}}

==Etymology==

The English name for the element ''potassium'' comes from the word "[[potash]]",<ref>{{cite journal|first=Humphry|last=Davy|title=On some new phenomena of chemical changes produced by electricity, in particular the decomposition of the fixed alkalies, and the exhibition of the new substances that constitute their bases; and on the general nature of alkaline bodies|page=32|year=1808|volume=98|journal=Philosophical Transactions of the Royal Society|url=https://books.google.com/?id=gpwEAAAAYAAJ&pg=PA32|doi=10.1098/rstl.1808.0001}}</ref> which refers to an early method of extracting various potassium salts: placing in a ''pot'' the ''ash'' of burnt wood or tree leaves, adding water, heating, and evaporating the solution. When [[Humphry Davy]] first isolated the pure element using [[electrolysis]] in 1807, he named it ''potassium'', which he derived from the word potash.

The symbol "K" stems from ''kali'', itself from the root word ''[[alkali]]'', which in turn comes from ''{{lang-ar|القَلْيَه}}'' ''al-qalyah'' "plant ashes". In 1797, the German chemist [[Martin Heinrich Klaproth|Martin Klaproth]] discovered "potash" in the minerals [[leucite]] and [[lepidolite]], and realized that "potash" was not a product of plant growth but actually contained a new element, which he proposed to call ''kali''.<ref>M. Klaproth (1797) "Nouvelles données relatives à l'histoire naturelle de l'alcali végétal" (New data regarding the natural history of the vegetable alkali), ''Mémoires de l'Académie royale des sciences et belles-lettres'' (Berlin), pp. 9-13 ; [https://babel.hathitrust.org/cgi/pt?id=mdp.39015073704093;view=1up;seq=103 see p. 13.] From p. 13: ''"Cet alcali ne pouvant donc plus être envisagé comme un produit de la végétation dans les plantes, occupe une place propre dans la série des substances primitivement simples du règne minéral, &I il devient nécessaire de lui assigner un nom, qui convienne mieux à sa nature. 
''La dénomination de ''Potasche'' (potasse) que la nouvelle nomenclature françoise a consacrée comme nom de tout le genre, ne sauroit faire fortune auprès des chimistes allemands, qui sentent à quel point la dérivation étymologique en est vicieuse. Elle est prise en effet de ce qu'anciennement on se servoit pour la calcination des lessives concentrées des cendres, de pots de fer (''pott'' en dialecte de la Basse-Saxe) auxquels on a substitué depuis des fours à calciner. 
''Je propose donc ici, de substituer aux mots usités jusqu'ici d'alcali des plantes, alcali végétal, potasse, &c. celui de ''kali'', & de revenir à l'ancienne dénomination de ''natron'', au lieu de dire alcali minéral, soude &c."'' 
(This alkali [i.e., potash] — [which] therefore can no longer be viewed as a product of growth in plants — occupies a proper place in the originally simple series of the mineral realm, and it becomes necessary to assign it a name that is better suited to its nature. 
The name of "potash" (''potasse''), which the new French nomenclature has bestowed as the name of the entire species [i.e., substance], would not find acceptance among German chemists, who feel to some extent [that] the etymological derivation of it is faulty. Indeed, it is taken from [the vessels] that one formerly used for the roasting of washing powder concentrated from cinders: iron pots (''pott'' in the dialect of Lower Saxony), for which roasting ovens have been substituted since then. 
Thus I now propose to substitute for the until now common words of "plant alkali", "vegetable alkali", "potash", etc., that of ''kali'' ; and to return to the old name of ''natron'' instead of saying "mineral alkali", "soda", etc.)</ref> In 1807, [[Humphry Davy]] produced the element via electrolysis: in 1809, [[Ludwig Wilhelm Gilbert]] proposed the name ''Kalium'' for Davy's "potassium".<ref>{{cite journal|author=Davy, Humphry |year=1809|title=Ueber einige neue Erscheinungen chemischer Veränderungen, welche durch die Electricität bewirkt werden; insbesondere über die Zersetzung der feuerbeständigen Alkalien, die Darstellung der neuen Körper, welche ihre Basen ausmachen, und die Natur der Alkalien überhaupt|trans-title=On some new phenomena of chemical changes that are achieved by electricity; particularly the decomposition of flame-resistant alkalis [i.e., alkalies that cannot be reduced to their base metals by flames], the preparation of new substances that constitute their [metallic] bases, and the nature of alkalies generally|journal=Annalen der Physik|volume=31|issue=2|pages=113–175|url=https://books.google.com/books?id=vyswAAAAYAAJ&pg=PA157|quote=p. 157: In unserer deutschen Nomenclatur würde ich die Namen ''Kalium'' und ''Natronium'' vorschlagen, wenn man nicht lieber bei den von Herrn Erman gebrauchten und von mehreren angenommenen Benennungen ''Kali-Metalloid'' and ''Natron-Metalloid'', bis zur völligen Aufklärung der chemischen Natur dieser räthzelhaften Körper bleiben will. Oder vielleicht findet man es noch zweckmässiger fürs Erste zwei Klassen zu machen, ''Metalle'' und ''Metalloide'', und in die letztere ''Kalium'' und ''Natronium'' zu setzen. — Gilbert. (In our German nomenclature, I would suggest the names ''Kalium'' and ''Natronium'', if one would not rather continue with the appellations ''Kali-metalloid'' and ''Natron-metalloid'' which are used by Mr. Erman [i.e., German physics professor [[Paul Erman]] (1764–1851)] and accepted by several [people], until the complete clarification of the chemical nature of these puzzling substances. Or perhaps one finds it yet more advisable for the present to create two classes, ''metals'' and ''metalloids'', and to place ''Kalium'' and ''Natronium'' in the latter — Gilbert.)|bibcode=1809AnP....31..113D|doi=10.1002/andp.18090310202}}</ref> In 1814, the Swedish chemist [[Jöns Jacob Berzelius|Berzelius]] advocated the name ''kalium'' for potassium, with the chemical symbol "K".<ref>Berzelius, J. Jacob (1814) ''Försök, att, genom användandet af den electrokemiska theorien och de kemiska proportionerna, grundlägga ett rent vettenskapligt system för mineralogien'' [Attempt, by the use of electrochemical theory and chemical proportions, to found a pure scientific system for mineralogy]. Stockholm, Sweden: A. Gadelius., [https://archive.org/stream/bub_gb_Uw0-AAAAcAAJ#page/n91/mode/2up p. 87.]</ref>

The English and French speaking countries adopted Davy and Gay-Lussac/Thénard's name Potassium, while the Germanic countries adopted Gilbert/Klaproth's name Kalium.<ref>[http://www.vanderkrogt.net/elements/element.php?sym=K 19. Kalium (Potassium) - Elementymology & Elements Multidict]</ref> The "Gold Book" of the International Union of Physical and Applied Chemistry has designated the official chemical symbol as '''K'''.<ref>IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997)</ref>

==Properties==
===Physical===
[[File:FlammenfärbungK.png|thumb|right|The [[flame test]] of potassium.]]
Potassium is the second least dense metal after [[lithium]]. It is a soft solid with a low [[melting point]], and can be easily cut with a knife. Freshly cut potassium is silvery in appearance, but it begins to tarnish toward gray immediately on exposure to air.<ref name=g76>[[#Greenwood|Greenwood]], p. 76</ref> In a [[flame test]], potassium and its compounds emit a lilac color with a peak emission wavelength of 766.5 nanometers.<ref>[[#Greenwood|Greenwood]], p. 75</ref>

===Chemical===

Neutral potassium atoms have 19 electrons, one more than the extremely stable configuration of the [[noble gas]] [[argon]]. Because of this and its low first [[ionization energy]] of 418.8 kJ/mol, the potassium atom is much more likely to lose the last electron and acquire a positive charge than to gain one and acquire a negative charge (though negatively charged [[alkalide]] {{chem|K|−}} ions are not impossible).<ref name="K-">{{cite journal|journal = [[Angewandte Chemie International Edition]]|year = 1979|last = Dye|first=J. L. |title = Compounds of Alkali Metal Anions|volume = 18|issue = 8|pages = 587–598|doi = 10.1002/anie.197905871}}</ref><ref name="K+++">{{cite book|first1=A. M.| last1=James|first2=M. P.|last2=Lord|title=Macmillan's chemical and physical data|publisher=Macmillan| location=London| date=1992|isbn=978-0-333-51167-1}}</ref> This process requires so little energy that potassium is readily oxidized by atmospheric oxygen. In contrast, the second ionization energy is very high (3052 kJ/mol), because removal of two electrons breaks the stable noble gas electronic configuration (the configuration of the inert argon).<ref name="K+++"/> Potassium therefore does not form compounds with the oxidation state of +2 or higher.<ref name="K-"/>

Potassium is an extremely active metal that reacts violently with oxygen in water and air. With oxygen it forms [[potassium peroxide]], and with water potassium forms [[potassium hydroxide]]. The reaction of potassium with water is dangerous because of its violent [[exothermic]] character and the production of [[hydrogen]] gas. Hydrogen reacts again with atmospheric oxygen, producing water, which reacts with the remaining potassium. This reaction requires only traces of water; because of this, potassium and the liquid sodium-potassium ([[NaK]]) alloy are potent [[desiccant]]s that can be used to dry [[solvent]]s prior to distillation.<ref name=b35>[[#Burkhardt|Burkhardt]], p. 35</ref>

Because of the sensitivity of potassium to water and air, reactions with other elements are possible only in an inert atmosphere such as [[argon]] gas using [[air-free technique]]s. Potassium does not react with most hydrocarbons such as mineral oil or [[kerosene]].<ref name="HollemanAF">{{cite book|publisher = Walter de Gruyter|date = 1985|edition = 91–100|isbn = 978-3-11-007511-3|title = Lehrbuch der Anorganischen Chemie|first1 = Arnold F.|last1 = Holleman|last2 = Wiberg|first2 = Egon|last3 = Wiberg|first3 = Nils|chapter = Potassium| language = German}}</ref> It readily dissolves in liquid [[ammonia]], up to 480 g per 1000 g of ammonia at 0 °C. Depending on the concentration, the ammonia solutions are blue to yellow, and their electrical conductivity is similar to that of liquid metals. In a pure solution, potassium slowly reacts with ammonia to form [[Potassium amide|{{chem|KNH|2}}]], but this reaction is accelerated by minute amounts of transition metal salts.<ref name=b32>[[#Burkhardt|Burkhardt]], p. 32</ref> Because it can reduce the [[salt (chemistry)|salt]]s to the metal, potassium is often used as the reductant in the preparation of finely divided metals from their salts by the [[Rieke metal|Rieke method]].<ref>{{cite journal| author=Rieke, R. D.|title=Preparation of Organometallic Compounds from Highly Reactive Metal Powders|journal= [[Science (journal)|Science]]|year= 1989|volume= 246| pages= 1260–4|doi=10.1126/science.246.4935.1260| pmid=17832221| issue=4935|bibcode = 1989Sci...246.1260R }}</ref> For example, the preparation of magnesium by this method employs potassium as the reductant:

:{{chem|link=Magnesium chloride|MgCl|2}} + 2 K → Mg + 2 KCl

===Compounds===
:[[Image:potassium-superoxide-unit-cell-3D-ionic.png|thumb|right|upright|Structure of solid potassium superoxide ({{chem|KO|2}}).]]
The only common oxidation state for potassium is +1. Potassium metal is a powerful [[reducing agent]] that is easily oxidized to the monopositive [[cation]], {{chem|K|+}}. Once oxidized, it is very stable and difficult to reduce back to the metal.<ref name="K-"/>

Potassium oxidizes faster than most metals and often forms [[oxide]]s containing oxygen-oxygen bonds, as do all alkali metals except lithium. There are three possible oxides of potassium: [[potassium oxide]] (K2O), [[potassium peroxide]] (K2O2), and [[potassium superoxide]] (KO2);<ref>{{cite book|last = Lide|first = David R.|date = 1998|title = Handbook of Chemistry and Physics|edition = 87th|location = Boca Raton, Florida, United States|publisher = CRC Press|isbn = 978-0-8493-0594-8|pages = 477; 520}}</ref> they contain three different oxygen-based ions: [[oxide]] ({{chem|O|2-}}), [[peroxide]] ({{chem|O|2|2-}}), and [[superoxide]] ({{chem|O|2|-}}). The latter two species, especially the [[superoxide]], are rare and are formed only in reaction of very [[electronegativity|electropositive]] metals (Na, K, Rb, Cs, etc.) with oxygen; these species contain oxygen-oxygen bonds.<ref name=b32/> All potassium-oxygen binary compounds are known to react with water violently, forming [[potassium hydroxide]].

Potassium hydroxide (KOH) is a very strong alkali, and up to 1.21 [[kilogram|kg]] of it can dissolve in a single liter of water.<ref>{{RubberBible86th|page=4–80}}</ref><ref>[[#Schultz|Schultz]], p. 94</ref> KOH reacts readily with carbon dioxide to produce [[potassium carbonate]], and is used to remove traces of the gas from air.

In general, potassium compounds are highly ionic and, owing to the high hydration energy of the {{chem|K|+}} ion, have excellent water solubility. The main species in water solution are the aquated complexes {{chem|[K|(H|2|O)|n|]|+}} where n = 6 and 7.<ref name=Lincoln>Lincoln, S. F.; Richens, D. T. and Sykes, A. G. "Metal Aqua Ions" in J. A. McCleverty and T. J. Meyer (eds.) [http://www.sciencedirect.com/science/referenceworks/9780080437484 ''Comprehensive Coordination Chemistry II''], Vol. 1, pp. 515–555, {{ISBN|978-0-08-043748-4}}.</ref> The potassium ion is colorless in water and is very difficult to [[Precipitation (chemistry)|precipitate]]; possible precipitation methods include reactions with [[sodium tetraphenylborate]], [[hexachloroplatinic acid]], and [[sodium cobaltinitrite]] into [[potassium tetraphenylborate]], [[potassium hexachloroplatinate]], and [[potassium cobaltinitrite]].<ref name="HollemanAF"/>

===Isotopes===
{{main|Isotopes of potassium}}
There are 24 known [[isotope]]s of potassium, three of which occur naturally: {{chem|39|K}} (93.3%), {{chem|40|K}} (0.0117%), and {{chem|41|K}} (6.7%). Naturally occurring {{chem|link=potassium-40|40|K}} has a [[half-life]] of 1.250×109 years. It decays to stable {{chem|link=Argon|40|Ar}} by [[electron capture]] or [[positron emission]] (11.2%) or to stable {{chem|link=Calcium|40|Ca}} by [[beta decay]] (88.8%).<ref name="NUBASE">{{NUBASE 2003}}</ref> The decay of {{chem|40|K}} to {{chem|40|Ar}} is the basis of a common method for dating rocks. The conventional [[Potassium-argon dating|K-Ar dating method]] depends on the assumption that the rocks contained no argon at the time of formation and that all the subsequent radiogenic argon ({{chem|40|Ar}}) was quantitatively retained. [[Mineral]]s are dated by measurement of the concentration of potassium and the amount of radiogenic {{chem|40|Ar}} that has accumulated. The minerals best suited for dating include [[biotite]], [[muscovite]], metamorphic [[hornblende]], and volcanic [[feldspar]]; [[Petrography|whole rock]] samples from volcanic flows and shallow [[Igneous rock|instrusives]] can also be dated if they are unaltered.<ref name="NUBASE"/><ref>{{cite book|chapter-url = https://books.google.com/books?id=k90iAnFereYC&pg=PA207|pages =203–8|chapter= Theory and Assumptions in Potassium–Argon Dating|title = Isotopes in the Earth Sciences|isbn = 978-0-412-53710-3|last1 = Bowen|first1 = Robert|last2 = Attendorn|first2 = H. G.|date = 1988|publisher=Springer}}</ref> Apart from dating, potassium isotopes have been used as [[radioactive tracer|tracers]] in studies of [[weathering]] and for [[nutrient cycling]] studies because potassium is a [[macronutrient (ecology)|macronutrient]] required for [[life]].<ref>{{cite book|author=Anaç, D.|author2=Martin-Prével, P.|last-author-amp=yes |title=Improved crop quality by nutrient management|url=https://books.google.com/books?id=9Hr4w6QhPGsC&pg=PA290|date=1999|publisher=Springer|isbn=978-0-7923-5850-3|pages=290–}}</ref>

{{chem|40|K}} occurs in natural potassium (and thus in some commercial salt substitutes) in sufficient quantity that large bags of those substitutes can be used as a radioactive source for classroom demonstrations. {{chem|40|K}} is the radioisotope with the largest abundance in the body. In healthy animals and people, {{chem|40|K}} represents the largest source of radioactivity, greater even than {{chem|link=Carbon-14|14|C}}. In a human body of 70 kg mass, about 4,400 nuclei of {{chem|40|K}} decay per second.<ref>{{cite web |url=http://sciencedemonstrations.fas.harvard.edu/presentations/radioactive-human-body|title=Radiation and Radioactive Decay. Radioactive Human Body |accessdate= July 2, 2016|publisher =Harvard Natural Sciences Lecture Demonstrations}}</ref> The activity of natural potassium is 31 [[Becquerel|Bq]]/g.<ref>{{cite book|url = https://books.google.com/books?id=KRVXMiQWi0cC&pg=PA32|page =32|title = Radioactive fallout in soils, crops and food: a background review|isbn = 978-92-5-102877-3|author1 = Winteringham, F. P. W|author2 = Effects, F.A.O. Standing Committee on Radiation, Land And Water Development Division, Food and Agriculture Organization of the United Nations|date = 1989|publisher=Food & Agriculture Org.}}</ref>

==Cosmic formation and distribution==
[[File:PotassiumFeldsparUSGOV.jpg|thumb|right|upright|Potassium in [[feldspar]]]]
Potassium is formed in [[supernova]]e by [[nucleosynthesis]] from lighter atoms. Potassium is principally created in Type II supernovae via an [[Supernova nucleosynthesis|explosive oxygen-burning process]].<ref>{{cite journal|first= V.|display-authors= 4|last= Shimansky|title=Observational constraints on potassium synthesis during the formation of stars of the Galactic disk| journal=Astronomy Reports|date=September 2003|bibcode = 2003ARep...47..750S|last2= Bikmaev|first2=I. F.|last3= Galeev|first3=A. I.|last4= Shimanskaya|first4=N. N.|last5= Ivanova|first5=D. V.|last6= Sakhibullin|first6=N. A.|last7= Musaev|first7=F. A.|last8= Galazutdinov|first8=G. A.|volume= 47|pages= 750–762|doi= 10.1134/1.1611216|issue= 9}}</ref> {{chem|40|K}} is also formed in [[s-process]] nucleosynthesis and the [[neon burning process]].<ref>{{Cite journal|last=The|first=L.-S.|last2=Eid|first2=M. F. El|last3=Meyer|first3=B. S.|date=2000|title=A New Study of s-Process Nucleosynthesis in Massive Stars|journal=The Astrophysical Journal|volume=533|issue=2|pages=998|doi=10.1086/308677|issn=0004-637X|arxiv=astro-ph/9812238}}</ref>

Potassium is the 20th most abundant element in the solar system and the 17th most abundant element by weight in the earth. It makes up about 2.6% of the weight of the [[earth's crust]] and is the seventh most abundant element in the crust.<ref>[[#Greenwood|Greenwood]], p. 69</ref> The potassium concentration in seawater is 0.39 g/L<ref name="seawaterconcentration"/> (0.039 wt/v%), about one twenty-seventh the concentration of sodium.<ref name=geo>{{cite book|url = https://books.google.com/books?id=NXEmcGHScV8C&pg=PA3| publisher = Springer| date = 2009|title = Seawater Desalination: Conventional and Renewable Energy Processes|first1= Giorgio |last1=Micale| first2=Andrea |last2=Cipollina| first3=Lucio |last3=Rizzuti|page = 3| isbn = 978-3-642-01149-8}}</ref><ref name="indus">{{cite book|chapter-url = https://books.google.com/books?id=zNicdkuulE4C&pg=PA723| title =Industrial minerals & rocks: commodities, markets, and uses|publisher = Society for Mining, Metallurgy, and Exploration|date= 2006| first1= Michel|last1=Prud'homme|first2= Stanley T.| last2 = Krukowski|chapter = Potash|pages = 723–740|isbn = 978-0-87335-233-8}}</ref>

==Potash==
{{main|Potash}}
Potash is primarily a mixture of potassium salts because plants have little or no sodium content, and the rest of a plant's major mineral content consists of calcium salts of relatively low solubility in water. While potash has been used since ancient times, it was not understood for most of its history to be a fundamentally different substance from sodium mineral salts. [[Georg Ernst Stahl]] obtained experimental evidence that led him to suggest the fundamental difference of sodium and potassium salts in 1702,<ref name="1702Suspect">{{cite book|url = https://books.google.com/books?id=b-ATAAAAQAAJ&pg=PA167|page = 167|title = Chymische Schriften|last1 = Marggraf|first = Andreas Siegmund|date = 1761}}</ref> and [[Henri Louis Duhamel du Monceau]] was able to prove this difference in 1736.<ref>{{cite journal|url = http://gallica.bnf.fr/ark:/12148/bpt6k3533j/f73.image.r=Memoires%20de%20l%27Academie%20royale%20des%20Sciences.langEN|journal = Memoires de l'Academie Royale des Sciences| title = Sur la Base de Sel Marin| last = du Monceau|first = H. L. D.| pages = 65–68| language = French|date = 1702–1797}}</ref> The exact chemical composition of potassium and sodium compounds, and the status as chemical element of potassium and sodium, was not known then, and thus [[Antoine Lavoisier]] did not include the alkali in his list of chemical elements in 1789.<ref name="weeks">{{cite journal|doi = 10.1021/ed009p1035|title = The discovery of the elements. IX. Three alkali metals: Potassium, sodium, and lithium|year = 1932|last1 = Weeks|first1 = Mary Elvira|authorlink1=Mary Elvira Weeks|journal = Journal of Chemical Education|volume = 9|issue = 6|pages = 1035|bibcode = 1932JChEd...9.1035W}}</ref><ref name="disco">{{cite journal|jstor = 228541|pages = 247–258|last1 = Siegfried|first1 = R.|title = The Discovery of Potassium and Sodium, and the Problem of the Chemical Elements|volume = 54|issue = 2|journal = Isis|year = 1963|doi = 10.1086/349704}}</ref> For a long time the only significant applications for potash were the production of glass, bleach, soap and [[gunpowder]] as potassium nitrate.<ref>{{cite journal|doi = 10.1021/ed003p749|title = Historical notes upon the domestic potash industry in early colonial and later times|year = 1926|last1 = Browne|first1 = C. A.|journal = Journal of Chemical Education|volume = 3|issue = 7|pages = 749–756|bibcode = 1926JChEd...3..749B}}</ref> Potassium soaps from animal fats and vegetable oils were especially prized because they tend to be more water-soluble and of softer texture, and are therefore known as soft [[soap]]s.<ref name=g73/> The discovery by [[Justus Liebig]] in 1840 that potassium is a necessary element for plants and that most types of soil lack potassium<ref>{{cite book|url = https://books.google.com/?id=Ya85AAAAcAAJ|title = Die organische Chemie in ihrer Anwendung auf Agricultur und Physiologie|author = Liebig, Justus von|date = 1840| language = German}}</ref> caused a steep rise in demand for potassium salts. Wood-ash from fir trees was initially used as a potassium salt source for fertilizer, but, with the discovery in 1868 of mineral deposits containing [[potassium chloride]] near [[Staßfurt]], Germany, the production of potassium-containing fertilizers began at an industrial scale.<ref>{{cite book|author=Cordel, Oskar |title=Die Stassfurter Kalisalze in der Landwirthschalt: Eine Besprechung ...|url=https://books.google.com/books?id=EYpIAAAAYAAJ|date=1868|publisher=L. Schnock| language = German}}</ref><ref>{{cite book|url = https://books.google.com/?id=J8Q6AAAAcAAJ|title = Die Kalidüngung in ihren Vortheilen und Gefahren|last1 = Birnbaum| first1= Karl|date = 1869| language = German}}</ref><ref>{{cite book|url = https://books.google.com/books?id=qPkoOU4BvEsC&pg=PA417|title = Fertilizer Manual|isbn = 978-0-7923-5032-3|author = United Nations Industrial Development Organization and Int'l Fertilizer Development Center|date = 1998|pages=46, 417}}</ref> Other potash deposits were discovered, and by the 1960s Canada became the dominant producer.<ref>{{cite journal|jstor = 3103338|pages = 187–208|last1 = Miller|first1 = H.|title = Potash from Wood Ashes: Frontier Technology in Canada and the United States|volume = 21|issue = 2|journal = Technology and Culture|year = 1980|doi=10.2307/3103338}}</ref><ref>{{cite journal|doi = 10.2113/gsecongeo.74.2.353|title = Potash and politics|year = 1979|last1 = Rittenhouse|first1 = P. A.|journal = Economic Geology|volume = 74|issue = 2|pages = 353–7}}</ref>

==Metal==
[[File:Sir Humphry Davy, Bt by Thomas Phillips.jpg|thumb| left|[[Humphry Davy]] ]]
[[File:Potassium.JPG|thumb|right|Pieces of potassium metal]]
Potassium ''metal'' was first isolated in 1807 by Sir [[Humphry Davy]], who derived it from [[Potassium hydroxide|caustic potash]] (KOH, potassium hydroxide) by electrolysis of molten KOH with the newly discovered [[voltaic pile]]. Potassium was the first metal that was isolated by electrolysis.<ref name="Enghag2004">{{cite book|last=Enghag|first= P.|date=2004| title=Encyclopedia of the elements| publisher=Wiley-VCH Weinheim| isbn=978-3-527-30666-4| chapter=11. Sodium and Potassium}}</ref> Later in the same year, Davy reported extraction of the metal [[sodium]] from a mineral derivative ([[caustic soda]], NaOH, or lye) rather than a plant salt, by a similar technique, demonstrating that the elements, and thus the salts, are different.<ref name="weeks"/><ref name="disco"/><ref name="Davy1807">{{cite journal|first=Humphry|last=Davy|title=On some new phenomena of chemical changes produced by electricity, in particular the decomposition of the fixed alkalies, and the exhibition of the new substances that constitute their bases; and on the general nature of alkaline bodies|pages=1–44|year=1808|volume=98|journal=Philosophical Transactions of the Royal Society|url=https://books.google.com/?id=gpwEAAAAYAAJ&pg=PA57&q|doi=10.1098/rstl.1808.0001}}</ref><ref name="200disco">{{cite journal|doi = 10.1134/S1061934807110160|title = History of the discovery of potassium and sodium (on the 200th anniversary of the discovery of potassium and sodium)|year = 2007|last1 = Shaposhnik|first1 = V. A.|journal = Journal of Analytical Chemistry|volume = 62|issue = 11|pages = 1100–2}}</ref> Although the production of potassium and sodium metal should have shown that both are elements, it took some time before this view was universally accepted.<ref name="disco"/>

==Geology==
Elemental potassium does not occur in nature because of its high reactivity. It reacts violently with water (see section Precautions below)<ref name="HollemanAF"/> and also reacts with oxygen. [[Orthoclase]] (potassium feldspar) is a common rock-forming mineral. [[Granite]] for example contains 5% potassium, which is well above the average in the Earth's crust. [[Sylvite]] (KCl), [[carnallite]] {{chem|(KCl·MgCl|2|·6(H|2|O))}}, [[kainite]] {{chem|(MgSO|4|·KCl·3H|2|O)}} and [[langbeinite]] {{chem|(MgSO|4|·K|2|SO|4|)}} are the minerals found in large [[evaporite]] deposits worldwide. The deposits often show layers starting with the least soluble at the bottom and the most soluble on top.<ref name="indus"/> Deposits of niter ([[potassium nitrate]]) are formed by decomposition of organic material in contact with atmosphere, mostly in caves; because of the good water solubility of niter the formation of larger deposits requires special environmental conditions.<ref>{{cite book|chapter-url = https://books.google.com/books?id=NyUDAAAAMBAJ&pg=PA134|pages = 134–145| chapter = The Origin of Nitrate Deposits| first = William H.| last = Ross|title = Popular Science|date = 1914|publisher=Bonnier Corporation}}</ref>

==Biological role==
{{Main|Potassium in biology}}
Potassium is the eighth or ninth most common element by mass (0.2%) in the human body, so that a 60 kg adult contains a total of about 120 g of potassium.<ref>{{cite journal|doi = 10.1016/0883-2889(92)90208-V|title = A simple calibration of a whole-body counter for the measurement of total body potassium in humans|year = 1992|display-authors = 4|last1 = Abdel-Wahab|first1 = M.|last2 = Youssef|first2 = S.|last3 = Aly|first3 = A.|last4 = el-Fiki|first4 = S.|last5 = el-Enany|first5 = N.|last6 = Abbas|first6 = M.|journal = International Journal of Radiation Applications and Instrumentation. Part A. Applied Radiation and Isotopes|volume = 43|issue = 10|pages = 1285–9|pmid=1330980}}</ref> The [[Composition of the human body|body]] has about as much potassium as sulfur and chlorine, and only calcium and phosphorus are more abundant (with the exception of the ubiquitous [[CHON]] elements).<ref>{{cite book|author=Chang, Raymond |title=Chemistry|url=https://books.google.com/books?id=huSDQAAACAAJ|date= 2007|publisher=McGraw-Hill Higher Education|isbn=978-0-07-110595-8|page=52}}</ref> Potassium ions are present in a wide variety of proteins and enzymes.<ref>{{cite book|first1= Milan |last1= Vašák|first2= Joachim |last2= Schnabl|publisher= Springer|date= 2016|series= Metal Ions in Life Sciences|volume=16|title= The Alkali Metal Ions: Their Role in Life|editor1-last=Astrid|editor1-first= Sigel|editor2-last=Helmut|editor2-first=Sigel|editor3-last=Roland K.O.|editor3-first= Sigel|chapter= Chapter 8. Sodium and Potassium Ions in Proteins and Enzyme Catalysis |pages= 259–290
|doi=10.1007/978-4-319-21756-7_8|doi-broken-date= 2019-03-06}}</ref>

===Biochemical function===
Potassium levels influence multiple physiological processes, including<ref>ID, Linus S, Wingo CS. Disorders of potassium metabolism. In: Freehally J, Johnson RJ, Floege J, eds. Comprehensive clinical nephrology. 5th ed.St. Louis: Saunders, 2014:118-118</ref><ref>Malnic G, Giebisch G, Muto S, Wang W, Bailey MA, Satlin LM. Regulation of K+ excretion. In: Alpern RJ, Caplan MJ, Moe OW, eds. Seldin and Giebisch’s the kidney: physiology and pathophysiology. 5th ed. London: Academic Press, 2013:1659-1716</ref><ref>Mount DB, Zandi-Nejad K. Disorders of potassium balance. In: Taal MW, Chertow GM, Marsden PA, Skorecki KL, Yu ASL, Brenner BM, eds. The kidney. 9th ed. Philadelphia: Elsevier, 2012:640-688</ref>
* resting cellular-membrane potential and the propagation of action potentials in neuronal, muscular, and cardiac tissue. Due to the electrostatic and chemical properties, {{chem|K|+}} ions are larger than {{chem|Na|+}} ions, and ion channels and pumps in cell membranes can differentiate between the two ions, actively pumping or passively passing one of the two ions while blocking the other.<ref>{{cite journal|pmid=17472437|title=Structural and thermodynamic properties of selective ion binding in a K+ channel|last1=Lockless |first1 = S. W.| last2= Zhou|first2 =M.|last3= MacKinnon|first3 =R.|journal=PLoS Biol|year= 2007 |volume=5|issue=5|page=e121|doi=10.1371/journal.pbio.0050121|pmc=1858713}}</ref>
* hormone secretion and action
* vascular tone
* systemic blood pressure control
* gastrointestinal motility
* acid–base homeostasis
* glucose and insulin metabolism
* mineralocorticoid action
* renal concentrating ability
* fluid and electrolyte balance

===Homeostasis===
Potassium homeostasis denotes the maintenance of the total body potassium content, plasma potassium level, and the ratio of the intracellular to extracellular potassium concentrations within narrow limits, in the face of pulsatile intake (meals), obligatory renal excretion, and shifts between intracellular and extracellular compartments.

====Plasma levels====
Plasma potassium is normally kept at 3.5 to 5.0 millimoles (mmol) [or milliequivalents (mEq)] per liter by multiple mechanisms. Levels outside this range are associated with an increasing rate of death from multiple causes,<ref>{{cite journal | last1 = Goyal | first1 = Abhinav | last2 = Spertus | first2 = John A. | last3 = Gosch | first3 = Kensey | last4 = Venkitachalam | first4 = Lakshmi | last5 = Jones | first5 = Philip G. | last6 = Van den Berghe | first6 = Greet | last7 = Kosiborod | first7 = Mikhail | year = 2012 | title = Serum Potassium Levels and Mortality in Acute Myocardial Infarction | url = | journal = JAMA | volume = 307 | issue = 2| pages = 157–164 | doi = 10.1001/jama.2011.1967 | pmid = 22235086 }}</ref> and some cardiac, kidney,<ref>{{cite journal | last1 = Smyth | first1 = A. | last2 = Dunkler | first2 = D. | last3 = Gao | first3 = P. | display-authors = etal | year = 2014 | title = The relationship between estimated sodium and potassium excretion and subsequent renal outcomes | url = | journal = Kidney Int | volume = 86 | issue = 6| pages = 1205–1212 | doi=10.1038/ki.2014.214| pmid = 24918156 }}</ref> and lung diseases progress more rapidly if serum potassium levels are not maintained within the normal range.

An average meal of 40-50 mmol presents the body with more potassium than is present in all plasma (20-25 mmol). However, this surge causes the plasma potassium to rise only 10% at most as a result of prompt and efficient clearance by both renal and extra-renal mechanisms.<ref>{{cite journal | last1 = Moore-Ede | first1 = M. C. | year = 1986 | title = Physiology of the circadian timing system: predictive versus reactive homeostasis | url = | journal = Am J Physiol | volume = 250 | issue = | pages = R737–R752 }}</ref>

[[Hypokalemia]], a deficiency of potassium in the plasma, can be fatal if severe. Common causes are increased gastrintestinal loss ([[vomiting]], [[diarrhea]]), and increased renal loss ([[polyuria|diuresis]]).<ref>{{cite book|publisher=Lippincott Williams & Wilkins|chapter-url = https://books.google.com/books?id=_XavFllbnS0C&pg=PA812|page = 812| chapter = Potassium|title = Pediatric critical care medicine|isbn = 978-0-7817-9469-5|last1 = Slonim|first1= Anthony D.|last2 = Pollack|first2= Murray M.|date = 2006}}</ref> Deficiency symptoms include muscle weakness, [[paralytic ileus]], ECG abnormalities, decreased reflex response; and in severe cases, respiratory paralysis, [[alkalosis]], and [[cardiac arrhythmia]].<ref>{{cite book |chapter-url = https://books.google.com/books?id=c4xAdJhIi6oC&pg=PT257 |page =257|chapter = hypokalemia |title = Essentials of Nephrology|edition=2nd|publisher=BI Publications |isbn = 978-81-7225-323-3 |last1 = Visveswaran |first1= Kasi |date = 2009}}</ref>

====Control mechanisms====
Potassium content in the plasma is tightly controlled by four basic mechanisms, which have various names and classifications. The four are 1) a reactive negative-feedback system, 2) a reactive feed-forward system, 3) a predictive or [[circadian]] system, and 4) an internal or cell membrane transport system. Collectively, the first three are sometimes termed the "external potassium homeostasis system";<ref>{{Cite journal|last=Gumz|first=Michelle L.|last2=Rabinowitz|first2=Lawrence|last3=Wingo|first3=Charles S.|date=2015-07-02|title=An Integrated View of Potassium Homeostasis|journal=The New England Journal of Medicine|volume=373|issue=1|pages=60–72|doi=10.1056/NEJMra1313341|issn=0028-4793|pmc=5675534|pmid=26132942}}</ref> and the first two, the "reactive potassium homeostasis system".
* The reactive negative-feedback system refers to the system that induces renal secretion of potassium in response to a rise in the plasma potassium (potassium ingestion, shift out of cells, or intravenous infusion.)
* The reactive feed-forward system refers to an incompletely understood system that induces renal potassium secretion in response to potassium ingestion prior to any rise in the plasma potassium. This is probably initiated by gut cell potassium receptors that detect ingested potassium and trigger [[vagal]] [[afferent nerve fiber|afferent]] signals to the pituitary gland.
* The predictive or circadian system increases renal secretion of potassium during mealtime hours (e.g. daytime for humans, nighttime for rodents) independent of the presence, amount, or absence of potassium ingestion. It is mediated by a [[circadian oscillator]] in the [[suprachiasmatic nucleus]] of the brain (central clock), which causes the kidney (peripheral clock) to secrete potassium in this rhythmic circadian fashion.[[File:Scheme sodium-potassium pump-en.svg|thumb|right|upright=1.8|The action of the [[sodium-potassium pump]] is an example of primary [[active transport]]. The two carrier proteins embedded in the cell membrane on the left are using [[Adenosine triphosphate|ATP]] to move sodium out of the cell against the concentration gradient; The two proteins on the right are using secondary active transport to move potassium into the cell: this process results in reconstitution of ATP.]]
* The ion transport system moves potassium across the cell membrane using two mechanisms. One is active and pumps sodium out of, and potassium into, the cell. The other is passive and allows potassium to leak out of the cell. Potassium and sodium cations influence fluid distribution between intracellular and extracellular compartments by [[osmotic]] forces. The movement of potassium and sodium through the cell membrane is mediated by the [[Na+/K+-ATPase]] pump.<ref>{{cite book|last=Campbell|first=Neil|title=Biology|date=1987|isbn=978-0-8053-1840-1|page=795|publisher=Benjamin/Cummings Pub. Co.|location=Menlo Park, California}}</ref> This [[Ion transporter|ion pump]] uses [[Adenosine triphosphate|ATP]] to pump three sodium ions out of the cell and two potassium ions into the cell, creating an electrochemical gradient and electromotive force across the cell membrane. The highly selective [[potassium ion channels]] (which are [[tetramer]]s) are crucial for [[Hyperpolarization (biology)|hyperpolarization]] inside [[neuron]]s after an action potential is triggered, to cite one example. The most recently discovered potassium ion channel is KirBac3.1, which makes a total of five potassium ion channels (KcsA, KirBac1.1, KirBac3.1, KvAP, and MthK) with a determined structure. All five are from [[prokaryotic]] species.<ref name="pmid16253415">{{cite journal|first1=Mikko |last1 = Hellgren| first2= Lars |last2= Sandberg|first3= Olle |last3= Edholm|title=A comparison between two prokaryotic potassium channels (KirBac1.1 and KcsA) in a molecular dynamics (MD) simulation study|journal=Biophysical Chemistry| volume=120|issue=1|pages=1–9|year=2006|pmid=16253415|doi=10.1016/j.bpc.2005.10.002}}</ref>

====Renal filtration, reabsorption, and excretion====
Renal handling of potassium is closely connected to sodium handling. Potassium is the major cation (positive ion) inside animal cells [150 mmol/L, (4.8 g)], while sodium is the major cation of extracellular fluid [150 mmol/L, (3.345 g)]. In the kidneys, about 180 liters of plasma is filtered through the [[glomeruli]] and into the [[renal tubules]] per day.<ref name="Potts1964">{{cite book|author=Potts, W. T. W.|author2=Parry, G.|date=1964|title=Osmotic and ionic regulation in animals|publisher=[[Pergamon Press]]}}</ref> This filtering involves about 600 g of sodium and 33 g of potassium. Since only 1–10 g of sodium and 1–4 g of potassium are likely to be replaced by diet, renal filtering must efficiently reabsorb the remainder from the plasma.

Sodium is reabsorbed to maintain extracellular volume, osmotic pressure, and serum sodium concentration within narrow limits; potassium is reabsorbed to maintain serum potassium concentration within narrow limits.<ref>{{cite journal| last1=Lans |first1=H. S.|last2= Stein|first2=I. F.|last3= Meyer |first3=K. A.|title=The relation of serum potassium to erythrocyte potassium in normal subjects and patients with potassium deficiency|journal=American Journal of the Medical Sciences|volume=223| issue=1| pages=65–74|year=1952| pmid=14902792| doi=10.1097/00000441-195201000-00011}}</ref> [[Sodium pump]]s in the renal tubules operate to reabsorb sodium. Potassium must be conserved also, but, because the amount of potassium in the blood plasma is very small and the pool of potassium in the cells is about thirty times as large, the situation is not so critical for potassium. Since potassium is moved passively<ref>{{cite journal|last1=Bennett |first1=C. M.|last2= Brenner |first2=B. M.|last3= Berliner |first3=R. W.| title=Micropuncture study of nephron function in the rhesus monkey| journal=Journal of Clinical Investigation| volume=47|issue=1| pages=203–216|year=1968| pmid=16695942| doi=10.1172/JCI105710|pmc=297160}}</ref><ref>{{cite journal|last1=Solomon|first1=A. K. |title=Pumps in the living cell|journal=Scientific American| volume=207| pages=100–8|year=1962| pmid=13914986| doi=10.1038/scientificamerican0862-100| issue=2|bibcode=1962SciAm.207b.100S}}</ref> in counter flow to sodium in response to an apparent (but not actual) [[Donnan equilibrium]],<ref>{{cite book|last=Kernan|first= Roderick P.|title=Cell potassium (Transport in the life sciences)|publisher=[[John Wiley & Sons|Wiley]]|location=New York|date=1980|pages=40, 48|isbn= 978-0-471-04806-0}}</ref> the urine can never sink below the concentration of potassium in serum except sometimes by actively excreting water at the end of the processing. Potassium is excreted twice and reabsorbed three times before the urine reaches the collecting tubules.<ref>{{cite journal|last1=Wright|first1=F. S.|title=Sites and mechanisms of potassium transport along the renal tubule |journal=Kidney International |volume=11|issue=6 |pages=415–432 |year=1977 |pmid=875263 |doi=10.1038/ki.1977.60}}</ref> At that point, urine usually has about the same potassium concentration as plasma. At the end of the processing, potassium is secreted one more time if the serum levels are too high.{{citation needed|date=August 2017}}

With no potassium intake, it is excreted at about 200 mg per day until, in about a week, potassium in the serum declines to a mildly deficient level of 3.0–3.5 mmol/L.<ref>{{cite journal|last1=Squires |first1=R. D.|last2= Huth |first2 = E. J. |title=Experimental potassium depletion in normal human subjects. I. Relation of ionic intakes to the renal conservation of potassium |journal=Journal of Clinical Investigation |volume=38 |issue=7|pages=1134–48|year=1959 |pmid=13664789 |doi=10.1172/JCI103890|pmc=293261}}</ref> If potassium is still withheld, the concentration continues to fall until a severe deficiency causes eventual death.<ref>{{cite book|author=Fiebach, Nicholas H.|author2=Barker, Lee Randol|author3=Burton, John Russell|author4=Zieve, Philip D.|last-author-amp=yes |title=Principles of ambulatory medicine|url=https://books.google.com/books?id=UGVylX6g4i8C&pg=PA748|date=2007|publisher=Lippincott Williams & Wilkins|isbn=978-0-7817-6227-4|pages=748–750}}</ref>

The potassium moves passively through pores in the cell membrane. When ions move through pumps there is a gate in the pumps on either side of the cell membrane and only one gate can be open at once. As a result, approximately 100 ions are forced through per second. Pores have only one gate, and there only one kind of ion can stream through, at 10 million to 100 million ions per second.<ref>{{cite journal|last=Gadsby |first=D. C.|title=Ion transport: spot the difference |journal=Nature|volume=427 |issue=6977|pages=795–7|year=2004 |pmid=14985745 |doi=10.1038/427795a|bibcode = 2004Natur.427..795G}}; for a diagram of the potassium pores are viewed, see {{cite journal|author=Miller, C|title=See potassium run |journal=Nature |volume=414|issue=6859 |pages=23–24|year=2001 |pmid=11689922|doi=10.1038/35102126|bibcode = 2001Natur.414...23M }}</ref> Calcium is required to open the pores,<ref>{{cite journal|display-authors=4|last1=Jiang|first1=Y.|last2=Lee|first2=A.|last3=Chen|first3=J.|last4=Cadene|first4=M.|last5=Chait|first5=B. T.|last6=MacKinnon|first6=R.|url=http://einstein.ciencias.uchile.cl/CursoTroncal2007/Biblio/Jiang__MacKinnonNature417_515_2002.pdf|title=Crystal structure and mechanism of a calcium-gated potassium channel|journal=Nature|volume=417|issue=6888|pages=515–22|year=2002|pmid=12037559|doi=10.1038/417515a|bibcode=2002Natur.417..515J|deadurl=bot: unknown|archiveurl=https://web.archive.org/web/20090424074015/http://einstein.ciencias.uchile.cl/CursoTroncal2007/Biblio/Jiang__MacKinnonNature417_515_2002.pdf|archivedate=2009-04-24}}</ref> although calcium may work in reverse by blocking at least one of the pores.<ref>{{cite journal|display-authors=4|last1=Shi |first1=N.|last2= Ye |first2=S.|last3= Alam |first3=A.|last4= Chen |first4=L.|last5= Jiang |first5=Y. |title=Atomic structure of a Na+- and K+-conducting channel|journal=Nature |volume=440 |issue=7083 |pages=570–4 |year=2006 |pmid=16467789 |doi=10.1038/nature04508|bibcode = 2006Natur.440..570S}}; includes a detailed picture of atoms in the pump.</ref> Carbonyl groups inside the pore on the amino acids mimic the water hydration that takes place in water solution<ref>{{cite journal|last1=Zhou |first1=Y.|last2= Morais-Cabral |first2=J. H.|last3= Kaufman |first3=A.|last4= MacKinnon |first4=R.|title=Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 A resolution |journal=Nature |volume=414 |issue=6859|pages=43–48 |year=2001|pmid=11689936 |doi=10.1038/35102009|bibcode = 2001Natur.414...43Z }}</ref> by the nature of the electrostatic charges on four carbonyl groups inside the pore.<ref>{{cite journal|last1=Noskov |first1=S. Y.|last2= Bernèche |first2=S.|last3= Roux |first3=B.|title=Control of ion selectivity in potassium channels by electrostatic and dynamic properties of carbonyl ligands |journal=Nature |volume=431|issue=7010 |pages=830–4|year=2004 |pmid=15483608 |doi=10.1038/nature02943|bibcode = 2004Natur.431..830N}}</ref>

==Nutrition==

===Dietary recommendations===
The U.S. Institute of Medicine (IOM) sets Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs), or [[Adequate Intake]]s (AIs) for when there is not sufficient information to set EARs and RDAs. Collectively the EARs, RDAs, AIs and ULs are referred to as [[Dietary Reference Intake]]s. The AIs for potassium are: 400 mg of potassium for 0-6-month-old males, 700 mg of potassium for 7-12-month-old males, 3,000 mg of potassium for 1-3-year-old males, 3,800 mg of potassium for 4-8-year-old males, 4,500 mg of potassium for 9-13-year-old males, and 4,700 mg of potassium for males that are 14 years old and older.
The AIs for potassium are: 400 mg of potassium for 0-6-month-old females, 700 mg of potassium for 7-12-month-old females, 3,000 mg of potassium for 1-3-year-old females, 3,800 mg of potassium for 4-8-year-old females, 4,500 mg of potassium for 9-13-year-old females, and 4,700 mg of potassium for females that are 14 years old and older.
The AIs for potassium are: 4,700 mg of potassium for 14-50-year-old pregnant females; furthermore, 5,100 mg of potassium for 14-50-year-old lactating females. As for safety, the IOM also sets [[Tolerable upper intake level]]s (ULs) for vitamins and minerals, but for potassium the evidence was insufficient, so no UL established.<ref>Potassium. IN: [https://www.nap.edu/read/10925/chapter/7 Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate]. National Academy Press. 2005, PP.186-268.</ref>

Most Americans consume only half that amount per day.<ref name=iom_panel2005>{{cite book|author=Panel on Dietary Reference Intakes for Electrolytes and Water, Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition|title=DRI, dietary reference intakes for water, potassium, sodium, chloride, and sulfate|date=2004|publisher=National Academies Press|location=Washington, D.C.|isbn=978-0-309-53049-1|url=http://www.iom.edu/Reports/2004/Dietary-Reference-Intakes-Water-Potassium-Sodium-Chloride-and-Sulfate.aspx|deadurl=yes|archiveurl=https://web.archive.org/web/20111006174858/http://www.iom.edu/Reports/2004/Dietary-Reference-Intakes-Water-Potassium-Sodium-Chloride-and-Sulfate.aspx|archivedate=2011-10-06}}</ref>

Likewise, in the [[European Union]], in particular in [[Germany]] and [[Italy]], insufficient potassium intake is somewhat common.<ref>{{cite journal|last=Karger|first=S.|journal=Annals of Nutrition and Metabolism|year=2004|volume=48|issue=2 (suppl) |pages=1–16 |title=Energy and nutrient intake in the European Union|doi=10.1159/000083041}}</ref> However, the [[National Health Service|British National Health Service]] recommends a lower intake, saying that adults need 3,500 mg per day and that excess amounts may cause health problems such as stomach pain and diarrhoea.<ref>[https://www.nhs.uk/conditions/vitamins-and-minerals/others/#potassium%20NHS%20Choices%20-%20Other%20vitamins%20and%20minerals%20-%20Potassium https://www.nhs.uk/conditions/vitamins-and-minerals/others/#potassium NHS Choices - Other vitamins and minerals - Potassium]</ref>

===Food sources===
Potassium is present in all fruits, vegetables, meat and fish. Foods with high potassium concentrations include [[Yam (vegetable)|yam]], [[parsley]], dried [[apricot]]s, [[milk]], [[chocolate]], all [[nut (fruit)|nuts]] (especially [[almond]]s and [[pistachio]]s), [[potato]]es, [[bamboo shoot]]s, [[banana]]s, [[avocado]]s, [[coconut water]], [[soybean]]s, and [[bran]].<ref>{{cite web| url = http://apjcn.nhri.org.tw/server/info/books-phds/books/foodfacts/html/data/data5b.html|title = Potassium Food Charts|publisher =Asia Pacific Journal of Clinical Nutrition|accessdate = 2011-05-18}}</ref>

The [[United States Department of Agriculture|USDA]] lists [[tomato paste]], [[orange juice]], [[beet greens]], [[white beans]], [[potato]]es, [[Cooking banana|plantains]], [[banana]]s, apricots, and many other dietary sources of potassium, ranked in descending order according to potassium content. A day's worth of potassium is in 5 plantains or 11 bananas.<ref>{{cite news|title=Potassium Content of Selected Foods per Common Measure, sorted by nutrient content |publisher=USDA National Nutrient Database for Standard Reference, Release 20 |url=http://www.nal.usda.gov/fnic/foodcomp/Data/SR20/nutrlist/sr20w306.pdf |deadurl=yes |archiveurl=https://web.archive.org/web/20081217043521/http://www.nal.usda.gov/fnic/foodcomp/Data/SR20/nutrlist/sr20w306.pdf |archivedate=December 17, 2008 }}</ref>

===Deficient intake===
Diets low in potassium can lead to [[hypertension]]<ref>{{cite journal |vauthors=Whelton PK, He J, Cutler JA, Brancati FL, Appel LJ, Follmann D, Klag MJ |title=Effects of oral potassium on blood pressure. Meta-analysis of randomized controlled clinical trials |journal=JAMA |volume=277 |issue=20 |pages=1624–32 |year=1997 |pmid=9168293 |doi=10.1001/jama.1997.03540440058033 }}</ref> and [[hypokalemia]].

===Supplementation===
Supplements of potassium are most widely used in conjunction with [[diuretic]]s that block reabsorption of sodium and water upstream from the [[distal tubule]] ([[thiazide]]s and [[loop diuretics]]), because this promotes increased distal tubular potassium secretion, with resultant increased potassium excretion. A variety of prescription and over-the counter supplements are available. Potassium chloride may be dissolved in water, but the salty/bitter taste make liquid supplements unpalatable.<ref name=bitter/> Typical doses range from 10 mmol (400 mg), to 20 mmol (800 mg). Potassium is also available in tablets or capsules, which are formulated to allow potassium to leach slowly out of a matrix, since very high concentrations of potassium ion that occur adjacent to a solid tablet can injure the gastric or intestinal mucosa. For this reason, non-prescription potassium pills are limited by law in the US to a maximum of 99 mg of potassium.{{citation needed|date=September 2017}}

Since the kidneys are the site of potassium excretion, individuals with impaired kidney function are at risk for [[hyperkalemia]] if dietary potassium and supplements are not restricted. The more severe the impairment, the more severe is the restriction necessary to avoid hyperkalemia.{{citation needed|date=September 2017}}

A [[meta-analysis]] concluded that a 1640 mg increase in the daily intake of potassium was associated with a 21% lower risk of stroke.<ref>{{cite journal |last1=D'Elia |first1=L. |last2=Barba |first2=G. |last3=Cappuccio |first3=F. |last4=Strazzullo |year=2011 |title=Potassium Intake, Stroke, and Cardiovascular Disease: A Meta-Analysis of Prospective Studies |journal=J Am Coll Cardiol |volume=57 |issue=10 |pages=1210–9 |doi=10.1016/j.jacc.2010.09.070 |pmid=21371638}}</ref> [[Potassium chloride]] and [[potassium bicarbonate]] may be useful to control mild [[hypertension]].<ref>{{cite journal |vauthors=He FJ, Marciniak M, Carney C, Markandu ND, Anand V, Fraser WD, Dalton RN, Kaski JC, MacGregor GA |title=Effects of potassium chloride and potassium bicarbonate on endothelial function, cardiovascular risk factors, and bone turnover in mild hypertensives |journal=Hypertension |volume=55 |issue=3 |pages=681–8 |year=2010 |pmid=20083724 |doi=10.1161/HYPERTENSIONAHA.109.147488 }}</ref> In 2016 potassium was the 33rd most prescribed medication in the United States with more than 22 million prescriptions.<ref>{{cite web |title=The Top 300 of 2019 |url=https://clincalc.com/DrugStats/Top300Drugs.aspx |website=clincalc.com |accessdate=22 December 2018}}</ref>

===Detection by taste buds===
Potassium can be detected by taste because it triggers three of the five types of taste sensations, according to concentration. Dilute solutions of potassium ions taste sweet, allowing moderate concentrations in milk and juices, while higher concentrations become increasingly bitter/alkaline, and finally also salty to the taste. The combined bitterness and saltiness of high-potassium solutions makes high-dose potassium supplementation by liquid drinks a palatability challenge.<ref name=bitter>{{cite book|author1=Institute of Medicine (U.S.). Committee on Optimization of Nutrient Composition of Military Rations for Short-Term, High-Stress Situations|author2=Institute of Medicine (U.S.). Committee on Military Nutrition Research|title=Nutrient composition of rations for short-term, high-intensity combat operations|url=https://books.google.com/books?id=kFatoIBbMboC&pg=PT287|date=2006|publisher=National Academies Press|isbn=978-0-309-09641-6|pages=287–}}</ref><ref>{{cite book|last=Shallenberger|first=R. S. |title=Taste chemistry|url=https://books.google.com/books?id=8_bjyjgClq0C&pg=PA120|date=1993|publisher=Springer|isbn=978-0-7514-0150-9|pages=120–}}</ref>

==Commercial production==
===Mining===
[[File:Museo de La Plata - Silvita.jpg|thumb|right| [[Sylvite]] from New Mexico]]
Potassium salts such as [[carnallite]], [[langbeinite]], [[polyhalite]], and [[sylvite]] form extensive [[evaporite]] deposits in ancient lake bottoms and [[seabed]]s,<ref name=geo/> making extraction of potassium salts in these environments commercially viable. The principal source of potassium – [[potash]] – is mined in [[Canada]], [[Russia]], [[Belarus]], [[Kazakhstan]], [[Germany]], [[Israel]], [[United States]], [[Jordan]], and other places around the world.<ref>{{cite book|url = https://books.google.com/books?id=EHx51n3T858C|publisher=Springer|title = Potash: deposits, processing, properties and uses|isbn = 978-0-412-99071-7|last1 = Garrett|first1= Donald E.|date = 1995-12-31}}</ref><ref name="USGSCS2008">{{cite web|url=http://minerals.usgs.gov/minerals/pubs/commodity/potash/mcs-2008-potas.pdf|first=Joyce A.|last=Ober|publisher=United States Geological Survey|title=Mineral Commodity Summaries 2008:Potash|accessdate=2008-11-20}}</ref><ref name="USGSYB2006">{{cite web|url=http://minerals.usgs.gov/minerals/pubs/commodity/potash/myb1-2006-potas.pdf|first=Joyce A.|last=Ober|publisher=United States Geological Survey|title=Mineral Yearbook 2006:Potash|accessdate=2008-11-20}}</ref> The first mined deposits were located near Staßfurt, Germany, but the deposits span from [[Great Britain]] over Germany into Poland. They are located in the [[Zechstein]] and were deposited in the Middle to Late [[Permian]]. The largest deposits ever found lie {{convert|1000|m|ft|abbr=off|sp=us}} below the surface of the Canadian province of [[Saskatchewan]]. The deposits are located in the [[Elk Point Group]] produced in the [[Middle Devonian]]. Saskatchewan, where several large mines have operated since the 1960s pioneered the technique of freezing of wet sands (the Blairmore formation) to drive mine shafts through them. The main potash mining company in Saskatchewan is the [[Potash Corporation of Saskatchewan]].<ref>{{cite book|url = https://books.google.com/books?id=rtRFyFO4hpEC&pg=PA433|publisher=U of Nebraska Press|page = 433|title = Encyclopedia of the Great Plains|isbn = 978-0-8032-4787-1|last = Wishart| first=David J.|date = 2004}}</ref> The water of the [[Dead Sea]] is used by Israel and Jordan as a source of potash, while the concentration in normal oceans is too low for commercial production at current prices.<ref name="USGSCS2008"/><ref name="USGSYB2006"/>

[[File:Wintershall Monte Kali 12.jpg|thumb| left|[[Monte Kali (Heringen)|Monte Kali]], a potash mining and [[beneficiation]] waste heap in [[Hesse|Hesse, Germany]], consisting mostly of [[sodium chloride]].]]

===Chemical extraction===
Several methods are used to separate potassium salts from sodium and magnesium compounds. The most-used method is fractional precipitation using the solubility differences of the salts at different temperatures. Electrostatic separation of the ground salt mixture is also used in some mines. The resulting sodium and magnesium waste is either stored underground or piled up in [[slag heap]]s. Most of the mined potassium mineral ends up as [[potassium chloride]] after processing. The mineral industry refers to potassium chloride either as potash, muriate of potash, or simply MOP.<ref name="indus"/>

Pure potassium metal can be isolated by [[electrolysis]] of its [[potassium hydroxide|hydroxide]] in a process that has changed little since it was first used by [[Humphry Davy]] in 1807. Although the electrolysis process was developed and used in industrial scale in the 1920s, the thermal method by reacting sodium with [[potassium chloride]] in a chemical equilibrium reaction became the dominant method in the 1950s.

The production of [[NaK|sodium potassium alloys]] is accomplished by changing the reaction time and the amount of sodium used in the reaction. The Griesheimer process employing the reaction of [[potassium fluoride]] with [[calcium carbide]] was also used to produce potassium.<ref name="indus" /><ref>{{cite book|doi=10.1002/0471238961.1615200103080921.a01.pub2|isbn= 9780471238966
|last1=Chiu|first1=Kuen-Wai
|publisher=John Wiley & Sons, Inc.
|title=Kirk-Othmer Encyclopedia of Chemical Technology
|date=2000
|chapter= Potassium
}}</ref>
:Na + KCl → NaCl + K                      (Thermal method)
:2 KF + {{chem|CaC|2}} → 2 K + {{chem|CaF|2}} + 2 C    (Griesheimer process)

[[reagent|Reagent-grade]] potassium metal costs about $10.00/[[pound (mass)|pound]] ($22/[[kg]]) in 2010 when purchased by the [[tonne]]. Lower purity metal is considerably cheaper. The market is volatile because long-term storage of the metal is difficult. It must be stored in a dry [[inert gas]] atmosphere or [[anhydrous]] [[mineral oil]] to prevent the formation of a surface layer of [[potassium superoxide]], a pressure-sensitive [[explosive]] that [[Detonation|detonates]] when scratched. The resulting explosion often starts a fire difficult to extinguish.<ref>[[#Burkhardt|Burkhardt]], p. 34</ref><ref name="fire">{{cite journal|doi =10.1016/j.jchas.2006.09.010|title =Review of the safety of potassium and potassium oxides, including deactivation by introduction into water|year =2007|last1 =Delahunt|first1 = J.|last2 =Lindeman|first2 = T.|journal =Journal of Chemical Health and Safety|volume =14|issue =2|pages =21–32}}</ref>

==Cation identification==
Potassium ions can be identified using [[sodium cobaltnitrite]] in the presence of acetic acid.
: 3K+ + Na3[Co(NO2)] → K3[Co(NO2)] + 3Na+
K3[Co(NO2)] is a yellow crystalline precipitate. This reaction cannot be done in basic solution as Co(OH)3 would precipitate instead. It cannot be done in the presence of a [[mineral acid]] either as H3[Co(NO2)] would be formed.
Another method of identifying K+ is to treat a potassium salt with [[sodium tetraphenhylborate]].
: K+ + Na[BPh4] → K[BPh4] + 3Na+

==Commercial uses==
===Fertilizer===
[[File:Patentkali (Potassium sulfate with magnesium).jpg|thumb|Potassium sulfate/magnesium sulfate fertilizer]]
Potassium ions are an essential component of [[plant]] nutrition and are found in most [[soil]] types.<ref name=g73/> They are used as a [[fertilizer]] in [[agriculture]], [[horticulture]], and [[hydroponic]] culture in the form of [[potassium chloride|chloride]] (KCl), [[potassium sulfate|sulfate]] ({{chem|K|2|SO|4}}), or [[potassium nitrate|nitrate]] ({{chem|KNO|3}}), representing the 'K' [[labeling of fertilizer|in 'NPK']]. Agricultural fertilizers consume 95% of global potassium chemical production, and about 90% of this potassium is supplied as KCl.<ref name=g73/> The potassium content of most plants ranges from 0.5% to 2% of the harvested weight of crops, conventionally expressed as amount of {{chem|K|2|O}}. Modern high-[[Crop yield|yield]] agriculture depends upon fertilizers to replace the potassium lost at harvest. Most agricultural fertilizers contain potassium chloride, while potassium sulfate is used for chloride-sensitive crops or crops needing higher sulfur content. The sulfate is produced mostly by decomposition of the complex minerals [[kainite]] ({{chem|MgSO|4|·KCl·3H|2|O}}) and [[langbeinite]] ({{chem|MgSO|4|·K|2|SO|4}}). Only a very few fertilizers contain potassium nitrate.<ref name="Kent">{{cite book|pages = 1135–57|first = Amit H. |last = Roy| url = https://books.google.com/books?id=AYjFoLCNHYUC&pg=PA1135|isbn = 978-0-387-27843-8|publisher=Springer|title = Kent and Riegel's handbook of industrial chemistry and biotechnology|date = 2007}}</ref> In 2005, about 93% of world potassium production was consumed by the fertilizer industry.<ref name="USGSYB2006" /> Furthermore, potassium can play a key role in nutrient cycling by controlling litter composition.<ref>{{cite journal |last1=Ochoa-Hueso |first1=R |last2=Delgado-Baquerizo |first2=M |last3=King |first3=PTA |last4=Benham |first4=M |last5=Arca |first5=V |last6=Power |first6=SA |title=Ecosystem type and resource quality are more important than global change drivers in regulating early stages of litter decomposition |journal=Soil Biology and Biochemistry |date=2019 |volume=129 |pages=144–152 |doi=10.1016/j.soilbio.2018.11.009 |accessdate=27 April 2019 |url=https://www.sciencedirect.com/science/article/abs/pii/S0038071718303845}}</ref>

===Medical use===
{{see also|Potassium chloride (medical use)}}
Potassium, in the form of [[potassium chloride]] is used as a medication to treat and prevent [[low blood potassium]].<ref name=WHO2008>{{cite book|title=WHO Model Formulary 2008|date=2009|publisher=World Health Organization|isbn=9789241547659|page=491|url=http://apps.who.int/medicinedocs/documents/s16879e/s16879e.pdf|accessdate=8 January 2017|deadurl=no|archiveurl=https://web.archive.org/web/20161213060118/http://apps.who.int/medicinedocs/documents/s16879e/s16879e.pdf|archivedate=13 December 2016}}</ref> Low blood potassium may occur due to [[vomiting]], [[diarrhea]], or certain medications.<ref name=MTM2017>{{cite web|title=Potassium chloride medical facts from Drugs.com|url=https://www.drugs.com/mtm/potassium-chloride.html|website=www.drugs.com|accessdate=14 January 2017|deadurl=no|archiveurl=https://web.archive.org/web/20170118040410/https://www.drugs.com/mtm/potassium-chloride.html|archivedate=18 January 2017}}</ref> It is given by [[intravenous infusion|slow injection into a vein]] or by mouth.<ref name=BNF69>{{cite book|title=British national formulary : BNF 69|date=2015|publisher=British Medical Association|isbn=9780857111562|pages=680, 684|edition=69}}</ref>

===Food additives===
Potassium sodium tartrate ({{chem|KNaC|4|H|4|O|6}}, [[Rochelle salt]]) is the main constituent of [[baking powder]]; it is also used in the [[silvering]] of mirrors. [[Potassium bromate]] ({{chem|KBrO|3}}) is a strong oxidizer (E924), used to improve dough strength and rise height. [[Potassium bisulfite]] ({{chem|KHSO|3}}) is used as a food preservative, for example in [[wine]] and [[beer]]-making (but not in meats). It is also used to [[bleach]] textiles and straw, and in the tanning of [[leather]]s.<ref>{{cite book|chapter-url = https://books.google.com/books?id=XqKF7PqV02cC&pg=PA86|page = 86|chapter = Bleaching and Maturing Agents|title = How Baking Works: Exploring the Fundamentals of Baking Science|isbn = 978-0-470-39267-6|author = Figoni, Paula I|date= 2010|publisher=John Wiley and Sons}}</ref><ref>{{cite book|chapter-url = https://books.google.com/books?id=eblAtwEXffcC&pg=PA4|publisher=Academic Press|pages = 4–6| chapter = Uses and Exposure to Sulfites in Food|title = Advances in food research|isbn = 978-0-12-016430-1|author = Chichester, C. O.|date = July 1986}}</ref>

===Industrial===
Major potassium chemicals are potassium hydroxide, potassium carbonate, potassium sulfate, and potassium chloride. Megatons of these compounds are produced annually.<ref>[[#Schultz|Schultz]]</ref>

[[Potassium hydroxide]] {{chem|KOH}} is a strong base, which is used in industry to neutralize strong and weak [[acid]]s, to control [[pH]] and to manufacture potassium [[salt (chemistry)|salts]]. It is also used to [[saponification|saponify]] [[fat]]s and [[oils]], in industrial cleaners, and in [[hydrolysis]] reactions, for example of [[esters]].<ref>{{cite book|publisher=Greenwood Publishing Group|chapter-url = https://books.google.com/books?id=UnjD4aBm9ZcC&pg=PA4|chapter = Personal Cleansing Products: Bar Soap|title = Chemical composition of everyday products|isbn = 978-0-313-32579-3|author = Toedt, John|author2 = Koza, Darrell|author3 = Cleef-Toedt, Kathleen Van|last-author-amp = yes|date = 2005}}</ref><ref>[[#Schultz|Schultz]], p. 95</ref>

[[Potassium nitrate]] ({{chem|KNO|3}}) or saltpeter is obtained from natural sources such as [[guano]] and [[evaporites]] or manufactured via the [[Haber process]]; it is the [[oxidant]] in [[gunpowder]] ([[black powder]]) and an important agricultural fertilizer. [[Potassium cyanide]] (KCN) is used industrially to dissolve [[copper]] and precious metals, in particular [[silver]] and [[gold]], by forming [[complex (chemistry)|complexes]]. Its applications include [[gold mining]], [[electroplating]], and [[electroforming]] of these [[metal]]s; it is also used in [[organic synthesis]] to make [[nitriles]]. [[Potassium carbonate]] ({{chem|K|2|CO|3}} or potash) is used in the manufacture of glass, soap, color TV tubes, fluorescent lamps, textile dyes and pigments.<ref>[[#Schultz|Schultz]], p. 99</ref> Potassium permanganate ({{chem|KMnO|4}}) is an oxidizing, bleaching and purification substance and is used for production of [[saccharin]]. [[Potassium chlorate]] ({{chem|KClO|3}}) is added to matches and explosives. [[Potassium bromide]] (KBr) was formerly used as a sedative and in photography.<ref name=g73/>

[[Potassium chromate]] ({{chem|K|2|CrO|4}}) is used in [[ink]]s, [[dye]]s, [[stain]]s (bright yellowish-red color); in [[explosive]]s and [[fireworks]]; in the tanning of leather, in [[fly paper]] and [[safety match]]es,<ref>{{cite journal|doi = 10.1021/ed017p515|title = Ignition of the safety match|year = 1940|last1 = Siegel|first1 = Richard S.|journal = Journal of Chemical Education|volume = 17|issue = 11|pages = 515|bibcode = 1940JChEd..17..515S}}</ref> but all these uses are due to the chemistry of the [[chromate]] ion, rather than the potassium ion.<ref>{{Ullmann|contribution=Chromium Compounds|doi=10.1002/14356007.a07_067|volume=9|page=178|first1=Gerd|last1=Anger|first2=Jost|last2=Halstenberg|first3=Klaus|last3=Hochgeschwender|first4=Christoph|last4=Scherhag|first5=Ulrich|last5=Korallus|first6=Herbert|last6=Knopf|first7=Peter|last7=Schmidt|first8=Manfred|last8=Ohlinger}}</ref>

====Niche uses====
There are thousands of uses of various potassium compounds. One example is [[potassium superoxide]], {{chem|KO|2}}, an orange solid that acts as a portable source of oxygen and a carbon dioxide absorber. It is widely used in [[Rebreather#Rebreathers whose absorbent releases oxygen|respiration systems]] in mines, submarines and spacecraft as it takes less volume than the gaseous oxygen.<ref>[[#Greenwood|Greenwood]], p. 74</ref><ref>{{cite book|url = https://books.google.com/books?id=oiWFhoRzPBQC&pg=PA93|title = The history of underwater exploration|first = Robert F. |last = Marx|publisher =Courier Dover Publications| date = 1990|isbn = 978-0-486-26487-5|page=93}}</ref>
: 4 {{chem|KO|2}} + 2 {{CO2}} → 2 {{chem|K|2|CO|3}} + 3 {{chem|O|2}}

Another example is [[potassium cobaltinitrite]], {{chem|K|3|[Co(NO|2|)|6|]|}}, which is used as artist's pigment under the name of [[Aureolin]] or Cobalt Yellow.<ref name="Getts">{{cite book|publisher=Courier Dover Publications|url = https://books.google.com/books?id=bdQVgKWl3f4C&pg=PA109|title = Painting materials: A short encyclopaedia|isbn = 978-0-486-21597-6|author = Gettens, Rutherford John|author2 = Stout, George Leslie|last-author-amp = yes|date = 1966|pages =109–110}}</ref>

The stable isotopes of potassium can be [[Laser cooling|laser cooled]] and used to probe fundamental and [[Quantum technology|technological]] problems in [[Quantum mechanics|quantum physics]]. The two [[boson]]ic isotopes possess convenient [[Feshbach resonance]]s to enable studies requiring tunable interactions, while 40K is one of only two stable [[fermion]]s amongst the alkali metals.<ref>{{Cite journal|last=Modugno|first=G.|last2=Benkő|first2=C.|last3=Hannaford|first3=P.|last4=Roati|first4=G.|last5=Inguscio|first5=M.|date=1999-11-01|title=Sub-Doppler laser cooling of fermionic ${}^{40}\mathrm{K}$ atoms|journal=Physical Review A|volume=60|issue=5|pages=R3373–R3376|doi=10.1103/PhysRevA.60.R3373|arxiv=cond-mat/9908102|bibcode=1999PhRvA..60.3373M}}</ref>

====Laboratory uses====
An [[alloy]] of sodium and potassium, [[NaK]] is a liquid used as a heat-transfer medium and a [[desiccant]] for producing [[air-free technique|dry and air-free solvents]]. It can also be used in [[reactive distillation]].<ref>{{cite book |doi=10.1021/ba-1957-0019.ch018|volume=19 |isbn=978-0-8412-0020-3 |chapter=Ch. 18: The Manufacture of Potassium and NaK |pages=169–173 |last2=Werner |first2=R. C. |last1=Jackson |first1=C. B. |year=1957 |title=Handling and uses of the alkali metals |series=Advances in Chemistry}}</ref> The ternary alloy of 12% Na, 47% K and 41% Cs has the lowest melting point of −78 °C of any metallic compound.<ref name=g76/>

Metallic potassium is used in several types of [[magnetometer]]s.<ref>{{cite book|publisher=Wiley-Blackwell|chapter-url =https://books.google.com/books?id=R_Y925b97ncC&pg=PA164|chapter = Optical Pumped Magnetometer|pages = 164|title =An introduction to geophysical exploration|isbn =978-0-632-04929-5|author =Kearey, Philip|author2 =Brooks, M|author3 =Hill, Ian|last-author-amp =yes|date =2002}}</ref>

==Precautions==
{{Chembox
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|Section7={{Chembox Hazards
| ExternalSDS =
| GHSPictograms = {{GHS02}}{{GHS05}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|260|314}}
| PPhrases = {{P-phrases|223|231+232|280|305+351+338|370+378|422}}<ref>{{Cite web | url=https://www.sigmaaldrich.com/catalog/product/aldrich/244856?lang=en&region=US | title=Potassium 244856}}</ref>
| NFPA-H = 3
| NFPA-F = 3
| NFPA-R = 2
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[[File:Potassium water 20.theora.ogv|thumb|alt=A piece of potassium metal is dropped into a clear container of water and skates around, burning with a bright pinkish or lilac flame for a short time until finishing with a pop and splash.|A reaction of potassium metal with water. Hydrogen is produced, and with potassium vapor, burns with a pink or lilac flame. Strongly alkaline potassium hydroxide is formed in solution.]]

Potassium metal reacts violently with water producing [[potassium hydroxide]] (KOH) and [[hydrogen]] gas.

:2 K (s) + 2 {{H2O}} (l) → 2 KOH (aq) + {{chem|H|2}}↑ (g)

This reaction is exothermic and releases enough heat to ignite the resulting hydrogen in the presence of oxygen. Potassium tends to explode in contact with water and without the oxygen presence. It is called [[Coulomb explosion|coulombic explosion]], possibly splashing onlookers with [[potassium hydroxide]], which is a strong [[alkali]] that destroys living tissue and causes skin burns. Finely grated potassium ignites in air at room temperature. The bulk metal ignites in air if heated. Because its density is 0.89 g/cm3, burning potassium floats in water that exposes it to atmospheric oxygen. Many common fire extinguishing agents, including water, either are ineffective or make a potassium fire worse. [[Nitrogen]], [[argon]], [[sodium chloride]] (table salt), [[sodium carbonate]] (soda ash), and [[silicon dioxide]] (sand) are effective if they are dry. Some [[Fire extinguisher|Class D]] dry powder extinguishers designed for metal fires are also effective. These agents deprive the fire of oxygen and cool the potassium metal.<ref>{{cite book| url = https://books.google.com/books?id=2fHsoobsCNwC&pg=PA459 |page = 459| title = Fire and Life Safety Inspection Manual| isbn = 978-0-87765-472-8|publisher=Jones & Bartlett Learning| last = Solomon |first=Robert E.| date = 2002}}</ref>

Potassium reacts violently with [[halogens]] and detonates in the presence of [[bromine]]. It also reacts explosively with [[sulfuric acid]]. During combustion, potassium forms peroxides and superoxides. These peroxides may react violently with [[organic compound]]s such as oils. Both peroxides and superoxides may react explosively with metallic potassium.<ref>{{cite web|url=http://www.hss.doe.gov/nuclearsafety/ns/techstds/standard/hdbk1081/hbk1081d.html |title=DOE Handbook-Alkali Metals Sodium, Potassium, NaK, and Lithium |publisher=Hss.doe.gov |accessdate=2010-10-16 |archiveurl=https://web.archive.org/web/20100928002539/http://www.hss.doe.gov/nuclearsafety/ns/techstds/standard/hdbk1081/hbk1081d.html  |archivedate=2010-09-28}}</ref>

Because potassium reacts with water vapor in the air, it is usually stored under anhydrous mineral oil or kerosene. Unlike lithium and sodium, however, potassium should not be stored under oil for longer than six months, unless in an inert (oxygen free) atmosphere, or under vacuum. After prolonged storage in air dangerous shock-sensitive peroxides can form on the metal and under the lid of the container, and can detonate upon opening.<ref>{{cite web |url=https://www.ncsu.edu/ehs/www99/right/handsMan/lab/Peroxide.pdf |title=Danger: peroxidazable chemicals |last=Wray |first=Thomas K. |publisher=Environmental Health & Public Safety, [[North Carolina State University]] |deadurl=bot: unknown |archiveurl=https://web.archive.org/web/20160729111002/https://www.ncsu.edu/ehs/www99/right/handsMan/lab/Peroxide.pdf |archivedate=2016-07-29 }}</ref>

Because of the highly reactive nature of potassium metal, it must be handled with great care, with full skin and eye protection and preferably an explosion-resistant barrier between the user and the metal. Ingestion of large amounts of potassium compounds can lead to [[hyperkalemia]], strongly influencing the cardiovascular system.<ref name="hyper">{{cite book|publisher=Lippincott Williams & Wilkins|chapter-url = https://books.google.com/books?id=BfdighlyGiwC&pg=PA903| chapter = Potassium Chloride and Potassium Permanganate|pages = 903–5|title = Medical toxicology|isbn = 978-0-7817-2845-4|last = Schonwald|first = Seth|date = 2004}}</ref><ref>{{cite book|url =https://books.google.com/books?id=l8RkPU1-M5wC&pg=PA223 |publisher=Elsevier Health Sciences|page =223|title =Emergency medicine secrets|isbn =978-1-56053-503-4|last =Markovchick |first=Vincent J.|last2 =Pons |first2=Peter T.|last-author-amp =yes|date =2003}}</ref> Potassium chloride is used in the [[United States]] for [[lethal injection]] executions.<ref name="hyper"/>

==See also==
{{Subject bar
|portal1=Chemistry
|portal2=Medicine
|book1=Potassium
|book2=Period 4 elements
|book3=Alkali metals
|book4=Chemical elements (sorted alphabetically)
|book5=Chemical elements (sorted by number)
|commons=y
|wikt=y
|wikt-search=potassium
|v=y
|v-search=Potassium atom
|b=y
|b-search=Wikijunior:The Elements/Potassium}}

==References==
{{Reflist|30em}}

==Bibliography==
* {{cite book|doi = 10.1002/14356007.a22_031.pub2|title = Ullmann's Encyclopedia of Industrial Chemistry|date = 2006|ref=Burkhardt|last = Burkhardt |first=Elizabeth R.|chapter = Potassium and Potassium Alloys|isbn = 978-3-527-30673-2|volume=A22|pages=31–38 }}
* {{cite book|ref=Greenwood|last=Greenwood|first=Norman N.|last2=Earnshaw |first2=Alan|date=1997|title=Chemistry of the Elements |edition=2nd|publisher= Butterworth-Heinemann|isbn=978-0-08-037941-8}}
* {{cite book|ref=Holleman|publisher = Walter de Gruyter|date = 2007|edition = 91–100|isbn = 978-3110177701|chapter-url=https://books.google.com/books?id=mahxPfBdcxcC&printsec=frontcover|title = Lehrbuch der Anorganischen Chemie|first1 = Arnold F.|last1 = Holleman|last2 = Wiberg|first2 = Egon|last3 = Wiberg|first3 = Nils|chapter = Potassium| language = German}}
* {{cite book|doi = 10.1002/14356007.a22_031.pub2|title = Ullmann's Encyclopedia of Industrial Chemistry|date = 2006|ref=Schultz|last1= Schultz|first1 = H.|last2 = Bauer|first2 = G.|last3 = Schachl|first3 = E.|last4 = Hagedorn|first4 = F.|last5 = Schmittinger|first5 = P.|chapter = Potassium compounds|isbn = 978-3-527-30673-2|volume = A22|pages = 39–103|displayauthors = 1}}
* [http://ndb.nal.usda.gov/ndb/search/list National Nutrient Database] at [[USDA]] Website

==External links==
* [http://www.periodicvideos.com/videos/019.htm Potassium] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
* {{Britannica|472373|Potassium (K)}}

{{Compact periodic table}}
{{Potassium compounds}}
{{good article}}

{{Authority control}}

[[Category:Potassium| ]]
[[Category:Chemical elements]]
[[Category:Alkali metals]]
[[Category:Biology and pharmacology of chemical elements]]
[[Category:Dietary minerals]]
[[Category:Desiccants]]
[[Category:Reducing agents]]
[[Category:Articles containing video clips]]

Potassium

2019-04-30T16:34:44Z

173.165.237.1:

{{short description|Chemical element with atomic number 19}}
{{pp-move-indef}}
{{Infobox potassium}}
'''Potassium''' is a [[chemical element]] with symbol '''K''' (from [[New Latin|Neo-Latin]] ''[[wikt:kalium#Latin|kalium]]'') and [[atomic number]] 19. Potassium is a silvery-white metal that is soft enough to be cut with a knife, with little force. <ref>{{cite web |url=https://www.britannica.com/science/potassium |title=Potassium/ Chemical element |last=Augustyn |first=Adam |publisher=Encyclopedia Britannica |accessdate=2019-04-17 |quote=Potassium Physical properties }}</ref> Potassium metal reacts rapidly with atmospheric [[oxygen]] to form flaky white [[potassium peroxide]] in only seconds of exposure. It was first isolated from [[potash]], the ashes of plants, from which its name derives. In the [[periodic table]], potassium is one of the [[alkali metal]]s, all of which have a single outer-shell [[valence electron]] that is easily removed to create an ion with a positive charge – a [[cation]], that combines with [[anion]]s to form [[Salt (chemistry)|salts]]. Potassium in nature occurs only in ionic salts. Elemental potassium reacts vigorously with water, generating sufficient heat to ignite [[hydrogen]] emitted in the reaction, and burning with a [[lilac]]-[[flame color|colored flame]]. It is found dissolved in sea water (which is 0.04% potassium by weight<ref name="seawaterconcentration">{{cite journal |journal= [[The Journal of Experimental Biology]] |url= http://jeb.biologists.org/content/jexbio/16/2/178.full.pdf |title=The Sodium and Potassium Content of Sea Water |first=D. A. |last= Webb |page= 183 |date=April 1939 |issue=2}}</ref><ref>{{cite web |url= http://www.seafriends.org.nz/oceano/seawater.htm |title=Detailed composition of seawater at 3.5% salinity |first= J. |last= Anthoni |work=seafriends.org.nz |year=2006 |accessdate=2011-09-23}}</ref>), and occurs in many [[mineral]]s such as [[orthoclase]], a common constituent of [[granite]]s and other [[igneous rock]]s.

Potassium is chemically very similar to [[sodium]], the previous element in group 1 of the periodic table. They have a similar first [[ionization energy]], which allows for each atom to give up its sole outer electron. That they are different elements that combine with the same [[anion]]s to make similar salts was suspected in 1702,<ref name="1702Suspect" /> and was proven in 1807 using [[electrolysis]]. Naturally occurring potassium is composed of three [[isotope]]s, of which [[potassium-40|{{chem|40|K}}]] is [[radioactive]]. Traces of {{chem|40|K}} are found in all potassium, and it is the most common [[radioisotope]] in the human body.

Potassium ions are vital for the functioning of all living cells. The transfer of potassium ions across nerve cell membranes is necessary for normal nerve transmission; potassium deficiency and excess can each result in numerous signs and symptoms, including an abnormal heart rhythm and various [[Electrocardiography|electrocardiographic]] abnormalities. Fresh fruits and vegetables are good dietary sources of potassium. The body responds to the influx of dietary potassium, which raises [[serum (blood)|serum]] potassium levels, with a shift of potassium from outside to inside cells and an increase in potassium excretion by the kidneys.

Most industrial applications of potassium exploit the high [[solubility]] in water of potassium compounds, such as [[Saltwater soap|potassium]] [[soap]]s. Heavy crop production rapidly depletes the soil of potassium, and this can be remedied with agricultural fertilizers containing potassium, accounting for 95% of global potassium chemical production.<ref name="g73">[[#Greenwood|Greenwood]], p. 73</ref>
{{TOC limit}}

==Etymology==

The English name for the element ''potassium'' comes from the word "[[potash]]",<ref>{{cite journal|first=Humphry|last=Davy|title=On some new phenomena of chemical changes produced by electricity, in particular the decomposition of the fixed alkalies, and the exhibition of the new substances that constitute their bases; and on the general nature of alkaline bodies|page=32|year=1808|volume=98|journal=Philosophical Transactions of the Royal Society|url=https://books.google.com/?id=gpwEAAAAYAAJ&pg=PA32|doi=10.1098/rstl.1808.0001}}</ref> which refers to an early method of extracting various potassium salts: placing in a ''pot'' the ''ash'' of burnt wood or tree leaves, adding water, heating, and evaporating the solution. When [[Humphry Davy]] first isolated the pure element using [[electrolysis]] in 1807, he named it ''potassium'', which he derived from the word potash.

The symbol "K" stems from ''kali'', itself from the root word ''[[alkali]]'', which in turn comes from ''{{lang-ar|القَلْيَه}}'' ''al-qalyah'' "plant ashes". In 1797, the German chemist [[Martin Heinrich Klaproth|Martin Klaproth]] discovered "potash" in the minerals [[leucite]] and [[lepidolite]], and realized that "potash" was not a product of plant growth but actually contained a new element, which he proposed to call ''kali''.<ref>M. Klaproth (1797) "Nouvelles données relatives à l'histoire naturelle de l'alcali végétal" (New data regarding the natural history of the vegetable alkali), ''Mémoires de l'Académie royale des sciences et belles-lettres'' (Berlin), pp. 9-13 ; [https://babel.hathitrust.org/cgi/pt?id=mdp.39015073704093;view=1up;seq=103 see p. 13.] From p. 13: ''"Cet alcali ne pouvant donc plus être envisagé comme un produit de la végétation dans les plantes, occupe une place propre dans la série des substances primitivement simples du règne minéral, &I il devient nécessaire de lui assigner un nom, qui convienne mieux à sa nature. 
''La dénomination de ''Potasche'' (potasse) que la nouvelle nomenclature françoise a consacrée comme nom de tout le genre, ne sauroit faire fortune auprès des chimistes allemands, qui sentent à quel point la dérivation étymologique en est vicieuse. Elle est prise en effet de ce qu'anciennement on se servoit pour la calcination des lessives concentrées des cendres, de pots de fer (''pott'' en dialecte de la Basse-Saxe) auxquels on a substitué depuis des fours à calciner. 
''Je propose donc ici, de substituer aux mots usités jusqu'ici d'alcali des plantes, alcali végétal, potasse, &c. celui de ''kali'', & de revenir à l'ancienne dénomination de ''natron'', au lieu de dire alcali minéral, soude &c."'' 
(This alkali [i.e., potash] — [which] therefore can no longer be viewed as a product of growth in plants — occupies a proper place in the originally simple series of the mineral realm, and it becomes necessary to assign it a name that is better suited to its nature. 
The name of "potash" (''potasse''), which the new French nomenclature has bestowed as the name of the entire species [i.e., substance], would not find acceptance among German chemists, who feel to some extent [that] the etymological derivation of it is faulty. Indeed, it is taken from [the vessels] that one formerly used for the roasting of washing powder concentrated from cinders: iron pots (''pott'' in the dialect of Lower Saxony), for which roasting ovens have been substituted since then. 
Thus I now propose to substitute for the until now common words of "plant alkali", "vegetable alkali", "potash", etc., that of ''kali'' ; and to return to the old name of ''natron'' instead of saying "mineral alkali", "soda", etc.)</ref> In 1807, [[Humphry Davy]] produced the element via electrolysis: in 1809, [[Ludwig Wilhelm Gilbert]] proposed the name ''Kalium'' for Davy's "potassium".<ref>{{cite journal|author=Davy, Humphry |year=1809|title=Ueber einige neue Erscheinungen chemischer Veränderungen, welche durch die Electricität bewirkt werden; insbesondere über die Zersetzung der feuerbeständigen Alkalien, die Darstellung der neuen Körper, welche ihre Basen ausmachen, und die Natur der Alkalien überhaupt|trans-title=On some new phenomena of chemical changes that are achieved by electricity; particularly the decomposition of flame-resistant alkalis [i.e., alkalies that cannot be reduced to their base metals by flames], the preparation of new substances that constitute their [metallic] bases, and the nature of alkalies generally|journal=Annalen der Physik|volume=31|issue=2|pages=113–175|url=https://books.google.com/books?id=vyswAAAAYAAJ&pg=PA157|quote=p. 157: In unserer deutschen Nomenclatur würde ich die Namen ''Kalium'' und ''Natronium'' vorschlagen, wenn man nicht lieber bei den von Herrn Erman gebrauchten und von mehreren angenommenen Benennungen ''Kali-Metalloid'' and ''Natron-Metalloid'', bis zur völligen Aufklärung der chemischen Natur dieser räthzelhaften Körper bleiben will. Oder vielleicht findet man es noch zweckmässiger fürs Erste zwei Klassen zu machen, ''Metalle'' und ''Metalloide'', und in die letztere ''Kalium'' und ''Natronium'' zu setzen. — Gilbert. (In our German nomenclature, I would suggest the names ''Kalium'' and ''Natronium'', if one would not rather continue with the appellations ''Kali-metalloid'' and ''Natron-metalloid'' which are used by Mr. Erman [i.e., German physics professor [[Paul Erman]] (1764–1851)] and accepted by several [people], until the complete clarification of the chemical nature of these puzzling substances. Or perhaps one finds it yet more advisable for the present to create two classes, ''metals'' and ''metalloids'', and to place ''Kalium'' and ''Natronium'' in the latter — Gilbert.)|bibcode=1809AnP....31..113D|doi=10.1002/andp.18090310202}}</ref> In 1814, the Swedish chemist [[Jöns Jacob Berzelius|Berzelius]] advocated the name ''kalium'' for potassium, with the chemical symbol "K".<ref>Berzelius, J. Jacob (1814) ''Försök, att, genom användandet af den electrokemiska theorien och de kemiska proportionerna, grundlägga ett rent vettenskapligt system för mineralogien'' [Attempt, by the use of electrochemical theory and chemical proportions, to found a pure scientific system for mineralogy]. Stockholm, Sweden: A. Gadelius., [https://archive.org/stream/bub_gb_Uw0-AAAAcAAJ#page/n91/mode/2up p. 87.]</ref>

The English and French speaking countries adopted Davy and Gay-Lussac/Thénard's name Potassium, while the Germanic countries adopted Gilbert/Klaproth's name Kalium.<ref>[http://www.vanderkrogt.net/elements/element.php?sym=K 19. Kalium (Potassium) - Elementymology & Elements Multidict]</ref> The "Gold Book" of the International Union of Physical and Applied Chemistry has designated the official chemical symbol as '''K'''.<ref>IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997)</ref>

==Properties==
===Physical===
[[File:FlammenfärbungK.png|thumb|right|The [[flame test]] of potassium.]]
Potassium is the second least dense metal after [[lithium]]. It is a soft solid with a low [[melting point]], and can be easily cut with a knife. Freshly cut potassium is silvery in appearance, but it begins to tarnish toward gray immediately on exposure to air.<ref name=g76>[[#Greenwood|Greenwood]], p. 76</ref> In a [[flame test]], potassium and its compounds emit a lilac color with a peak emission wavelength of 766.5 nanometers.<ref>[[#Greenwood|Greenwood]], p. 75</ref>

===Chemical===

Neutral potassium atoms have 19 electrons, one more than the extremely stable configuration of the [[noble gas]] [[argon]]. Because of this and its low first [[ionization energy]] of 418.8 kJ/mol, the potassium atom is much more likely to lose the last electron and acquire a positive charge than to gain one and acquire a negative charge (though negatively charged [[alkalide]] {{chem|K|−}} ions are not impossible).<ref name="K-">{{cite journal|journal = [[Angewandte Chemie International Edition]]|year = 1979|last = Dye|first=J. L. |title = Compounds of Alkali Metal Anions|volume = 18|issue = 8|pages = 587–598|doi = 10.1002/anie.197905871}}</ref><ref name="K+++">{{cite book|first1=A. M.| last1=James|first2=M. P.|last2=Lord|title=Macmillan's chemical and physical data|publisher=Macmillan| location=London| date=1992|isbn=978-0-333-51167-1}}</ref> This process requires so little energy that potassium is readily oxidized by atmospheric oxygen. In contrast, the second ionization energy is very high (3052 kJ/mol), because removal of two electrons breaks the stable noble gas electronic configuration (the configuration of the inert argon).<ref name="K+++"/> Potassium therefore does not form compounds with the oxidation state of +2 or higher.<ref name="K-"/>

Potassium is an extremely active metal that reacts violently with oxygen in water and air. With oxygen it forms [[potassium peroxide]], and with water potassium forms [[potassium hydroxide]]. The reaction of potassium with water is dangerous because of its violent [[exothermic]] character and the production of [[hydrogen]] gas. Hydrogen reacts again with atmospheric oxygen, producing water, which reacts with the remaining potassium. This reaction requires only traces of water; because of this, potassium and the liquid sodium-potassium ([[NaK]]) alloy are potent [[desiccant]]s that can be used to dry [[solvent]]s prior to distillation.<ref name=b35>[[#Burkhardt|Burkhardt]], p. 35</ref>

Because of the sensitivity of potassium to water and air, reactions with other elements are possible only in an inert atmosphere such as [[argon]] gas using [[air-free technique]]s. Potassium does not react with most hydrocarbons such as mineral oil or [[kerosene]].<ref name="HollemanAF">{{cite book|publisher = Walter de Gruyter|date = 1985|edition = 91–100|isbn = 978-3-11-007511-3|title = Lehrbuch der Anorganischen Chemie|first1 = Arnold F.|last1 = Holleman|last2 = Wiberg|first2 = Egon|last3 = Wiberg|first3 = Nils|chapter = Potassium| language = German}}</ref> It readily dissolves in liquid [[ammonia]], up to 480 g per 1000 g of ammonia at 0 °C. Depending on the concentration, the ammonia solutions are blue to yellow, and their electrical conductivity is similar to that of liquid metals. In a pure solution, potassium slowly reacts with ammonia to form [[Potassium amide|{{chem|KNH|2}}]], but this reaction is accelerated by minute amounts of transition metal salts.<ref name=b32>[[#Burkhardt|Burkhardt]], p. 32</ref> Because it can reduce the [[salt (chemistry)|salt]]s to the metal, potassium is often used as the reductant in the preparation of finely divided metals from their salts by the [[Rieke metal|Rieke method]].<ref>{{cite journal| author=Rieke, R. D.|title=Preparation of Organometallic Compounds from Highly Reactive Metal Powders|journal= [[Science (journal)|Science]]|year= 1989|volume= 246| pages= 1260–4|doi=10.1126/science.246.4935.1260| pmid=17832221| issue=4935|bibcode = 1989Sci...246.1260R }}</ref> For example, the preparation of magnesium by this method employs potassium as the reductant:

:{{chem|link=Magnesium chloride|MgCl|2}} + 2 K → Mg + 2 KCl

===Compounds===
:[[Image:potassium-superoxide-unit-cell-3D-ionic.png|thumb|right|upright|Structure of solid potassium superoxide ({{chem|KO|2}}).]]
The only common oxidation state for potassium is +1. Potassium metal is a powerful [[reducing agent]] that is easily oxidized to the monopositive [[cation]], {{chem|K|+}}. Once oxidized, it is very stable and difficult to reduce back to the metal.<ref name="K-"/>

Potassium oxidizes faster than most metals and often forms [[oxide]]s containing oxygen-oxygen bonds, as do all alkali metals except lithium. There are three possible oxides of potassium: [[potassium oxide]] (K2O), [[potassium peroxide]] (K2O2), and [[potassium superoxide]] (KO2);<ref>{{cite book|last = Lide|first = David R.|date = 1998|title = Handbook of Chemistry and Physics|edition = 87th|location = Boca Raton, Florida, United States|publisher = CRC Press|isbn = 978-0-8493-0594-8|pages = 477; 520}}</ref> they contain three different oxygen-based ions: [[oxide]] ({{chem|O|2-}}), [[peroxide]] ({{chem|O|2|2-}}), and [[superoxide]] ({{chem|O|2|-}}). The latter two species, especially the [[superoxide]], are rare and are formed only in reaction of very [[electronegativity|electropositive]] metals (Na, K, Rb, Cs, etc.) with oxygen; these species contain oxygen-oxygen bonds.<ref name=b32/> All potassium-oxygen binary compounds are known to react with water violently, forming [[potassium hydroxide]].

Potassium hydroxide (KOH) is a very strong alkali, and up to 1.21 [[kilogram|kg]] of it can dissolve in a single liter of water.<ref>{{RubberBible86th|page=4–80}}</ref><ref>[[#Schultz|Schultz]], p. 94</ref> KOH reacts readily with carbon dioxide to produce [[potassium carbonate]], and is used to remove traces of the gas from air.

In general, potassium compounds are highly ionic and, owing to the high hydration energy of the {{chem|K|+}} ion, have excellent water solubility. The main species in water solution are the aquated complexes {{chem|[K|(H|2|O)|n|]|+}} where n = 6 and 7.<ref name=Lincoln>Lincoln, S. F.; Richens, D. T. and Sykes, A. G. "Metal Aqua Ions" in J. A. McCleverty and T. J. Meyer (eds.) [http://www.sciencedirect.com/science/referenceworks/9780080437484 ''Comprehensive Coordination Chemistry II''], Vol. 1, pp. 515–555, {{ISBN|978-0-08-043748-4}}.</ref> The potassium ion is colorless in water and is very difficult to [[Precipitation (chemistry)|precipitate]]; possible precipitation methods include reactions with [[sodium tetraphenylborate]], [[hexachloroplatinic acid]], and [[sodium cobaltinitrite]] into [[potassium tetraphenylborate]], [[potassium hexachloroplatinate]], and [[potassium cobaltinitrite]].<ref name="HollemanAF"/>

===Isotopes===
{{main|Isotopes of potassium}}
There are 24 known [[isotope]]s of potassium, three of which occur naturally: {{chem|39|K}} (93.3%), {{chem|40|K}} (0.0117%), and {{chem|41|K}} (6.7%). Naturally occurring {{chem|link=potassium-40|40|K}} has a [[half-life]] of 1.250×109 years. It decays to stable {{chem|link=Argon|40|Ar}} by [[electron capture]] or [[positron emission]] (11.2%) or to stable {{chem|link=Calcium|40|Ca}} by [[beta decay]] (88.8%).<ref name="NUBASE">{{NUBASE 2003}}</ref> The decay of {{chem|40|K}} to {{chem|40|Ar}} is the basis of a common method for dating rocks. The conventional [[Potassium-argon dating|K-Ar dating method]] depends on the assumption that the rocks contained no argon at the time of formation and that all the subsequent radiogenic argon ({{chem|40|Ar}}) was quantitatively retained. [[Mineral]]s are dated by measurement of the concentration of potassium and the amount of radiogenic {{chem|40|Ar}} that has accumulated. The minerals best suited for dating include [[biotite]], [[muscovite]], metamorphic [[hornblende]], and volcanic [[feldspar]]; [[Petrography|whole rock]] samples from volcanic flows and shallow [[Igneous rock|instrusives]] can also be dated if they are unaltered.<ref name="NUBASE"/><ref>{{cite book|chapter-url = https://books.google.com/books?id=k90iAnFereYC&pg=PA207|pages =203–8|chapter= Theory and Assumptions in Potassium–Argon Dating|title = Isotopes in the Earth Sciences|isbn = 978-0-412-53710-3|last1 = Bowen|first1 = Robert|last2 = Attendorn|first2 = H. G.|date = 1988|publisher=Springer}}</ref> Apart from dating, potassium isotopes have been used as [[radioactive tracer|tracers]] in studies of [[weathering]] and for [[nutrient cycling]] studies because potassium is a [[macronutrient (ecology)|macronutrient]] required for [[life]].<ref>{{cite book|author=Anaç, D.|author2=Martin-Prével, P.|last-author-amp=yes |title=Improved crop quality by nutrient management|url=https://books.google.com/books?id=9Hr4w6QhPGsC&pg=PA290|date=1999|publisher=Springer|isbn=978-0-7923-5850-3|pages=290–}}</ref>

{{chem|40|K}} occurs in natural potassium (and thus in some commercial salt substitutes) in sufficient quantity that large bags of those substitutes can be used as a radioactive source for classroom demonstrations. {{chem|40|K}} is the radioisotope with the largest abundance in the body. In healthy animals and people, {{chem|40|K}} represents the largest source of radioactivity, greater even than {{chem|link=Carbon-14|14|C}}. In a human body of 70 kg mass, about 4,400 nuclei of {{chem|40|K}} decay per second.<ref>{{cite web |url=http://sciencedemonstrations.fas.harvard.edu/presentations/radioactive-human-body|title=Radiation and Radioactive Decay. Radioactive Human Body |accessdate= July 2, 2016|publisher =Harvard Natural Sciences Lecture Demonstrations}}</ref> The activity of natural potassium is 31 [[Becquerel|Bq]]/g.<ref>{{cite book|url = https://books.google.com/books?id=KRVXMiQWi0cC&pg=PA32|page =32|title = Radioactive fallout in soils, crops and food: a background review|isbn = 978-92-5-102877-3|author1 = Winteringham, F. P. W|author2 = Effects, F.A.O. Standing Committee on Radiation, Land And Water Development Division, Food and Agriculture Organization of the United Nations|date = 1989|publisher=Food & Agriculture Org.}}</ref>

==Cosmic formation and distribution==
[[File:PotassiumFeldsparUSGOV.jpg|thumb|right|upright|Potassium in [[feldspar]]]]
Potassium is formed in [[supernova]]e by [[nucleosynthesis]] from lighter atoms. Potassium is principally created in Type II supernovae via an [[Supernova nucleosynthesis|explosive oxygen-burning process]].<ref>{{cite journal|first= V.|display-authors= 4|last= Shimansky|title=Observational constraints on potassium synthesis during the formation of stars of the Galactic disk| journal=Astronomy Reports|date=September 2003|bibcode = 2003ARep...47..750S|last2= Bikmaev|first2=I. F.|last3= Galeev|first3=A. I.|last4= Shimanskaya|first4=N. N.|last5= Ivanova|first5=D. V.|last6= Sakhibullin|first6=N. A.|last7= Musaev|first7=F. A.|last8= Galazutdinov|first8=G. A.|volume= 47|pages= 750–762|doi= 10.1134/1.1611216|issue= 9}}</ref> {{chem|40|K}} is also formed in [[s-process]] nucleosynthesis and the [[neon burning process]].<ref>{{Cite journal|last=The|first=L.-S.|last2=Eid|first2=M. F. El|last3=Meyer|first3=B. S.|date=2000|title=A New Study of s-Process Nucleosynthesis in Massive Stars|journal=The Astrophysical Journal|volume=533|issue=2|pages=998|doi=10.1086/308677|issn=0004-637X|arxiv=astro-ph/9812238}}</ref>

Potassium is the 20th most abundant element in the solar system and the 17th most abundant element by weight in the earth. It makes up about 2.6% of the weight of the [[earth's crust]] and is the seventh most abundant element in the crust.<ref>[[#Greenwood|Greenwood]], p. 69</ref> The potassium concentration in seawater is 0.39 g/L<ref name="seawaterconcentration"/> (0.039 wt/v%), about one twenty-seventh the concentration of sodium.<ref name=geo>{{cite book|url = https://books.google.com/books?id=NXEmcGHScV8C&pg=PA3| publisher = Springer| date = 2009|title = Seawater Desalination: Conventional and Renewable Energy Processes|first1= Giorgio |last1=Micale| first2=Andrea |last2=Cipollina| first3=Lucio |last3=Rizzuti|page = 3| isbn = 978-3-642-01149-8}}</ref><ref name="indus">{{cite book|chapter-url = https://books.google.com/books?id=zNicdkuulE4C&pg=PA723| title =Industrial minerals & rocks: commodities, markets, and uses|publisher = Society for Mining, Metallurgy, and Exploration|date= 2006| first1= Michel|last1=Prud'homme|first2= Stanley T.| last2 = Krukowski|chapter = Potash|pages = 723–740|isbn = 978-0-87335-233-8}}</ref>

==Potash==
{{main|Potash}}
Potash is primarily a mixture of potassium salts because plants have little or no sodium content, and the rest of a plant's major mineral content consists of calcium salts of relatively low solubility in water. While potash has been used since ancient times, it was not understood for most of its history to be a fundamentally different substance from sodium mineral salts. [[Georg Ernst Stahl]] obtained experimental evidence that led him to suggest the fundamental difference of sodium and potassium salts in 1702,<ref name="1702Suspect">{{cite book|url = https://books.google.com/books?id=b-ATAAAAQAAJ&pg=PA167|page = 167|title = Chymische Schriften|last1 = Marggraf|first = Andreas Siegmund|date = 1761}}</ref> and [[Henri Louis Duhamel du Monceau]] was able to prove this difference in 1736.<ref>{{cite journal|url = http://gallica.bnf.fr/ark:/12148/bpt6k3533j/f73.image.r=Memoires%20de%20l%27Academie%20royale%20des%20Sciences.langEN|journal = Memoires de l'Academie Royale des Sciences| title = Sur la Base de Sel Marin| last = du Monceau|first = H. L. D.| pages = 65–68| language = French|date = 1702–1797}}</ref> The exact chemical composition of potassium and sodium compounds, and the status as chemical element of potassium and sodium, was not known then, and thus [[Antoine Lavoisier]] did not include the alkali in his list of chemical elements in 1789.<ref name="weeks">{{cite journal|doi = 10.1021/ed009p1035|title = The discovery of the elements. IX. Three alkali metals: Potassium, sodium, and lithium|year = 1932|last1 = Weeks|first1 = Mary Elvira|authorlink1=Mary Elvira Weeks|journal = Journal of Chemical Education|volume = 9|issue = 6|pages = 1035|bibcode = 1932JChEd...9.1035W}}</ref><ref name="disco">{{cite journal|jstor = 228541|pages = 247–258|last1 = Siegfried|first1 = R.|title = The Discovery of Potassium and Sodium, and the Problem of the Chemical Elements|volume = 54|issue = 2|journal = Isis|year = 1963|doi = 10.1086/349704}}</ref> For a long time the only significant applications for potash were the production of glass, bleach, soap and [[gunpowder]] as potassium nitrate.<ref>{{cite journal|doi = 10.1021/ed003p749|title = Historical notes upon the domestic potash industry in early colonial and later times|year = 1926|last1 = Browne|first1 = C. A.|journal = Journal of Chemical Education|volume = 3|issue = 7|pages = 749–756|bibcode = 1926JChEd...3..749B}}</ref> Potassium soaps from animal fats and vegetable oils were especially prized because they tend to be more water-soluble and of softer texture, and are therefore known as soft [[soap]]s.<ref name=g73/> The discovery by [[Justus Liebig]] in 1840 that potassium is a necessary element for plants and that most types of soil lack potassium<ref>{{cite book|url = https://books.google.com/?id=Ya85AAAAcAAJ|title = Die organische Chemie in ihrer Anwendung auf Agricultur und Physiologie|author = Liebig, Justus von|date = 1840| language = German}}</ref> caused a steep rise in demand for potassium salts. Wood-ash from fir trees was initially used as a potassium salt source for fertilizer, but, with the discovery in 1868 of mineral deposits containing [[potassium chloride]] near [[Staßfurt]], Germany, the production of potassium-containing fertilizers began at an industrial scale.<ref>{{cite book|author=Cordel, Oskar |title=Die Stassfurter Kalisalze in der Landwirthschalt: Eine Besprechung ...|url=https://books.google.com/books?id=EYpIAAAAYAAJ|date=1868|publisher=L. Schnock| language = German}}</ref><ref>{{cite book|url = https://books.google.com/?id=J8Q6AAAAcAAJ|title = Die Kalidüngung in ihren Vortheilen und Gefahren|last1 = Birnbaum| first1= Karl|date = 1869| language = German}}</ref><ref>{{cite book|url = https://books.google.com/books?id=qPkoOU4BvEsC&pg=PA417|title = Fertilizer Manual|isbn = 978-0-7923-5032-3|author = United Nations Industrial Development Organization and Int'l Fertilizer Development Center|date = 1998|pages=46, 417}}</ref> Other potash deposits were discovered, and by the 1960s Canada became the dominant producer.<ref>{{cite journal|jstor = 3103338|pages = 187–208|last1 = Miller|first1 = H.|title = Potash from Wood Ashes: Frontier Technology in Canada and the United States|volume = 21|issue = 2|journal = Technology and Culture|year = 1980|doi=10.2307/3103338}}</ref><ref>{{cite journal|doi = 10.2113/gsecongeo.74.2.353|title = Potash and politics|year = 1979|last1 = Rittenhouse|first1 = P. A.|journal = Economic Geology|volume = 74|issue = 2|pages = 353–7}}</ref>

==Metal==
[[File:Sir Humphry Davy, Bt by Thomas Phillips.jpg|thumb| left|[[Humphry Davy]] ]]
[[File:Potassium.JPG|thumb|right|Pieces of potassium metal]]
Potassium ''metal'' was first isolated in 1807 by Sir [[Humphry Davy]], who derived it from [[Potassium hydroxide|caustic potash]] (KOH, potassium hydroxide) by electrolysis of molten KOH with the newly discovered [[voltaic pile]]. Potassium was the first metal that was isolated by electrolysis.<ref name="Enghag2004">{{cite book|last=Enghag|first= P.|date=2004| title=Encyclopedia of the elements| publisher=Wiley-VCH Weinheim| isbn=978-3-527-30666-4| chapter=11. Sodium and Potassium}}</ref> Later in the same year, Davy reported extraction of the metal [[sodium]] from a mineral derivative ([[caustic soda]], NaOH, or lye) rather than a plant salt, by a similar technique, demonstrating that the elements, and thus the salts, are different.<ref name="weeks"/><ref name="disco"/><ref name="Davy1807">{{cite journal|first=Humphry|last=Davy|title=On some new phenomena of chemical changes produced by electricity, in particular the decomposition of the fixed alkalies, and the exhibition of the new substances that constitute their bases; and on the general nature of alkaline bodies|pages=1–44|year=1808|volume=98|journal=Philosophical Transactions of the Royal Society|url=https://books.google.com/?id=gpwEAAAAYAAJ&pg=PA57&q|doi=10.1098/rstl.1808.0001}}</ref><ref name="200disco">{{cite journal|doi = 10.1134/S1061934807110160|title = History of the discovery of potassium and sodium (on the 200th anniversary of the discovery of potassium and sodium)|year = 2007|last1 = Shaposhnik|first1 = V. A.|journal = Journal of Analytical Chemistry|volume = 62|issue = 11|pages = 1100–2}}</ref> Although the production of potassium and sodium metal should have shown that both are elements, it took some time before this view was universally accepted.<ref name="disco"/>

==Geology==
Elemental potassium does not occur in nature because of its high reactivity. It reacts violently with water (see section Precautions below)<ref name="HollemanAF"/> and also reacts with oxygen. [[Orthoclase]] (potassium feldspar) is a common rock-forming mineral. [[Granite]] for example contains 5% potassium, which is well above the average in the Earth's crust. [[Sylvite]] (KCl), [[carnallite]] {{chem|(KCl·MgCl|2|·6(H|2|O))}}, [[kainite]] {{chem|(MgSO|4|·KCl·3H|2|O)}} and [[langbeinite]] {{chem|(MgSO|4|·K|2|SO|4|)}} are the minerals found in large [[evaporite]] deposits worldwide. The deposits often show layers starting with the least soluble at the bottom and the most soluble on top.<ref name="indus"/> Deposits of niter ([[potassium nitrate]]) are formed by decomposition of organic material in contact with atmosphere, mostly in caves; because of the good water solubility of niter the formation of larger deposits requires special environmental conditions.<ref>{{cite book|chapter-url = https://books.google.com/books?id=NyUDAAAAMBAJ&pg=PA134|pages = 134–145| chapter = The Origin of Nitrate Deposits| first = William H.| last = Ross|title = Popular Science|date = 1914|publisher=Bonnier Corporation}}</ref>

==Biological role==
{{Main|Potassium in biology}}
Potassium is the eighth or ninth most common element by mass (0.2%) in the human body, so that a 60 kg adult contains a total of about 120 g of potassium.<ref>{{cite journal|doi = 10.1016/0883-2889(92)90208-V|title = A simple calibration of a whole-body counter for the measurement of total body potassium in humans|year = 1992|display-authors = 4|last1 = Abdel-Wahab|first1 = M.|last2 = Youssef|first2 = S.|last3 = Aly|first3 = A.|last4 = el-Fiki|first4 = S.|last5 = el-Enany|first5 = N.|last6 = Abbas|first6 = M.|journal = International Journal of Radiation Applications and Instrumentation. Part A. Applied Radiation and Isotopes|volume = 43|issue = 10|pages = 1285–9|pmid=1330980}}</ref> The [[Composition of the human body|body]] has about as much potassium as sulfur and chlorine, and only calcium and phosphorus are more abundant (with the exception of the ubiquitous [[CHON]] elements).<ref>{{cite book|author=Chang, Raymond |title=Chemistry|url=https://books.google.com/books?id=huSDQAAACAAJ|date= 2007|publisher=McGraw-Hill Higher Education|isbn=978-0-07-110595-8|page=52}}</ref> Potassium ions are present in a wide variety of proteins and enzymes.<ref>{{cite book|first1= Milan |last1= Vašák|first2= Joachim |last2= Schnabl|publisher= Springer|date= 2016|series= Metal Ions in Life Sciences|volume=16|title= The Alkali Metal Ions: Their Role in Life|editor1-last=Astrid|editor1-first= Sigel|editor2-last=Helmut|editor2-first=Sigel|editor3-last=Roland K.O.|editor3-first= Sigel|chapter= Chapter 8. Sodium and Potassium Ions in Proteins and Enzyme Catalysis |pages= 259–290
|doi=10.1007/978-4-319-21756-7_8|doi-broken-date= 2019-03-06}}</ref>

===Biochemical function===
Potassium levels influence multiple physiological processes, including<ref>ID, Linus S, Wingo CS. Disorders of potassium metabolism. In: Freehally J, Johnson RJ, Floege J, eds. Comprehensive clinical nephrology. 5th ed.St. Louis: Saunders, 2014:118-118</ref><ref>Malnic G, Giebisch G, Muto S, Wang W, Bailey MA, Satlin LM. Regulation of K+ excretion. In: Alpern RJ, Caplan MJ, Moe OW, eds. Seldin and Giebisch’s the kidney: physiology and pathophysiology. 5th ed. London: Academic Press, 2013:1659-1716</ref><ref>Mount DB, Zandi-Nejad K. Disorders of potassium balance. In: Taal MW, Chertow GM, Marsden PA, Skorecki KL, Yu ASL, Brenner BM, eds. The kidney. 9th ed. Philadelphia: Elsevier, 2012:640-688</ref>
* resting cellular-membrane potential and the propagation of action potentials in neuronal, muscular, and cardiac tissue. Due to the electrostatic and chemical properties, {{chem|K|+}} ions are larger than {{chem|Na|+}} ions, and ion channels and pumps in cell membranes can differentiate between the two ions, actively pumping or passively passing one of the two ions while blocking the other.<ref>{{cite journal|pmid=17472437|title=Structural and thermodynamic properties of selective ion binding in a K+ channel|last1=Lockless |first1 = S. W.| last2= Zhou|first2 =M.|last3= MacKinnon|first3 =R.|journal=PLoS Biol|year= 2007 |volume=5|issue=5|page=e121|doi=10.1371/journal.pbio.0050121|pmc=1858713}}</ref>
* hormone secretion and action
* vascular tone
* systemic blood pressure control
* gastrointestinal motility
* acid–base homeostasis
* glucose and insulin metabolism
* mineralocorticoid action
* renal concentrating ability
* fluid and electrolyte balance

===Homeostasis===
Potassium homeostasis denotes the maintenance of the total body potassium content, plasma potassium level, and the ratio of the intracellular to extracellular potassium concentrations within narrow limits, in the face of pulsatile intake (meals), obligatory renal excretion, and shifts between intracellular and extracellular compartments.

====Plasma levels====
Plasma potassium is normally kept at 3.5 to 5.0 millimoles (mmol) [or milliequivalents (mEq)] per liter by multiple mechanisms. Levels outside this range are associated with an increasing rate of death from multiple causes,<ref>{{cite journal | last1 = Goyal | first1 = Abhinav | last2 = Spertus | first2 = John A. | last3 = Gosch | first3 = Kensey | last4 = Venkitachalam | first4 = Lakshmi | last5 = Jones | first5 = Philip G. | last6 = Van den Berghe | first6 = Greet | last7 = Kosiborod | first7 = Mikhail | year = 2012 | title = Serum Potassium Levels and Mortality in Acute Myocardial Infarction | url = | journal = JAMA | volume = 307 | issue = 2| pages = 157–164 | doi = 10.1001/jama.2011.1967 | pmid = 22235086 }}</ref> and some cardiac, kidney,<ref>{{cite journal | last1 = Smyth | first1 = A. | last2 = Dunkler | first2 = D. | last3 = Gao | first3 = P. | display-authors = etal | year = 2014 | title = The relationship between estimated sodium and potassium excretion and subsequent renal outcomes | url = | journal = Kidney Int | volume = 86 | issue = 6| pages = 1205–1212 | doi=10.1038/ki.2014.214| pmid = 24918156 }}</ref> and lung diseases progress more rapidly if serum potassium levels are not maintained within the normal range.

An average meal of 40-50 mmol presents the body with more potassium than is present in all plasma (20-25 mmol). However, this surge causes the plasma potassium to rise only 10% at most as a result of prompt and efficient clearance by both renal and extra-renal mechanisms.<ref>{{cite journal | last1 = Moore-Ede | first1 = M. C. | year = 1986 | title = Physiology of the circadian timing system: predictive versus reactive homeostasis | url = | journal = Am J Physiol | volume = 250 | issue = | pages = R737–R752 }}</ref>

[[Hypokalemia]], a deficiency of potassium in the plasma, can be fatal if severe. Common causes are increased gastrintestinal loss ([[vomiting]], [[diarrhea]]), and increased renal loss ([[polyuria|diuresis]]).<ref>{{cite book|publisher=Lippincott Williams & Wilkins|chapter-url = https://books.google.com/books?id=_XavFllbnS0C&pg=PA812|page = 812| chapter = Potassium|title = Pediatric critical care medicine|isbn = 978-0-7817-9469-5|last1 = Slonim|first1= Anthony D.|last2 = Pollack|first2= Murray M.|date = 2006}}</ref> Deficiency symptoms include muscle weakness, [[paralytic ileus]], ECG abnormalities, decreased reflex response; and in severe cases, respiratory paralysis, [[alkalosis]], and [[cardiac arrhythmia]].<ref>{{cite book |chapter-url = https://books.google.com/books?id=c4xAdJhIi6oC&pg=PT257 |page =257|chapter = hypokalemia |title = Essentials of Nephrology|edition=2nd|publisher=BI Publications |isbn = 978-81-7225-323-3 |last1 = Visveswaran |first1= Kasi |date = 2009}}</ref>

====Control mechanisms====
Potassium content in the plasma is tightly controlled by four basic mechanisms, which have various names and classifications. The four are 1) a reactive negative-feedback system, 2) a reactive feed-forward system, 3) a predictive or [[circadian]] system, and 4) an internal or cell membrane transport system. Collectively, the first three are sometimes termed the "external potassium homeostasis system";<ref>{{Cite journal|last=Gumz|first=Michelle L.|last2=Rabinowitz|first2=Lawrence|last3=Wingo|first3=Charles S.|date=2015-07-02|title=An Integrated View of Potassium Homeostasis|journal=The New England Journal of Medicine|volume=373|issue=1|pages=60–72|doi=10.1056/NEJMra1313341|issn=0028-4793|pmc=5675534|pmid=26132942}}</ref> and the first two, the "reactive potassium homeostasis system".
* The reactive negative-feedback system refers to the system that induces renal secretion of potassium in response to a rise in the plasma potassium (potassium ingestion, shift out of cells, or intravenous infusion.)
* The reactive feed-forward system refers to an incompletely understood system that induces renal potassium secretion in response to potassium ingestion prior to any rise in the plasma potassium. This is probably initiated by gut cell potassium receptors that detect ingested potassium and trigger [[vagal]] [[afferent nerve fiber|afferent]] signals to the pituitary gland.
* The predictive or circadian system increases renal secretion of potassium during mealtime hours (e.g. daytime for humans, nighttime for rodents) independent of the presence, amount, or absence of potassium ingestion. It is mediated by a [[circadian oscillator]] in the [[suprachiasmatic nucleus]] of the brain (central clock), which causes the kidney (peripheral clock) to secrete potassium in this rhythmic circadian fashion.[[File:Scheme sodium-potassium pump-en.svg|thumb|right|upright=1.8|The action of the [[sodium-potassium pump]] is an example of primary [[active transport]]. The two carrier proteins embedded in the cell membrane on the left are using [[Adenosine triphosphate|ATP]] to move sodium out of the cell against the concentration gradient; The two proteins on the right are using secondary active transport to move potassium into the cell: this process results in reconstitution of ATP.]]
* The ion transport system moves potassium across the cell membrane using two mechanisms. One is active and pumps sodium out of, and potassium into, the cell. The other is passive and allows potassium to leak out of the cell. Potassium and sodium cations influence fluid distribution between intracellular and extracellular compartments by [[osmotic]] forces. The movement of potassium and sodium through the cell membrane is mediated by the [[Na+/K+-ATPase]] pump.<ref>{{cite book|last=Campbell|first=Neil|title=Biology|date=1987|isbn=978-0-8053-1840-1|page=795|publisher=Benjamin/Cummings Pub. Co.|location=Menlo Park, California}}</ref> This [[Ion transporter|ion pump]] uses [[Adenosine triphosphate|ATP]] to pump three sodium ions out of the cell and two potassium ions into the cell, creating an electrochemical gradient and electromotive force across the cell membrane. The highly selective [[potassium ion channels]] (which are [[tetramer]]s) are crucial for [[Hyperpolarization (biology)|hyperpolarization]] inside [[neuron]]s after an action potential is triggered, to cite one example. The most recently discovered potassium ion channel is KirBac3.1, which makes a total of five potassium ion channels (KcsA, KirBac1.1, KirBac3.1, KvAP, and MthK) with a determined structure. All five are from [[prokaryotic]] species.<ref name="pmid16253415">{{cite journal|first1=Mikko |last1 = Hellgren| first2= Lars |last2= Sandberg|first3= Olle |last3= Edholm|title=A comparison between two prokaryotic potassium channels (KirBac1.1 and KcsA) in a molecular dynamics (MD) simulation study|journal=Biophysical Chemistry| volume=120|issue=1|pages=1–9|year=2006|pmid=16253415|doi=10.1016/j.bpc.2005.10.002}}</ref>

====Renal filtration, reabsorption, and excretion====
Renal handling of potassium is closely connected to sodium handling. Potassium is the major cation (positive ion) inside animal cells [150 mmol/L, (4.8 g)], while sodium is the major cation of extracellular fluid [150 mmol/L, (3.345 g)]. In the kidneys, about 180 liters of plasma is filtered through the [[glomeruli]] and into the [[renal tubules]] per day.<ref name="Potts1964">{{cite book|author=Potts, W. T. W.|author2=Parry, G.|date=1964|title=Osmotic and ionic regulation in animals|publisher=[[Pergamon Press]]}}</ref> This filtering involves about 600 g of sodium and 33 g of potassium. Since only 1–10 g of sodium and 1–4 g of potassium are likely to be replaced by diet, renal filtering must efficiently reabsorb the remainder from the plasma.

Sodium is reabsorbed to maintain extracellular volume, osmotic pressure, and serum sodium concentration within narrow limits; potassium is reabsorbed to maintain serum potassium concentration within narrow limits.<ref>{{cite journal| last1=Lans |first1=H. S.|last2= Stein|first2=I. F.|last3= Meyer |first3=K. A.|title=The relation of serum potassium to erythrocyte potassium in normal subjects and patients with potassium deficiency|journal=American Journal of the Medical Sciences|volume=223| issue=1| pages=65–74|year=1952| pmid=14902792| doi=10.1097/00000441-195201000-00011}}</ref> [[Sodium pump]]s in the renal tubules operate to reabsorb sodium. Potassium must be conserved also, but, because the amount of potassium in the blood plasma is very small and the pool of potassium in the cells is about thirty times as large, the situation is not so critical for potassium. Since potassium is moved passively<ref>{{cite journal|last1=Bennett |first1=C. M.|last2= Brenner |first2=B. M.|last3= Berliner |first3=R. W.| title=Micropuncture study of nephron function in the rhesus monkey| journal=Journal of Clinical Investigation| volume=47|issue=1| pages=203–216|year=1968| pmid=16695942| doi=10.1172/JCI105710|pmc=297160}}</ref><ref>{{cite journal|last1=Solomon|first1=A. K. |title=Pumps in the living cell|journal=Scientific American| volume=207| pages=100–8|year=1962| pmid=13914986| doi=10.1038/scientificamerican0862-100| issue=2|bibcode=1962SciAm.207b.100S}}</ref> in counter flow to sodium in response to an apparent (but not actual) [[Donnan equilibrium]],<ref>{{cite book|last=Kernan|first= Roderick P.|title=Cell potassium (Transport in the life sciences)|publisher=[[John Wiley & Sons|Wiley]]|location=New York|date=1980|pages=40, 48|isbn= 978-0-471-04806-0}}</ref> the urine can never sink below the concentration of potassium in serum except sometimes by actively excreting water at the end of the processing. Potassium is excreted twice and reabsorbed three times before the urine reaches the collecting tubules.<ref>{{cite journal|last1=Wright|first1=F. S.|title=Sites and mechanisms of potassium transport along the renal tubule |journal=Kidney International |volume=11|issue=6 |pages=415–432 |year=1977 |pmid=875263 |doi=10.1038/ki.1977.60}}</ref> At that point, urine usually has about the same potassium concentration as plasma. At the end of the processing, potassium is secreted one more time if the serum levels are too high.{{citation needed|date=August 2017}}

With no potassium intake, it is excreted at about 200 mg per day until, in about a week, potassium in the serum declines to a mildly deficient level of 3.0–3.5 mmol/L.<ref>{{cite journal|last1=Squires |first1=R. D.|last2= Huth |first2 = E. J. |title=Experimental potassium depletion in normal human subjects. I. Relation of ionic intakes to the renal conservation of potassium |journal=Journal of Clinical Investigation |volume=38 |issue=7|pages=1134–48|year=1959 |pmid=13664789 |doi=10.1172/JCI103890|pmc=293261}}</ref> If potassium is still withheld, the concentration continues to fall until a severe deficiency causes eventual death.<ref>{{cite book|author=Fiebach, Nicholas H.|author2=Barker, Lee Randol|author3=Burton, John Russell|author4=Zieve, Philip D.|last-author-amp=yes |title=Principles of ambulatory medicine|url=https://books.google.com/books?id=UGVylX6g4i8C&pg=PA748|date=2007|publisher=Lippincott Williams & Wilkins|isbn=978-0-7817-6227-4|pages=748–750}}</ref>

The potassium moves passively through pores in the cell membrane. When ions move through pumps there is a gate in the pumps on either side of the cell membrane and only one gate can be open at once. As a result, approximately 100 ions are forced through per second. Pores have only one gate, and there only one kind of ion can stream through, at 10 million to 100 million ions per second.<ref>{{cite journal|last=Gadsby |first=D. C.|title=Ion transport: spot the difference |journal=Nature|volume=427 |issue=6977|pages=795–7|year=2004 |pmid=14985745 |doi=10.1038/427795a|bibcode = 2004Natur.427..795G}}; for a diagram of the potassium pores are viewed, see {{cite journal|author=Miller, C|title=See potassium run |journal=Nature |volume=414|issue=6859 |pages=23–24|year=2001 |pmid=11689922|doi=10.1038/35102126|bibcode = 2001Natur.414...23M }}</ref> Calcium is required to open the pores,<ref>{{cite journal|display-authors=4|last1=Jiang|first1=Y.|last2=Lee|first2=A.|last3=Chen|first3=J.|last4=Cadene|first4=M.|last5=Chait|first5=B. T.|last6=MacKinnon|first6=R.|url=http://einstein.ciencias.uchile.cl/CursoTroncal2007/Biblio/Jiang__MacKinnonNature417_515_2002.pdf|title=Crystal structure and mechanism of a calcium-gated potassium channel|journal=Nature|volume=417|issue=6888|pages=515–22|year=2002|pmid=12037559|doi=10.1038/417515a|bibcode=2002Natur.417..515J|deadurl=bot: unknown|archiveurl=https://web.archive.org/web/20090424074015/http://einstein.ciencias.uchile.cl/CursoTroncal2007/Biblio/Jiang__MacKinnonNature417_515_2002.pdf|archivedate=2009-04-24}}</ref> although calcium may work in reverse by blocking at least one of the pores.<ref>{{cite journal|display-authors=4|last1=Shi |first1=N.|last2= Ye |first2=S.|last3= Alam |first3=A.|last4= Chen |first4=L.|last5= Jiang |first5=Y. |title=Atomic structure of a Na+- and K+-conducting channel|journal=Nature |volume=440 |issue=7083 |pages=570–4 |year=2006 |pmid=16467789 |doi=10.1038/nature04508|bibcode = 2006Natur.440..570S}}; includes a detailed picture of atoms in the pump.</ref> Carbonyl groups inside the pore on the amino acids mimic the water hydration that takes place in water solution<ref>{{cite journal|last1=Zhou |first1=Y.|last2= Morais-Cabral |first2=J. H.|last3= Kaufman |first3=A.|last4= MacKinnon |first4=R.|title=Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 A resolution |journal=Nature |volume=414 |issue=6859|pages=43–48 |year=2001|pmid=11689936 |doi=10.1038/35102009|bibcode = 2001Natur.414...43Z }}</ref> by the nature of the electrostatic charges on four carbonyl groups inside the pore.<ref>{{cite journal|last1=Noskov |first1=S. Y.|last2= Bernèche |first2=S.|last3= Roux |first3=B.|title=Control of ion selectivity in potassium channels by electrostatic and dynamic properties of carbonyl ligands |journal=Nature |volume=431|issue=7010 |pages=830–4|year=2004 |pmid=15483608 |doi=10.1038/nature02943|bibcode = 2004Natur.431..830N}}</ref>

==Nutrition==

===Dietary recommendations===
The U.S. Institute of Medicine (IOM) sets Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs), or [[Adequate Intake]]s (AIs) for when there is not sufficient information to set EARs and RDAs. Collectively the EARs, RDAs, AIs and ULs are referred to as [[Dietary Reference Intake]]s. The AIs for potassium are: 400 mg of potassium for 0-6-month-old males, 700 mg of potassium for 7-12-month-old males, 3,000 mg of potassium for 1-3-year-old males, 3,800 mg of potassium for 4-8-year-old males, 4,500 mg of potassium for 9-13-year-old males, and 4,700 mg of potassium for males that are 14 years old and older.
The AIs for potassium are: 400 mg of potassium for 0-6-month-old females, 700 mg of potassium for 7-12-month-old females, 3,000 mg of potassium for 1-3-year-old females, 3,800 mg of potassium for 4-8-year-old females, 4,500 mg of potassium for 9-13-year-old females, and 4,700 mg of potassium for females that are 14 years old and older.
The AIs for potassium are: 4,700 mg of potassium for 14-50-year-old pregnant females; furthermore, 5,100 mg of potassium for 14-50-year-old lactating females. As for safety, the IOM also sets [[Tolerable upper intake level]]s (ULs) for vitamins and minerals, but for potassium the evidence was insufficient, so no UL established.<ref>Potassium. IN: [https://www.nap.edu/read/10925/chapter/7 Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate]. National Academy Press. 2005, PP.186-268.</ref>

Most Americans consume only half that amount per day.<ref name=iom_panel2005>{{cite book|author=Panel on Dietary Reference Intakes for Electrolytes and Water, Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition|title=DRI, dietary reference intakes for water, potassium, sodium, chloride, and sulfate|date=2004|publisher=National Academies Press|location=Washington, D.C.|isbn=978-0-309-53049-1|url=http://www.iom.edu/Reports/2004/Dietary-Reference-Intakes-Water-Potassium-Sodium-Chloride-and-Sulfate.aspx|deadurl=yes|archiveurl=https://web.archive.org/web/20111006174858/http://www.iom.edu/Reports/2004/Dietary-Reference-Intakes-Water-Potassium-Sodium-Chloride-and-Sulfate.aspx|archivedate=2011-10-06}}</ref>

Likewise, in the [[European Union]], in particular in [[Germany]] and [[Italy]], insufficient potassium intake is somewhat common.<ref>{{cite journal|last=Karger|first=S.|journal=Annals of Nutrition and Metabolism|year=2004|volume=48|issue=2 (suppl) |pages=1–16 |title=Energy and nutrient intake in the European Union|doi=10.1159/000083041}}</ref> However, the [[National Health Service|British National Health Service]] recommends a lower intake, saying that adults need 3,500 mg per day and that excess amounts may cause health problems such as stomach pain and diarrhoea.<ref>[https://www.nhs.uk/conditions/vitamins-and-minerals/others/#potassium%20NHS%20Choices%20-%20Other%20vitamins%20and%20minerals%20-%20Potassium https://www.nhs.uk/conditions/vitamins-and-minerals/others/#potassium NHS Choices - Other vitamins and minerals - Potassium]</ref>

===Food sources===
Potassium is present in all fruits, vegetables, meat and fish. Foods with high potassium concentrations include [[Yam (vegetable)|yam]], [[parsley]], dried [[apricot]]s, [[milk]], [[chocolate]], all [[nut (fruit)|nuts]] (especially [[almond]]s and [[pistachio]]s), [[potato]]es, [[bamboo shoot]]s, [[banana]]s, [[avocado]]s, [[coconut water]], [[soybean]]s, and [[bran]].<ref>{{cite web| url = http://apjcn.nhri.org.tw/server/info/books-phds/books/foodfacts/html/data/data5b.html|title = Potassium Food Charts|publisher =Asia Pacific Journal of Clinical Nutrition|accessdate = 2011-05-18}}</ref>

The [[United States Department of Agriculture|USDA]] lists [[tomato paste]], [[orange juice]], [[beet greens]], [[white beans]], [[potato]]es, [[Cooking banana|plantains]], [[banana]]s, apricots, and many other dietary sources of potassium, ranked in descending order according to potassium content. A day's worth of potassium is in 5 plantains or 11 bananas.<ref>{{cite news|title=Potassium Content of Selected Foods per Common Measure, sorted by nutrient content |publisher=USDA National Nutrient Database for Standard Reference, Release 20 |url=http://www.nal.usda.gov/fnic/foodcomp/Data/SR20/nutrlist/sr20w306.pdf |deadurl=yes |archiveurl=https://web.archive.org/web/20081217043521/http://www.nal.usda.gov/fnic/foodcomp/Data/SR20/nutrlist/sr20w306.pdf |archivedate=December 17, 2008 }}</ref>

===Deficient intake===
Diets low in potassium can lead to [[hypertension]]<ref>{{cite journal |vauthors=Whelton PK, He J, Cutler JA, Brancati FL, Appel LJ, Follmann D, Klag MJ |title=Effects of oral potassium on blood pressure. Meta-analysis of randomized controlled clinical trials |journal=JAMA |volume=277 |issue=20 |pages=1624–32 |year=1997 |pmid=9168293 |doi=10.1001/jama.1997.03540440058033 }}</ref> and [[hypokalemia]].

===Supplementation===
Supplements of potassium are most widely used in conjunction with [[diuretic]]s that block reabsorption of sodium and water upstream from the [[distal tubule]] ([[thiazide]]s and [[loop diuretics]]), because this promotes increased distal tubular potassium secretion, with resultant increased potassium excretion. A variety of prescription and over-the counter supplements are available. Potassium chloride may be dissolved in water, but the salty/bitter taste make liquid supplements unpalatable.<ref name=bitter/> Typical doses range from 10 mmol (400 mg), to 20 mmol (800 mg). Potassium is also available in tablets or capsules, which are formulated to allow potassium to leach slowly out of a matrix, since very high concentrations of potassium ion that occur adjacent to a solid tablet can injure the gastric or intestinal mucosa. For this reason, non-prescription potassium pills are limited by law in the US to a maximum of 99 mg of potassium.{{citation needed|date=September 2017}}

Since the kidneys are the site of potassium excretion, individuals with impaired kidney function are at risk for [[hyperkalemia]] if dietary potassium and supplements are not restricted. The more severe the impairment, the more severe is the restriction necessary to avoid hyperkalemia.{{citation needed|date=September 2017}}

A [[meta-analysis]] concluded that a 1640 mg increase in the daily intake of potassium was associated with a 21% lower risk of stroke.<ref>{{cite journal |last1=D'Elia |first1=L. |last2=Barba |first2=G. |last3=Cappuccio |first3=F. |last4=Strazzullo |year=2011 |title=Potassium Intake, Stroke, and Cardiovascular Disease: A Meta-Analysis of Prospective Studies |journal=J Am Coll Cardiol |volume=57 |issue=10 |pages=1210–9 |doi=10.1016/j.jacc.2010.09.070 |pmid=21371638}}</ref> [[Potassium chloride]] and [[potassium bicarbonate]] may be useful to control mild [[hypertension]].<ref>{{cite journal |vauthors=He FJ, Marciniak M, Carney C, Markandu ND, Anand V, Fraser WD, Dalton RN, Kaski JC, MacGregor GA |title=Effects of potassium chloride and potassium bicarbonate on endothelial function, cardiovascular risk factors, and bone turnover in mild hypertensives |journal=Hypertension |volume=55 |issue=3 |pages=681–8 |year=2010 |pmid=20083724 |doi=10.1161/HYPERTENSIONAHA.109.147488 }}</ref> In 2016 potassium was the 33rd most prescribed medication in the United States with more than 22 million prescriptions.<ref>{{cite web |title=The Top 300 of 2019 |url=https://clincalc.com/DrugStats/Top300Drugs.aspx |website=clincalc.com |accessdate=22 December 2018}}</ref>

===Detection by taste buds===
Potassium can be detected by taste because it triggers three of the five types of taste sensations, according to concentration. Dilute solutions of potassium ions taste sweet, allowing moderate concentrations in milk and juices, while higher concentrations become increasingly bitter/alkaline, and finally also salty to the taste. The combined bitterness and saltiness of high-potassium solutions makes high-dose potassium supplementation by liquid drinks a palatability challenge.<ref name=bitter>{{cite book|author1=Institute of Medicine (U.S.). Committee on Optimization of Nutrient Composition of Military Rations for Short-Term, High-Stress Situations|author2=Institute of Medicine (U.S.). Committee on Military Nutrition Research|title=Nutrient composition of rations for short-term, high-intensity combat operations|url=https://books.google.com/books?id=kFatoIBbMboC&pg=PT287|date=2006|publisher=National Academies Press|isbn=978-0-309-09641-6|pages=287–}}</ref><ref>{{cite book|last=Shallenberger|first=R. S. |title=Taste chemistry|url=https://books.google.com/books?id=8_bjyjgClq0C&pg=PA120|date=1993|publisher=Springer|isbn=978-0-7514-0150-9|pages=120–}}</ref>

==Commercial production==
===Mining===
[[File:Museo de La Plata - Silvita.jpg|thumb|right| [[Sylvite]] from New Mexico]]
Potassium salts such as [[carnallite]], [[langbeinite]], [[polyhalite]], and [[sylvite]] form extensive [[evaporite]] deposits in ancient lake bottoms and [[seabed]]s,<ref name=geo/> making extraction of potassium salts in these environments commercially viable. The principal source of potassium – [[potash]] – is mined in [[Canada]], [[Russia]], [[Belarus]], [[Kazakhstan]], [[Germany]], [[Israel]], [[United States]], [[Jordan]], and other places around the world.<ref>{{cite book|url = https://books.google.com/books?id=EHx51n3T858C|publisher=Springer|title = Potash: deposits, processing, properties and uses|isbn = 978-0-412-99071-7|last1 = Garrett|first1= Donald E.|date = 1995-12-31}}</ref><ref name="USGSCS2008">{{cite web|url=http://minerals.usgs.gov/minerals/pubs/commodity/potash/mcs-2008-potas.pdf|first=Joyce A.|last=Ober|publisher=United States Geological Survey|title=Mineral Commodity Summaries 2008:Potash|accessdate=2008-11-20}}</ref><ref name="USGSYB2006">{{cite web|url=http://minerals.usgs.gov/minerals/pubs/commodity/potash/myb1-2006-potas.pdf|first=Joyce A.|last=Ober|publisher=United States Geological Survey|title=Mineral Yearbook 2006:Potash|accessdate=2008-11-20}}</ref> The first mined deposits were located near Staßfurt, Germany, but the deposits span from [[Great Britain]] over Germany into Poland. They are located in the [[Zechstein]] and were deposited in the Middle to Late [[Permian]]. The largest deposits ever found lie {{convert|1000|m|ft|abbr=off|sp=us}} below the surface of the Canadian province of [[Saskatchewan]]. The deposits are located in the [[Elk Point Group]] produced in the [[Middle Devonian]]. Saskatchewan, where several large mines have operated since the 1960s pioneered the technique of freezing of wet sands (the Blairmore formation) to drive mine shafts through them. The main potash mining company in Saskatchewan is the [[Potash Corporation of Saskatchewan]].<ref>{{cite book|url = https://books.google.com/books?id=rtRFyFO4hpEC&pg=PA433|publisher=U of Nebraska Press|page = 433|title = Encyclopedia of the Great Plains|isbn = 978-0-8032-4787-1|last = Wishart| first=David J.|date = 2004}}</ref> The water of the [[Dead Sea]] is used by Israel and Jordan as a source of potash, while the concentration in normal oceans is too low for commercial production at current prices.<ref name="USGSCS2008"/><ref name="USGSYB2006"/>

[[File:Wintershall Monte Kali 12.jpg|thumb| left|[[Monte Kali (Heringen)|Monte Kali]], a potash mining and [[beneficiation]] waste heap in [[Hesse|Hesse, Germany]], consisting mostly of [[sodium chloride]].]]

===Chemical extraction===
Several methods are used to separate potassium salts from sodium and magnesium compounds. The most-used method is fractional precipitation using the solubility differences of the salts at different temperatures. Electrostatic separation of the ground salt mixture is also used in some mines. The resulting sodium and magnesium waste is either stored underground or piled up in [[slag heap]]s. Most of the mined potassium mineral ends up as [[potassium chloride]] after processing. The mineral industry refers to potassium chloride either as potash, muriate of potash, or simply MOP.<ref name="indus"/>

Pure potassium metal can be isolated by [[electrolysis]] of its [[potassium hydroxide|hydroxide]] in a process that has changed little since it was first used by [[Humphry Davy]] in 1807. Although the electrolysis process was developed and used in industrial scale in the 1920s, the thermal method by reacting sodium with [[potassium chloride]] in a chemical equilibrium reaction became the dominant method in the 1950s.

The production of [[NaK|sodium potassium alloys]] is accomplished by changing the reaction time and the amount of sodium used in the reaction. The Griesheimer process employing the reaction of [[potassium fluoride]] with [[calcium carbide]] was also used to produce potassium.<ref name="indus" /><ref>{{cite book|doi=10.1002/0471238961.1615200103080921.a01.pub2|isbn= 9780471238966
|last1=Chiu|first1=Kuen-Wai
|publisher=John Wiley & Sons, Inc.
|title=Kirk-Othmer Encyclopedia of Chemical Technology
|date=2000
|chapter= Potassium
}}</ref>
:Na + KCl → NaCl + K                      (Thermal method)
:2 KF + {{chem|CaC|2}} → 2 K + {{chem|CaF|2}} + 2 C    (Griesheimer process)

[[reagent|Reagent-grade]] potassium metal costs about $10.00/[[pound (mass)|pound]] ($22/[[kg]]) in 2010 when purchased by the [[tonne]]. Lower purity metal is considerably cheaper. The market is volatile because long-term storage of the metal is difficult. It must be stored in a dry [[inert gas]] atmosphere or [[anhydrous]] [[mineral oil]] to prevent the formation of a surface layer of [[potassium superoxide]], a pressure-sensitive [[explosive]] that [[Detonation|detonates]] when scratched. The resulting explosion often starts a fire difficult to extinguish.<ref>[[#Burkhardt|Burkhardt]], p. 34</ref><ref name="fire">{{cite journal|doi =10.1016/j.jchas.2006.09.010|title =Review of the safety of potassium and potassium oxides, including deactivation by introduction into water|year =2007|last1 =Delahunt|first1 = J.|last2 =Lindeman|first2 = T.|journal =Journal of Chemical Health and Safety|volume =14|issue =2|pages =21–32}}</ref>

==Cation identification==
Potassium ions can be identified using [[sodium cobaltnitrite]] in the presence of acetic acid.
: 3K+ + Na3[Co(NO2)] → K3[Co(NO2)] + 3Na+
K3[Co(NO2)] is a yellow crystalline precipitate. This reaction cannot be done in basic solution as Co(OH)3 would precipitate instead. It cannot be done in the presence of a [[mineral acid]] either as H3[Co(NO2)] would be formed.
Another method of identifying K+ is to treat a potassium salt with [[sodium tetraphenhylborate]].
: K+ + Na[BPh4] → K[BPh4] + 3Na+

==Commercial uses==
===Fertilizer===
[[File:Patentkali (Potassium sulfate with magnesium).jpg|thumb|Potassium sulfate/magnesium sulfate fertilizer]]
Potassium ions are an essential component of [[plant]] nutrition and are found in most [[soil]] types.<ref name=g73/> They are used as a [[fertilizer]] in [[agriculture]], [[horticulture]], and [[hydroponic]] culture in the form of [[potassium chloride|chloride]] (KCl), [[potassium sulfate|sulfate]] ({{chem|K|2|SO|4}}), or [[potassium nitrate|nitrate]] ({{chem|KNO|3}}), representing the 'K' [[labeling of fertilizer|in 'NPK']]. Agricultural fertilizers consume 95% of global potassium chemical production, and about 90% of this potassium is supplied as KCl.<ref name=g73/> The potassium content of most plants ranges from 0.5% to 2% of the harvested weight of crops, conventionally expressed as amount of {{chem|K|2|O}}. Modern high-[[Crop yield|yield]] agriculture depends upon fertilizers to replace the potassium lost at harvest. Most agricultural fertilizers contain potassium chloride, while potassium sulfate is used for chloride-sensitive crops or crops needing higher sulfur content. The sulfate is produced mostly by decomposition of the complex minerals [[kainite]] ({{chem|MgSO|4|·KCl·3H|2|O}}) and [[langbeinite]] ({{chem|MgSO|4|·K|2|SO|4}}). Only a very few fertilizers contain potassium nitrate.<ref name="Kent">{{cite book|pages = 1135–57|first = Amit H. |last = Roy| url = https://books.google.com/books?id=AYjFoLCNHYUC&pg=PA1135|isbn = 978-0-387-27843-8|publisher=Springer|title = Kent and Riegel's handbook of industrial chemistry and biotechnology|date = 2007}}</ref> In 2005, about 93% of world potassium production was consumed by the fertilizer industry.<ref name="USGSYB2006" /> Furthermore, potassium can play a key role in nutrient cycling by controlling litter composition.<ref>{{cite journal |last1=Ochoa-Hueso |first1=R |last2=Delgado-Baquerizo |first2=M |last3=King |first3=PTA |last4=Benham |first4=M |last5=Arca |first5=V |last6=Power |first6=SA |title=Ecosystem type and resource quality are more important than global change drivers in regulating early stages of litter decomposition |journal=Soil Biology and Biochemistry |date=2019 |volume=129 |pages=144–152 |doi=10.1016/j.soilbio.2018.11.009 |accessdate=27 April 2019 |url=https://www.sciencedirect.com/science/article/abs/pii/S0038071718303845}}</ref>

===Medical use===
{{see also|Potassium chloride (medical use)}}
Potassium, in the form of [[potassium chloride]] is used as a medication to treat and prevent [[low blood potassium]].<ref name=WHO2008>{{cite book|title=WHO Model Formulary 2008|date=2009|publisher=World Health Organization|isbn=9789241547659|page=491|url=http://apps.who.int/medicinedocs/documents/s16879e/s16879e.pdf|accessdate=8 January 2017|deadurl=no|archiveurl=https://web.archive.org/web/20161213060118/http://apps.who.int/medicinedocs/documents/s16879e/s16879e.pdf|archivedate=13 December 2016}}</ref> Low blood potassium may occur due to [[vomiting]], [[diarrhea]], or certain medications.<ref name=MTM2017>{{cite web|title=Potassium chloride medical facts from Drugs.com|url=https://www.drugs.com/mtm/potassium-chloride.html|website=www.drugs.com|accessdate=14 January 2017|deadurl=no|archiveurl=https://web.archive.org/web/20170118040410/https://www.drugs.com/mtm/potassium-chloride.html|archivedate=18 January 2017}}</ref> It is given by [[intravenous infusion|slow injection into a vein]] or by mouth.<ref name=BNF69>{{cite book|title=British national formulary : BNF 69|date=2015|publisher=British Medical Association|isbn=9780857111562|pages=680, 684|edition=69}}</ref>

===Food additives===
Potassium sodium tartrate ({{chem|KNaC|4|H|4|O|6}}, [[Rochelle salt]]) is the main constituent of [[baking powder]]; it is also used in the [[silvering]] of mirrors. [[Potassium bromate]] ({{chem|KBrO|3}}) is a strong oxidizer (E924), used to improve dough strength and rise height. [[Potassium bisulfite]] ({{chem|KHSO|3}}) is used as a food preservative, for example in [[wine]] and [[beer]]-making (but not in meats). It is also used to [[bleach]] textiles and straw, and in the tanning of [[leather]]s.<ref>{{cite book|chapter-url = https://books.google.com/books?id=XqKF7PqV02cC&pg=PA86|page = 86|chapter = Bleaching and Maturing Agents|title = How Baking Works: Exploring the Fundamentals of Baking Science|isbn = 978-0-470-39267-6|author = Figoni, Paula I|date= 2010|publisher=John Wiley and Sons}}</ref><ref>{{cite book|chapter-url = https://books.google.com/books?id=eblAtwEXffcC&pg=PA4|publisher=Academic Press|pages = 4–6| chapter = Uses and Exposure to Sulfites in Food|title = Advances in food research|isbn = 978-0-12-016430-1|author = Chichester, C. O.|date = July 1986}}</ref>

===Industrial===
Major potassium chemicals are potassium hydroxide, potassium carbonate, potassium sulfate, and potassium chloride. Megatons of these compounds are produced annually.<ref>[[#Schultz|Schultz]]</ref>

[[Potassium hydroxide]] {{chem|KOH}} is a strong base, which is used in industry to neutralize strong and weak [[acid]]s, to control [[pH]] and to manufacture potassium [[salt (chemistry)|salts]]. It is also used to [[saponification|saponify]] [[fat]]s and [[oils]], in industrial cleaners, and in [[hydrolysis]] reactions, for example of [[esters]].<ref>{{cite book|publisher=Greenwood Publishing Group|chapter-url = https://books.google.com/books?id=UnjD4aBm9ZcC&pg=PA4|chapter = Personal Cleansing Products: Bar Soap|title = Chemical composition of everyday products|isbn = 978-0-313-32579-3|author = Toedt, John|author2 = Koza, Darrell|author3 = Cleef-Toedt, Kathleen Van|last-author-amp = yes|date = 2005}}</ref><ref>[[#Schultz|Schultz]], p. 95</ref>

[[Potassium nitrate]] ({{chem|KNO|3}}) or saltpeter is obtained from natural sources such as [[guano]] and [[evaporites]] or manufactured via the [[Haber process]]; it is the [[oxidant]] in [[gunpowder]] ([[black powder]]) and an important agricultural fertilizer. [[Potassium cyanide]] (KCN) is used industrially to dissolve [[copper]] and precious metals, in particular [[silver]] and [[gold]], by forming [[complex (chemistry)|complexes]]. Its applications include [[gold mining]], [[electroplating]], and [[electroforming]] of these [[metal]]s; it is also used in [[organic synthesis]] to make [[nitriles]]. [[Potassium carbonate]] ({{chem|K|2|CO|3}} or potash) is used in the manufacture of glass, soap, color TV tubes, fluorescent lamps, textile dyes and pigments.<ref>[[#Schultz|Schultz]], p. 99</ref> Potassium permanganate ({{chem|KMnO|4}}) is an oxidizing, bleaching and purification substance and is used for production of [[saccharin]]. [[Potassium chlorate]] ({{chem|KClO|3}}) is added to matches and explosives. [[Potassium bromide]] (KBr) was formerly used as a sedative and in photography.<ref name=g73/>

[[Potassium chromate]] ({{chem|K|2|CrO|4}}) is used in [[ink]]s, [[dye]]s, [[stain]]s (bright yellowish-red color); in [[explosive]]s and [[fireworks]]; in the tanning of leather, in [[fly paper]] and [[safety match]]es,<ref>{{cite journal|doi = 10.1021/ed017p515|title = Ignition of the safety match|year = 1940|last1 = Siegel|first1 = Richard S.|journal = Journal of Chemical Education|volume = 17|issue = 11|pages = 515|bibcode = 1940JChEd..17..515S}}</ref> but all these uses are due to the chemistry of the [[chromate]] ion, rather than the potassium ion.<ref>{{Ullmann|contribution=Chromium Compounds|doi=10.1002/14356007.a07_067|volume=9|page=178|first1=Gerd|last1=Anger|first2=Jost|last2=Halstenberg|first3=Klaus|last3=Hochgeschwender|first4=Christoph|last4=Scherhag|first5=Ulrich|last5=Korallus|first6=Herbert|last6=Knopf|first7=Peter|last7=Schmidt|first8=Manfred|last8=Ohlinger}}</ref>

====Niche uses====
There are thousands of uses of various potassium compounds. One example is [[potassium superoxide]], {{chem|KO|2}}, an orange solid that acts as a portable source of oxygen and a carbon dioxide absorber. It is widely used in [[Rebreather#Rebreathers whose absorbent releases oxygen|respiration systems]] in mines, submarines and spacecraft as it takes less volume than the gaseous oxygen.<ref>[[#Greenwood|Greenwood]], p. 74</ref><ref>{{cite book|url = https://books.google.com/books?id=oiWFhoRzPBQC&pg=PA93|title = The history of underwater exploration|first = Robert F. |last = Marx|publisher =Courier Dover Publications| date = 1990|isbn = 978-0-486-26487-5|page=93}}</ref>
: 4 {{chem|KO|2}} + 2 {{CO2}} → 2 {{chem|K|2|CO|3}} + 3 {{chem|O|2}}

Another example is [[potassium cobaltinitrite]], {{chem|K|3|[Co(NO|2|)|6|]|}}, which is used as artist's pigment under the name of [[Aureolin]] or Cobalt Yellow.<ref name="Getts">{{cite book|publisher=Courier Dover Publications|url = https://books.google.com/books?id=bdQVgKWl3f4C&pg=PA109|title = Painting materials: A short encyclopaedia|isbn = 978-0-486-21597-6|author = Gettens, Rutherford John|author2 = Stout, George Leslie|last-author-amp = yes|date = 1966|pages =109–110}}</ref>

The stable isotopes of potassium can be [[Laser cooling|laser cooled]] and used to probe fundamental and [[Quantum technology|technological]] problems in [[Quantum mechanics|quantum physics]]. The two [[boson]]ic isotopes possess convenient [[Feshbach resonance]]s to enable studies requiring tunable interactions, while 40K is one of only two stable [[fermion]]s amongst the alkali metals.<ref>{{Cite journal|last=Modugno|first=G.|last2=Benkő|first2=C.|last3=Hannaford|first3=P.|last4=Roati|first4=G.|last5=Inguscio|first5=M.|date=1999-11-01|title=Sub-Doppler laser cooling of fermionic ${}^{40}\mathrm{K}$ atoms|journal=Physical Review A|volume=60|issue=5|pages=R3373–R3376|doi=10.1103/PhysRevA.60.R3373|arxiv=cond-mat/9908102|bibcode=1999PhRvA..60.3373M}}</ref>

====Laboratory uses====
An [[alloy]] of sodium and potassium, [[NaK]] is a liquid used as a heat-transfer medium and a [[desiccant]] for producing [[air-free technique|dry and air-free solvents]]. It can also be used in [[reactive distillation]].<ref>{{cite book |doi=10.1021/ba-1957-0019.ch018|volume=19 |isbn=978-0-8412-0020-3 |chapter=Ch. 18: The Manufacture of Potassium and NaK |pages=169–173 |last2=Werner |first2=R. C. |last1=Jackson |first1=C. B. |year=1957 |title=Handling and uses of the alkali metals |series=Advances in Chemistry}}</ref> The ternary alloy of 12% Na, 47% K and 41% Cs has the lowest melting point of −78 °C of any metallic compound.<ref name=g76/>

Metallic potassium is used in several types of [[magnetometer]]s.<ref>{{cite book|publisher=Wiley-Blackwell|chapter-url =https://books.google.com/books?id=R_Y925b97ncC&pg=PA164|chapter = Optical Pumped Magnetometer|pages = 164|title =An introduction to geophysical exploration|isbn =978-0-632-04929-5|author =Kearey, Philip|author2 =Brooks, M|author3 =Hill, Ian|last-author-amp =yes|date =2002}}</ref>

==Precautions==
{{Chembox
| show_footer = no
|Section7={{Chembox Hazards
| ExternalSDS =
| GHSPictograms = {{GHS02}}{{GHS05}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|260|314}}
| PPhrases = {{P-phrases|223|231+232|280|305+351+338|370+378|422}}<ref>{{Cite web | url=https://www.sigmaaldrich.com/catalog/product/aldrich/244856?lang=en&region=US | title=Potassium 244856}}</ref>
| NFPA-H = 3
| NFPA-F = 3
| NFPA-R = 2
| NFPA-S = w
| NFPA_ref =
}}
}}
[[File:Potassium water 20.theora.ogv|thumb|alt=A piece of potassium metal is dropped into a clear container of water and skates around, burning with a bright pinkish or lilac flame for a short time until finishing with a pop and splash.|A reaction of potassium metal with water. Hydrogen is produced, and with potassium vapor, burns with a pink or lilac flame. Strongly alkaline potassium hydroxide is formed in solution.]]

Potassium metal reacts violently with water producing [[potassium hydroxide]] (KOH) and [[hydrogen]] gas.

:2 K (s) + 2 {{H2O}} (l) → 2 KOH (aq) + {{chem|H|2}}↑ (g)

This reaction is exothermic and releases enough heat to ignite the resulting hydrogen in the presence of oxygen. Potassium tends to explode in contact with water and without the oxygen presence. It is called [[Coulomb explosion|coulombic explosion]], possibly splashing onlookers with [[potassium hydroxide]], which is a strong [[alkali]] that destroys living tissue and causes skin burns. Finely grated potassium ignites in air at room temperature. The bulk metal ignites in air if heated. Because its density is 0.89 g/cm3, burning potassium floats in water that exposes it to atmospheric oxygen. Many common fire extinguishing agents, including water, either are ineffective or make a potassium fire worse. [[Nitrogen]], [[argon]], [[sodium chloride]] (table salt), [[sodium carbonate]] (soda ash), and [[silicon dioxide]] (sand) are effective if they are dry. Some [[Fire extinguisher|Class D]] dry powder extinguishers designed for metal fires are also effective. These agents deprive the fire of oxygen and cool the potassium metal.<ref>{{cite book| url = https://books.google.com/books?id=2fHsoobsCNwC&pg=PA459 |page = 459| title = Fire and Life Safety Inspection Manual| isbn = 978-0-87765-472-8|publisher=Jones & Bartlett Learning| last = Solomon |first=Robert E.| date = 2002}}</ref>

Potassium reacts violently with [[halogens]] and detonates in the presence of [[bromine]]. It also reacts explosively with [[sulfuric acid]]. During combustion, potassium forms peroxides and superoxides. These peroxides may react violently with [[organic compound]]s such as oils. Both peroxides and superoxides may react explosively with metallic potassium.<ref>{{cite web|url=http://www.hss.doe.gov/nuclearsafety/ns/techstds/standard/hdbk1081/hbk1081d.html |title=DOE Handbook-Alkali Metals Sodium, Potassium, NaK, and Lithium |publisher=Hss.doe.gov |accessdate=2010-10-16 |archiveurl=https://web.archive.org/web/20100928002539/http://www.hss.doe.gov/nuclearsafety/ns/techstds/standard/hdbk1081/hbk1081d.html  |archivedate=2010-09-28}}</ref>

Because potassium reacts with water vapor in the air, it is usually stored under anhydrous mineral oil or kerosene. Unlike lithium and sodium, however, potassium should not be stored under oil for longer than six months, unless in an inert (oxygen free) atmosphere, or under vacuum. After prolonged storage in air dangerous shock-sensitive peroxides can form on the metal and under the lid of the container, and can detonate upon opening.<ref>{{cite web |url=https://www.ncsu.edu/ehs/www99/right/handsMan/lab/Peroxide.pdf |title=Danger: peroxidazable chemicals |last=Wray |first=Thomas K. |publisher=Environmental Health & Public Safety, [[North Carolina State University]] |deadurl=bot: unknown |archiveurl=https://web.archive.org/web/20160729111002/https://www.ncsu.edu/ehs/www99/right/handsMan/lab/Peroxide.pdf |archivedate=2016-07-29 }}</ref>

Because of the highly reactive nature of potassium metal, it must be handled with great care, with full skin and eye protection and preferably an explosion-resistant barrier between the user and the metal. Ingestion of large amounts of potassium compounds can lead to [[hyperkalemia]], strongly influencing the cardiovascular system.<ref name="hyper">{{cite book|publisher=Lippincott Williams & Wilkins|chapter-url = https://books.google.com/books?id=BfdighlyGiwC&pg=PA903| chapter = Potassium Chloride and Potassium Permanganate|pages = 903–5|title = Medical toxicology|isbn = 978-0-7817-2845-4|last = Schonwald|first = Seth|date = 2004}}</ref><ref>{{cite book|url =https://books.google.com/books?id=l8RkPU1-M5wC&pg=PA223 |publisher=Elsevier Health Sciences|page =223|title =Emergency medicine secrets|isbn =978-1-56053-503-4|last =Markovchick |first=Vincent J.|last2 =Pons |first2=Peter T.|last-author-amp =yes|date =2003}}</ref> Potassium chloride is used in the [[United States]] for [[lethal injection]] executions.<ref name="hyper"/>

==See also==
{{Subject bar
|portal1=Chemistry
|portal2=Medicine
|book1=Potassium
|book2=Period 4 elements
|book3=Alkali metals
|book4=Chemical elements (sorted alphabetically)
|book5=Chemical elements (sorted by number)
|commons=y
|wikt=y
|wikt-search=potassium
|v=y
|v-search=Potassium atom
|b=y
|b-search=Wikijunior:The Elements/Potassium}}

==References==
{{Reflist|30em}}

==Bibliography==
* {{cite book|doi = 10.1002/14356007.a22_031.pub2|title = Ullmann's Encyclopedia of Industrial Chemistry|date = 2006|ref=Burkhardt|last = Burkhardt |first=Elizabeth R.|chapter = Potassium and Potassium Alloys|isbn = 978-3-527-30673-2|volume=A22|pages=31–38 }}
* {{cite book|ref=Greenwood|last=Greenwood|first=Norman N.|last2=Earnshaw |first2=Alan|date=1997|title=Chemistry of the Elements |edition=2nd|publisher= Butterworth-Heinemann|isbn=978-0-08-037941-8}}
* {{cite book|ref=Holleman|publisher = Walter de Gruyter|date = 2007|edition = 91–100|isbn = 978-3110177701|chapter-url=https://books.google.com/books?id=mahxPfBdcxcC&printsec=frontcover|title = Lehrbuch der Anorganischen Chemie|first1 = Arnold F.|last1 = Holleman|last2 = Wiberg|first2 = Egon|last3 = Wiberg|first3 = Nils|chapter = Potassium| language = German}}
* {{cite book|doi = 10.1002/14356007.a22_031.pub2|title = Ullmann's Encyclopedia of Industrial Chemistry|date = 2006|ref=Schultz|last1= Schultz|first1 = H.|last2 = Bauer|first2 = G.|last3 = Schachl|first3 = E.|last4 = Hagedorn|first4 = F.|last5 = Schmittinger|first5 = P.|chapter = Potassium compounds|isbn = 978-3-527-30673-2|volume = A22|pages = 39–103|displayauthors = 1}}
* [http://ndb.nal.usda.gov/ndb/search/list National Nutrient Database] at [[USDA]] Website

==External links==
* [http://www.periodicvideos.com/videos/019.htm Potassium] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
* {{Britannica|472373|Potassium (K)}}

{{Compact periodic table}}
{{Potassium compounds}}
{{good article}}

{{Authority control}}

[[Category:Potassium| ]]
[[Category:Chemical elements]]
[[Category:Alkali metals]]
[[Category:Biology and pharmacology of chemical elements]]
[[Category:Dietary minerals]]
[[Category:Desiccants]]
[[Category:Reducing agents]]
[[Category:Articles containing video clips]]

Keurig

2019-04-09T18:57:03Z

173.165.237.1: /* Inception and development */ linked Minneapolis

{{Infobox brand
| name = Keurig
| logo = Keurig.png
| image =
| caption =
| producttype = Brewing systems Beverage pods
| currentowner = [[Keurig Dr Pepper]]
| producedby =
| country = U.S.
| introduced = {{start date and age|1998}}
| discontinued =
| related =
| markets =
| previousowners = Keurig, Inc.
| trademarkregistrations =
| ambassadors =
| tagline =
| website = [http://www.keurig.com/ Keurig.com]
}}

'''Keurig''' ({{IPAc-en|ˈ|k|j|ʊər|ɪ|g}}) is a beverage brewing system for home and commercial use. It is manufactured by the American company [[Keurig Dr Pepper]] via its east-coast headquarters in [[Burlington, Massachusetts]]. The main Keurig products are: K-Cup pods, which are [[single-serve coffee container]]s; other beverage pods; and the proprietary machines that brew the beverages in these pods.

Keurig beverage varieties include hot and cold coffees, teas, cocoas, dairy-based beverages, lemonades, cider, and fruit-based drinks. Through its own brands and its partnership licensed brands, Keurig has over 400 different varieties and over 60 brands of coffee and other beverages. In addition to K-Cup pods it includes Vue, K-Carafe, and K-Mug pods as well.

The original single-serve brewer and coffee-pod manufacturing company, Keurig, Inc., was founded in Massachusetts in 1992. It launched its first brewers and K-Cup pods in 1998, targeting the office market. As the single-cup brewing system gained popularity, brewers for home use were added in 2004. In 2006 the publicly traded Vermont-based specialty-coffee company Green Mountain Coffee Roasters acquired Keurig, sparking rapid growth for both companies. In 2012 Keurig's main patent on its K-Cup pods expired, leading to new product launches, including brewer models that only accept pods from Keurig brands.

From 2006 to 2014 Keurig, Inc. was a wholly owned subsidiary of [[Green Mountain Coffee Roasters]]. When Green Mountain Coffee Roasters changed its name to [[Keurig Green Mountain]] in March 2014, Keurig ceased to be a separate business unit and subsidiary, and instead became Keurig Green Mountain's main brand.<ref>[[Associated Press]]. [https://www.usatoday.com/story/money/business/2014/03/10/green-mountain-keurig/6261731/ "New Green Mountain name shows Keurig connection"]. ''[[USA Today]]''. March 10, 2014.</ref><ref name=2014AR>[http://files.shareholder.com/downloads/GMCR/4146826546x0x800137/17B2E475-5C40-47AE-A563-C65C86B282DF/2014_Keurig_Annual_Report.pdf FISCAL 2014 ANNUAL REPORT]. [[Keurig Green Mountain]]. November 2014.</ref><ref name=vermontbiz.com>[http://www.vermontbiz.com/news/march/green-mountain-coffee-roasters-changes-name-keurig-green-mountain-inc "Green Mountain Coffee Roasters changes name to Keurig Green Mountain Inc"]. ''[[Vermont Business Magazine]]''. March 10, 2014.</ref> In 2016 Keurig Green Mountain was acquired by an investor group led by [[private equity|private-equity]] firm [[JAB Holding Company]] for nearly $14 billion.<ref name=bwcompletes>[http://www.businesswire.com/news/home/20160303005794/en/JAB-Holding-Company-Led-Investor-Group-Completes-Acquisition "JAB Holding Company-Led Investor Group Completes Acquisition of Keurig Green Mountain, Inc."]. ''[[Business Wire]]''. March 3, 2016.</ref><ref name=masunaga>Masunaga, Samantha. [http://www.latimes.com/business/la-fi-keurig-sale-20151207-story.html "Owner of Peet's to buy coffee pod pioneer Keurig for almost $14 billion"]. ''[[Los Angeles Times]]''. December 7, 2015.</ref><ref name=vbcompletes>[http://www.vermontbiz.com/news/march/jab-completes-acquisition-keurig-green-mountain "JAB completes acquisition of Keurig Green Mountain"]. ''[[Vermont Business Magazine]]''. March 3, 2016.</ref> In July 2018, Keurig Green Mountain merged with [[Dr Pepper Snapple Group]] in a deal worth $18.7 billion, creating [[Keurig Dr Pepper]], a publicly traded conglomerate which is the third largest beverage company in North America.<ref name="bevnet merger">{{Cite web|url=https://www.bevnet.com/news/2018/keurig-dr-pepper-completes-merger-keurig-green-mountain-dr-pepper-snapple-group|title=Keurig Dr Pepper Completes Merger between Keurig Green Mountain and Dr Pepper Snapple Group - BevNET.com|website=BevNET.com|language=en-US|access-date=2018-07-13}}</ref><ref name="Keurig to Take Control">{{Cite news|url=https://www.bloomberg.com/news/articles/2018-01-29/keurig-to-buy-dr-pepper-snapple-group-for-103-75-a-share|title=Keurig to Take Control of Dr Pepper in $18.7 Billion Deal|work=Bloomberg.com|access-date=2018-07-13|language=en}}</ref>

==History==

===Inception and development===
Keurig founders John Sylvan and Peter Dragone had been college roommates at [[Colby College]] in Maine in the late 1970s.<ref>[http://www.colby.edu/colby.mag/issues/84n4/70snotes.html "The Seventies – NEWSMAKERS"]. ''Colby Magazine''. Volume 84, Issue 4. [[Colby College]]. ''Colby.edu''. Retrieved May 9, 2015.</ref><ref name=buzz /> In the early 1990s Sylvan, a tinkerer, had quit his tech job in [[Massachusetts]], and wanted to solve the commonplace problem of office coffee – a full pot of brewed coffee which sits and grows bitter, dense, and stale – by creating a single-serving pod of coffee grounds and a machine that would brew it.<ref name=buzz /> Living in [[Greater Boston]], he went through extensive trial and error trying to create a pod and a brewing machine.<ref name=buzz /> By 1992, to help create a business plan, he brought in Dragone, then working as director of finance for [[Chiquita]], as a partner.<ref name=buzz>McGinn, Daniel. [http://www.boston.com/yourtown/needham/articles/2011/08/07/the_inside_story_of_keurigs_rise_to_a_billion_dollar_coffee_empire/?page=full "The Buzz Machine"]. ''[[Boston Globe]]''. August 24, 2011.</ref> They founded the company in 1992,<ref name=bloomberg>[https://www.bloomberg.com/research/stocks/private/snapshot.asp?privcapId=30522 Keurig, Incorporated] – Company Overview at ''[[Bloomberg L.P.|Bloomberg]]''.</ref> calling it Keurig; Sylvan later said that the name came from his having "looked up the word ''excellence'' in Dutch".<ref name=atlantic>Hamblin, James. [https://www.theatlantic.com/technology/archive/2015/03/the-abominable-k-cup-coffee-pod-environment-problem/386501/ "A Brewing Problem"]. ''[[The Atlantic]]''. March 2, 2015.</ref>

By 1993 Sylvan and Dragone were still making the pods by hand, and brought in manufacturing consultant [[Dick Sweeney]] to serve as co-founder and to automate the manufacturing process.<ref name=buzz /><ref name=sweeney>Margherita, Dan. [http://diversitycareers.com/articles/college/14-sumfall/atthetop_keurig.htm "Keurig co-founder Dick Sweeney brews success"]. ''Diversity/Careers''. Summer/Fall 2014.</ref> The prototype brewing machines were also a work in progress and unreliable, and the company needed funds for development.<ref name=buzz /> That year, they approached what was then [[Green Mountain Coffee Roasters]], and the specialty coffee company first invested in Keurig at that time.<ref name=brew>[https://web.archive.org/web/20150222111339/http://www.brewabetterday.com:80/meet_us/history Green Mountain Coffee – History]. ''BrewaBetterDay.com''. Archived February 22, 2015.</ref><ref name=booming>Luna, Taryn. [https://www.bostonglobe.com/business/2014/02/07/green-mountain-booming-with-coca-cola-partnership-for-new-cold-drink-system/m24yzEzI4T8KnWtX6ZoFYP/story.html "Green Mountain booming with Coca-Cola partnership for new cold drink system"]. ''[[Boston Globe]]''. February 7, 2014.</ref> Keurig needed sizeable [[venture capital]]; and after pitching to numerous potential investors the three partners finally obtained $50,000 from [[Minneapolis]]-based investor Food Fund in 1994, and later the Cambridge-based fund MDT Advisers contributed $1,000,000.<ref name=buzz /> In 1995 Larry Kernan, a principal at MDT Advisers, became Chairman of Keurig, a position he retained through 2002.<ref name=buzz /><ref name=kernan>[https://www.linkedin.com/in/larrykernan Larry Kernan] at [[LinkedIn]].</ref> Sylvan did not work well with the new investors, and in 1997 he was forced out, selling his stake in the company for $50,000.<ref name=buzz /> Dragone left a few months later but decided to retain his stake.<ref name=buzz /> Sweeney stayed on as the company's vice president of engineering.<ref name=sweeney />

===Launch===
In 1997, Green Mountain Coffee Roasters became the first roaster to offer its coffee in the Keurig "K-Cup" pod for the newly market-ready Keurig Single-Cup Brewing System,<ref name=brew /> and in 1998 Keurig delivered its first brewing system, the B2000, designed for offices.<ref name=buzz /><ref name=canada>[http://corp.keurig.ca/en-CA/OurCompany/OurHistory.aspx Keurig Canada – Our History]. ''Corp.Keurig.ca''. Retrieved March 16, 2015.</ref><ref name=timeline>[https://www.timetoast.com/timelines/a-brief-history-of-keurig A brief history of Keurig]. ''TimeToast.com''. Retrieved May 1, 2015.</ref> Distribution began in New York and New England.<ref>[https://web.archive.org/web/20060307163017/http://www.keurig.com/keurig_CoProfile.pdf Keurig – Corporate Profile]. ''Keurig.com''. 2006. Archived from the original on March 7, 2006.</ref> The target market at that time was still office use, and Keurig hoped to capture some of [[Starbucks]]' market.<ref name=buzz /> To satisfy brand loyalty and individual tastes, Keurig found and enlisted a variety of regionally known coffee brands that catered to various flavor preferences.<ref name=ackerman>Ackerman, Alliston. [http://m.consumergoods.edgl.com/MagazineDetailPage.aspx?article=46137 "GMCR's Path to Disruptive Innovation"]. ''Consumer Goods Technology''. November 16, 2012.</ref> The first of these was Green Mountain Coffee Roasters, and additional licensees for the K-Cup line included [[Tully's Coffee]], [[Timothy's World Coffee]], [[Diedrich Coffee]], and [[Van Houtte]], although Green Mountain was the dominant brand.<ref name=ackerman /> Keurig also partnered with a variety of established national U.S. coffee brands for K-Cup varieties, and in 2000 the company also branched out the beverage offerings in its K-Cup pods to include hot chocolate and a variety of teas.<ref name=timeline /> The brewing machines were large, and hooked up to an office's water supply; Keurig sold them to local coffee distributors, who installed them in offices for little or no money, relying on the K-Cups for profits.<ref name=buzz /><ref name=inc />

Keurig is credited with [[Category design|creating a new category]] with their cup-at-a-time pod-style brewing that was both a breakthrough product and a breakthrough business model.<ref>{{cite news |last=Yoon |first=Eddie |last2=Deeken |first2=Linda |url=https://hbr.org/2013/03/why-it-pays-to-be-a-category-creator |title=Why It Pays to Be a Category Creator |work=[[Harvard Business Review]] |date=2013-03-01 |accessdate=2019-03-28 }}</ref>

In 2002, Keurig sold 10,000 commercial brewers.<ref name=buzz /> Consumer demand for a home-use brewer version increased,<ref>Lerner, Jill. [http://www.bizjournals.com/boston/stories/2003/06/09/newscolumn1.html?page=all "Keurig has some ideas brewing about consumer market"]. ''[[Boston Business Journal]]''.
June 9, 2003.</ref> but manufacturing a model small enough to fit on a kitchen counter, and making them inexpensively enough to be affordable to consumers, took time. Office models were profitable because the profits came from the high-margin K-Cups, and one office might go through up to hundreds of those a day.<ref name=buzz /><ref name=inc>Leder, Michelle. [http://www.inc.com/magazine/20040101/casestudy.html "Taking a Niche Player Big-Time"]. ''[[Inc. (magazine)|Inc.]]'' January 1, 2004.</ref>

By 2004, Keurig had a prototype ready for home use, but so did large corporate competitors like [[Salton Inc.|Salton]], [[Sara Lee Corporation|Sara Lee]], and [[Procter & Gamble]], which introduced their own single-serve brewers and pods. Keurig capitalized on the increased awareness of the concept, and sent representatives into stores to do live demonstrations of its B100 home brewer and give out free samples.<ref name=buzz /><ref name=timeline /> Keurig and K-Cups quickly became the dominant brand of home brewers and single-serve pods.<ref name=buzz />

===Acquisition by Green Mountain Coffee Roasters===
In 2006, the publicly traded Vermont-based specialty-coffee company Green Mountain Coffee Roasters (GMCR) – which had successively invested in and acquired increasing percentage ownership of Keurig in 1993, 1996, and 2003, by which time it had a 43% ownership – completed its full acquisition of Keurig.<ref name=completed>[http://www.bizjournals.com/boston/stories/2006/06/12/daily53.html "Green Mountain Coffee's purchase of Keurig Inc. completed"]. ''[[Boston Business Journal]]''. June 16, 2006.</ref> Green Mountain also acquired the four additional Keurig licensees, Tully's Coffee, Timothy's World Coffee, Diedrich Coffee, and Van Houtte, in 2009 and 2010.<ref name=rogers>Rogers, Jim. [http://www.rogersfamilyco.com/index.php/story-keurig-k-cup-2-0-brewer/ "The story of the Keurig K-Cup and the 2.0 Brewer"]. ''The Inside Scoop''. ''RogersFamilyCo.com''. December 16, 2014.</ref><ref>Morgan, Brian. [http://blog.euromonitor.com/2011/03/starbucks-alliance-with-green-mountain-puts-spotlight-on-coffee-pods.html "Starbucks Alliance With Green Mountain Puts Spotlight on Coffee Pods"]. ''Euromonitor International''. March 21, 2011.</ref><ref name=fred>[http://fredtalks.com/wp-content/uploads/2013/09/Green-Mountain-Coffee-Roasters.pdf "Premier Employers of Food Processing: Green Mountain Coffee Roasters"]. [[The Hitachi Foundation]], and Northwest Food Processors Education & Research Institute. Retrieved March 16, 2015.</ref><ref>
*[http://www.streetinsider.com/Mergers+and+Acquisitions/Green+Mountain+(GMCR)+Makes+Key+Strategic+Acquisition+of+Canada%E2%80%99s+Van+Houtte/5967105.html "Green Mountain (GMCR) Makes Key Strategic Acquisition of Canada’s Van Houtte"]. ''StreetInsider.com''. September 14, 2010.
*[http://investor.keuriggreenmountain.com/releasedetail.cfm?releaseid=470651 "Green Mountain Coffee Roasters, Inc. Completes Acquisition of Tully's Brand and Wholesale Business"]. ''Investor.KeurigGreenMountain.com'' (press release). March 30, 2009.
*[http://investor.keuriggreenmountain.com/releasedetail.cfm?releaseid=470411 "Green Mountain Coffee Roasters, Inc. Acquires Timothy’s Coffees of the World, Inc."]. ''Investor.KeurigGreenMountain.com''. November 13, 2009.
*[http://articles.latimes.com/2009/dec/08/business/la-fi-diedrich9-2009dec09 "Green Mountain Coffee to buy Diedrich for $290 Million"]. ''[[Los Angeles Times]]''. December 8, 2009.
*LaSalle, LuAnn. [https://www.thestar.com/business/2010/09/14/green_mountain_coffee_buys_van_houtte_for_915m.html "Green Mountain Coffee buys Van Houtte for $915M"]. ''[[The Canadian Press]]''. September 14, 2010.</ref>

The joining of Keurig and Green Mountain combined a highly technological brewing-machine manufacturer and a nationwide high-end coffee provider into one company, and created an effective "[[freebie marketing|razor/razorblade]]" model that allowed for explosive growth and high profits.<ref name=ackerman /> By 2008, K-Cup pods became available for sale in [[supermarket]]s across the U.S.<ref name=ackerman /> Coffee pod machine sales overall multiplied more than six-fold over the six years from 2008 to 2014.<ref>Ferdman, Roberto A. [http://qz.com/193138/the-worlds-growing-love-affair-with-the-most-wasteful-form-of-coffee-there-is/ "The world’s growing love affair with the most wasteful form of coffee there is"]. ''[[Quartz (publication)|Quartz]]''. March 31, 2014.</ref> In 2010 Keurig and K-Cup sales topped $1.2{{nbsp}}billion.<ref name=timeline /> The high-margin profits from K-Cup pods are the bulk of the company's income; for fiscal year 2014, Keurig generated $822.3 million in sales from brewers and accessories, while the pods had $3.6 billion in sales.<ref name=hot>Kell, John. [http://fortune.com/2014/12/23/keurigs-too-hot-coffee-machines-stung-by-recall/ "Keurig's too-hot coffee machines stung by recall"]. ''[[Fortune (magazine)|Fortune]]''. December 23, 2014.</ref>

In February 2011 Green Mountain announced an agreement with [[Dunkin' Donuts]] to make Dunkin’ Donuts coffee available in single-serve K-Cup pods for use with Keurig Single-Cup Brewers. In addition, participating Dunkin’ Donuts restaurants on occasion offer Keurig Single-Cup Brewers for sale.<ref name=gmcrpr2011>[http://www.businesswire.com/news/home/20110222005683/en/Green-Mountain-Coffee-Roasters-Dunkin%E2%80%99-Donuts-America%E2%80%99s "Green Mountain Coffee Roasters, Inc. and Dunkin' Donuts to Make America's Favorite Coffee Available in K-Cup Portion Packs for Keurig Single-Cup Brewers"]. ''[[Business Wire]]''. February 22, 2011.</ref> In March 2011, Green Mountain Coffee and [[Starbucks]] announced a similar deal whereby Starbucks would sell its coffee and tea in Keurig single-serve pods, and would in return sell Keurig machines in their stores as part of the deal.<ref>Allison, Melissa. [http://seattletimes.nwsource.com/html/businesstechnology/2014455453_greenmountain11.html "Starbucks, Green Mountain ink deal, but it's not an acquisition"]. ''[[The Seattle Times]]''. March 10, 2010.</ref>

===Additional products and developments===
The company introduced the Keurig Vue brewer, paired with new Vue pods, in February 2012,<ref name =VuePR>[http://investor.keuriggreenmountain.com/releasedetail.cfm?releaseid=648706 "Green Mountain Coffee Roasters Unveils New Keurig Brewing Platform"]. ''Investor.KeurigGreenMountain.com'' (press release). February 15, 2012.</ref> seven months before the key patent on the K-Cup expired in September 2012.<ref>Gara, Tom. [https://blogs.wsj.com/corporate-intelligence/2012/11/28/the-k-cup-patent-is-dead-long-live-the-k-cup/ "The K-Cup Patent Is Dead, Long Live The K-Cup"]. ''[[Wall Street Journal]]''. November 28, 2012.</ref><ref>Keurig's patent on the original K-Cup ({{US patent|5325765|US5325765}})</ref><ref name=pt-5325765>{{cite patent
| country = US | number = 5325765 | status = patent | title = Beverage filter cartridge | pubdate = | gdate = 1994-07-05 | fdate = | pridate = 1992-09-16 | invent1 = Sylvan, John E. | invent2 = Dragone, Peter B. | assign1 = Keurig, Inc.}}</ref> The Vue system was announced as having customizable features so consumers had control over the strength, size, and temperature of their beverages, and the Vue pod is made of [[recyclable]] #5 plastic.<ref name=VuePR /> The Vue brewer was discontinued in 2014,<ref>Golden, Seth. [http://seekingalpha.com/article/2108813-keurig-green-mountains-keurig-2_0-has-opportunities-and-downside-risk "Keurig Green Mountain's Keurig 2.0 Has Opportunities And Downside Risk"]. ''[[Seeking Alpha]]''. March 25, 2014.</ref> although Keurig still sells the Vue pods.<ref>[http://www.keurig.com/Beverages/c/beverages101?text=&show=Page&layoutStatus=grid&categoryCode=coffee101&q=%3Arelevance&terms=%3APackageType%3AVue&selectedFacets=%26selectedFacetsSeperator%3BPackageTypeVue%3AVue Beverages – Vue]. ''Keurig.com''. Retrieved May 10, 2015.</ref>

In November 2012, GMCR released its espresso, cappuccino, and latte brewer, the Rivo, co-developed with the Italian coffee company [[Lavazza]];<ref>Geller, Martinne. [https://www.reuters.com/article/2012/11/08/us-greenmountain-machine-idUSBRE8A70Z120121108 "Green Mountain unveils Keurig Rivo cappuccino maker"]. ''[[Reuters]]''. November 8, 2012.</ref> it was discontinued in December 2016.<ref>Quirk, Mary Beth. [https://consumerist.com/2017/02/27/owners-of-discontinued-keurig-rivo-having-trouble-buying-coffee-pods-that-will-work/ "Owners Of Discontinued Keurig Rivo Having Trouble Buying Coffee Pods That Will Work"]. ''[[Consumerist]]''. February 28, 2017.</ref> In the fall of 2013, the company released a full-pot brewer, the Keurig Bolt, for use mainly in offices;<ref>Gasparro, Annie. [https://www.wsj.com/articles/SB10001424127887324694904578600162104741542 "Green Mountain Coffee Unveils Full-Pot Keurig"]. ''[[Wall Street Journal]]''. July 11, 2013.</ref> it was discontinued in December 2016.<ref>{{Cite web|url=https://uscoffee.com/coffee-brewers/keurig-bolt/|title=Keurig Bolt {{!}} US Coffee Inc|website=uscoffee.com|language=en-US|access-date=2017-01-26}}</ref>

In November 2013 Keurig opened a [[retail store]] inside the [[Burlington Mall (Massachusetts)|Burlington Mall]] in [[Burlington, Massachusetts|Burlington]], [[Massachusetts]]. The store features the full line of Keurig machines and accessories, and nearly 200 varieties of K-Cups for creating individualized 3-, 6-, or 12-pod boxes.<ref>Luna, Taryn. [https://www.bostonglobe.com/business/2013/11/09/world-first-keurig-store-opens-burlington/A4IWnCQqm9LcK1zLizx3bJ/story.html "Burlington Mall hosts Keurig’s first-ever retail outlet"]. ''[[Boston Globe]]''. November 9, 2013.</ref><ref>[http://www.simon.com/mall/burlington-mall/stores/keurig Burlington Mall – Keurig]. ''Simon.com''. Retrieved May 4, 2015.</ref>

In February 2014, [[The Coca-Cola Company]] purchased a 10% stake in Green Mountain Coffee Roasters, valued at $1.25 billion, with an option to increase their stake to 16%, which was exercised in May 2014.<ref name=K-Coke>Stafford, Leon. [http://www.myajc.com/news/business/coca-cola-ups-stake-in-keurig/nft8H/ "Coca-Cola ups stake in Keurig"]. ''[[Atlanta Journal-Constitution]]''. May 13, 2014.</ref> The partnership was part of Coca-Cola's support of a cold beverage system developed by Keurig to allow customers to make Coca-Cola and other brand beverages at home.<ref name=K-Coke /> In January 2015, the company made a similar deal with [[Dr Pepper Snapple Group]], but without a stockholder stake.<ref name=gasparro2015>Gasparro, Annie; Esterl, Mike. [http://www.marketwatch.com/story/keurig-reels-in-dr-pepper-for-its-coming-soda-machine-2015-01-07 "Keurig Reels In Dr Pepper for Its Coming Soda Machine"]. ''[[Wall Street Journal]]''. January 7, 2015.</ref> The cold beverage system, Keurig Kold, launched in September 2015.<ref name=kold>[http://investor.keuriggreenmountain.com/releasedetail.cfm?releaseid=934131 "Keurig Green Mountain Announces the Launch of Keurig KOLD"] (press release). ''Investor.KeurigGreenMountain.com''. September 29, 2015.</ref>

====Keurig Green Mountain====
In early March 2014, shareholders of Keurig's parent company, Green Mountain Coffee Roasters, voted to change its name to Keurig Green Mountain to reflect its business of selling Keurig coffee makers.<ref>[[Associated Press]]. [https://www.usatoday.com/story/money/business/2014/03/10/green-mountain-keurig/6261731 "New Green Mountain name shows Keurig connection"]. ''[[USA Today]]''. March 10, 2014.</ref> Keurig Green Mountain's stock-market symbol remained "GMCR".<ref name=vermontbiz.com/>

In the fall of 2014, Keurig Green Mountain introduced the Keurig 2.0 brewer, with technology to prevent old or unlicensed pods being used in the brewer.<ref>Gasparro, Annie. [https://www.wsj.com/articles/keurig-warns-currency-to-hurt-full-year-results-1423087615 "Keurig Stumbles With New K-Cup Brewer"]. ''[[Wall Street Journal]]''. February 4, 2015.</ref> The digital lock-out sparked hacking attempts and anti-trust lawsuits.<ref>Munarriz, Rick Aristotle. [http://www.dailyfinance.com/2014/10/09/keurig-2.0-bitter-taste-coffee-drinkers-competitors/ "Keurig 2.0 Is Leaving a Bitter Taste in a Lot of Mouths"]. ''Daily Finance''. October 9, 2014.</ref><ref name=claim>D'Ambrosio, Dan. [http://www.burlingtonfreepress.com/story/news/2014/04/12/lawsuits-claim-keurig-green-mountain-violating-antitrust-laws/7612125/ "Lawsuits claim Keurig Green Mountain violating antitrust laws"]. ''[[Burlington Free Press]]''. April 12, 2014.</ref><ref>Kirsner, Scott. [https://www.bostonglobe.com/business/2014/12/19/hacking-cups-latest-keurig-pod-people/AJoPnKbMkf8e7eAPKyjgmN/story.html "Hacked K-cups latest in battle over Keurig coffeemakers"]. ''[[Boston Globe]]''. December 19, 2014.</ref><ref>Kline, Daniel. [http://www.fool.com/investing/general/2014/09/08/keurig-20-can-survive-knockoff-k-cups.aspx "Keurig 2.0 Can Survive Knockoff K-Cups"]. ''[[The Motley Fool]]''. September 8, 2014.</ref> The Keurig 2.0 K-Cup pods come in 400 varieties from 60 brands,<ref name=pr899238 /><ref name=beverages101 /> and as of 2015 the 2.0 K-Cup, K-Carafe, and K-Mug pods encompass 500 varieties from 75 brands.<ref name=keurig2>[http://www.keurig.com/content/keurig2 Keurig Plus]. ''Keurig.com''. Retrieved March 21, 2018.</ref> The 2.0 brewer also has the capacity to brew full carafes in three settings from 2 to 5 cups, via the use of the new K-Carafe pod.<ref>Crist, Ry. [http://www.cnet.com/news/keurig-2-0-brews-up-drm-to-freeze-out-copycat-cups/ "Keurig 2.0 brews up DRM to freeze out copycat cups"]. ''[[CNET]]''. March 3, 2014.</ref><ref>Dzieza, Josh. [https://www.theverge.com/2014/6/30/5857030/keurig-digital-rights-management-coffee-pod-pirates "Inside Keurig's plan to stop you from buying knockoff K-Cups"]. ''[[The Verge]]''. June 30, 2014.</ref><ref>[http://www.businesswire.com/news/home/20140129005384/en/Green-Mountain-Coffee-Roasters-Unveils-Next-Generation-Keurig "Green Mountain Coffee Roasters Unveils Next-Generation Keurig Carafe Innovation"]. ''[[Business Wire]]''. January 29, 2014.</ref><ref>[http://www.keurig.com/support/k-carafe-packs Beverage Support – K-Carafe Pods]. ''Keurig.com''. Retrieved May 20, 2015.</ref>

In March 2015, Keurig launched the K-Mug pod, a recyclable pod which brews large travel mug–sized portions.<ref>Prafder, Erika. [http://www.digitaltrends.com/home/coffee-keurig-recyclable/ "K-CUPS’ SERVING SIZE TOO SMALL? KEURIG INTRODUCES PODS THAT WILL FILL UP YOUR MUG"]. ''[[Digital Trends]]''. March 24, 2015.</ref> The K-Mug pods, for use in the Keurig 2.0 brewing system, brew 12-, 14-, and 16-ounce cups, and the plastic is recyclable [[Polypropylene|#5 polypropylene plastic]].<ref>Jed, Emily. [http://www.vendingtimes.com/ME2/dirmod.asp?nm=Vending+Features&type=Publishing&mod=Publications%3A%3AArticle&tier=4&id=5141947C8D3D4EA393230DC1A94C6167 "Keurig Launches K-Mug Pods For Travel Mugs"]. ''[[Vending Times]]''. Vol. 55, No. 4, April 2015.</ref><ref>[http://www.businesswire.com/news/home/20150323005953/en/Keurig-Coffee-To-Go-Easier-Launch-K-Mug%C2%AE-Pods "Keurig Makes Coffee To-Go Easier with Launch of K-Mug® Pods"]. ''[[Business Wire]]''. March 23, 2015.</ref>

In mid 2015 Keurig debuted the K200, a smaller Keurig 2.0 model that can brew single cups or four-cup carafes and comes in a variety of colors.<ref>Bennett, Brian. [http://www.cnet.com/products/keurig-k200-brewer/ "Keurig's new compact coffeemaker makes a splash in fresh kitchen-friendly colors"]. ''[[CNET]]''. March 1, 2015.</ref><ref>[http://investor.keuriggreenmountain.com/releasedetail.cfm?ReleaseID=899238 "The Keurig 2.0 Brewing System Lineup Expands with the Addition of the New K200 Series"]. [[Keurig Green Mountain]] (press release). ''Investor.KeurigGreenMountain.com''. March 2, 2015.</ref> [[General Electric]] announced that its new Café French Door refrigerator, due out in late 2015, will have a Keurig coffee machine built into the door.<ref>Liszewski, Andrew. [https://gizmodo.com/ges-new-fridge-has-a-keurig-coffee-machine-built-right-1679284319 "GE's New Fridge Has a Keurig Coffee Machine Built Right Into the Door"]. ''[[Gizmodo]]''. January 14, 2015.</ref><ref>Bowerman, Mary. [https://www.usatoday.com/story/money/2015/01/19/three-thousand-dollar-fridge-will-make-keurig-coffee/21994007/ "$3,300 refrigerator will make you coffee with Keurig"]. ''[[USA Today]]''. January 19, 2015.</ref>

In September 2015, Keurig launched a line of [[Campbell's Soup]] available in K-Cups.<ref name=bowerman>Bowerman, Mary. [https://www.usatoday.com/story/news/nation-now/2015/09/10/keurig-campbells-soup-k-cups-chicken-noodle-coffee-tea/72012554/ "Keurig unveils Campbell's Soup K-Cups"]. ''[[USA Today]]''. September 10, 2015.</ref><ref name=hotsoup>[http://investor.keuriggreenmountain.com/releasedetail.cfm?releaseid=930847 "Campbell's Fresh-Brewed Soup, The First-Ever Hot Soup Made Exclusively for the Keurig Hot Brewing System, Now Available on Keurig.com"] (press release). ''Investor.KeurigGreenMountain.com''. September 9, 2015.</ref> The Campbell's Fresh-Brewed Soup Kits come with a packet of noodles and a K-Cup pod of soup.<ref name=bowerman /> The product is available in two varieties: Homestyle Chicken Broth & Noodle, and Southwest Style Chicken Broth & Noodle.<ref name=hotsoup />

Also in September 2015, Keurig launched Keurig Kold, a brewer which creates a variety of cold beverages including soft drinks, functional beverages, and sparkling waters.<ref name=kold /> The machine brews beverages from The Coca-Cola Company (e.g. [[Coca-Cola]], [[Diet Coke]], [[Coke Zero]], [[Sprite (soft drink)|Sprite]], [[Fanta]]) and the Dr Pepper Snapple Group (e.g. [[Dr Pepper]], [[Canada Dry]]) and Keurig's own line of flavored sparkling and non-sparkling waters and teas, sports drinks, and soda-fountain drinks.<ref name=kold />

In December 2015 it was announced that Keurig Green Mountain would be sold to an investor group led by [[private equity|private-equity]] firm [[JAB Holding Company]] for nearly $14 billion.<ref name=masunaga/> The acquisition was completed in March 2016.<ref name=bwcompletes/><ref name=vbcompletes/>

====Keurig Dr Pepper====
In July 2018, [[Keurig Green Mountain]] merged with [[Dr Pepper Snapple Group]] in a deal worth $18.7 billion, creating a publicly traded conglomerate which is the third largest beverage company in North America.<ref name="bevnet merger"/><ref name="Keurig to Take Control"/>

Keurig launched Drinksworks Home Bar in late 2018, developed by Keurig Dr Pepper and [[AB-InBev|AB InBev]]. The machine creates cocktails, beers and ciders through 24 different pods. The device is available in Missouri, and expected to launch to the general public in 2019. <ref>{{Cite web|url=https://www.thedrinksbusiness.com/2018/11/ab-inbev-and-keurig-launch-home-cocktail-machine/|title=AB InBev and Keurig launch home cocktail machine|website=www.thedrinksbusiness.com|language=en-US|access-date=2018-11-29}}</ref><ref>{{cite web|url=https://www.cbsnews.com/news/keurig-for-cocktails-drinkworks-home-bar-rolls-out-but-its-hard-to-find/|title=Keurig for cocktails: Drinkworks home bar rolls out, but it's hard to find|website=www.cbsnews.com}}</ref>

== Products ==

===Keurig K-Cup brewing systems===
[[File:InsideKCup.jpg|thumb|The inside of a used K-Cup pod, with the top foil and the used coffee grounds removed, revealing the filter]]
The company's flagship products, Keurig K-Cup brewing systems, are designed to [[coffee preparation|brew]] a single cup of [[coffee]], [[tea]], [[hot chocolate]], or other hot beverage. The grounds are in a [[single-serve coffee container]], called a "K-Cup" pod, consisting of a plastic cup, aluminum lid, and filter. Each K-Cup pod is filled with coffee grounds, tea leaves, cocoa powder, fruit powder, or other contents, and is nitrogen flushed, sealed for freshness, and impermeable to oxygen, light, and moisture.<ref name=atlantic /><ref>[http://www.keurig.com/support/k-cup-packs Beverage Support]. ''Keurig.com''. Retrieved July 16, 2015.</ref>

The machines brew the K-Cup beverage by piercing the foil seal with a spray nozzle, while piercing the bottom of the plastic pod with a discharge nozzle. Grounds contained inside the K-Cup pod are in a [[coffee filter|paper filter]]. Hot water is forced under pressure through the K-Cup pod, passing through the grounds and through the filter. A brewing temperature of {{convert|192|F|C}} is the default setting, with some models permitting users to adjust the temperature downward by five degrees.<ref>[http://www.keurig.com/support/k-cup-brewers Keurig – Brewer Support]. Retrieved May 4, 2015.</ref>

The key original patent on the K-Cup expired in 2012.<ref name=bg-2012-06>Johnston, Katie.[http://www.boston.com/business/articles/2012/06/12/another_challenge_for_k_cup_maker "Another challenge for K-Cup maker"]. ''[[Boston Globe]]''. 12 June 2012.</ref> Keurig has later patents, including on the filtration cartridge used in K-Cups,<ref name=ml-2012-07>{{cite web
|title=Green Mountain Coffee Roaster's Patent Expiration Could Create Glut Of K-Cup Copies
|url=http://www.mandourlaw.com/blog/patent-registration/green-mountain-coffee-roasters-patent-expiration-could-create-glut-of-k-cup-copies |publisher=Mandour & Associates|date=July 18, 2012 |archiveurl=https://web.archive.org/web/20150310004508/http://www.mandourlaw.com/blog/patent-registration/green-mountain-coffee-roasters-patent-expiration-could-create-glut-of-k-cup-copies/
|archivedate=March 10, 2015}}</ref> and has also launched a number of new pods since the beginning of 2012.

===Brewing system models===
[[File:Keurig Coffee Machine.jpg|thumb|A Keurig coffee maker (2013)]]
Keurig sells many brewing system models, for household and commercial use. Licensed models from [[Breville]], [[Cuisinart]], and [[Mr. Coffee]], were introduced in 2010.<ref name=2014AR />

Keurig's brewing systems for home use include single-cup brewers, and brewers that brew both single-cups and carafes. Many of the brewers are programmable for brew size and strength.

Keurig also offers commercial brewing models specifically for offices,<ref>[http://www.keurig.com/content/business-solutions/office Keurig Business Solutions – Office]. ''Keurig.com''. Retrieved May 9, 2015.</ref> [[food service]],<ref>[http://www.keurig.com/content/business-solutions/foodservice The Breakthrough Foodservice Solution]. ''Keurig.com''. Retrieved May 9, 2015.</ref> [[convenience store]]s,<ref>[http://www.keurig.com/content/business-solutions/convenience-store Keurig Business Solutions – Convenience Store]. ''Keurig.com''. Retrieved May 9, 2015.</ref> health care,<ref>[http://www.keurig.com/content/business-solutions/healthcare Keurig Business Solutions – Healthcare]. ''Keurig.com''. Retrieved May 9, 2015.</ref> hotels and hospitality,<ref>[http://www.keurig.com/content/business-solutions/hospitality Keurig Business Solutions – Hospitality] ''Keurig.com''. Retrieved May 9, 2015.</ref> and college and university campuses.<ref>[http://www.keurig.com/content/business-solutions/college-university Keurig Business Solutions – College and University]. ''Keurig.com''. Retrieved May 9, 2015.</ref>

=== Beverage varieties and brands===
[[File:K-Cup-Silo.gif|thumb|Five K-Cups]]
Through its owned brands and through its partnerships and licensing, as of 2015 Keurig's K-Cups and other pods offer more than 400 beverage varieties from 60 brands, including the top ten best-selling coffee brands in the U.S.<ref name=pr899238>[http://investor.keuriggreenmountain.com/releasedetail.cfm?ReleaseID=899238 "The Keurig 2.0 Brewing System Lineup Expands with the Addition of the New K200 Series"]. ''Investor.KeurigGreenMountain.com'' (press release). March 2, 2015.</ref><ref name=beverages101>[http://www.keurig.com/Beverages/c/beverages101 Beverages]. ''Keurig.com''. Retrieved May 20, 2015.</ref> The beverages include coffees, teas, hot chocolates and cocoas, dairy-based beverages, lemonades, cider, and fruit-based drinks.<ref>[http://www.keurig.com/ ''Keurig.com'']. Retrieved March 15, 2016.</ref> Keurig also offers Brew Over Ice pods for cold versions of teas, fruit drinks, and coffees.<ref>[http://www.keurig.com/Beverages/Iced-Beverages/c/icedBeverages101 Iced Beverages]. ''Keurig.com''. Retrieved May 9, 2015.</ref><ref>[http://summer.brewoverice.com/how-brew-over-ice How to Brew Over Ice]. ''Summer.BrewOverIce.com''. Retrieved May 9, 2015.</ref><ref>[https://www.youtube.com/watch?v=6b12OUIiia0 Brew Over Ice: Iced Coffee & Iced Tea in Your Keurig Brewer]. [[Green Mountain Coffee]]. April 28, 2011.</ref>

====Keurig-owned brands====
As of 2015, brands owned by Keurig/Keurig Green Mountain, and used in its K-Cup and other pods, include:<ref>[http://www.keuriggreenmountain.com/en/OurBrands.aspx Keurig Green Mountain – Our Brands]. [[Keurig Green Mountain]]. ''KeurigGreenMountain.com''. Retrieved May 5, 2015.</ref>
{{div col|colwidth=30em}}
*[[Green Mountain Coffee Roasters|Green Mountain Coffee]]
*[[Green Mountain Coffee Roasters|Green Mountain Naturals]]
*Barista Prima Coffeehouse
*Café Escapes
*[[Coffee People]]
*[[Diedrich Coffee]]
*Donut House Collection
*The Original Donut Shop
*Revv
*[[Timothy's World Coffee]]
*[[Tully's Coffee]]
*[[Van Houtte]]
*Vitamin Burst
{{div col end}}

== Awards ==
Keurig was named Single Serve Coffee Maker Brand of the Year for four consecutive years from 2012–2015 by the [[Harris Poll]] EquiTrend Study.<ref>[https://finance.yahoo.com/news/keurig-named-single-serve-coffee-130000461.html "Keurig Named Single Serve Coffee Maker Brand of the Year in 2015 Harris Poll EquiTrend Study"]. ''[[Yahoo! Finance]]''/''[[Business Wire]]''. March 25, 2015.</ref>

Some of Keurig's additional awards since 2012 have included:

*2013 "Best All Around" in Best Single-Serve Coffeemakers – Keurig Vue ([[Good Housekeeping#Good Housekeeping Research Institute|Good Housekeeping Research Institute]])<ref>[http://www.goodhousekeeping.com/appliances/coffee-maker-reviews/g350/best-single-serve-coffeemakers/?slide=3 Best Single-Serve Coffeemakers]. [[Good Housekeeping]]. ''GoodHousekeeping.com''. 2013. Retrieved May 10, 2015.</ref>
*2013 [[Edison Award]]s Gold Award for Consumer Packaged Goods, Beverage Preparation – Keurig Vue<ref>[http://www.edisonawards.com/winners2013.php 2013 EDISON AWARD WINNERS]. [[Edison Award]]s. ''EdisonAwards.com''.</ref>
*2014 Top 10 Breakaway Brands ([[Landor Associates]])<ref>[http://landor.com/#!/talk/articles-publications/articles/breakaway-brands-2014/ Breakaway Brands 2014]. [[Landor Associates]]. ''Landor.com''.</ref>
*2014 Food and Beverage Innovators Award – Bolt Packs ([[National Restaurant Association]])<ref>[http://www.restaurant.org/Pressroom/Press-Releases/National-Restaurant-Association-Announces-2014-FAB "National Restaurant Association Announces 2014 FABI Award Recipients"]. [[National Restaurant Association]]. ''Restaurant.org''. March 5, 2014.</ref>
*2014 U.S. 500 Most Valuable Brands ([[Brand Finance]])<ref>[http://brandirectory.com/league_tables/table/usa-500-2014 The Brand Finance US 500 2014]. [[Brand Finance]]. ''Brandirectory.com''.</ref><ref>[http://brandirectory.com/profile/keurig Keurig] – Profile at [[Brand Finance]]. Retrieved May 10, 2015.</ref>
*Most Recommended Single Serve Pod Coffee Maker 2014 (Women's Choice Award)<ref>[http://www.womenschoiceaward.com/best-home/best-kitchen-small-appliances/ Most Recommended Small Appliances]. ''WomensChoiceAward.com''. 2014.</ref>
*50 Best U.S. Manufacturers 2014 (''[[IndustryWeek]]'')<ref>[http://www.industryweek.com/resources/iw50best/2014 The 2014 IndustryWeek 50 Best U.S. Manufacturers]. ''[[IndustryWeek]]''. ''IndustryWeek.com''. Retrieved May 10, 2015.</ref>

==Corporate affairs==

===Environmental impact===
In the 2010s, beginning primarily with a 2010 article in the ''[[New York Times]]'',<ref name=carpenter>Carpenter, Murray. [https://www.nytimes.com/2010/08/04/business/energy-environment/04coffee.html "A Coffee Conundrum"]. ''[[New York Times]]''. August 3, 2010.</ref> Keurig has been publicly criticized by environmental advocates and journalists for the billions of non-recyclable and non-biodegradable K-Cups consumers purchase and dispose of every year, which end up in landfills.<ref name=motherjones>Oatman, Maddie. [https://www.motherjones.com/blue-marble/2014/03/coffee-k-cups-green-mountain-polystyrene-plastic "Your Coffee Pods' Dirty Secret"]. ''[[Mother Jones (magazine)|Mother Jones]]''. March 19, 2014.</ref><ref name=az>''[[E–The Environmental Magazine]]''. [http://azdailysun.com/lifestyles/columnists/billions-of-k-cups-wind-up-in-landfills-each-year/article_28df7460-b6e1-11e3-ba32-001a4bcf887a.html "Billions of K-Cups wind up in landfills each year"]. ''[[Arizona Daily Sun]]''. March 30, 2014.</ref><ref name=gunther>Gunther, Mark. [https://www.theguardian.com/sustainable-business/green-mountain-keurig-coffee-pods-waste-recycling "Trouble brewing: has success spoiled Green Mountain?"]. ''[[The Guardian]]''. May 28, 2014.</ref><ref>Khalili, Olivia. [http://causecapitalism.com/trouble-brewing-for-green-mountain-coffee/ "Trouble Brewing For Green Mountain Coffee: Do 3 Billion Plastic Cups Negate 30 Years of Sustainability?"]. ''CauseCapitalism.com''. August 2010.</ref><ref>Craves, Julie. [http://www.coffeehabitat.com/2014/03/greenwashing-at-keurig-green-mountain/ "Greenwashing at Keurig Green Mountain"]. ''Coffee & Conservation''. ''CoffeeHabitat.com''. March 24, 2014.</ref> Some competing single-cup brands have single-serve pods that are recyclable, reuseable, compostable, or biodegradable.<ref name=carpenter /><ref name=motherjones /><ref>Craves, Julie. [http://www.coffeehabitat.com/2012/11/k-cup-alternatives/ "K-Cup alternatives: summary and parting thoughts"]. ''Coffee & Conservation''. ''CoffeeHabitat.com''. November 22, 2012.</ref><ref>Anderle, Megan. [https://www.theguardian.com/sustainable-business/2014/oct/02/keurig-k-cup-coffee-monopoly-biodegradable-compost-pods "Brewing a coffee monopoly at Keurig, one single-serving cup at a time"]. ''[[The Guardian]]''. October 2, 2014.</ref>

The cup portion of the K-Cup is made of [[Resin identification code|#7 plastic]], and although according to the company it is [[Bisphenol A|BPA]]-free, safe, and meets or exceeds applicable FDA standards,<ref name=motherjones /> it cannot be recycled in most places.<ref name=motherjones /><ref name=gunther /> Even in the few locations in Canada where #7 plastic is recycled, the small size of the pods means they can fall through sorting grates.<ref name=buzz />

In late 2005 Green Mountain and Keurig launched the My K-Cup reusable and refillable pod, which could be filled with any brand of coffee.<ref>Brewer, Jay. [http://www.singleservecoffee.com/archives/003140.php "Reusable Coffee Filter for Keurig"]. ''SingleServeCoffee.com''. September 28, 2005.</ref><ref>Brewer, Jay. [http://www.singleservecoffee.com/archives/004250.php "Review: My K-Cup Keurig Reusable Filter"]. ''SingleServeCoffee.com''. January 5, 2006.</ref><ref name=barbash>Barbash, Fred. [https://www.washingtonpost.com/news/morning-mix/wp/2015/05/07/keurigs-k-cup-screw-up-and-how-it-k-pitulated-wednesday-to-angry-consumers/ "Keurig’s K-Cup screw-up and how it K-pitulated Wednesday to angry consumers"]. ''[[Washington Post]]''. May 7, 2015.</ref> The product was discontinued in August 2014 with the launch of the Keurig 2.0 brewing system, and the 2.0 did not accept the My K-Cup pods. Consumer backlash prompted the company to announce in May 2015 that it was bringing back the My K-Cup and making it compatible with the 2.0 brewers.<ref name=barbash />

In 2011 GMCR launched the Grounds to Grow On program, in which office customers purchase recovery bins for used K-Cups, which are shipped to Keurig's disposal partner, which composts the coffee grounds and sends the pods to be incinerated in a [[waste-to-energy power plant]].<ref name=az /><ref>[https://www.groundstogrowon.com Grounds to Grow On]. ''GroundsToGrowOn.com''. Retrieved May 7, 2015.</ref><ref>Craves, Julie. [http://www.coffeehabitat.com/2011/09/k-cups-recycling/ "K-Cups are now recyclable! Not really."] ''Coffee & Conservation''. ''CoffeeHabitat.com''. September 1, 2011.</ref> Critics point out that incineration produces airborne pollutants.<ref name=az /><ref>Allen, Ginger. [http://dfw.cbslocal.com/2011/10/12/coffee-machine-maker-in-hot-water-over-plastic-cups/ "Coffee Machine Maker In Hot Water Over Plastic Cups"]. [[CBS]] [[KTVT|Dallas–Fort Worth]]. ''DFW.CBSLocal.com''. October 12, 2011.</ref>

Regarding potential recyclability, GMCR's vice president of sustainability stated in 2013 that "The system has a lot of pretty demanding technical requirements in terms of being able to withstand certain amount of temperature and to have a certain kind of rigidity, and provide the right kinds of moisture barriers and oxygen barriers and the like. So it isn't the simplest challenge."<ref>Kalish, Jennifer. [http://www.plasticsnews.com/article/20130603/NEWS/130609998/coffee-makers-wrestle-with-recyclability-of-single-serve-pods "Coffee makers wrestle with recyclability of single-serve pods"]. ''[[Plastics News]]''. June 3, 2013.</ref> In 2015, Keurig Green Mountain's chief sustainability officer stated that every new K-Cup spin-off product introduced since 2006 – including the Vue, Bolt, K-Carafe, and K-Mug pods – is recyclable if disassembled into paper, plastic, and metal components.<ref>Hamblin, James. [https://www.theatlantic.com/technology/archive/2015/03/the-abominable-k-cup-coffee-pod-environment-problem/386501 "A Brewing Problem"]. ''[[The Atlantic]]''. March 2, 2015.</ref> In its 2014 Sustainability Report, released in February 2015, Keurig Green Mountain re-affirmed that a priority for the company is ensuring that 100% of K-Cup pods are recyclable by 2020.<ref>[https://finance.yahoo.com/news/keurig-green-mountain-inc-releases-170000882.html "Keurig Green Mountain, Inc. Releases 2014 Sustainability Report, 'Beyond The Cup'"]. ''[[Yahoo! Finance]]''. February 19, 2015.</ref><ref>[http://investor.keuriggreenmountain.com/releasedetail.cfm?releaseid=897260 "Keurig Green Mountain, Inc. Releases 2014 Sustainability Report, 'Beyond The Cup'"]. ''[[Business Wire]]''. ''Investor.KeurigGreenMountain.com''. February 19, 2015.</ref><ref>[http://www.keuriggreenmountain.com/en/OurStories/SustainabilityStories/KCupUpdate.aspx Update on a Recyclable K-Cup Pack]. ''KeurigGreenMountain.com''. Retrieved March 20, 2015.</ref><ref name=creating>[http://www.keuriggreenmountain.com/en/Sustainability/SustainableProducts/Overview.aspx Sustainability – Creating Sustainable Products]. ''KeurigGreenMountain.com''. Retrieved March 20, 2015.</ref><ref name=addressing>[http://www.keuriggreenmountain.com/EnviroJourney/~/media/Sustainability/PDF/Environment/Environmental%20Impact%20-%20Keurig%20Brewing%20Systems%202_2012.ashx Addressing Our Environmental Impact – Keurig® Brewing Systems]. ''KeurigGreenMountain.com''. Retrieved March 20, 2015.</ref>

In August 2014, the Canadian chain [[Grand & Toy|OfficeMax Grand & Toy]] partnered with the New Jersey company [[TerraCycle]] to launch a K-Cup recycling program for businesses in Canada, using a recycling box purchased by the businesses and shipped to TerraCycle for recycling when full.<ref>Kaye, Leon. [http://www.triplepundit.com/2014/08/officemax-terracycle-k-cup-recycling-program/ "OfficeMax, TerraCycle Launch K-Cup Recycling in Canada"]. ''TriplePundit.com''. August 25, 2014.</ref> In February 2015 TerraCycle launched a similar program for residential use in the U.S.: consumers purchase a Zero Waste Box which can hold 600 capsules, and when full the box, which has a pre-paid [[United Parcel Service|UPS]] label, is shipped to TerraCycle for recycling.<ref>[http://www.coffeeforless.com/blog/over-a-single-cup-coffee/how-to-recycle-k-cups/ "Easily Recycle Your K-Cups With Zero Waste Boxes From TerraCycle"]. ''CoffeeForLess.com''. February 4, 2015.</ref><ref>Levans, Katie. [http://ecowatch.com/2015/03/05/k-cup-inventor-john-sylvan-regrets-inventing-them/ "K-Cup Inventor Admits He Doesn’t Have a Keurig, Regrets Inventing Them ... Find Out Why"]. ''EcoWatch''. March 5, 2015.</ref><ref>[http://zerowasteboxes.terracycle.com/products/coffee-discs-zero-waste-boxes Coffee Capsules - Zero Waste Box™]. [[TerraCycle]]. ''ZeroWasteBoxes.TerraCycle.com''. Retrieved May 8, 2015.</ref><ref>Pizzi, Jenna. [http://www.nj.com/mercer/index.ssf/2015/05/nj_company_embarks_on_campaign_to_recylce_k-cups.html "Are K-Cups the cigarette butt of the coffee industry? N.J.'s TerraCycle accepts recycling challenge"]. ''[[NJ.com]]''. May 6, 2015.</ref>

===Legal and media issues===
In early 2014, following the announcement of its Keurig 2.0 machines engineered to lock out unlicensed pods, seven competitors and a number of purchasers filed lawsuits in Canada and in various United States federal courts.<ref name=claim /><ref name=gm-2014-11-17>Atkins, Eric. [https://www.theglobeandmail.com/report-on-business/industry-news/the-law-page/keurig-denies-allegations-of-anti-competitive-business-practices/article21632192/ "Keurig head denies allegations of anti-competitive business practices"]. ''[[The Globe and Mail]]''. November 17, 2014.</ref> The complaints contain numerous allegations of anti-competitive actions designed to drive competitors out of Keurig's market.<ref name=claim /><ref name=gm-2014-11-17 /><ref name=topclass />

To handle the U.S. anti-competitive lawsuits, in June 2014 the [[Judicial Panel on Multidistrict Litigation|United States Judicial Panel on Multidistrict Litigation]] consolidated the litigation into one docket in the [[Southern District of New York]], where Judge [[Vernon S. Broderick]] is hearing the consolidated case.<ref name=topclass>Gilbert, Sarah. [http://topclassactions.com/lawsuit-settlements/lawsuit-news/30109-keurig-coffee-monopoly-class-action-lawsuits-consolidated/ "Keurig Coffee Monopoly Class Action Lawsuits Consolidated"]. ''TopClassActions.com''. June 11, 2014.</ref><ref name=law360>Gurrieri, Vin. [http://www.law360.com/articles/544654/consolidated-keurig-antitrust-cases-to-brew-in-ny "Consolidated Keurig Antitrust Cases To Brew In NY"]. ''[[Law360]]''. June 4, 2014.</ref><ref name=mdl-2542>{{cite court
|litigants=IN RE: KEURIG GREEN MOUNTAIN SINGLE-SERVE COFFEE ANTITRUST LITIGATION
|vol=Google Scholar
|reporter=
|opinion=
|pinpoint=MDL No. 2542 TRANSFER ORDER
|court=[[United States Judicial Panel on Multidistrict Litigation]]
|date=June 9, 2014
|url=https://scholar.google.com/scholar_case?case=15903429679416392153
|accessdate=7 March 7, 2015
|quote=We conclude that the Southern District of New York is an appropriate transferee district for this litigation.
}}</ref> The case, which as of early 2016 is in process, has 46 plaintiffs, consisting of indirect purchasers, direct purchasers, and two competitors.<ref name=topclass /><ref name=case02542-vsb>{{cite web
|url=http://www.plainsite.org/dockets/2ahbtxsm7/new-york-southern-district-court/in-re-keurig-green-mountain-singleserve-coffee-antitrust-litigation/
|title=In re: Keurig Green Mountain Single-Serve Coffee Antitrust Litigation
|author=New York Southern District Court
|website=''PlainSite.org''
|date=February 11, 2015
|publisher=
|accessdate=March 15, 2016
}}</ref> Common allegations of the [[multidistrict litigation]] include claims that Keurig improperly acquired competitors, entered into exclusionary agreements with suppliers and distributors to prevent competitors from entering the market, engaged in unwarranted patent-infringement litigation, and unfairly introduced a product redesign that locks out non–Keurig branded cups.<ref name=topclass /><ref name=law360 />

The introduction of the Keurig 2.0 brewer also sparked a number of hacks and workarounds by competitors and consumers in 2014.<ref name=list>Abel, Jennifer. [http://www.consumeraffairs.com/news/heres-a-list-of-ways-around-keurig-20-machine-restrictions-020415.html "Here's a list of ways around Keurig 2.0 machine restrictions"]. ''[[ConsumerAffairs]]''. February 4, 2015.</ref> Rogers Family Coffee, one of the plaintiffs in the anti-trust lawsuits, created a "Freedom Clip" allowing unauthorized pods to work in the brewer.<ref>D’Ambrosio, Dan. [https://www.usatoday.com/story/money/business/2014/12/19/freedom-clip-deactivates-keurig-lock-out-technology/20639143/ "'Freedom Clip' deactivates Keurig's lock-out technology"]. ''[[USA Today]]''. December 19, 2014.</ref><ref>[http://www.click2houston.com/news/brewing-cups-from-any-coffee-company-in-new-keurig-machine/30196412 "Brewing cups from any coffee company in new Keurig machine"]. [[KPRC-TV]]. ''Click2Houston.com''. December 12, 2014.</ref> Another plaintiff, [[TreeHouse Foods]], claimed to be able to produce its own pods that would work in the 2.0 system.<ref name=list /><ref>Abel, Jennifer. [http://www.consumeraffairs.com/news/keurig-competitors-crack-companys-drm-code-082814.html "Keurig competitors crack company's DRM code"]. ''[[ConsumerAffairs]]''. August 28, 2014.</ref> A Canadian company, Mother Parkers Tea & Coffee, announced a capsule which would be compatible with the Keurig 2.0.<ref name=list /><ref>Jed, Emily. [http://www.vendingtimes.com/ME2/dirmod.asp?sid=EB79A487112B48A296B38C81345C8C7F&nm=Vending+Features&type=Publishing&mod=Publications%3A%3AArticle&mid=8F3A7027421841978F18BE895F87F791&tier=4&id=DA95C18D5316444FAD7766C5E4559E2E "Mother Parkers Introduces Keurig 2.0-Compatible Capsules"]. ''[[Vending Times]]''. Vol. 54, No. 12, December 2014.</ref>

In December 2014, the company recalled about 7 million of its Keurig Mini Plus Brewing Systems manufactured between December 2009 and July 2014 and sold in the U.S. and Canada. The recall was due to burn injuries reported from water overheating and spewing out of some of the machines, particularly if used to brew more than two cups in quick succession.<ref name=hot /><ref name=cpsc-2014-12>[http://www.cpsc.gov/en/Recalls/2015/Keurig-Recalls-MINI-Plus-Brewing-Systems "Keurig Recalls MINI Plus Brewing Systems Due to Burn Hazard"]. [[U.S. Consumer Product Safety Commission]]. December 23, 2014.</ref><ref name=kmp-2014-12>[http://miniplusbrewer.com/StandardRegister/LPR.asp SAFETY RECALL NOTICE – REPAIR REQUIRED]. Keurig Product Information. December 2014.</ref><ref name=hc-2014-12>{{cite web|url=http://healthycanadians.gc.ca/recall-alert-rappel-avis/hc-sc/2014/43015r-eng.php|title=Keurig Green Mountain, Inc. recalls KEURIG MINI Plus Brewers|website=[[Health Canada]]|date=December 23, 2014}}</ref>

In November 2017, Keurig posted on its Twitter account that it had ended its advertisements with [[Sean Hannity]]'s program on [[Fox News]], in reaction to Hannity's defense of Senate candidate [[Roy Moore]], who had been accused of sexual misconduct against teenage girls. In response, videos of Hannity's fans destroying their Keurig machines proliferated on the Internet,<ref>{{cite news|last1=Bromwich|first1=Jonah Engel|title=Hannity Fans Destroy Keurig Coffee Makers After Company Pulls Advertising|url=https://www.nytimes.com/2017/11/13/business/media/keurig-hannity.html|accessdate=13 November 2017|work=The New York Times|date=13 November 2017}}</ref> with automated Russian accounts supporting Hannity's position on Twitter.<Ref>{{cite news|url=http://www.newsweek.com/sean-hannity-advertiser-keurig-attacked-russian-bots-after-far-right-protest-709128|title=Russian Bots Are Sticking Up For Sean Hannity By Attacking Keurig, As Fans Smash Coffee Makers|first=Graham|last=Langtree|accessdate=December 26, 2017|newspaper=[[Newsweek]]|date=November 13, 2017}}</ref> In an internal email, Keurig CEO Bob Gamgort wrote that the way Keurig handled the situation was "highly unusual" and gave the unintended impression that the company had taken sides. Gamgort also announced an overhaul of Keurig's communications policies.<ref name="WaPo-Keurig">{{cite web|url=https://www.washingtonpost.com/blogs/erik-wemple/wp/2017/11/13/keurig-ceo-tweet-regarding-hannity-created-an-unacceptable-situation/|title=Keurig CEO: Tweet regarding ‘Hannity’ created an ‘unacceptable situation’|author=Erik Wemple|work=washingtonpost.com|publisher=The Washington Post|date=13 November 2017|accessdate=13 November 2017}}</ref>

===Corporate governance===
John Sylvan and Peter Dragone founded Keurig, Inc. in 1992,<ref name=bloomberg /> and they brought in Dick Sweeney as co-founder in 1993.<ref name=buzz /><ref name=sweeney /> In 1995 Larry Kernan, a principal at MDT Advisers – an investment fund which had contributed $1,000,000 to the company – became Chairman of Keurig; he retained the position through 2002.<ref name=buzz /><ref name=kernan /> Sylvan was forced out of the company in 1997, and Dragone left a few months later.<ref name=buzz /> Sweeney stayed on as the company's vice president of engineering;<ref name=sweeney /> he later became Vice President of Contract Manufacturing and Quality Assurance.<ref name=bloomberg /><ref>Riggs, Jonathan. [http://www.tuck.dartmouth.edu/newsroom/articles/brewing-up-a-billion-dollar-company "BREWING UP A BILLION-DOLLAR COMPANY"]. [[Tuck School of Business]], [[Dartmouth College]]. September 29, 2014.</ref>

Nick Lazaris was President and CEO of Keurig, Inc. from 1997 to 2006.<ref>[https://www.sec.gov/Archives/edgar/data/909954/000090995403000012/keurig8k.htm A Progress Update from Bob Stiller (CEO) on Green Mountain's Investment in Keurig, Inc.] ''SEC.gov''. May 15, 2003.</ref> Keurig, Inc. was fully acquired by Green Mountain Coffee Roasters in 2006;<ref name=completed /> at the time, GMCR's founder [[Bob Stiller]] was its President and CEO.<ref name=blanford>[http://www.businesswire.com/news/home/20070503005308/en/Green-Mountain-Coffee-Roasters-Announces-Appointment-Lawrence "Green Mountain Coffee Roasters Announces Appointment of Lawrence J. Blanford as President and CEO"]. ''[[Business Wire]]''. May 3, 2007.</ref><ref name=shakes>D'Ambrosio, Dan. [http://www.burlingtonfreepress.com/article/20120508/NEWS01/120508009/Green-Mountain-Coffee-shakes-up-top-board-members-over-stock-sales "Green Mountain Coffee shakes up top board members over stock sales"]. ''[[Burlington Free Press]]''. May 8, 2012.</ref> Stiller stepped down in 2007, but remained Chairman until May 2012.<ref name=blanford /><ref name=shakes /> Lawrence J. Blanford became Green Mountain Coffee Roasters' President and CEO in 2007.<ref name=blanford /><ref>[https://www.bloomberg.com/research/stocks/people/person.asp?personId=287990&ticker=GMCR Lawrence J. Blanford] – Executive Profile at ''[[Bloomberg L.P.|Bloomberg]]''.</ref> Brian Kelley, previously chief product supply officer of [[Coca-Cola Refreshments]], became the President and CEO of Green Mountain Coffee Roasters (later Keurig Green Mountain) in December 2012.<ref>Julie Jargon. [https://www.wsj.com/articles/SB10001424127887324352004578130663632962402 "Green Mountain Names Coke's Brian Kelley as New CEO"]. ''[[Wall Street Journal]]''. November 20, 2012.</ref><ref>[http://investor.keuriggreenmountain.com/releasedetail.cfm?releaseid=722540 "Green Mountain Coffee Roasters, Inc. Appoints Brian Kelley CEO Effective December 3, 2012"]. ''Investor.KeurigGreenMountain.com'' (press release). November 20, 2012.</ref> Robert Gamgort, who had been CEO of [[Pinnacle Foods]], replaced Brian Kelley as Keurig Green Mountain's CEO in May 2016 after KGM was acquired by an investor group led by [[private equity|private-equity]] firm [[JAB Holding Company]],<ref>[https://www.bloomberg.com/research/stocks/people/person.asp?personId=29897909&privcapId=1064020 Robert J. Gamgort] – Executive Profile at ''[[Bloomberg L.P.|Bloomberg]]''. Retrieved July 15, 2016.</ref><ref>{{Cite web|url=https://www.usatoday.com/story/money/2016/03/23/pinnacle-foods-ceo-leaves-for-keurig-green-mountain/82156668/|title=Pinnacle Foods CEO Robert Gamgort to head Keurig Green Mountain|website=USA TODAY|access-date=2016-03-23}}</ref><ref>Beilfuss, Lisa. [https://www.wsj.com/articles/keurig-green-mountain-snags-pinnacle-foods-ceo-1458736507 "Keurig Green Mountain Snags Pinnacle Food’s CEO"]. ''[[Wall Street Journal]]''. March 23, 2016.</ref> and he remains CEO of the newly merged, publicly traded conglomerate Keurig Dr Pepper.

==References==
{{reflist|2}}

== External links ==
* {{official website|http://www.keurig.com|Keurig website}}
{{Keurig Dr Pepper brands}}
[[Category:Coffee appliance vendors]]
[[Category:Coffee brands]]
[[Category:Companies established in 1992]]
[[Category:1991 establishments in Massachusetts]]
[[Category:Food packaging]]
[[Category:Single-serving coffee containers]]
[[Category:Single-serving coffee makers]]

Field (physics)

2019-03-07T20:35:59Z

173.165.237.1:

{{Use American English|date=January 2019}}{{Short description|Physical quantities taking values at each point in space and time}}[[Image:VFPt charges plus minus thumb.svg|220px|thumb|right|Illustration of the electric field surrounding a positive (red) and a negative (blue) charge.]]
In physics, a '''field''' is a [[Quantity#Quantity in physical science|physical quantity]], represented by a number or [[tensor]], that has a value for each [[Point (geometry)|point]] in space-time. For example, on a weather map, the surface [[temperature]] is described by assigning a real number to each point on a map; the temperature can be considered at a fixed point in time or over some time interval, if one wants to study the dynamics of temperature change. A surface wind map, assigning a vector to each point on a map that describes the wind [[velocity]] at that point, would be an example of a 1 dimensional tensor field. Field theories, mathematical descriptions of how field values change in space and time, are ubiquitous in physics. For instance, the [[electric field]] is another rank 1 tensor field, and the full description of electrodynamics can be formulated in terms of [[Mathematical descriptions of the electromagnetic field|two interacting vector fields]] at each point in space-time, or as a [[Covariant formulation of classical electromagnetism|single rank 2 tensor]] field theory.
<ref>[https://youtube.com/watch?v=0Eeuqh9QfNI&t=1139 Lecture 1 | Quantum Entanglements, Part 1 (Stanford)], Leonard Susskind, Stanford, Video, 2006-09-25.</ref>
<ref name=Feynman102>{{cite book |author=Richard P. Feynman|title=The Feynman Lectures on Physics Vol I|publisher=Addison Wesley Longman| year=1970 |url=http://www.feynmanlectures.caltech.edu/I_02.html}}</ref>
<ref name=Gribbin>{{cite book |author=John Gribbin|title=Q is for Quantum: Particle Physics from A to Z|publisher=Weidenfeld & Nicolson|location=London|year=1998|isbn=0-297-81752-3|page=138}}</ref>
<ref name=Feynman2Ch1S2>{{cite book |author=Richard Feynman |title=The Feynman Lectures on Physics Vol II |publisher=Addison Wesley Longman |year=1970 |isbn=978-0-201-02115-8 |url=http://www.feynmanlectures.caltech.edu/II_01.html#Ch1-S2 |quote="A “field” is any physical quantity which takes on different values at different points in space."}}</ref>
<ref>{{cite journal |author=Ernan McMullin |journal=Phys. Perspect. |date=2002 |volume=4|pages=13–39|title=The Origins of the Field Concept in Physics |url=http://physics.gmu.edu/~rubinp/courses/416/pip_fields.pdf|bibcode = 2002PhP.....4...13M |doi=10.1007/s00016-002-8357-5}}</ref>
<ref name=Feynman204>{{cite book |author=Richard P. Feynman|title=The Feynman Lectures on Physics Vol II|publisher=Addison Wesley Longman| year=1970 |url=http://www.feynmanlectures.caltech.edu/II_04.html}}</ref>

In the modern framework of the [[quantum theory of fields]], even without referring to a test particle, a field occupies space, contains energy, and its presence precludes a classical "true vacuum".<ref name=Wheeler>{{cite book |author=John Archibald Wheeler|title=Geons, Black Holes, and Quantum Foam: A Life in Physics.|publisher=Norton|location=London|year=1998|page=163}}</ref>
This has led physicists to consider [[electromagnetic field]]s to be a physical entity, making the field concept a supporting [[paradigm]] of the edifice of modern physics. "The fact that the electromagnetic field can possess momentum and energy makes it very real ... a particle makes a field, and a field acts on another particle, and the field has such familiar properties as energy content and momentum, just as particles can have."<ref name=Feynman110>{{cite book |author=Richard P. Feynman|title=The Feynman Lectures on Physics Vol I|publisher=Addison Wesley Longman| year=1970 |url=http://www.feynmanlectures.caltech.edu/I_10.html}}</ref> In practice, the strength of most fields has been found to diminish with distance to the point of being undetectable. For instance the strength of many relevant classical fields, such as the gravitational field in [[Newton's law of universal gravitation|Newton's theory of gravity]] or the [[electrostatic field]] in classical electromagnetism, is inversely proportional to the square of the distance from the source (i.e., they follow [[Gauss's law]]). One consequence is that the Earth's gravitational field quickly becomes undetectable on cosmic scales.

A field can be classified as a [[scalar field]], a [[vector field]], a [[spinor field]] or a [[tensor field]] according to whether the represented physical quantity is a [[scalar (physics)|scalar]], a [[Euclidean vector|vector]], a [[spinor]], or a [[tensor]], respectively. A field has a unique tensorial character in every point where it is defined: i.e. a field cannot be a scalar field somewhere and a vector field somewhere else. For example, the [[Newtonian gravity|Newtonian]] [[gravitational field]] is a vector field: specifying its value at a point in spacetime requires three numbers, the components of the gravitational field vector at that point. Moreover, within each category (scalar, vector, tensor), a field can be either a ''classical field'' or a ''quantum field'', depending on whether it is characterized by numbers or [[operator (physics)|quantum operators]] respectively. In fact in this theory an equivalent representation of field is a [[field particle]], namely a [[boson]].<ref>{{cite journal |author=Steven Weinberg |journal=New York Review of Books |date=November 7, 2013 |title=Physics: What We Do and Don’t Know |url=http://www.nybooks.com/articles/archives/2013/nov/07/physics-what-we-do-and-dont-know/}}</ref>

==History==
To [[Isaac Newton]], his [[law of universal gravitation]] simply expressed the gravitational [[force]] that acted between any pair of massive objects. When looking at the motion of many bodies all interacting with each other, such as the planets in the [[Solar System]], dealing with the force between each pair of bodies separately rapidly becomes computationally inconvenient. In the eighteenth century, a new quantity was devised to simplify the bookkeeping of all these gravitational forces. This quantity, the [[gravitational field]], gave at each point in space the total gravitational acceleration which would be felt by a small object at that point. This did not change the physics in any way: it did not matter if all the gravitational forces on an object were calculated individually and then added together, or if all the contributions were first added together as a gravitational field and then applied to an object.<ref name=Weinberg1977>{{cite journal
|title=The Search for Unity: Notes for a History of Quantum Field Theory
|first=Steven |last=Weinberg
|journal=Daedalus |volume=106 |number=4 |year=1977 |pages=17–35
|jstor=20024506
}}</ref>

The development of the independent concept of a field truly began in the nineteenth century with the development of the theory of [[electromagnetism]]. In the early stages, [[André-Marie Ampère]] and [[Charles-Augustin de Coulomb]] could manage with Newton-style laws that expressed the forces between pairs of [[electric charge]]s or [[electric current]]s. However, it became much more natural to take the field approach and express these laws in terms of [[electric field|electric]] and [[magnetic field]]s; in 1849 [[Michael Faraday]] became the first to coin the term "field".<ref name=Weinberg1977/>

The independent nature of the field became more apparent with [[James Clerk Maxwell]]'s discovery that [[electromagnetic wave|waves in these fields]] propagated at a finite speed. Consequently, the forces on charges and currents no longer just depended on the positions and velocities of other charges and currents at the same time, but also on their positions and velocities in the past.<ref name=Weinberg1977/>

Maxwell, at first, did not adopt the modern concept of a field as a fundamental quantity that could independently exist. Instead, he supposed that the [[electromagnetic field]] expressed the deformation of some underlying medium—the [[luminiferous aether]]—much like the tension in a rubber membrane. If that were the case, the observed velocity of the electromagnetic waves should depend upon the velocity of the observer with respect to the aether. Despite much effort, no experimental evidence of such an effect was ever found; the situation was resolved by the introduction of the [[special theory of relativity]] by [[Albert Einstein]] in 1905. This theory changed the way the viewpoints of moving observers were related to each other. They became related to each other in such a way that velocity of electromagnetic waves in Maxwell's theory would be the same for all observers. By doing away with the need for a background medium, this development opened the way for physicists to start thinking about fields as truly independent entities.<ref name=Weinberg1977/>

In the late 1920s, the new rules of [[quantum mechanics]] were first applied to the electromagnetic fields. In 1927, [[Paul Dirac]] used [[quantum field]]s to successfully explain how the decay of an [[atom]] to a lower [[quantum state]] lead to the [[spontaneous emission]] of a [[photon]], the quantum of the electromagnetic field. This was soon followed by the realization (following the work of [[Pascual Jordan]], [[Eugene Wigner]], [[Werner Heisenberg]], and [[Wolfgang Pauli]]) that all particles, including [[electron]]s and [[proton]]s, could be understood as the quanta of some quantum field, elevating fields to the status of the most fundamental objects in nature.<ref name=Weinberg1977/> That said, [[John Archibald Wheeler|John Wheeler]] and [[Richard Feynman]] seriously considered Newton's pre-field concept of [[Action at a distance (physics)|action at a distance]] (although they set it aside because of the ongoing utility of the field concept for research in [[general relativity]] and [[quantum electrodynamics]]).

==Classical fields==
{{Main|Classical field theory}}
There are several examples of [[Classical field theory|classical fields]]. Classical field theories remain useful wherever quantum properties do not arise, and can be active areas of research. [[Elasticity (physics)|Elasticity]] of materials, [[fluid dynamics]] and [[Maxwell's equations]] are cases in point.

Some of the simplest physical fields are vector force fields. Historically, the first time that fields were taken seriously was with [[Michael Faraday|Faraday's]] [[lines of force]] when describing the [[electric field]]. The [[gravitational field]] was then similarly described.

===Newtonian gravitation===
[[File:Newtonian gravity field (physics).svg|thumb|upright|In [[classical gravitation]], mass is the source of an attractive [[gravitational field]] '''g'''.]]
A classical field theory describing gravity is [[gravitation|Newtonian gravitation]], which describes the gravitational force as a mutual interaction between two [[mass]]es.

Any body with mass ''M'' is associated with a [[gravitational field]] '''g''' which describes its influence on other bodies with mass. The gravitational field of ''M'' at a point '''r''' in space corresponds to the ratio between force '''F''' that ''M'' exerts on a small or negligible [[test mass]] ''m'' located at '''r''' and the test mass itself:<ref name="kleppner85">{{cite book|last1=Kleppner|first1=Daniel|last2=Kolenkow|first2=Robert|title=An Introduction to Mechanics|page=85}}</ref>
:<math> \mathbf{g}(\mathbf{r}) = \frac{\mathbf{F}(\mathbf{r})}{m}.</math>
Stipulating that ''m'' is much smaller than ''M'' ensures that the presence of ''m'' has a negligible influence on the behavior of ''M''.

According to [[Newton's law of universal gravitation]], '''F'''('''r''') is given by<ref name="kleppner85" />
:<math>\mathbf{F}(\mathbf{r}) = -\frac{G M m}{r^2}\hat{\mathbf{r}},</math>
where <math>\hat{\mathbf{r}}</math> is a [[unit vector]] lying along the line joining ''M'' and ''m'' and pointing from ''m'' to ''M''. Therefore, the gravitational field of '''M''' is<ref name="kleppner85" />
:<math>\mathbf{g}(\mathbf{r}) = \frac{\mathbf{F}(\mathbf{r})}{m} = -\frac{G M}{r^2}\hat{\mathbf{r}}.</math>

The experimental observation that inertial mass and gravitational mass are equal [[equivalence principle#Tests of the weak equivalence principle|to an unprecedented level of accuracy]] leads to the identity that gravitational field strength is identical to the acceleration experienced by a particle. This is the starting point of the [[equivalence principle]], which leads to [[general relativity]].

Because the gravitational force '''F''' is [[conservative field|conservative]], the gravitational field '''g''' can be rewritten in terms of the [[gradient]] of a scalar function, the [[gravitational potential]] Φ('''r'''):
:<math>\mathbf{g}(\mathbf{r}) = -\nabla \Phi(\mathbf{r}).</math>

===Electromagnetism===
{{Main|Electromagnetism}}
[[Michael Faraday]] first realized the importance of a field as a physical quantity, during his investigations into [[magnetism]]. He realized that [[Electric field|electric]] and [[magnetic field|magnetic]] fields are not only fields of force which dictate the motion of particles, but also have an independent physical reality because they carry energy.

These ideas eventually led to the creation, by [[James Clerk Maxwell]], of the first unified field theory in physics with the introduction of equations for the [[electromagnetic field]]. The modern version of these equations is called [[Maxwell's equations]].

====Electrostatics====
{{Main|Electrostatics}}

A [[test charge|charged test particle]] with charge ''q'' experiences a force '''F''' based solely on its charge. We can similarly describe the [[electric field]] '''E''' so that {{nowrap|'''F''' {{=}} ''q'''''E'''}}. Using this and [[Coulomb's law]] tells us that the electric field due to a single charged particle is

:<math>\mathbf{E} = \frac{1}{4\pi\epsilon_0}\frac{q}{r^2}\hat{\mathbf{r}}.</math>

The electric field is [[conservative field|conservative]], and hence can be described by a scalar potential, ''V''('''r'''):
:<math> \mathbf{E}(\mathbf{r}) = -\nabla V(\mathbf{r}).</math>

====Magnetostatics====
{{Main|Magnetostatics}}

A steady current ''I'' flowing along a path ''ℓ'' will exert a force on nearby moving charged particles that is quantitatively different from the electric field force described above. The force exerted by ''I'' on a nearby charge ''q'' with velocity '''v''' is
:<math>\mathbf{F}(\mathbf{r}) = q\mathbf{v} \times \mathbf{B}(\mathbf{r}),</math>
where '''B'''('''r''') is the [[magnetic field]], which is determined from ''I'' by the [[Biot–Savart law]]:
:<math>\mathbf{B}(\mathbf{r}) = \frac{\mu_0 I}{4\pi} \int \frac{d\boldsymbol{\ell} \times d\hat{\mathbf{r}}}{r^2}.</math>

The magnetic field is not conservative in general, and hence cannot usually be written in terms of a scalar potential. However, it can be written in terms of a [[magnetic vector potential|vector potential]], '''A'''('''r'''):
:<math> \mathbf{B}(\mathbf{r}) = \boldsymbol{\nabla} \times \mathbf{A}(\mathbf{r}) </math>

[[File:em dipoles.svg|size=250|thumb|right| The [[electric field|'''E''' fields]] and [[magnetic field|'''B''' fields]] due to [[electric charge]]s (black/white) and [[magnet|magnetic poles]] (red/blue).<ref name="Mc Graw Hill">{{cite book |title=McGraw Hill Encyclopaedia of Physics |first1=C.B. |last1= Parker|edition=2nd|publisher=Mc Graw Hill|year=1994|isbn=0-07-051400-3}}</ref><ref name="M. Mansfield, C. O’Sullivan 2011">{{cite book |author1=M. Mansfield |author2=C. O’Sullivan |title= Understanding Physics|edition= 4th |year= 2011|publisher= John Wiley & Sons|isbn=978-0-47-0746370}}</ref> '''Top:''' '''E''' field due to an [[electric dipole moment]] '''d'''. '''Bottom left:''' '''B''' field due to a ''mathematical'' [[magnetic dipole]] '''m''' formed by two magnetic monopoles. '''Bottom right:''' '''B''' field due to a pure [[magnetic dipole moment]] '''m''' found in ordinary matter (''not'' from monopoles).]]

====Electrodynamics====
{{Main|Electrodynamics}}

In general, in the presence of both a charge density ρ('''r''', ''t'') and current density '''J'''('''r''', ''t''), there will be both an electric and a magnetic field, and both will vary in time. They are determined by [[Maxwell's equations]], a set of differential equations which directly relate '''E''' and '''B''' to ρ and '''J'''.<ref name="griffiths326">{{cite book|last=Griffiths|first=David|title=Introduction to Electrodynamics|edition=3rd|page=326}}</ref>

Alternatively, one can describe the system in terms of its scalar and vector potentials ''V'' and '''A'''. A set of integral equations known as ''[[retarded potential]]s'' allow one to calculate ''V'' and '''A''' from ρ and '''J''',<ref group="note">This is contingent on the correct choice of [[gauge fixing|gauge]]. ''V'' and '''A''' are not completely determined by ρ and '''J'''; rather, they are only determined up to some scalar function ''f''('''r''', ''t'') known as the gauge. The retarded potential formalism requires one to choose the [[Lorenz gauge]].</ref> and from there the electric and magnetic fields are determined via the relations<ref name="wangsness469">{{cite book|last=Wangsness|first=Roald|title=Electromagnetic Fields|edition=2nd|page=469}}</ref>

:<math> \mathbf{E} = -\boldsymbol{\nabla} V - \frac{\partial \mathbf{A}}{\partial t}</math>
:<math> \mathbf{B} = \boldsymbol{\nabla} \times \mathbf{A}.</math>

At the end of the 19th century, the [[electromagnetic field]] was understood as a collection of two vector fields in space. Nowadays, one recognizes this as a single antisymmetric 2nd-rank tensor field in spacetime.

[[File:em monopoles.svg|size=250|thumb|right| The [[electric field|'''E''' fields]] and [[magnetic field|'''B''' fields]] due to [[electric charge]]s (black/white) and [[magnet|magnetic poles]] (red/blue).<ref name="Mc Graw Hill"/><ref name="M. Mansfield, C. O’Sullivan 2011"/> '''E''' fields due to stationary electric charges and '''B''' fields due to stationary [[magnetic monopole|magnetic charges]] (note in nature N and S monopoles do not exist). In motion ([[velocity]] '''v'''), an ''electric'' charge induces a '''B''' field while a ''magnetic'' charge (not found in nature) would induce an '''E''' field. [[Conventional current]] is used.]]

===Gravitation in general relativity===
[[File:Relativistic gravity field (physics).svg|350px|left|thumb|In [[general relativity]], mass-energy warps space time ([[Einstein tensor]] '''G'''),<ref>{{cite book |title=Gravitation|author1=J.A. Wheeler |author2=C. Misner |author3=K.S. Thorne |publisher=W.H. Freeman & Co|year=1973|isbn=0-7167-0344-0}}</ref> and rotating asymmetric mass-energy distributions with [[angular momentum]] '''J''' generate [[Gravitoelectromagnetism|GEM fields]] '''H'''<ref>{{cite book |title=Gravitation and Inertia|author1=I. Ciufolini |author2=J.A. Wheeler |publisher=Princeton Physics Series|year=1995|isbn=0-691-03323-4}}</ref>]]
Einstein's theory of gravity, called [[general relativity]], is another example of a field theory. Here the principal field is the [[metric tensor (general relativity)|metric tensor]], a symmetric 2nd-rank tensor field in [[spacetime]]. This replaces [[Newton's law of universal gravitation]].

===Waves as fields===
[[Wave]]s can be constructed as physical fields, due to their [[speed of light|finite propagation speed]] and [[causality|causal nature]] when a simplified [[physical model]] of an [[Physical system#The concept of closed systems in physics|isolated closed system]] is set {{clarify|date=March 2013}}. They are also subject to the [[inverse-square law]].

For electromagnetic waves, there are [[optical field]]s, and terms such as [[Near and far field|near- and far-field]] limits for diffraction. In practice though, the field theories of optics are superseded by the electromagnetic field theory of Maxwell.

==Quantum fields==
{{main|Quantum field theory}}
It is now believed that [[quantum mechanics]] should underlie all physical phenomena, so that a classical field theory should, at least in principle, permit a recasting in quantum mechanical terms; success yields the corresponding [[quantum field theory]]. For example, [[Quantization (physics)|quantizing]] [[classical electrodynamics]] gives [[quantum electrodynamics]]. Quantum electrodynamics is arguably the most successful scientific theory; [[experiment]]al [[data]] confirm its predictions to a higher [[Accuracy and precision|precision]] (to more [[significant digit]]s) than any other theory.<ref>{{Cite book|last1=Peskin |first1=Michael E. |last2=Schroeder |first2=Daniel V. |title=An Introduction to Quantum Fields |page=198 |year=1995 |publisher= Westview Press |isbn=0-201-50397-2|ref=harv|postscript=}}. Also see [[precision tests of QED]].</ref> The two other fundamental quantum field theories are [[quantum chromodynamics]] and the [[electroweak theory]].

[[File:Qcd fields field (physics).svg|400px|right|thumb|Fields due to [[color charge]]s, like in [[quark]]s ('''G''' is the [[gluon field strength tensor]]). These are "colorless" combinations. '''Top:''' Color charge has "ternary neutral states" as well as binary neutrality (analogous to [[electric charge]]). '''Bottom:''' The quark/antiquark combinations.<ref name="Mc Graw Hill"/><ref name="M. Mansfield, C. O’Sullivan 2011"/>]]

In quantum chromodynamics, the color field lines are coupled at short distances by [[gluon]]s, which are polarized by the field and line up with it. This effect increases within a short distance (around 1 [[femtometre|fm]] from the vicinity of the quarks) making the color force increase within a short distance, [[Color confinement|confining the quarks]] within [[hadron]]s. As the field lines are pulled together tightly by gluons, they do not "bow" outwards as much as an electric field between electric charges.<ref>{{cite book|title=Quantum Physics of Atoms, Molecules, Solids, Nuclei and Particles|edition=2nd|author1=R. Resnick |author2=R. Eisberg |publisher=John Wiley & Sons|year=1985|page=684|isbn=978-0-471-87373-0}}</ref>

These three quantum field theories can all be derived as special cases of the so-called [[standard model]] of [[particle physics]]. [[General relativity]], the Einsteinian field theory of gravity, has yet to be successfully quantized. However an extension, [[thermal field theory]], deals with quantum field theory at ''finite temperatures'', something seldom considered in quantum field theory.

In [[BRST formalism|BRST theory]] one deals with odd fields, e.g. [[Faddeev–Popov ghost]]s. There are different descriptions of odd classical fields both on [[graded manifold]]s and [[supermanifold]]s.

As above with classical fields, it is possible to approach their quantum counterparts from a purely mathematical view using similar techniques as before. The equations governing the quantum fields are in fact PDEs (specifically, [[relativistic wave equations]] (RWEs)). Thus one can speak of [[Yang–Mills field|Yang–Mills]], [[Dirac field|Dirac]], [[Klein–Gordon field|Klein–Gordon]] and [[Schrödinger field]]s as being solutions to their respective equations. A possible problem is that these RWEs can deal with complicated [[mathematical objects]] with exotic algebraic properties (e.g. [[spinors]] are not [[tensors]], so may need calculus over [[spinor field]]s), but these in theory can still be subjected to analytical methods given appropriate [[Generalization (mathematics)|mathematical generalization]].

==Field theory==
Field theory usually refers to a construction of the dynamics of a field, i.e. a specification of how a field changes with time or with respect to other independent physical variables on which the field depends. Usually this is done by writing a [[Lagrangian (field theory)|Lagrangian]] or a [[Hamiltonian mechanics|Hamiltonian]] of the field, and treating it as a [[classical mechanics|classical]] or [[quantum mechanics|quantum mechanical]] system with an infinite number of [[degrees of freedom (physics and chemistry)|degrees of freedom]]. The resulting field theories are referred to as classical or quantum field theories.

The dynamics of a classical field are usually specified by the [[Lagrangian (field theory)|Lagrangian density]] in terms of the field components; the dynamics can be obtained by using the [[Action (physics)|action principle]].

It is possible to construct simple fields without any prior knowledge of physics using only mathematics from [[multivariable calculus|several variable calculus]], [[potential theory]] and [[partial differential equation]]s (PDEs). For example, scalar PDEs might consider quantities such as amplitude, density and pressure fields for the wave equation and [[fluid dynamics]]; temperature/concentration fields for the [[heat equation|heat]]/[[diffusion equation]]s. Outside of physics proper (e.g., radiometry and computer graphics), there are even [[light fields]]. All these previous examples are [[scalar fields]]. Similarly for vectors, there are vector PDEs for displacement, velocity and vorticity fields in (applied mathematical) fluid dynamics, but vector calculus may now be needed in addition, being calculus over [[vector fields]] (as are these three quantities, and those for vector PDEs in general). More generally problems in [[continuum mechanics]] may involve for example, directional [[elasticity tensor|elasticity]] (from which comes the term ''tensor'', derived from the [[Latin]] word for stretch), [[complex fluid]] flows or [[anisotropic diffusion]], which are framed as matrix-tensor PDEs, and then require matrices or tensor fields, hence [[matrix calculus|matrix]] or [[tensor calculus]]. It should be noted that the scalars (and hence the vectors, matrices and tensors) can be real or complex as both are [[field (algebra)|fields]] in the abstract-algebraic/[[ring theory|ring-theoretic]] sense.

In a general setting, classical fields are described by sections of [[fiber bundle]]s and their dynamics is formulated in the terms of [[jet bundle|jet manifolds]] ([[covariant classical field theory]]).<ref>Giachetta, G., Mangiarotti, L., [[Gennadi Sardanashvily|Sardanashvily, G.]] (2009) ''Advanced Classical Field Theory''. Singapore: World Scientific, {{ISBN|978-981-283-895-7}} ([http://xxx.lanl.gov/abs/0811.0331 arXiv: 0811.0331v2])</ref>

In [[modern physics]], the most often studied fields are those that model the four [[fundamental forces]] which one day may lead to the [[Unified Field Theory]].

===Symmetries of fields=== 
A convenient way of classifying a field (classical or quantum) is by the [[Symmetry in physics|symmetries]] it possesses. Physical symmetries are usually of two types:

====Spacetime symmetries====
{{main|Global symmetry|Spacetime symmetries}}

Fields are often classified by their behaviour under transformations of [[spacetime]]. The terms used in this classification are:
* [[scalar field]]s (such as [[temperature]]) whose values are given by a single variable at each point of space. This value does not change under transformations of space.
* [[vector field]]s (such as the magnitude and direction of the [[force (physics)|force]] at each point in a [[magnetic field]]) which are specified by attaching a vector to each point of space. The components of this vector transform between themselves [[covariance and contravariance of vectors|contravariantly]] under rotations in space. Similarly, a dual (or co-) vector field attaches a dual vector to each point of space, and the components of each dual vector transform covariantly.
* [[tensor field]]s, (such as the [[Stress (physics)|stress tensor]] of a crystal) specified by a tensor at each point of space. Under rotations in space, the components of the tensor transform in a more general way which depends on the number of covariant indices and contravariant indices.
* [[spinor field]]s (such as the [[Dirac spinor]]) arise in [[quantum field theory]] to describe particles with [[spin (physics)|spin]] which transform like vectors except for the one of their component; in other words, when one rotates a vector field 360 degrees around a specific axis, the vector field turns to itself; however, spinors would turn to their negatives in the same case.

====Internal symmetries====
{{main|Internal symmetry}}
Fields may have internal symmetries in addition to spacetime symmetries. In many situations, one needs fields which are a list of space-time scalars: (φ1, φ2, ... φ''N''). For example, in weather prediction these may be temperature, pressure, humidity, etc. In [[particle physics]], the [[color charge|color]] symmetry of the interaction of [[quark]]s is an example of an internal symmetry, that of the [[strong interaction]]. Other examples are [[isospin]], [[weak isospin]], [[strangeness]] and any other [[flavour (particle physics)|flavour]] symmetry.

If there is a symmetry of the problem, not involving spacetime, under which these components transform into each other, then this set of symmetries is called an ''internal symmetry''. One may also make a classification of the charges of the fields under internal symmetries.

===Statistical field theory===
{{main|Statistical field theory}}

Statistical field theory attempts to extend the field-theoretic [[paradigm]] toward many-body systems and [[statistical mechanics]]. As above, it can be approached by the usual infinite number of degrees of freedom argument.

Much like statistical mechanics has some overlap between quantum and classical mechanics, statistical field theory has links to both quantum and classical field theories, especially the former with which it shares many methods. One important example is [[mean field theory]].

===Continuous random fields===
Classical fields as above, such as the [[electromagnetic field]], are usually infinitely differentiable functions, but they are in any case almost always twice differentiable. In contrast, [[generalized functions]] are not continuous. When dealing carefully with classical fields at finite temperature, the mathematical methods of continuous random fields are used, because [[Thermal fluctuations|thermally fluctuating]] classical fields are [[nowhere differentiable]]. [[Random field]]s are indexed sets of [[random variable]]s; a continuous random field is a random field that has a set of functions as its index set. In particular, it is often mathematically convenient to take a continuous random field to have a [[Schwartz space]] of functions as its index set, in which case the continuous random field is a [[Distribution (mathematics)|tempered distribution]].

We can think about a continuous random field, in a (very) rough way, as an ordinary function that is <math>\pm\infty</math> almost everywhere, but such that when we take a [[weighted average]] of all the [[infinity|infinities]] over any finite region, we get a finite result. The infinities are not well-defined; but the finite values can be associated with the functions used as the weight functions to get the finite values, and that can be well-defined. We can define a continuous random field well enough as a [[linear map]] from a space of functions into the [[real number]]s.

==See also==
* [[Conformal field theory]]
* [[Covariant Hamiltonian field theory]]
* [[Field strength]]
* [[History of the philosophy of field theory]]
* [[Lagrangian and Eulerian specification of the flow field|Lagrangian and Eulerian specification of a field]]
* [[Scalar field theory]]

==Notes==
{{reflist|group=note}}

==References==
<references />

==Further reading==
* {{cite book|edition=fifteenth|title=Principles of Physical Science|section= Fields |work= [[Encyclopædia Britannica]] (Macropaedia)|year=1994|volume=25|page=815}}
* [[Lev Landau|Landau, Lev D.]] and [[Evgeny Lifshitz|Lifshitz, Evgeny M.]] (1971). ''Classical Theory of Fields'' (3rd ed.). London: Pergamon. {{ISBN|0-08-016019-0}}. Vol. 2 of the [[Course of Theoretical Physics]]. 
* {{Cite journal|first= Kathryn |last= Jepsen |date = July 18, 2013| title = Real talk: Everything is made of fields|journal=Symmetry Magazine|url=http://www.symmetrymagazine.org/sites/default/files/pdf-cache/pdf_views/pdf_1/d4de115572451d8eb544faa6e2f21379/Real%20talk%3A%20Everything%20is%20made%20of%20fields.pdf}}

==External links==
*{{Commonscat-inline|Field theory (physics)}}
*[https://web.archive.org/web/20080503073240/http://www-dick.chemie.uni-regensburg.de/group/stephan_baeurle/index.html Particle and Polymer Field Theories]

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{{DEFAULTSORT:Field (Physics)}}
[[Category:Theoretical physics]]
[[Category:Concepts in physics]]

Phosphorus pentoxide

2019-02-18T18:42:16Z

173.165.237.1: /* Fiction */

{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 464205408
| Name = Phosphorus pentoxide
| ImageFileL1 = Phosphorus-pentoxide-2D-dimensions.png
| ImageSizeL1 = 150px
| ImageNameL1 = Phosphorus pentoxide
| ImageFileR1 = Phosphorus-pentoxide-3D-balls.png
| ImageSizeR1 = 150px
| ImageNameR1 = Phosphorus pentoxide
| ImageFile2 = Sample of Phosphorus pentoxide.jpg
| ImageSize2 = 150
| OtherNames = Diphosphorus pentoxide Phosphorus(V) oxide Phosphoric anhydride Tetraphosphorus decaoxide Tetraphosphorus decoxide
|Section1={{Chembox Identifiers
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChI = 1S/P6o5
/c1-11-5-12(2)8-13(3,6-11)10-14(4,7-11)9-12
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = DLYUQMMRRRQYAE-UHFFFAOYSA-N
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 37376
| SMILES = O=P13OP2(=O)OP(=O)(O1)OP(=O)(O2)O3
| SMILES_Comment = molecular form
| SMILES1 = P12(=O)OP3(=O)OP4(=O)OP5(=O)OP6(=O)OP(=O)(O1)OP7(=O)OP(=O)OP(=O)OP(=O)(O2)OP(=O)OP(=O)OP(=O)(O3)OP(=O)OP(=O)OP(=O)(O4)OP(=O)OP(=O)OP(=O)(O5)OP(=O)OP(=O)OP(=O)(O6)OP(=O)OP(=O)(O7)O
| SMILES1_Comment = crystal o′ form
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 1314-56-3
| CASNo2_Ref = {{cascite|changed|??}}
| CASNo2 = 16752-60-6
| CASNo2_Comment = (P4O10)
| PubChem = 14812
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 14128
| RTECS = TH3945000
}}
|Section2={{Chembox Properties
| Formula = P4O10
| MolarMass = 141.9 g mol−1
| Appearance = white powder very [[deliquescent]] odorless
| Density = 2.39 g/cm3
| Solubility = [[exothermic]] hydrolysis
| MeltingPt = sublimes
| BoilingPtC = 360
| VaporPressure = 1 mmHg @ 385 °C (stable form)
}}
|Section7={{Chembox Hazards
| ExternalSDS = [http://hazard.com/msds/mf/baker/baker/files/p4116.htm MSDS]
| EUClass =
| NFPA-H = 3
| NFPA-R = 3
| NFPA-F = 0
| NFPA-S = W
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}}

'''Phosphorus pentoxide''' is a [[chemical compound]] with molecular formula [[Phosphorus|P]]4[[Oxygen|O]]10 (with its common name derived from its [[empirical formula]], P2O5). This white crystalline solid is the [[anhydride]] of [[phosphoric acid]]. It is a powerful [[desiccant]] and [[dehydration reaction|dehydrating agent]].

==Structure==
Phosphorus pentoxide crystallizes in at least four forms or [[polymorphism (materials science)|polymorphs]]. The most familiar one, a metastable form,<ref name="Greenwood">{{Greenwood&Earnshaw2nd}}</ref> shown in the figure, comprises molecules of P4O10. Weak [[van der Waals force]]s hold these molecules together in a hexagonal lattice (However, in spite of the high symmetry of the molecules, the crystal packing is not a close packing<ref>{{cite journal|author=Cruickshank, D.W.J. |title=Refinements of Structures Containing Bonds between Si, P, S or Cl and O or N: V. P4O10|journal=Acta Crystallogr. |year=1964|volume=17|issue=6|pages=677–9|doi=10.1107/S0365110X64001669}}</ref>). The structure of the P4O10 cage is reminiscent of [[adamantane]] with ''T''d [[symmetry point group]].<ref>D. E. C. Corbridge "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam. {{ISBN|0-444-89307-5}}.</ref> It is closely related to the corresponding anhydride of [[phosphorous acid]], [[phosphorus trioxide|P4O6]]. The latter lacks terminal oxo groups. Its density is 2.30 g/cm3. It boils at 423 °C under atmospheric pressure; if heated more rapidly it can sublimate. This form can be made by condensing the vapor of phosphorus pentoxide rapidly, the result is an extremely hygroscopic solid.<ref name="InorgChem">.{{cite book
| title = Inorganic Chemistry, 3rd Edition
| chapter = Chapter 15: The group 15 elements
| author1 = Catherine E. Housecroft
| author2 = Alan G. Sharpe
| publisher = Pearson
| year = 2008
| isbn = 978-0-13-175553-6
| page = 473
}}</ref>

The other polymorphs are polymeric, but in each case the phosphorus atoms are bound by a tetrahedron of oxygen atoms, one of which forms a terminal P=O bond involving the donation of the terminal oxygen p-orbital electrons to the antibonding phosphorus-oxygen single bonds. The macromolecular form can be made by heating the compound in a sealed tube for several hours, and maintaining the melt at a high temperature before cooling the melt to the solid.<ref name="InorgChem" /> The metastable orthorhombic, "O"-form (density 2.72 g/cm3, [[melting point]] 562 °C), adopts a layered structure consisting of interconnected P6O6 rings, not unlike the structure adopted by certain poly[[silicate]]s. The stable form is a higher density phase, also orthorhombic, the so-called O' form. It consists of a 3-dimensional framework, density 3.5 g/cm3.<ref name="Greenwood"/><ref>{{cite journal|journal = Acta Crystallogr. C |volume = 51|issue = 6|date=June 1995|pages = 1049–1050|doi = 10.1107/S0108270194012126|title = Phosphorus Pentoxide at 233 K|author = D. Stachel, I. Svoboda and H. Fuess}}</ref> The remaining polymorph is a [[glass]] or amorphous form; it can be made by fusing any of the others.

<center>
{|align="center" class="wikitable"
| <center>[[File:Phosphorus-pentoxide-sheet-from-xtal-3D-balls.png|300px]]</center>||<center>[[File:Phosphorus-pentoxide-xtal-3D-balls.png|250px]]</center>
|-
| <center>part of an o′-(P2O5)∞ layer</center>||<center>o′-(P2O5)∞ layers stacking</center>
|}
</center>

==Preparation==
P4O10 is prepared by burning [[tetraphosphorus]] with sufficient supply of oxygen:
: P4 + 5 O2 → P4O10
For most of the 20th century, phosphorus pentoxide was used to provide a supply of concentrated pure [[phosphoric acid]]. In the thermal process, the phosphorus pentoxide obtained by burning white phosphorus was dissolved in dilute [[phosphoric acid]] to produce concentrated acid.<ref>Threlfall, Richard E., (1951). ''The story of 100 years of Phosphorus Making: 1851 - 1951''. Oldbury: Albright & Wilson Ltd</ref> Improvements in filter technology is leading to the "wet phosphoric acid process" taking over from the thermal process, obviating the need to produce [[Allotropes of phosphorus#White phosphorus|white phosphorus]] as a starting material.<ref>Podger, Hugh (2002). ''Albright & Wilson: The Last 50 Years''. Studley: Brewin Books. {{ISBN|1-85858-223-7}}</ref> The dehydration of phosphoric acid to give phosphorus pentoxide is not possible as on heating metaphosphoric acid will boil without losing all its water.

==Applications==
Phosphorus pentoxide is a potent [[dehydration reaction|dehydrating]] agent as indicated by the exothermic nature of its hydrolysis:
:P4O10 + 6 H2O → 4 H3PO4   (–177 [[joule|kJ]])

However, its utility for drying is limited somewhat by its tendency to form a protective viscous coating that inhibits further dehydration by unspent material. A granular form of P4O10 is used in [[desiccator]]s.

Consistent with its strong desiccating power, P4O10 is used in [[organic synthesis]] for dehydration. The most important application is for the conversion of primary [[amide]]s into [[nitriles]]:<ref>Meier, M. S. "Phosphorus(V) Oxide" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. {{doi|10.1002/047084289}}.</ref>
:P4O10 + RC(O)NH2 → P4O9(OH)2 + RCN
The indicated coproduct P4O9(OH)2 is an idealized formula for undefined products resulting from the hydration of P4O10.

Alternatively, when combined with a [[carboxylic acid]], the result is the corresponding [[anhydride]]:<ref>{{cite book|url=https://books.google.com/books?id=pzRpQC7CO6sC&pg=PA1417|page=1417|title=Polymeric materials encyclopedia: C, Volume 2|editor=Joseph C. Salamone|publisher=CRC Press|year=1996|isbn=0-8493-2470-X}}</ref>
:P4O10 + RCO2H → P4O9(OH)2 + [RC(O)]2O

The "Onodera reagent", a solution of P4O10 in [[Dimethyl sulfoxide|DMSO]], is employed for the oxidation of [[alcohol]]s.<ref>Tidwell,
T. T. "Dimethyl Sulfoxide–Phosphorus Pentoxide" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. {{doi|10.1002/047084289}}.</ref> This reaction is reminiscent of the [[Swern oxidation]].

The desiccating power of P4O10 is strong enough to convert many mineral acids to their anhydrides. Examples: [[nitric acid|HNO3]] is converted to [[dinitrogen pentoxide|N2O5]];  [[sulfuric acid|H2SO4]] is converted to [[sulfur trioxide|SO3]];  [[perchloric acid|HClO4]] is converted to [[dichlorine heptoxide|Cl2O7]];  [[Triflic acid|CF3SO3H]] is converted to [[Triflic anhydride|(CF3)2S2O5]].

==Related phosphorus oxides==
Between the commercially important [[phosphorus trioxide|P4O6]] and P4O10, phosphorus oxides are known with intermediate structures.<ref>Luer, B.; Jansen, M. "Crystal Structure Refinement of Tetraphosphorus Nonaoxide, P4O9" Zeitschrift fur Kristallographie 1991, volume 197, pages 247-8.</ref>

[[File:Structures of phosphorus oxides.png|600px|Phosphorus oxides: P4O6, P4O7, P4O8, P4O9, and P4O10.]]

==Hazards==
Phosphorus pentoxide is not flammable. Just like [[sulfur trioxide]], it reacts vigorously with water and water-containing substances like wood or cotton, liberates much heat and may even cause fire. It is corrosive to metal and is very irritating – it may cause severe burns to the eye, skin, [[mucous membrane]], and [[respiratory tract]] even at concentrations as low as 1 mg/m3.<ref>[http://hazard.com/msds/mf/baker/baker/files/p4116.htm Phosphorus pentoxide MSDS]</ref>

==Fiction==
*In [[Anthony Burgess]]' ''[[The Wanting Seed]]'', phosphorus pentoxide is a highly prized [[Chemical compound|compound]].{{Clarify|date=June 2010}}
*In [[Detective Comics]] #825, [[Batman]] notices that phosphorus pentoxide was at the scene of a fire, indicating that the villain [[Dr. Phosphorus]] was involved.
*In [[Aldous Huxley]]'s ''[[Point Counter Point]]'', to his assistant Illidge, Lord Edward bemoans societal loss of phosphorous pentoxide .
*In [[Aldous Huxley]]'s ''[[Brave New World]]'', Henry Foster tells Lenina about the recovery of phosphorus pentoxide.
*In ''[[The Tunnel (TV series)|The Tunnel]]'', ([[The_Tunnel_(TV_series)#Episodes|season 1, episode 6]]), a victim was consumed by a fire started with phosphorus pentoxide.

==See also==
*[[Eaton's reagent]]

==References==
{{Reflist|2}}

==External links==
*[http://www.osha.gov/dts/chemicalsampling/data/CH_262830.html OSHA]
*[http://www.chemicalland21.com/arokorhi/industrialchem/inorganic/PHOSPHORUS%20PENTOXIDE.htm Spec sheet]
*[http://www.thermphos.com/pages/phos_pent.htm Definition]
*[http://www.phosphorus-recovery.tu-darmstadt.de Website of the Technische Universität Darmstadt and the CEEP about Phosphorus Recovery]

{{Phosphorus compounds}}
{{Oxides}}

[[Category:Inorganic phosphorus compounds]]
[[Category:Acid anhydrides]]
[[Category:Acidic oxides]]
[[Category:Glass compositions]]
[[Category:Dehydrating agents]]
[[Category:Adamantane-like molecules]]

Gradient copolymer

2019-02-08T19:42:45Z

173.165.237.1:

[[Image:Example of gradient copolymer.png|500px|thumb|''Figure 1: Example of a (a) diblock copolymer, (b) gradient copolymer and (c) random copolymer'']]
[[Copolymer]]s are [[polymer]]s that are synthesized with more than one kind of repeat unit (or [[monomer]]). Gradient copolymers exhibit a gradual change in monomer composition from predominantly one species to predominantly the other,<ref name="C">{{cite journal|last=Kryszewski|first=M|year=1998|title=Gradient Polymers and Copolymers|journal=Polymers for Advanced Technologies|volume=9|pages=224–259| issn=1042-7147}}</ref> unlike with [[block copolymers]], which have an abrupt change in composition,<ref>{{Cite journal | doi = 10.1002/ppap.201700053| title = Tunable wettability and pH-responsiveness of plasma copolymers of acrylic acid and octafluorocyclobutane| journal = Plasma Processes and Polymers| volume = 14| issue = 10| pages = 1700053| year = 2017| last1 = Muzammil| first1 = Iqbal| last2 = Li| first2 = Yupeng| last3 = Lei| first3 = Mingkai}}</ref><ref name="A">{{cite journal|last=Beginn|first=Uwe|year=2008|title=Gradient Copolymer|journal=Colloid Polym Sci|volume=286|issue=13|pages=1465–1474| doi=10.1007/s00396-008-1922-y}}</ref> and random copolymers, which have no continuous change in composition (see Figure 1).<ref name="B">{{cite journal|last=Matyjaszewski|first=Krzyszytof |author2=Michael J. Ziegler |author3=Stephen V. Arehart |author4=Dorota Greszta |author5=Tadeusz Pakula|year=2000|title=Gradient Copolymers by Atom Transfer Radical Copolymerization|journal=J. Phys. Org. Chem.|volume=13|pages=775–786| doi=10.1002/1099-1395|doi-broken-date=2018-09-10 }}</ref><ref>{{cite book|last=Cowie|first=J.M.G.|author2=Valeria Arrighi|title=Polymers: Chemistry and Physics of Modern Materials|publisher=CRC Press|year=2008|edition=Third|pages=147–148| isbn=9780849398131}}</ref>
In the gradient copolymer, as a result of the gradual compositional change along the length of the polymer chain less intrachain and interchain repulsion are observed.<ref name="E">{{cite journal|last=Mok|first=Michelle|author2=Jungki Kim |author3=John M. Torkelson |year=2008|title=Gradient Copolymers with Broad Glass Transition Temperature Regions: Design of Purely Interphase Compositions for Damping Applications|journal=Journal of Polymer Science|volume=46|issue=1|pages=48–58| doi=10.1002/polb.21341|bibcode=2008JPoSB..46...48M}}</ref>

The development of [[controlled radical polymerization]] as a synthetic methodology in the 1990s allowed for increased study of the concepts and properties of gradient copolymers because the synthesis of this group of novel polymers was now straightforward.

Due to the similar properties of gradient copolymers to that of block copolymers, they have been considered as a cost effective alternative in applications for other preexisting copolymers.<ref name="E"/>

==Polymer Composition==
[[Image:Gradient Polym Composition2.png|thumb|right|300px|Figure 2: Graphical depiction of the composition of a gradient copolymer]]

In the gradient copolymer, there is a continuous change in monomer composition along the polymer chain (see Figure 2). This change in composition can be depicted in a mathematical expression. The local composition gradient fraction <math>g(X)</math> is described by molar fraction of monomer 1 in the copolymer <math>(F_1)</math> and degree of polymerization <math>(X)</math> and its relationship is as follows:<ref name="E"/>

<math>g(X)=\frac{dF_1(X)}{dX}</math>

The above equation supposes all of the local monomer composition is continuous. To make up for this assumption, another equation of [[ensemble average]] is used:<ref name="E"/>

<math>F^{(loc)}_1(X)=\frac{1}{N}\sum_{i=1}^NF_{1,i}(X)</math>

The <math>F^{(loc)}_1(X)</math> refers [[ensemble average]] of the local chain composition, <math>X</math> refers degree of polymerization, <math>N</math> refers number of polymer chains in the sample and <math>F_{1,i}(X)</math> refers composition of polymer chain i at position <math>X</math>.

This second equation identifies the average composition over all present polymer chains at a given position, <math>X</math>.<ref name="E"/>

==Synthesis==

Prior to the development of [[controlled radical polymerization]] (CRP), gradient copolymers (as distinguished from statistical copolymers) were not synthetically possible. While a "gradient" can be achieved through compositional drift due to a difference in reactivity of the two monomers, this drift will not encompass the entire possible compositional range. All of the common CRP methods<ref name="R">{{Cite book|last=Davis|first=Kelly|author2=Krzysztof Matyjaszewski|year=2002|title=Statistical, Gradient, Block, and Graft Copolymers by Controlled/Living Radical Polymerizations|journal=Advanced in Polymer Science|volume=159|pages=1–13| doi= 10.1007/3-540-45806-9_1|series=Advances in Polymer Science|isbn=978-3-540-43244-9}}</ref> including [[atom transfer radical polymerization]] and [[Reversible addition−fragmentation chain transfer polymerization]] as well as other [[living polymerization]] techniques including [[anionic addition polymerization]] and [[ring-opening polymerization]] have been used to synthesize gradient copolymers.<ref name="E"/>

The gradient can be formed through either a spontaneous or a forced gradient. Spontaneous gradient polymerization is due to a difference in reactivity of the monomers. The resulting change in composition throughout the polymerization creates an inconsistent gradient along the polymer. Forced gradient polymerization involves varying the comonomer composition of the feed being throughout the reaction time. Because the rate of addition of the second monomer influences the polymerization and therefore properties of the formed polymer, continuous information about the polymer composition is vital. The online compositional information is often gathered through [[automatic continuous online monitoring of polymerization reactions]], a process which provides ''in situ'' information allowing for constant composition adjustment to achieve the desired gradient composition.

== Properties ==

The wide range of composition possible in a gradient polymer due to the variety of monomers incorporated and the change of the composition results in a large variety of properties. In general, the [[glass transition temperature]] (Tg) is broad in comparison with the homopolymers. [[Micelles]] of the gradient copolymer can form when the gradient copolymer concentration is too high in a block copolymer solution. As the micelles form, the micelle diameter actually shrinks creating a "reel in" effect. The general structure of these copolymers in solution is not yet well established.

The composition can be determined by [[gel permeation chromatography]](GPC) and [[nuclear magnetic resonance]] (NMR). Generally the composition has a narrow [[polydispersity index]] (PDI) and the molecular weight increases with time as the polymer forms.

== Applications ==

===Compatibilizing phase-separated polymer blends===
[[Image:Wikipic3 1.png|280px|thumb|''Figure 3: a) random copolymer blend with annealing b) gradient copolymer blend with annealing'']]
For the compatiabilization of immiscible blends, the gradient copolymer can be used by improving mechanical and optical properties of immiscible polymers and decreasing its dispersed phase to droplet size.<ref name="G">{{cite journal|last=Ramic|first=Anthony J.|author2=Julia C. Stehlin |author3=Steven D. Hudson |author4=Alexander M. Jamieson |author5=Ica Manas-Zloczower |year=2000|title=Influence of Block Copolymer on Droplet Brekup and Coalescence in Model Immiscible Polymer Blends|journal=Macromolecules|volume=33|issue=2|pages=371–374| doi=10.1021/ma990420c|bibcode = 2000MaMol..33..371R }}</ref> The compatibilization has been tested by reduction in interfacial tension and steric hindrance against coalescence. This application is not available for block and graft copolymer because of its very low [[critical micelle concentration]] (cmc). However, the gradient copolymer, which has higher cmc and exhibits a broader interfacial coverage, can be applied to effective blend compatibilizers.<ref name="D">{{cite journal|last=Kim|first=Jungki|author2=Maisha K. Gray |author3=Hongying Zhou |author4=SonBinh T. Nguyen |author5=John M. Torkelson |date=Feb 22, 2005|title=Polymer Blend Compatibilization by Gradient Copolymer Addition during Melt Processing: Stabilization nof Dispersed Phase to Static Coarsening|journal=Macromolecules|volume=38|issue=4|pages=1037–1040| doi=10.1021/ma047549t|bibcode = 2005MaMol..38.1037K }}</ref>

A small amount of gradient copolymer (i.e.styrene/4-hydroxystyrene) is added to a polymer blend (i.e. polystyrene/polycaprolactone) during melt processing. The resulting interfacial copolymer helps to stabilize the dispersed phase due to the hydrogen-bonding effects of hydroxylstyrene with the polycaprolactone ester group.

===Impact modifiers and sound or vibration dampers===
The gradient copolymer have very broad [[glass transition temperature]] (Tg) in comparison with other copolymers, at least four times bigger than that of a random copolymer. This broad glass transition is one of the important features for vibration and acoustic damping applications. The broad Tg gives wide range of mechanical properties of material. The glass transition breadth can be adjusted by selection of monomers with different degrees of reactivity in their [[controlled radical polymerization]] (CRP). The strongly segregated styrene/4-hydroxystyrene (S/HS) gradient copolymer is used to study damping properties due to its unusual broad glass transition breadth.<ref name="E"/>

===Potential applications===

There are many possible applications for gradient copolymer like pressure-sensitive adhesives, wetting agent, coating, or dispersion. However, these applications are not proved about its practical performance and stability as gradient copolymers.<ref name="E"/><ref>{{Cite journal | doi = 10.1002/ppap.201700053| title = Tunable wettability and pH-responsiveness of plasma copolymers of acrylic acid and octafluorocyclobutane| journal = Plasma Processes and Polymers| volume = 14| issue = 10| pages = 1700053| year = 2017| last1 = Muzammil| first1 = Iqbal| last2 = Li| first2 = Yupeng| last3 = Lei| first3 = Mingkai}}</ref>

==References==
<references/>

==External links==
* http://torkelson.northwestern.edu/Research/GCP/gcp.html
* http://www.cmu.edu/maty/materials/index.html

[[Category:Copolymers]]

Corn wet-milling

2018-12-14T14:39:15Z

173.165.237.1: /* Germ recovery */

{{Multiple issues|
{{Underlinked|date=May 2016}}
{{Refimprove|date=May 2016}}}}
The '''corn wet-milling''' is a process of breaking [[Corn kernel|corn kernels]] into their component parts: [[corn oil]], [[Protein crop|protein]], [[corn starch]], and [[Fiber crop|fiber]]. It uses water and a series of steps to separate the parts to be used for various products.

==History==
The [[corn]] [[wet-milling]] industry has been a primary component of American manufacturing for more than 150 years. Corn refiners established the process of separating [[Corn kernel|corn kernels]] into their component parts to produce a variety of value-added products. The four main component such as [[oil]], [[protein]], [[starch]], and [[Fiber (food)|fiber]] are the primary product from the corn wet-milling process. The Associated Manufacturers of Products from Corn was formed in 1913 when the group of corn refining companies’ industry successfully grew.<ref>{{cite web|url=http://corn.org/about/history/|title=About Us – Corn Refiners Association|date=|website=Corn.org|accessdate=2016-05-14}}</ref>

==Description==
Corn wet-milling is a process where components of corn kernels are extracted to produce a highly purified product. Most of the products from this process are valuable and mainly required by the food industry. Through this process, every part of the corn is useful to produce the quality ingredients. The characteristics of this process are based on physical separation of components, mostly by weight and size. Water is needed as it is a wet process and it works as separation/carrier agents in washing steps. Therefore, this process can be considered as having high capital cost.<ref>{{cite web|url=https://www.energystar.gov/ia/business/industry/LBNL-52307.pdf |format=PDF |title=Energy Efficiency Improvement and Cost Saving Opportunities for the Corn Wet Milling Industry |website=Enerystar.gov |accessdate=2016-05-14}}</ref> The only chemical use in this process is [[Aqueous solution|aqueous]] [[sulfur dioxide]] solution, which is used in the [[steeping]] process. The corn is soaked in this solution to soften the kernel so that the oil in the germ will not contaminate other products and is easy to separate.

== Process steps ==
{{Underlinked section|date=September 2017}}

=== Cleaning ===
As per the standards of the [[U.S. Department of Agriculture]], Grade 2{{Explain|date=September 2017|reason=In what grading system and why?}} corn is usually used for wet-milling.<ref name="corn.org">{{cite web|url=http://corn.org/wp-content/uploads/2009/12/Feed2006.pdf|title=Archived copy|archiveurl=https://web.archive.org/web/20131021152323/http://www.corn.org/wp-content/uploads/2009/12/Feed2006.pdf|archivedate=October 21, 2013|deadurl=yes|accessdate=May 3, 2016}}</ref> Harvested corn has to be cleaned before it is milled. [[Dockage]] tester with appropriate [[sieve]] number is used to removes particles other than the required grain like cob pieces, foreign seeds, metal pieces, leaves, dirt and the percentage of dockage contained can be calculated.<ref>{{cite web|url=http://www.flamangraincleaning.com/pdfs/downloads/Carter-Dockage-Tester.pdf|title=Instruction Manual : Carter Dockage Tester|website=Flamangraincleaning.com|format=PDF|accessdate=2016-05-14}}</ref> The cleaned corn is then analyzed for its composition using NIR spectrometer. The compositional analysis of Yellow dent corn carried out at the Center for Crops Utilization Research, Iowa State University, is recorded in the table below.

{| class="wikitable"
|+ '''NIR Compositional Properties'''
|-
! Moisture (in %) !! Protein (in %, dry basis) !! Oil (in %, db) !! Starch (in %, db) !! Density (in g/cc) !! Test Weight (in lb/bu)
|-
| 13.8 || 8.93 || 4.29 || 70.4 || 1.282 || 65.6
|}

=== Steeping ===
In this process, the corn is [[Tissue hydration|hydrated]] in order to loosen starch granules from the protein matrix and to make germ resilient to milling. This process reduces the germ density and softens the kernel making the milling easy. Chemicals like sulphur dioxide and [[lactic acid]] are added to the water too. Lactic acid breaks down the endosperm protein matrix and helps in better separation of starch. It also lowers pH preventing growth of microbes. SO2 reacts with the disulphide bonds and weaken matrix allowing starch granules to separate out cleanly. It also serves as an anti-microbial. At the end of steeping, the protein matrix is weakened, endosperm proteins are solubilized and some soluble solids diffuse out into the steepwater.
The clean corn is steeped in large tanks with water at 125-130˚F containing Lactic acid and SO2 for nearly 40 hours. The steepwater is then drained using appropriate sized mesh screen and concentrated using multiple effect evaporators.<ref name="corn.org"/>
Use of concentrated Steepwater: This extract is protein rich and can be used as nutrient media for fermentation to produce enzymes or antibodies. It is also used in animal feed.

=== Germ recovery ===
As the process step suggests, in this step the germ is separated from the other parts of the corn. Recovering germ as intact as possible is necessary to prevent any oil contamination in the final products. Attrition mills such as a disk mill are used to coarse grind the softened corn kernels. The grinding is slow and the elements used to grind are blunt to ensure intact removal of germ. Water is added to the ground material to make a thick slurry of macerated kernels and whole germ.<ref name="corn.org"/> 40-50% of crude oil in germ makes it less dense than other particles and as a result germ floats in the mixture. The mixture is then passed through germ hydrocyclones with an over and underflow. Overflow will be composed majorly of germ and water and underflow will have fiber, starch, protein and water. The overflow is passed through the hydroclone multiple times since 100% separation cannot be achieved in single pass.
The separated germ is cleaned, dried and passed through germ press to extract oil from it. Solvent extraction can also be used alternatively. The solid particles remaining after oil extraction is called germ meal which is further dried.
Use of germ meal: It is a good source of amino acids and is carrier of micro-ingredients in animal food formulations.
Use of corn oil: The refined corn oil can be used as salad oil and cooking oil. It is also used to prepare corn oil margarines.

=== Fiber recovery ===
The underflow from the hydroclone consisting of fiber, protein and starch is finely ground and screened using multiple grind mills and pressure fed screens. Screens are used to separate the fiber from the mixture. Various screen sizes are used to remove coarse and fine fibers. A wedge bar or profile bar screen is used. Starch and protein passes through the screen and collected whereas the fibers remain on the screen and it is called corn gluten feed. The principle of separation is difference in size. The corn gluten feed has approximately 21% protein, 1% fat and 10% fiber and 15% starch.
Use of Gluten Feed: Since it is high in water-soluble nutrients, it is used as one of the main ingredients in animal feed. It can also be used to produce refined corn fiber to be used for human consumption.<ref name="corn.org"/>

=== Gluten recovery ===
The slurry containing just the protein (gluten) and starch is called millstarch. Water is removed from the millstarch in a thickener before moving it into a separator. Centrifugal forces are applied to separate starch and gluten which differ in density. The heavier starch slurry is then washed multiple times in [[hydrocyclone]]s with fresh water. The starch stream typically has 90% starch and the gluten stream consists of 60% protein.<ref name="corn.org"/> The lighter gluten, separated out from the top, is thickened and the heavy gluten is further sent for dewatering into vacuum rotary filter. This corn gluten meal consist of approximately 60% protein, 1% fat and 3% fiber. The process water from both the processes are either added to steepwater or removed.
Use of Gluten Meal: Since it has around 60% protein, it is used as Animal feed and zein products.

=== Starch processing ===
Starch goes through multiple stage washing using [[hydrocyclone]]s. The supernatant are separated at each washing stage. The water from each stage is recycled to the previous hydrocyclones to ensure maximum amount of starch is separated. A very high purity of starch (>99.5% db) can be recovered by wet-milling. Purity is important when the end product is high fructose corn syrup or when we need to modify starch (using chemicals or enzymes) but it is not important during ethanol production. After centrifugation and washing, the starch is dried.<ref name="corn.org"/>

=== Co-product manufacture ===
Co-products account for 34% of wet-milled yield. In fact, 23% of corn that is processed has very low or no value.
The fiber, concentrated steepwater and germ meal are mixed to produce corn gluten feed. As mentioned before, corn gluten meal is also used as animal feed. Although both have ‘gluten’ in the name, no gluten protein is present in them – there is none in corn on whole.<ref>{{cite web|url=http://nfscfaculty.tamu.edu/talcott/courses/FSTC311/Textbook/13-Chapter%2013%20Cereal%20Crops.pdf|title=Crops - Cereals|website=Nfscfaculty.tamu.edu|format=PDF|accessdate=2016-05-14}}</ref>

A typical solid yield (on db) data for yellow dent corn is shown in the table below.<ref>Singh, N, Eckhoff, S.R.. 1996. Wet milling of Corn- A review of Laboratory-Scale and Pilot Plant-Scale Porcedure. Cereal Chem. 73(6):659-667</ref>

{| class="wikitable"
|-
! Fraction !! Yield on dry basis (in %)
|-
| Starch || 58-68
|-
| Gluten Meal || 5.8-15.4
|-
| Fiber (coarse+fine) || 8.8-19.2
|-
| Germ || 5.2-10.5
|-
| Steepwater solubles|| 5.1-7.5
|-
| Total solids recovery|| 97.3-99.9
|}

== Primary products ==
The wet-milling process will have five major products: steep water solids, germ, fiber, starch, and [[gluten]]. However, the co-product from this process will produce corn oil, [[corn gluten meal]], [[corn germ meal]], corn gluten and feed steep water. The average of one bushel of corn generally will have about 32 lb of starch or 33 lb sweeteners or 2.5 gallons of fuel ethanol and 11.4 lb gluten feed and 3 lb gluten meal and 1.6 lb corn oil.<ref>{{cite web|url=https://www.e-education.psu.edu/egee439/node/672 |title=7.3.1 Composition of Corn and Yield of Ethanol from Corn | EGEE 439: |website=E-education.psu.edu |date= |accessdate=2016-05-14}}</ref><ref>{{cite web|url=http://www.adm.com/en-US/products/feed/corn-co/Pages/wet_milling.aspx |title=Wet Milling Products |website=Adm.com |date=2007-08-17 |accessdate=2016-05-14}}</ref>

== Research in the field of corn wet-milling ==
Even though corn wet-milling has been used for years to produce food products, animal feed and fuel, research in this field is still going on to make the process more and more efficient. Studies have shown that the steeping time can be decreased from 40 hours to 6–8 hours if enzymes like protease are added and the milling is modified to a two-stage procedure. This even eliminates the need of sulphur dioxide. The yield were found to be equivalent to the conventional process.<ref>Johnston, David B., Singh, Vijay. 2001. Use of Protease to reduce steep time and SO2 requirements in corn wet-milling process. Cereal Chem. 78(4):401-411</ref>
In a similar study, it was shown that adding [[phytic acid]] degrading enzyme reduced the steeping time. Phytic acid is present in the corn which largely ends up in corn steep liquor. Adding phytic acid degrading enzymes along with cellulose can decrease the steeping time.<ref>Ing, Carsana A. et al, 1988. A Novel Enzyme Application for Corn Wet Milling. Starch Bio. 40(11):409-411</ref>
Effect of drying was tested on the final yield of corn wet-milling and it was found that decreasing the initial moisture content of corn and increasing the drying air temperature decreased the yield. This is because low water content made protein and starch separation difficult.<ref>Haros, Monica, Suarez, Costantino. 1997. Effect of drying, initial moisture and variety in corn wet milling. Journal of Food Engineering 34(4):473-481</ref>

== See also ==
* [[Corn kernel]]
* [[Maize]]

==References==
{{Reflist}}

{{Corn}}

[[Category:Maize]]
[[Category:Food processing]]

Precipitated silica

2018-10-29T17:00:48Z

173.165.237.1:

'''Precipitated silica''' is an [[Amorphous solid|amorphous]] form of [[silica]] (silicon dioxide, SiO2); it is a white, powdery material. Precipitated silica is produced by [[Precipitation (chemistry)|precipitation]] from a solution containing silicate salts.

The three main classes of amorphous silica are pyrogenic silica, precipitated silica and silica gel. Among them, precipitated silica has the greatest commercial significance. In 1999, more than one million tons were produced, half of it is used in tires and shoe soles.<ref name=Ull>Otto W. Flörke, et al. "Silica" in Ullmann's Encyclopedia of Industrial Chemistry, 2008, Weinheim: Wiley-VCH. {{DOI|10.1002/14356007.a23_583.pub3}}.</ref>

Like pyrogrenic silica, precipitated silica is essentially not microporous (unless prepared by the [[Stöber process]]).

==Production==
The production of precipitated silica starts with the reaction of an alkaline [[silicate]] solution with a [[mineral acid]]. [[Sulfuric acid]] and [[sodium silicate]] solutions are added simultaneously with agitation to water. [[Precipitation (chemistry)|Precipitation]] is carried out under [[alkaline]] conditions. The choice of [[agitation (action)|agitation]], duration of precipitation, the addition rate of reactants, their temperature and concentration, and pH can vary the properties of the silica. The formation of a gel stage is avoided by stirring at elevated temperatures. The resulting white [[precipitate]] is filtered, washed and dried in the manufacturing process.<ref>{{cite book |title=Defoaming. Theory and Industrial applications. |last= Garrett |first= P.R. |authorlink= |coauthors= |year=1992 |publisher= CRC Press |location= U.S.A. |isbn=0-8247-8770-6 |page= |pages= 238–239 |url= }}</ref>

: Na2(SiO2)7 + H2SO4 + O → 7 SiO2 + Na2SO4 + H2O
: Na2SiO3 + H2SO4 → SiO2 + Na2SO4 + H2O

==Properties==
The particles are [[porous]]. Primary particles with a diameter of 5 - 100 nm, and specific surface area 5-100 m2/g. [[Agglomerate]] size is 1 - 40 µm with average pore size is > 30 nm. Density: 1.9 - 2.1 g/cm3.

==Applications==
*[[Filler (materials)|Filler]], [[Plasticizer|softener]] and performance improvement in [[rubber]] and [[plastics]]
*Cleaning, [[thickening agent|thickening]] and polishing agent in [[toothpastes]] for [[oral health care]]
*[[Food processing]] and [[pharmaceuticals]] additive as [[Anti-caking agent|anti-caking]], thickening agent, absorbent to make liquids into powders.
*[[Food rheology]] modifier
*[[Defoamer]]

==See related companies==
* [http://www.zjsilica.com Zheng Yuan Chemical Co., Ltd. ]
* [http://www.antenchem.com/en/products/precipitated_silicas.htm Anten Chemical Co., Ltd.]
* [http://www.ppgsilica.com PPG Industries Co.]
* [http://www.sipernat.com/product/sipernat/en/Pages/default.aspx Evonik Industries AG]

==See also==
*[[Colloidal silica]]
*[[Fumed silica]]
*[[Hydrophobic silica]]
*[[Silica gel]]

==References==
{{Reflist}}

[[Category:Silicon dioxide]]
[[Category:Plasticizers]]

[[ru:Белая_сажа]]

Orthosilicic acid

2018-10-29T16:28:52Z

173.165.237.1: /* The silicic acids */

{{short description|chemical compound assumed present in dilute solutions of silicon dioxide in water}}
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid =
| IUPACName =
| OtherNames =
| ImageFile =
| ImageSize =
| ImageName =
|Section1={{Chembox Identifiers
| InChI1 = 1/H4O4Si/c1-5(2,3)4/h1-4H
| InChIKey1 = RMAQACBXLXPBSY-UHFFFAOYAS
| CASNo = 62647-18-1
| CASNo_Ref = {{cascite|changed|CAS}}
| UNII_Ref = {{fdacite|changed|FDA}}
| UNII = 623B93YABH
| PubChem = 14942
| ChemSpiderID = 14236
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| EINECS = 233-477-0
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 26675
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/H4O4Si/c1-5(2,3)4/h1-4H
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = RMAQACBXLXPBSY-UHFFFAOYSA-N
| SMILES = O[Si](O)(O)O
| InChI = 1S/H4O4Si/c1-5(2,3)4/h1-4H
| InChIKey = RMAQACBXLXPBSY-UHFFFAOYSA-N
| Gmelin = 2009
}}
|Section2={{Chembox Properties
| H=4 | O=4 | Si=1
| ConjugateBase = [[Orthosilicate]]
| pKa = 
| MagSus = }}
|Section3=
}}

'''Orthosilicic acid''' is the [[chemical compound]] with formula {{chem|Si(|OH|)|4}}. It is assumed to be present in dilute solutions of [[silicon dioxide]] (silica) {{chem|SiO|2}} in water. It can be synthesized in [[non-aqueous solution]]s.

==Introduction==
The term "silicic acid" has traditionally been used as a [[synonym]] for [[silicon dioxide]], SiO2, also known as "silica". Strictly speaking, silica is the [[anhydride]] of orthosilicic acid, Si(OH)4, from which it can be obtained by a [[dehydration reaction]].
:Si(OH)4 → SiO2↓ + 2H2O
The solubility of silica in pure water is about 1.5mM, or less, depending on the solid state structure of the compound. Because the concentration of orthosilicic acid is so low, it has not been fully characterized. It has been predicted to be "a very weak acid".<ref>{{cite book |last1=Pauling |first1=Linus |title=The nature of the chemical bond |date=1960 |publisher=Cornell University Press |location=Ithaka, New York |page=557 |edition=3rd.}}</ref> More concentrated solutions of orthosilicic acid are unstable and turn into [[silica gel]] and other species.<ref name=gye/>

The situation changed in 2017, when the orthosilicic acid monomer was obtained by [[hydrogenolysis]] of tetrakis(benzoyloxy)silane, (Si(OCH2C6H5)4, in solution in [[dimethylacetamide]] or related solvents. The crystal structure of this compound was determined by [[X-ray crystallography]]. [[Neutron diffraction]] was also used to determine the location of the hydrogen atoms. Di-silicic acid was synthesized by hydrogenation of its hexa-benzoyloxy derivative, R3-SiOSi-R3, R=CH3C6H4O. Cyclic trisilicic acid, Si3O3(OH)6 and cyclic tetrasilicic acid, Si4O4(OH)8 were synthesized by variations of this method.<ref name=synthesis>{{cite journal |last1=Igarashi |first1=Masayasu |last2=Matsumoto |first2=Tomohiro |last3=Yagahashi |first3=Fujio |last4=Yamashita |first4=Hiroshi |last5=Ohhara |first5=Takashi |last6=Hanashima |first6=Takayasu |last7=Nakao |first7=Akiko |last8=Moyosh |first8=Taketo |last9=Sato |first9=Kazuhiko |last10=Shimada |first10=Shigeru |title=Non-aqueous selective synthesis of orthosilicic acid and its oligomers |journal=Nature Communications |date=2017 |volume=8 |issue=1 |pages=140 |doi=10.1038/s41467-017-00168-5|pmid=28747652|pmc=5529440}}</ref>

With these new discoveries, the term ''silicic acid'' has become ambiguous: it has been applied traditionally as a synonym for silica, SiO2, but it can now also be used for the compound Si(OH)4. The traditional meaning is retained in this article when it was used as such in a cited publication.

==Plants and animals==
Outside the marine environment compounds of silicon have very little biological function. Small quantities of silica are absorbed from the soil by some plants, to be then excreted in the form of [[phytolith]]s.<ref name=snyder>G.H.Snyder (2001): "Methods for silicon analysis in plants, soils, and fertilizers". ''Studies in Plant Science'', volume 8, chapter 11, Pages 185-196 {{doi|10.1016/S0928-3420(01)80015-X}}</ref>

Subcutaneous injections of orthosilicic acid solutions (around 1%) in [[mice]] were found to cause local [[inflammation]] and [[edema]]. [[peritoneum|Peritoneal]] injections of 0.1 [[milliliter|mL]] of freshly prepared acid were often lethal. The toxicity decreased markedly as the solution aged, to the point that after the solution turned to a gel it had no effects other than mechanical ones. The solutions were equally toxic when administed by [[intravenous injection]], but seasoned or gelled solutions were about as toxic as fresh ones.<ref name=gye>W. E. Gye and W. J. Purdy (1922): "The Poisonous Properties of Colloidal Silica. I: The Effects of the Parenteral Administration of Large Doses" ''British Journal of Experimental Pathology'', volume 3, issue 2, pages 75–85. {{PMC|2047780}}</ref>

Research concerning the correlation of [[aluminium]] and [[Alzheimer's disease]] has included the ability of silicic acid in beer to reduce aluminium uptake in the digestive system as well as to increase renal excretion of aluminium <ref name="pmid16988476">{{cite journal |vauthors=Exley C, Korchazhkina O, Job D, Strekopytov S, Polwart A, Crome P |title=Non-invasive therapy to reduce the body burden of aluminium in Alzheimer's disease |journal=J. Alzheimers Dis. |volume=10 |issue=1 |pages=17–24; discussion 29–31 |year=2006 |pmid=16988476 |doi=10.3233/jad-2006-10103}}</ref><ref name="pmid17697731">{{cite journal |vauthors=González-Muñoz MJ, Peña A, Meseguer I |title=Role of beer as a possible protective factor in preventing Alzheimer's disease |journal=Food Chem. Toxicol. |volume=46 |issue=1 |pages=49–56 |year=2008 |pmid=17697731 |doi=10.1016/j.fct.2007.06.036}}</ref>

[[Choline]]-stabilized orthosilicic acid (ch-OSA) is a [[dietary supplement]]. It has been shown to prevent the loss of tensile strength in human hair;<ref name="pmid17960402">{{cite journal |author=Wickett RR |title=Effect of oral intake of choline-stabilized orthosilicic acid on hair tensile strength and morphology in women with fine hair |journal=Arch. Dermatol. Res. |volume=299 |issue=10 |pages=499–505 |year=2007 |pmid=17960402 |doi=10.1007/s00403-007-0796-z |name-list-format=vanc|author2=Kossmann E |author3=Barel A |display-authors=3 |last4=Demeester |first4=N. |last5=Clarys |first5=P. |last6=Vanden Berghe |first6=D. |last7=Calomme |first7=M.}}</ref> to have a positive effect on the surface and mechanical properties of skin, and on the brittleness of hair and nails;<ref name="pmid16205932">{{cite journal |author=Barel A |title=Effect of oral intake of choline-stabilized orthosilicic acid on skin, nails and hair in women with photodamaged skin |journal=Arch. Dermatol. Res. |volume=297 |issue=4 |pages=147–53 |year=2005 |pmid=16205932 |doi=10.1007/s00403-005-0584-6 |name-list-format=vanc|author2=Calomme M |author3=Timchenko A |display-authors=3 |last4=Paepe |first4=K. De. |last5=Demeester |first5=N. |last6=Rogiers |first6=V. |last7=Clarys |first7=P. |last8=Vanden Berghe |first8=D.}}</ref> to abate brittle nail syndrome;<ref name="pmid17763607">{{cite journal |vauthors=Scheinfeld N, Dahdah MJ, Scher R |title=Vitamins and minerals: their role in nail health and disease |journal=J Drugs Dermatol |volume=6 |issue=8 |pages=782–7 |year=2007 |pmid=17763607 |doi=}}</ref> to partially prevent femoral bone loss in aged [[ovariectomized rat]]s;<ref name="pmid16604283">{{cite journal |author=Calomme M |title=Partial prevention of long-term femoral bone loss in aged ovariectomized rats supplemented with choline-stabilized orthosilicic acid |journal=Calcif. Tissue Int. |volume=78 |issue=4 |pages=227–32 |year=2006 |pmid=16604283 |doi=10.1007/s00223-005-0288-0 |name-list-format=vanc|author2=Geusens P |author3=Demeester N |display-authors=3 |last4=Behets |first4=G. J. |last5=d’Haese |first5=P. |last6=Sindambiwe |first6=J. B. |last7=Hoof |first7=V. |last8=Berghe |first8=D. Vanden}}</ref> to increase the concentration of collagen in calves;<ref name="pmid9164661">{{cite journal |vauthors=Calomme MR, Vanden Berghe DA |title=Supplementation of calves with stabilized orthosilicic acid. Effect on the Si, Ca, Mg, and P concentrations in serum and the collagen concentration in skin and cartilage |journal=Biol Trace Elem Res |volume=56 |issue=2 |pages=153–65 |year=1997 |pmid=9164661 |doi=10.1007/BF02785389}}</ref> and to have a potentially beneficial effect on the formation of collagen in the bones of osteopenic women.<ref name="pmid18547426">{{cite journal |author=Spector TD |title=Choline-stabilized orthosilicic acid supplementation as an adjunct to Calcium/Vitamin D3 stimulates markers of bone formation in osteopenic females: a randomized, placebo-controlled trial |journal=BMC Musculoskelet Disord |volume=9|pages=85 |year=2008 |pmid=18547426 |pmc=2442067 |doi=10.1186/1471-2474-9-85 |url= |name-list-format=vanc|author2=Calomme MR |author3=Anderson SH |display-authors=3 |last4=Clement |first4=Gail |last5=Bevan |first5=Liisa |last6=Demeester |first6=Nathalie |last7=Swaminathan |first7=Rami |last8=Jugdaohsingh |first8=Ravin |last9=Berghe |first9=Dirk}}</ref>

== Oceanic silicic acid ==
[[File:WOA09 sea-surf H4SIO4 AYool.png|thumb|2009 silicic acid concentration in the upper [[pelagic zone]].<ref>{{cite web|url=http://www.nodc.noaa.gov/OC5/WOA09/pr_woa09.html|title=World Ocean Atlas 2009|first=US Department of Commerce, NOAA National Centers for Environmental|last=Information|date=|website=www.nodc.noaa.gov|accessdate=17 April 2018}}</ref>]]

''Dissolved silica'' (DSi) is a term used in the field of oceanography to describe the form of water-soluble [[silica]], which is assumed to be {{chem|Si(OH)|4}} (orthoslicic acid) or its conjugate bases (orthosilicate anions) such as {{chem|Si(OH)|3|O|-}} and {{chem|Si(OH)|2|O|2|2-}}. Theoretical computations indicate that the dissolution of silica in water proceeds through the formation of a {{chem|SiO|2}}·2{{chem|H|2|O}} complex and then orthosilicic acid.<ref>Bhaskar Mondal, Deepanwita Ghosh, and Abhijit K. Das (2009): "Thermochemistry for silicic acid formation reaction: Prediction of new reaction pathway". ''Chemical Physics Letters'', volume 478, issues 4–6, pages 115-119. {{doi|10.1016/j.cplett.2009.07.063}}</ref>
The [[biogeochemical cycle]] of silica is regulated by the [[algae]] known as the [[diatom]]s.<ref name=siever91>Siever, R. (1991). Silica in the oceans: biological-geological interplay. In: Schneider, S. H., Boston, P. H. (eds.), ''Scientists On Gaia'', The MIT Press, Cambridge MA, USA, pp. 287-295.</ref><ref name=treg95>{{cite journal|authors=Treguer, P., Nelson, D. M., Van Bennekom, A. J., DeMaster, D. J., Leynaert, A. Queguiner, B.|year=1995|journal=Science|title=The silica balance in the world ocean: A reestimate|volume=268|pages=375–379|doi=10.1126/science.268.5209.375}}</ref> These algae [[polymer]]ise the silicic acid to so-called [[biogenic silica]], used to construct their [[cell wall]]s (called [[frustule]]s).<ref>Del Amo, Y., and M. A. Brzezinski. 1999. The chemical form of dissolved Si taken up by marine diatoms. J. Phycol. 35:1162-1170. https://onlinelibrary.wiley.com/doi/10.1046/j.1529-8817.1999.3561162.x/abstract</ref>

In the uppermost water column the surface [[ocean]] is undersaturated with respect to dissolved silica, except for the [[Antarctic Circumpolar Current]] south of 55°S.

[[File:Levitus94-10m.gif]]

The dissolved silica concentration increases with increasing water depth, and along the conveyor belt from the Atlantic over the Indian into the Pacific Ocean.<ref>The figures here have been drawn using the interactive web site which feeds on annual DSi values from ''LEVITUS94: [[World Ocean Atlas]] 1994, an atlas of objectively analyzed fields of major ocean parameters at the annual, seasonal, and monthly time scales''. Superseded by WOA98. Edited by Syd Levitus.</ref><ref>{{cite web|url= http://iridl.ldeo.columbia.edu/SOURCES/.LEVITUS94/|title= World Ocean Atlas 1994}}</ref>

[[File:Levitus94-1000m.gif]]

[[File:Z-bar.gif]]

==The silicic acids==
[[File:Orthosilicic-acid-3D-balls.png|110px|thumb|left|Orthosilicic acid]]
[[File:Pyrosilicic-acid-3D-balls.png|150px|thumb|Disilicic acid]]

For many decades it was debated whether orthosilicic acid, Si(OH)4, exists in [[aqueous solution]]s at ambient temperature;<ref name = Iler>{{cite book |last1=Iler |first1=Ralph K. |title=The Chemistry of Silica: Solubility, Polymerization, Colloid and Surface Properties and Biochemistry of Silica |date=1970 |publisher=Wley |location=New York |isbn= 978-0-471-02404-0}}</ref> this uncertainty originated from the poor solubility of [[silicon dioxide]], SiO2.
:Si(OH)4 (aq) <chem> <=>></chem> SiO2↓ + 2 H2O

The [[solubility product|solubility]] of silicon dioxide in water strongly depends on its crystal structure.<ref>{{cite journal |last1=Fournier |first1=Robert O. |last2=Rowe |first2=Jack J. |title=The solubility of amorphous silica in water at high temperatures and high pressures |journal=American Mineralogist |date=1977 |volume=62 |pages=1052–1056|url=http://www.minsocam.org/ammin/AM62/AM62_1052.pdf}}</ref> The species that are present in a solution in equilibrium with a solid have not been definitively characterised because of their low concentrations. Many authors have speculated that silicic acid may be present, at [[Molar concentration|sub-millimolar]] concentrations, in rivers, lakes and sea water.<ref name="Iler"/>

Orthosilicic acid was synthesized for the first time in the year 2017.<ref name=synthesis>{{cite journal |last1=Igarashi |first1=Masayasu |last2=Matsumoto |first2=Tomohiro |last3=Yagahashi |first3=Fujio |last4=Yamashita |first4=Hiroshi |last5=Ohhara |first5=Takashi |last6=Hanashima |first6=Takayasu |last7=Nakao |first7=Akiko |last8=Moyosh |first8=Taketo |last9=Sato |first9=Kazuhiko |last10=Shimada |first10=Shigeru |title=Non-aqueous selective synthesis of orthosilicic acid and its oligomers |journal=Nature Communications |date=2017 |volume=8 |issue=1 |pages=140 |doi=10.1038/s41467-017-00168-5|pmid=28747652|pmc=5529440}}</ref> It was obtained by [[hydrogenolysis]] of tetrakis(benzoyloxy)silane, (Si(OCH2C6H5)4, in solution in [[dimethylacetamide]] or related solvents. The crystal structure of this compound was determined by [[X-ray crystallography]]. [[Neutron diffraction]] was also used to determine the location of the hydrogen atoms.

The conversion of mono-silicic acid to di-silicic acid
:2 Si(OH)4 → (HO)3SiOSi((OH)3 + H2O
is a [[dehydration reaction]], not an [[acid-base reaction]]; in consequence, di-silicic acid cannot be easily obtained from mono-silicic acid. Di-silicic acid was synthesized by hydrogenation of its hexa-benzoyloxy derivative, R3-SiOSi-R3, R=CH3C6H4O. Cyclic trisilicic acid, Si3O3(OH)6 and cyclic tetrasilicic acid, Si4O4(OH)8 were synthesized by variations of this method.<ref name=synthesis/>

The derivative Si(OH)3F has been characterized in aqueous solutions containing "silicic acid" and the [[fluoride]] ion. A fluoride [[Ion selective electrode]] was used to determine its [[Acid dissociation constant|stability constant]].<ref>{{cite journal |last1=Ciavatta |first1=Liberato |last2=Iuliano |first2=Mauro |last3=Porto |first3=Raffaella |title=Fluorosilicate equilibria in acid solution |journal=Polyhedron |date=1988 |volume=7 |issue=18 |pages=1773–1779 |doi=10.1016/S0277-5387(00)80410-6}}</ref> The concentration of silicic acid was maintained below 2.5×10−3 mol/L.

==References==
{{reflist}}

[[Category:Oceanography]]
[[Category:Aquatic ecology]]
[[Category:Silicon compounds]]

Natural gas vehicle

2018-10-15T17:04:08Z

173.165.237.1:

{{redirect|NGV|the art gallery in Melbourne, Australia|National Gallery of Victoria}}
{{multiple issues|
{{original research|date=September 2017}}
{{unreliable sources|date=September 2017}}
{{very long|date=September 2017}}
}}
[[File:Guidetti cng truck.jpg|thumb|200px|Truck running with Guidetti CNG system]]
[[Image:FillingUpCNG.jpg|thumb|200px|Fueling ([[Fiat Multipla]])]]
[[Image:2009 Honda Civic NGV--DC.jpg|thumb|right|200px|2009 [[Honda Civic GX]] hooked up to Phill refueling system.]]

A '''natural gas vehicle''' ('''NGV''') is an [[alternative fuel vehicle]] that uses [[Compressed natural gas|compressed natural gas (CNG)]] or [[liquefied natural gas|liquefied natural gas (LNG)]]. Natural gas vehicles should not be confused with [[autogas|vehicles powered by LPG]] (mainly [[propane]]), which is a fuel with a fundamentally different composition.

In a natural gas powered vehicle, energy is released by combustion of essentially [[Methane]] gas (CH4) fuel with Oxygen (O2) from the air to CO2 and water vapor (H2O) in an [[internal combustion engine]]. Methane is the cleanest burning [[hydrocarbon]] and many contaminants present in [[natural gas]] are removed at source.

Safe, convenient and cost effective gas storage and fuelling is more of a challenge compared to petrol and diesel vehicles since the natural gas is pressurized and/or - in the case of LNG - the tank needs to be kept cold. This makes LNG unsuited for vehicles that are not in frequent use. The lower [[energy density]] of gases compared to liquid fuels is mitigated to a great extent by high compression or gas liquefaction, but requires a trade-off in terms of size/complexity/weight of the storage container, range of the vehicle between refueling stops, and time to refuel.

Although similar storage technologies may be used for and similar compromises would apply to a [[hydrogen vehicle]] as part of a proposed new [[hydrogen economy]], methane as a gaseous fuel is safer than hydrogen due to its [[flammability limit|lower flammability]], low corrosivity and better leak tightness due to larger [[molecular weight]]/ size, resulting in lower price hardware solutions based on proven technology and conversions. A key advantage of using natural gas is the existence, in principle, of most of the infrastructure and the supply chain, which is non-interchangeable with hydrogen. Methane today mostly comes from non-renewable sources but can be supplied or produced from [[renewable]] sources, offering net carbon neutral mobility. In many markets, especially the Americas, natural gas may trade at a discount to other [[fossil fuel]] products such as petrol, diesel or coal, or indeed be a less valuable by-product associated with their production that has to be disposed. Many countries also provide tax incentives for natural gas powered vehicles due to the environmental benefits to society. Lower operating costs and government incentives to reduce pollution from heavy vehicles in urban areas have driven the adoption of NGV for commercial and public uses, i.e. trucks and buses.

Many factors hold back NGV popularization for [[individual mobility]] applications, i.e. private vehicles, including: relatively price and environmentally insensitive but convenience seeking private individuals; good profits and taxes extractable from small batch sales of value-added, branded petrol and diesel fuels via established trade channels and oil refiners; resistance and safety concerns to increasing gas inventories in urban areas; dual-use of utility distribution networks originally built for home gas supply and allocation of network expansion costs; reluctance, effort and costs associated with switching; prestige and nostalgia associated with petroleum vehicles; fear of redundancy and disruption. A particular challenge may be the fact that refiners are currently set up to produce a certain fuels mix from crude oil. [[Aviation fuel]] is likely to remain the fuel of choice for aircraft due to their weight sensitivity for the foreseeable future.

Worldwide, there were 24.452 million NGVs by 2016, led by [[China]] (5.0 million), [[Iran]] (4.00 million), [[India]] (3.045 million), [[Pakistan]] (3.0 million), [[Argentina]] (2.295 million), [[Brazil]] (1.781 million), and [[Italy]] (1.001 million).<ref name=NGVJournal>{{cite web|url=http://www.iangv.org/current-ngv-stats/|title=Current Natural Gas Vehicle Statistics|publisher=IANGV}}</ref> The [[Asia-Pacific]] region leads the world with 6.8 million vehicles, followed by [[Latin America]] with 4.2 million.<ref name=IANGV>{{cite web |url=http://www.iangv.org/tools-resources/statistics.html |title=Natural Gas Vehicle Statistics: Summary Data 2010 |publisher=International Association for Natural Gas Vehicles |accessdate=2011-08-02 |deadurl=yes |archiveurl=https://web.archive.org/web/20100110101111/http://www.iangv.org/tools-resources/statistics.html |archivedate=2010-01-10 |df= }} ''Click on Summary Data (2010).''</ref> In Latin America, almost 90% of NGVs have [[bi-fuel engine]]s, allowing these vehicles to run on either gasoline or CNG.<ref>{{cite web|url=http://green.autoblog.com/2011/09/26/pike-research-predicts-68-jump-in-global-cng-vehicle-sales-by-2/#continued|title=Pike Research predicts 68% jump in global CNG vehicle sales by 2016|author=Pike Research|publisher=[[AutoblogGreen]] |date=2011-09-14|accessdate=2011-09-26}}</ref> In Pakistan, almost every vehicle converted to (or manufactured for) alternative fuel use typically retains the capability of running on gasoline.

As of 2016, the U.S. had a fleet of 160,000 NG vehicles, including 3,176 LNG vehicles. Other countries where natural gas-powered buses are popular include India, [[Australia]], Argentina, [[Germany]], and [[Greece]].<ref name="TwoBillion">{{Cite book |author1=Sperling, Daniel |author2=Deborah Gordon |lastauthoramp=yes | title = Two billion cars: driving toward sustainability | year = 2009 | pages= 93–94 | publisher = [[Oxford University Press]], New York| isbn = 978-0-19-537664-7}}</ref> In [[OECD]] countries, there are around 500,000 CNG vehicles.<ref name="SusTransp">{{Cite book |author1=Ryan, Lisa |author2=Turton, Hal | year = 2007 | title = Sustainable Automobile Transport| publisher = Edward Elgar Publishing Ltd, England| isbn = 978-1-84720-451-6| pages = 40–41}}</ref> Pakistan's market share of NGVs was 61.1% in 2010, follow by [[Armenia]] with more than 77% (2014), and [[Bolivia]] with 20%.<ref name=IANGV/> The number of NGV refueling stations has also increased, to 18,202 worldwide as of 2010, up 10.2% from the previous year.<ref name=IANGV/>

Existing gasoline-powered vehicles may be converted to run on CNG or LNG, and can be dedicated (running only on natural gas) or bi-fuel (running on either gasoline or natural gas). Diesel engines for heavy trucks and busses can also be converted and can be dedicated with the addition of new heads containing spark ignition systems, or can be run on a blend of diesel and natural gas, with the primary fuel being natural gas and a small amount of diesel fuel being used as an ignition source. It is also possible to generate energy in a small gas turbine and couple the gas engine or turbine with a small electric battery to create a hybrid electric motor driven vehicle. An increasing number of vehicles worldwide are being manufactured to run on CNG by major carmakers. Until recently, the [[Honda Civic GX]] was the only NGV commercially available in the US market. More recently, [[Ford]], [[General Motors]] and [[Ram Trucks]] have bi-fuel offerings in their vehicle lineup. In 2006, the Brazilian subsidiary of [[FIAT]] introduced the [[Fiat Siena|Fiat Siena Tetra fuel]], a four-fuel car that can run on natural gas (CNG).<ref name="TreeH"/>

NGV filling stations can be located anywhere that natural gas lines exist. Compressors (CNG) or liquifaction plants (LNG) are usually built on large scale but with CNG small home refueling stations are possible. A company called FuelMaker pioneered such a system called Phill Home Refueling Appliance (known as "Phill"), which they developed in partnership with [[Honda]] for the American GX model.<ref>{{Cite web |url=http://www.fuelmaker.com/Research/PhillQandA.htm |publisher=FuelMaker Corporation - World Leader in Convenient On-Site Refueling Systems |title=Phill: Questions and Answers |deadurl=yes |archiveurl=https://web.archive.org/web/20051016173628/http://www.fuelmaker.com/research/phillqanda.htm |archivedate=October 16, 2005 |df= }}</ref><ref>{{cite web | url = http://www.evworld.com/view.cfm?section=article&storyid=847 | publisher = EVWorld | title = FEATURE: Honda's Phill-way to Hydrogen | first= Bill |last = Moore | date = May 6, 2005 | work = Open Access}}</ref> Phill is now manufactured and sold by BRC FuelMaker, a division of Fuel Systems Solutions, Inc.<ref>{{Cite web|url=http://blogs.edmunds.com/greencaradvisor/2011/03/brc-fuelmaker-again-selling-phill-home-cng-fuel-station.html|title=BRC FuelMaker Again Selling Phill Home CNG Fuel Station|accessdate=2011-04-04|archive-url=https://web.archive.org/web/20110325155026/http://blogs.edmunds.com/greencaradvisor/2011/03/brc-fuelmaker-again-selling-phill-home-cng-fuel-station.html|archive-date=2011-03-25|dead-url=yes|df=}}</ref>

CNG may be generated and used for bulk storage and pipeline transport of renewable energy and also be mixed with [[biomethane]], itself derived from [[biogas]] from [[landfill]]s or [[anaerobic digestion]]. This would allow the use of CNG for mobility without increasing the concentration of carbon in the atmosphere. It would also allow continued use of CNG vehicles currently powered by non-renewable fossil fuels that do not become obsolete when stricter CO2 emissions regulations are mandated to combat global warming.

Despite its advantages, the use of natural gas vehicles faces several limitations, including fuel storage and infrastructure available for delivery and distribution at fueling stations. CNG must be stored in high pressure cylinders (3000psi to 3600psi operation pressure), and LNG must be stored in cryogenic cylinders (-260F to -200F). These cylinders take up more space than gasoline or diesel tanks that can be molded in intricate shapes to store more fuel and use less on-vehicle space. CNG tanks are usually located in the vehicle's trunk or pickup bed, reducing the space available for other cargo. This problem can be solved by installing the tanks under the body of the vehicle, or on the roof (typical for busses), leaving cargo areas free. As with other alternative fuels, other barriers for widespread use of NGVs are natural gas distribution to and at fueling stations as well as the low number of CNG and LNG stations.<ref name="SusTransp"/>

CNG-powered vehicles are considered to be safer than gasoline-powered vehicles.<ref>{{Cite web|url=http://ngvamerica.org/pdfs/TechBul2.pdf|title=How Safe are Natural Gas Vehicles?|publisher=Clean Vehicle Education Foundation|accessdate=2008-05-08|format=PDF}}</ref><ref>{{Cite web|url=http://alternativefuels.about.com/od/naturalgaspropane/a/safenaturalgas.htm|title=How Safe is Natural Gas?|accessdate=2008-05-08}}</ref><ref>{{cite web|url=http://www.firetrainingresources.net/items/CNGAutoFire-FIREFIGHTERNEARMISScompressedpics.pdf|title=Fighting CNG fires|accessdate=2008-05-08|format=PDF|deadurl=yes|archiveurl=https://web.archive.org/web/20080528041023/http://www.firetrainingresources.net/items/CNGAutoFire-FIREFIGHTERNEARMISScompressedpics.pdf|archivedate=2008-05-28|df=}}</ref>

==CNG/LNG as fuel for automobiles==

===Available production cars===
[[File:Meriva Flex GNV SAO 10 2009 7797 with logo flex.jpg|thumb|Brazilian [[flexible-fuel vehicle|flexible-fuel]] [[Taxicab|taxi]] retrofitted to run also as a NGV. The [[Compressed Natural Gas|compressed natural gas (CNG)]] tanks are located underneath the body in the rear.]]

Existing gasoline-powered vehicles may be converted to run on CNG or LNG, and can be dedicated (running only on natural gas) or bi-fuel (running on either gasoline or natural gas). However, an increasing number of vehicles worldwide are being manufactured to run on CNG.{{citation needed|date=October 2016}} Until recently, the now-discontinued [[Honda Civic GX]] was the only NGV commercially available in the US market.<ref>{{cite web |url=http://alternativefuels.about.com/od/2008ngvavailable/a/2008CNGvehicles.htm |title=2008 Natural Gas Vehicles (NGVs) Available |author1=Christine Gable |author2=Scott Gable |lastauthoramp=yes |publisher=About.com: Hybrid Cars & Alt Fuels |date= |accessdate=2008-10-18 |deadurl=yes |archiveurl=https://web.archive.org/web/20081011214336/http://alternativefuels.about.com/od/2008ngvavailable/a/2008CNGvehicles.htm |archivedate=2008-10-11 |df= }}</ref><ref>{{cite web|url=http://automobiles.honda.com/civic-gx/ |title=2009 Honda Civic GX Natural Gas Vehicle |publisher=Honda |date= |accessdate=2008-10-18}}</ref> More recently, [[Ford]], [[General Motors]] and [[Ram Trucks]] have bi-fuel offerings in their vehicle lineup.{{citation needed|date=October 2016}} Ford's approach is to offer a bi-fuel prep kit as a factory option, and then have the customer choose an authorized partner to install the natural gas equipment. Choosing GM's bi-fuel option sends the HD pickups with the 6.0L gasoline engine to IMPCO in Indiana to upfit the vehicle to run on CNG. Ram currently is the only pickup truck manufacturer with a truly CNG factory-installed bi-fuel system available in the U.S. market.{{citation needed|date=September 2014}}

Outside the U.S. [[General Motors do Brasil|GM do Brasil]] introduced the MultiPower engine in 2004, which was capable of using CNG, alcohol and gasoline ([[Common ethanol fuel mixtures#E20, E25|E20-E25 blend]]) as fuel, and it was used in the [[Opel Astra|Chevrolet Astra]] 2.0 model 2005, aimed at the taxi market.<ref name="GNVNews"/><ref>{{cite web|url=http://www.jornalexpress.com.br/noticias/detalhes.php?id_jornal=9095&id_noticia=1703|title=Astra é líder no segmento dos compactos em 2004: As versões do Chevrolet Astra 2005|publisher=Journal Express|date=2005-01-18|language=Portuguese|accessdate=2008-10-15}} {{pt icon}}</ref> In 2006, the Brazilian subsidiary of [[FIAT]] introduced the [[Fiat Siena|Fiat Siena Tetra fuel]], a four-fuel car developed under [[Magneti Marelli]] of [[Fiat]] Brazil. This automobile can run on natural gas (CNG); 100% ethanol ([[w:Common ethanol fuel mixtures#E100|E100]]); [[w:Common ethanol fuel mixtures#E20, E25|E20 to E25]] gasoline blend, Brazil's mandatory gasoline; and pure gasoline, though no longer available in Brazil it is used in neighboring countries.<ref name="TreeH"/><ref>{{cite web |url=http://www.webmotors.com.br/wmpublicador/Noticias_Conteudo.vxlpub?hnid=36391 |author=Agência AutoInforme |title=Siena Tetrafuel vai custar R$ 41,9 mil |publisher=WebMotor |date=2006-06-19 |accessdate=2008-08-14 |language=Portuguese |deadurl=yes |archiveurl=https://web.archive.org/web/20081210211007/http://www.webmotors.com.br/wmpublicador/Noticias_Conteudo.vxlpub?hnid=36391 |archivedate=2008-12-10 |df= }}{{pt icon}} The article argues that even though Fiat called it tetra fuel, it actually runs on three fuels: natural gas, ethanol, and gasoline, as Brazilian gasoline is an E20 to E25 blend.</ref>

In 2015, Honda announced its decision to phase out the commercialization of natural-gas powered vehicles to focus on the development of a new generation of [[electric vehicle|electrified vehicles]] such as [[hybrid electric vehicle|hybrids]], [[plug-in electric car]]s and hydrogen-powered [[fuel cell vehicle]]s. Since 2008, Honda sold about 16,000 natural-gas vehicles, mainly to taxi and commercial fleets.<ref>{{cite news | url=http://www.autonews.com/article/20150615/OEM05/150619915/honda-will-drop-cng-vehicles-to-focus-on-hybrids-evs | title=Honda will drop CNG vehicles to focus on hybrids, EVs | first=Neal E. | last=Boudette | work=[[Automotive News]] | date=2015-06-15 | accessdate=2016-05-28}}</ref>

===Differences between LNG and CNG fuels===
Though LNG and CNG are both considered NGVs, the technologies are vastly different. Refueling equipment, fuel cost, pumps, tanks, hazards, capital costs are all different.

One thing they share is that due to engines made for gasoline, computer controlled valves to control fuel mixtures are required for both of them, often being proprietary and specific to the manufacturer. The on-engine technology for fuel metering is the same for LNG and CNG.

===CNG as an auto fuel===
CNG, or compressed natural gas, is stored at high pressure, {{Convert|3000|to|3600|psi|MPa}}. The required tank is more massive and costly than a conventional fuel tank. Commercial on-demand refueling stations are more expensive to operate than LNG stations because of the energy required for compression, the compressor requires 100 times more electrical power, however, slow-fill (many hours) can be cost-effective with LNG stations [missing citation - the initial liquefaction of natural gas by cooling requires more energy than gas compression]. Time to fill a CNG tank varies greatly depending on the station. Home refuelers typically fill at about 0.4 [[Gasoline gallon equivalent|GGE]]/hr. "Fast-fill" stations may be able to refill a 10 GGE tank in 5–10 minutes. Also, because of the lower energy density, the range on CNG is limited by comparison to LNG. Gas composition and throughput allowing, it should be feasible to connect commercial CNG fueling stations to city gas networks, or enable home fueling of CNG vehicles directly using a gas compressor. Similar to a car battery, the CNG tank of a car could double as a home energy storage device and the compressor could be powered at times when there is excess/ free renewable electrical energy.

===LNG as an auto fuel===
LNG, or liquified natural gas, is natural gas that has been cooled to a point that it is a cryogenic liquid. In its liquid state, it is still more than 2 times as dense as CNG. LNG is usually dispensed from bulk storage tanks at LNG fuel stations at rates exceeding 20 [[Diesel gallon equivalent|DGE]]/min. Sometimes LNG is made locally from utility pipe. Because of its cryogenic nature, it is stored in specially designed insulated tanks. Generally speaking, these tanks operate at fairly low pressures (about 70-150 psi) when compared to CNG. A vaporizer is mounted in the fuel system that turns the LNG into a gas (which may simply be considered low pressure CNG). When comparing building a commercial LNG station with a CNG station, utility infrastructure, capital cost, and electricity heavily favor LNG over CNG. There are existing LCNG stations (both CNG and LNG), where fuel is stored as LNG, then vaporized to CNG on-demand. LCNG stations require less capital cost than fast-fill CNG stations alone, but more than LNG stations.

===Advantages over gasoline and diesel===
LNG – and especially CNG – tends to corrode and wear the parts of an engine less rapidly than gasoline. Thus it is quite common to find diesel-engine NGVs with high mileages (over 500,000 miles). CNG also emits 20-29% less CO2 than diesel and gasoline.<ref>{{Cite web|url=http://www.gas-south.com/business/compressed-natural-gas.aspx|title=Gas South Compressed Natural Gas|website=www.gas-south.com|access-date=2016-04-08}}</ref> Emissions are cleaner, with lower emissions of carbon and lower particulate emissions per equivalent distance traveled. There is generally less wasted fuel. However, cost (monetary, environmental, pre-existing infrastructure) of distribution, compression, cooling must be taken into account.

===Inherent advantages/disadvantages between autogas (LPG) power and NGV===
[[Autogas]], also known as LPG, has different chemical composition, but still a petroleum based gas, has a number of inherent advantages and disadvantages, as well as noninherent ones. The inherent advantage of autogas over CNG is that it requires far less compression (20% of CNG cost),<ref>{{cite web |url=http://www.energ2.com/home/applications/adsorbed-natural-gas.html |title=Archived copy |accessdate=2013-08-08 |deadurl=yes |archiveurl=https://web.archive.org/web/20131010015546/http://www.energ2.com/home/applications/adsorbed-natural-gas.html |archivedate=2013-10-10 |df= }}</ref> is denser as it is a liquid at room temperature, and thus requires far cheaper tanks (consumer) and fuel compressors (provider) than CNG. As compared to LNG, it requires no chilling (and thus less energy), or problems associated with extreme cold such as [[frostbite]]. Like NGV, it also has advantages over gasoline and diesel in cleaner emissions, along with less wear on engines over gasoline. The major drawback of LPG is its safety. The fuel is volatile and the fumes are heavier than air, which causes them to collect in a low spot in the event of a leak, making it far more hazardous to use and more care is needed in handling. Besides this, LPG (40% from Crude Oil refining) is more expensive than Natural Gas.

====Current advantages of LPG power over NGV====
In places like the US, Thailand, and India, there are five to ten times more stations thus making the fuel more accessible than NGV stations. Other countries like Poland, South Korea, and Turkey, LPG stations and autos are widespread while NGVs are not. In addition, in some countries such as Thailand, the retail LPG fuel is considerably cheaper in cost.

===Future possibilities===
Though ANG (adsorbed natural gas) has not yet been used in either providing stations nor consumer storage tanks, its low compression (500psi vs 3600 psi)<ref>http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/41_1_NEW%20ORLEANS_03-96_0246.pdf</ref> has the potential to drive down costs of NGV infrastructure and vehicle tanks.

==LNG fueled vehicles==

===Use of LNG to fuel large over-the-road trucks===
LNG is being evaluated and tested for over-the-road trucking,<ref>{{cite web| url=https://www.ngvamerica.org/vehicles/for-fleets/over-the-road/| title=Over the Road LNG vehicles in USA| accessdate=17 April 2015}}</ref> off-road,<ref>{{cite web| url=https://www.ngvamerica.org/vehicles/high-horsepower/| title= High horse power off-road LNG vehicles in USA| accessdate=17 April 2015}}</ref> marine, and railroad applications.<ref>{{cite web| url=https://af.reuters.com/article/commoditiesNews/idAFL6N0QI1Q920140812?sp=true| title=Next energy revolution will be on roads and railroads| accessdate=17 April 2015}}</ref> There are known problems with the fuel tanks and delivery of gas to the engine.<ref>{{cite web| url=http://www.cryogenicfuelsinc.com/tanks/systemAnalysis.cfm| title=LNG Tank System Analysis| accessdate=17 April 2015}}</ref>

China has been a leader in the use of LNG vehicles<ref>{{cite web|url= http://member.zeusintel.com/ZLFVR/news_details.aspx?newsid=31246| title=Development of LNG Fueling Stations in China vs. in U.S.| accessdate=17 April 2015}}</ref> with over 100,000 LNG powered vehicles on the road as of 2014.<ref>{{cite web| url=https://www.bloomberg.com/news/articles/2014-07-04/choking-smog-puts-chinese-driver-in-natural-gas-fast-lane| title=Choking Smog Puts Chinese Driver in Natural Gas Fast Lane| accessdate=17 April 2015}}</ref>

In the United States, there were 69 public truck LNG fuel centres as of February 2015.<ref>{{cite web| url=http://www.afdc.energy.gov/locator/stations/results?utf8=%E2%9C%93&location=&filtered=true&fuel=LNG&owner=all&payment=all&ev_level1=true&ev_level2=true&ev_dc_fast=true&radius_miles=5| title=Alternative Fueling Station Locator in USA| accessdate=17 April 2015}}</ref> The 2013 National Trucker's Directory lists approximately 7,000 truckstops,<ref>{{cite web| url=http://www.dieselboss.com/directory_DC.htm| title=The 2013 National Trucker's Directory| accessdate=17 April 2015}}</ref> thus approximately 1% of US truckstops have LNG available.

In 2013, Dillon Transport announced they were putting 25 LNG large trucks into service in Dallas Texas. They are refueling at a public LNG fuel center.<ref>{{cite web| url=http://www.fleetsandfuels.com/fuels/ngvs/2013/05/dillon-adding-25-lng-kenworth-t800s/| title=Dillon Adding 25 LNG Kenworth| accessdate=17 April 2015| archive-url=https://web.archive.org/web/20150410173419/http://www.fleetsandfuels.com/fuels/ngvs/2013/05/dillon-adding-25-lng-kenworth-t800s/| archive-date=2015-04-10| dead-url=yes| df=}}</ref> The same year Raven Transportation announced they were buying 36 LNG large trucks to be fueled by Clean Energy Fuels locations<ref>{{cite web|url= http://www.ngvjournal.com/clean-energy-commits-to-fueling-36-new-heavy-duty-lng-powered-trucks/|archive-url= https://web.archive.org/web/20160603031545/http://www.ngvjournal.com/clean-energy-commits-to-fueling-36-new-heavy-duty-lng-powered-trucks/|dead-url= yes|archive-date= 2016-06-03|title= Clean Energy commits to serving 36 new heavy-duty LNG-powered trucks}}</ref> and Lowe's finished converting one of its dedicated fleets to LNG fueled trucks.<ref>{{cite web| url=http://media.lowes.com/pr/2013/10/17/lowes-launches-natural-gas-powered-truck-fleet-at-texas-rdc/| title=Lowe’s Launches Natural Gas-Powered Truck Fleet At Texas RDC| accessdate=17 April 2015}}</ref>

UPS had over 1200 LNG fueled trucks on the roads in February 2015.<ref>{{cite web| url=http://www.ups.com/pressroom/us/press_releases/press_release/Press+Releases/Archive/2015/Q1/ci.Legislation+Introduced+by+Senators+Bennet+and+Burr+Would+End+the+Disparity+in+the+way+LNG+and+LPG+are+Taxed.syndication| title=Legislation Would End the Disparity in the way LNG and LPG are Taxed| accessdate=17 April 2015| archive-url=https://web.archive.org/web/20150402150742/http://www.ups.com/pressroom/us/press_releases/press_release/Press+Releases/Archive/2015/Q1/ci.Legislation+Introduced+by+Senators+Bennet+and+Burr+Would+End+the+Disparity+in+the+way+LNG+and+LPG+are+Taxed.syndication| archive-date=2 April 2015| dead-url=yes| df=dmy-all}}</ref> UPS has 16,000 tractor trucks in its fleet, and 60 of the new for 2014 large trucks will be placed in service in the Houston, Texas area, where UPS is building its own private LNG fuel center to avoid the lines at retail fuel centers.<ref>{{cite web| url=http://www.bizjournals.com/houston/blog/drilling-down/2014/06/new-lng-trucking-fleet-launches-in-houston.html?page=all| title=New LNG trucking fleet launches in Houston| accessdate=17 April 2015}}</ref> In Amarillo, Texas and Oklahoma City, Oklahoma, UPS is using public fuel centers.<ref>{{cite web|url= http://ttnews.com/articles/basetemplate.aspx?storyid=34594&t=Clean-Energy-Opens-Two-LNG-Highway-Stations| title=Clean Energy Opens Two LNG Highway Stations| accessdate=17 April 2015}}</ref>

Clean Energy Fuels has opened several public LNG Fuel Lanes along I-10 and claims that as of June 2014 LNG fueled trucks can use the route from Los Angeles, California to Houston, Texas by refueling exclusively at Clean Energy Fuels public facilities.<ref>{{cite web|url= http://investors.cleanenergyfuels.com/releasedetail.cfm?ReleaseID=854991| title=Clean Energy Opens Interstate 10 Highway Between Los Angeles and Houston to LNG Fueling| accessdate=17 April 2015}}</ref> In 2014 Shell and Travel Centers of America opened the first of a planned network of U.S. truck stop LNG stations in Ontario, California.<ref>{{cite web| url=http://www.fleetsandfuels.com/fuels/ngvs/2014/05/shell-opens-its-first-u-s-lng-lanes/| title=Shell, TA Open Their First U.S. LNG| accessdate=17 April 2015| archive-url=https://web.archive.org/web/20150410175127/http://www.fleetsandfuels.com/fuels/ngvs/2014/05/shell-opens-its-first-u-s-lng-lanes/| archive-date=2015-04-10| dead-url=yes| df=}}</ref> Per the alternative fuel fuelling centre tracking site there are 10 LNG capable public fuel stations in the greater Los Angeles area, making it the single most penetrated metro market. As of February 2015, Blu LNG has at least 23 operational LNG capable fuel centers across 8 states,<ref>{{cite web| url=http://www.blustations.com/| title=The Future of Fuel Starts Here| accessdate=17 April 2015| archive-url=https://web.archive.org/web/20150410213814/http://www.blustations.com/| archive-date=10 April 2015| dead-url=yes| df=dmy-all}}</ref> and Clean Energy had 39 operational public LNG facilities.<ref>{{cite web|url= http://www.cnglngstations.com/| title= LNG Station locator| accessdate=17 April 2015}}</ref>

As can be seen at the alternative fuel fueling center tracking site, as of early 2015 there is void of LNG fuel centers, public and private, from Illinois to the Rockies.<ref>{{cite web| url=http://www.afdc.energy.gov/locator/stations/results?utf8=%E2%9C%93&location=&fuel=LNG&private=false&private=true&planned=false&owner=all&payment=all&radius=false&radius_miles=5&lng_vehicle_class=all| title=Shell, TA Open Their First U.S. LNG| accessdate=17 April 2015}}</ref> A Noble Energy LNG production plant in northern Colorado was planned to go online in 1st quarter 2015<ref>{{cite web|url= http://www.lngworldnews.com/nobles-colorado-lng-facility-moving-forward/| title= Noble's LNG facility in Colorado remains on schedule| accessdate=17 April 2015}}</ref> and to have a capacity of 100,000 gallons of LNG per day for on-road, off-road, and drilling operations.<ref>{{cite web|url= http://www.lngworldnews.com/noble-energy-to-build-lng-plant-in-colorado-usa/| title=Noble Energy to Build LNG Plant in Colorado, USA| accessdate=17 April 2015}}</ref>

As of 2014, LNG fuel and NGV's had not achieved much usage in Europe.<ref>{{cite web|url= http://www.returnloads.net/news/lng-fuel-unlikely-fuel-of-choice-for-europe| title=LNG fuel unlikely to be fuel of choice for Europe| accessdate=17 April 2015}}</ref>

American Gas & Technology pioneered use of onsite liquefaction using van sized station to access Natural Gas from utility pipe and clean, liquefy, store and dispense it. Their stations make 300-5,000 gallons of LNG per day.

===Use of LNG to fuel high-horsepower/high-torque engines===

In internal combustion engines the volume of the cylinders is a common measure of the power of an engine. Thus a 2000cc engine would typically be more powerful than a 1800cc engine, but that assumes a similar air-fuel mixture is used.

If, via a turbocharger as an example, the 1800cc engine were using an air-fuel mixture that was significantly more energy dense, then it might be able to produce more power than a 2000cc engine burning a less energy dense air-fuel mixture. However, turbochargers are both complex and expensive. Thus it becomes clear for high-horsepower/high-torque engines a fuel that can inherently be used to create a more energy dense air-fuel mixture is preferred because a smaller and simpler engine can be used to produce the same power.

With traditional gasoline and diesel engines the energy density of the air-fuel mixture is limited because the liquid fuels do not mix well in the cylinder. Further, gasoline and diesel auto-ignite<ref>[[Autoignition temperature]]</ref> at temperatures and pressures relevant to engine design. An important part of traditional engine design is designing the cylinders, compression ratios, and fuel injectors such that pre-ignition is avoided,<ref>[[Engine knocking#Pre-ignition]]</ref> but at the same time as much fuel as possible can be injected, become well mixed, and still have time to complete the combustion process during the power stroke.

Natural gas does not auto-ignite at pressures and temperatures relevant to traditional gasoline and diesel engine design, thus providing more flexibility in the design of a natural gas engine. Methane, the main component of natural gas, has an autoignition temperature of 580C/1076F,<ref>{{cite web| url=http://www.engineeringtoolbox.com/fuels-ignition-temperatures-d_171.html| title=Fuels and Chemicals - Autoignition Temperatures| accessdate=17 April 2015}}</ref> whereas gasoline and diesel autoignite at approximately 250C and 210C respectively.

With a compressed natural gas (CNG) engine, the mixing of the fuel and the air is more effective since gases typically mix well in a short period of time, but at typical CNG compression pressures the fuel itself is less energy dense than gasoline or diesel thus the end result is a lower energy dense air-fuel mixture. Thus for the same cylinder displacement engine, a non turbocharged CNG powered engine is typically less powerful than a similarly sized gasoline or diesel engine. For that reason, turbochargers are popular on European CNG cars.<ref>{{cite web| url=http://wardsauto.com/ar/turbocharing_cng_europe_100308| title=Turbocharging Boosting Demand for CNG Vehicles in Europe| accessdate=17 April 2015}}</ref> Despite that limitation, the 12 liter Cummins Westport ISX12G engine<ref>{{cite web| url=http://www.cumminswestport.com/models/isx12-g| title=Cummins Westport ISX12 G natural gas engine| accessdate=17 April 2015}}</ref> is an example of a CNG capable engine designed to pull tractor/trailer loads up to 80,000 lbs showing CNG can be used in most if not all on-road truck applications. The original ISX G engines incorporated a turbocharger to enhance the air-fuel energy density.<ref>{{cite web| url=http://www.afdc.energy.gov/pdfs/36252.pdf| title=Development of the High-Pressure Direct-Injection ISX G Natural Gas Engine| accessdate=17 April 2015}}</ref>

LNG offers a unique advantage over CNG for more demanding high-horsepower applications by eliminating the need for a turbocharger. Because LNG boils at approximately -160C, using a simple heat exchanger a small amount of LNG can be converted to its gaseous form at extremely high pressure with the use of little or no mechanical energy. A properly designed high-horsepower engine can leverage this extremely high pressure energy dense gaseous fuel source to create a higher energy density air-fuel mixture than can be efficiently created with a CNG powered engine. The end result when compared to CNG engines is more overall efficiency in high-horsepower engine applications when high-pressure direct injection technology is used. The Westport HDMI2<ref>{{cite web| url=http://www.westport.com/is/core-technologies/hpdi-2| title=WESTPORT HPDI 2.0 LNG engine| accessdate=17 April 2015}}</ref> fuel system is an example of a high-pressure direct injection technology that does not require a turbocharger if teamed with appropriate LNG heat exchanger technology. The Volvo Trucks 13-liter LNG engine<ref>{{cite web| url=http://www.lngworldnews.com/volvo-trucks-north-america-to-launch-lng-engine/| title=Volvo Trucks North America to Launch LNG Engine| accessdate=17 April 2015}}</ref> is another example of a LNG engine leveraging advanced high pressure technology.

Westport recommends CNG for engines 7 liters or smaller and LNG with direct injection for engines between 20 and 150 liters. For engines between 7 and 20 liters either option is recommended. See slide 13 from their NGV BRUXELLES – INDUSTRY INNOVATION SESSION presentation<ref>{{cite web| url=http://www.ngvaeurope.eu/downloads/NGV_2014_BRUSSELS/1._Roberto_Defilippi.pdf| title=An innovative vision for LNG Fuel System for MD Diesel Dual Fuel Engine(DDF+LNG)| accessdate=17 April 2015}}</ref>

High horsepower engines in the oil drilling, mining, locomotive, and marine fields have been or are being developed. Paul Blomerous has written a paper<ref>{{cite web| url=http://www.gastechnology.org/Training/Documents/LNG17-proceedings/7-4-Paul_Blomerus.pdf| title=LNG AS A FUEL FOR DEMANDING HIGH HORSEPOWER ENGINE APPLICATIONS: TECHNOLOGY AND APPROACHES| accessdate=17 April 2015}}</ref> concluding as much as 40 million tonnes per annum of LNG (approximately 26.1 billion gallons/year or 71 million gallons/day) could be required just to meet the global needs of the high-horsepower engines by 2025 to 2030.

As of the end of 1st quarter 2015 Prometheus Energy Group Inc claims to have delivered over 100 million gallons of LNG within the previous 4 years into the industrial market,<ref>{{cite web| url=http://www.lngglobal.com/latest/prometheus-agreement-with-wpx-energy-to-supply-lng-and-equipment-for-drilling-operations.html| title=Prometheus agreement with WPX Energy to supply LNG and equipment for drilling operations| accessdate=17 April 2015| deadurl=yes| archiveurl=https://web.archive.org/web/20150926033722/http://www.lngglobal.com/latest/prometheus-agreement-with-wpx-energy-to-supply-lng-and-equipment-for-drilling-operations.html| archivedate=26 September 2015| df=}}</ref> and is continuing to add new customers.

===Ships===
The {{MV|Isla Bella}} is the world's first [[LNG]] powered [[container ship]].<ref name=Schuler>{{cite news|last1=Schuler|first1=Mike|title=Introducing ISLA BELLA – World’s First LNG-Powered Containership Launched at NASSCO|publisher=gCaptain|date=19 April 2015}}</ref> LNG carriers are sometimes powered by the boil-off of LNG from their storage tanks, although Diesel powered LNG carriers are also common to minimize loss of cargo and enable more versatile refueling.

===Aircraft===
[[Aviation fuel#LNG|Some airplanes]] use LNG to power their turbofans. Aircraft are particularly sensitive to weight and much of the weight of an aircraft goes into fuel carriage to allow the range. The low energy density of natural gas even in liquid form compared to conventional fuels give it a distinct disadvantage for flight applications.

== Chemical composition and energy content ==

=== Chemical composition ===

The primary component of [[natural gas]] is [[methane]] ([[carbon|C]][[hydrogen|H]]4), the shortest and lightest [[hydrocarbon]] molecule. It may also contain heavier gaseous hydrocarbons such as [[ethane]] ([[carbon|C]]2[[hydrogen|H]]6), [[propane]] ([[carbon|C]]3[[hydrogen|H]]8) and [[butane]] ([[carbon|C]]4[[hydrogen|H]]10), as well as other gases, in varying amounts. [[Hydrogen sulfide]] ([[hydrogen|H]]2[[sulfur|S]]) is a common contaminant, which must be removed prior to most uses.

===Energy content===

[[Combustion]] of one cubic meter yields 38 MJ (10.6 kWh). Natural gas has the highest energy/carbon ratio of any fossil fuel, and thus produces less carbon dioxide per unit of energy.

== Storage and transport ==

===Transport===

The major difficulty in the use of natural gas is [[transport]]ation. Natural gas [[pipeline transport|pipelines]] are economical and common on land and across medium-length stretches of water (like [[Langeled pipeline|Langeled]], [[Interconnector (North Sea)|Interconnector]] and [[Trans-Mediterranean Pipeline]]), but are impractical across large oceans. Liquefied natural gas ([[LNG]]) [[LNG carrier|tanker ships]], railway tankers, and [[tank truck]]s are also used.

===Storage===
[[File:Storage Density of Natural Gas.jpg|thumb|storage density of natural gas]]
CNG is typically stored in steel or [[composite overwrapped pressure vessel|composite containers]] at high pressure (3000 to 4000 psi, or 205 to 275 bar). These containers are not typically temperature controlled, but are allowed to stay at local ambient temperature. There are many standards for CNG cylinders, the most popular one is ISO 11439.<ref>{{cite web | url = http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=33298 | title = ISO 11439:2000, Gas cylinders -- High pressure cylinders for the on-board storage of natural gas as a fuel for automotive vehicles |publisher = ISO ([[International Organization for Standardization]])}}</ref><ref>{{cite web|url=http://www.iso11439.com |title=ISO 11439 Overview and FAQ |deadurl=yes |archiveurl=https://web.archive.org/web/20110713063142/http://www.iso11439.com/ |archivedate=July 13, 2011 }}</ref> For North America the standard is ANSI NGV-2.

LNG storage pressures are typically around 50-150 psi, or 3 to 10 bar. At atmospheric pressure, LNG is at a temperature of -260 °F (-162 °C), however, in a vehicle tank under pressure the temperature is slightly higher (see [[saturated fluid]]). Storage temperatures may vary due to varying composition and storage pressure. LNG is far denser than even the highly compressed state of CNG. As a consequence of the low temperatures, vacuum insulated storage tanks typically made of stainless steel are used to hold LNG.

CNG can be stored at lower pressure in a form known as an ANG ([[Adsorbed]] Natural Gas) tank at 35 bar (500 psi, the pressure of gas in natural gas pipelines) in various sponge like materials, such as [[activated carbon]]<ref>{{cite press release | date = February 16, 2007 | title = From Farm Waste to Fuel Tanks |url = https://www.nsf.gov/news/news_summ.jsp?cntn_id=108390 |publisher = US [[National Science Foundation]] (NSF)}}</ref> and [[metal-organic framework]]s (MOFs).<ref>{{cite journal | url = http://pubs.acs.org/doi/full/10.1021/ja0771639 | publisher = US [[National Science Foundation]] (NSF) | journal = Journal of the American Chemical Society | title = Metal-Organic Framework from an Anthracene Derivative Containing Nanoscopic Cages Exhibiting High Methane Uptake | author=Shengqian Ma |author2=Daofeng Sun |author3=Jason M. Simmons |author4=Christopher D. Collier |author5=Daqiang Yuan |author6=Hong-Cai Zhou | year = 2008 |volume = 130 |issue = 3 |pages = 1012–1016 | doi = 10.1021/ja0771639 | pmid=18163628}}</ref> The fuel is stored at similar or greater energy density than CNG. This means that vehicles can be refuelled from the natural gas network without extra gas compression, the fuel tanks can be slimmed down and made of lighter, less strong materials.

=== Conversion kits ===
Conversion kits for gasoline or diesel to LNG/CNG are available in many countries, along with the labor to install them. However, the range of prices and quality of conversion vary enormously.

Recently, regulations involving certification of installations in USA have been loosened to include certified private companies, those same kit installations for CNG have fallen to the $6,000+ range (depending on type of vehicle).{{Citation needed|date=February 2012}}

==Implementation==
{{Fancruft|section|date=September 2017|reason=This artilceis seriously bloated. Country-by-country breakdowns are one of the reasons this and many alternative fuel/electric vehicle articles are far too long.}}
{| style="float:right;" class="wikitable"
! colspan=6| '''Top ten countries with the largest NGV vehicle fleets - 2017<ref>http://www.ngvexpo.com/msg.php?id=1631</ref>''' (millions)
|-
!Rank||Country||Registered fleet ||Rank||Country|| Registered fleet
|-
|align=center| 1||China || style="text-align:right;"| 5.000||align=center| 6|| Brazil || style="text-align:right;"| 1.781
|-
|align=center| 2||Iran|| style="text-align:right;"| 4.000||align=center| 7|| Italy || style="text-align:right;"| 1.001
|-
|align=center| 3||India || style="text-align:right;"| 3.045||align=center| 8|| Colombia || style="text-align:right;"| 0.556
|-
|align=center| 4||Pakistan|| style="text-align:right;"| 3.000 ||align=center | 9|| Thailand || style="text-align:right;"| 0.474
|-
|align=center| 5||Argentina || style="text-align:right;"| 2.295||align=center| 10|| Uzbekistan || style="text-align:right;"| 0.450
|-
| align=center colspan=6| '''World Total = 24.452 million NGV vehicles'''
|}
===Overview===

Natural gas vehicles are popular in regions or countries where natural gas is abundant and where the government chooses to price CNG lower than gasoline.<ref name="TwoBillion"/> The use of natural gas began in the [[Po Valley|Po River Valley]] of [[Italy]] in the 1930s, followed by [[New Zealand]] in the 1980s, though its use has declined there. At the peak of New Zealand's natural gas use, 10% of the nation's cars were converted, around 110,000 vehicles.<ref name="TwoBillion"/> In the United States CNG powered buses are the favorite choice of several [[public transit]] agencies, with a fleet of more than 114,000 vehicles, mostly buses.<ref name="GreenCar">{{cite web|url=http://www.greencarcongress.com/2009/10/forecast-17m-natural-gas-vehicles-worldwide-by-2015.html#more|title=Forecast: 17M Natural Gas Vehicles Worldwide by 2015|author=Pike Research|date=2009-10-19|publisher=[[Green Car Congress]]|accessdate=2009-10-19}}</ref> India, Australia, Argentina, and Germany also have widespread use of natural gas-powered buses in their public transportation fleets.<ref name="TwoBillion"/>

===Europe===
[[File:Brescia Trasporti Iveco CityClass 632 via Sardegna 20120828.JPG|thumb|CNG-powered bus in Italy ]]
[[File:CNG-powered buses in Horlivka, Ukraine.tif|thumb|CNG-powered buses in [[Horlivka]], eastern Ukraine ]]

====Germany====
Germany hit the milestone of 900 CNG filling stations nationwide in December 2011. Gibgas, an independent consumer group, estimates that 21% of all CNG filling stations in the country offer a natural gas/[[biomethane]] mix to varying ratios, and 38 stations offer pure biomethane.<ref>{{cite web|url=http://www.ngvglobal.com/900th-cng-filling-station-for-germany-1221|title=900th CNG Filling Station for Germany|author=Gibgas|publisher=NGV Global News|date=2011-12-21|accessdate=2011-12-28}}</ref>

==== Greece ====
[[Greece]] uses natural gas buses for public transport in [[Athens]].
Also the Public Gas Company (DEPA) has a network of 11 stations (as of 2017), under brand "Fisikon", and plans more stations in next 5 years.

====Ireland====
[[Bus Éireann]] Introduced the first [[NGV]] on 17 July 2012. It will operate on the 216 city centre to Mount Oval, Rochestown, route until mid-August on a trial being undertaken in partnership with [[Ervia]]. The Eco-city bus is made by [[MAN SE|MAN]].<ref>{{cite news | url = http://www.irishexaminer.com/archives/2012/0717/ireland/natural-gas-bus-hits-the-streets-in-bid-to-cut-fuel-bill-201037.html| title = Natural gas bus hits the streets in bid to cut fuel bill | first = Eoin |last = English | date = July 17, 2012 | newspaper = Irish Examiner }}</ref>

====Italy====
Natural gas traction is quite popular in Italy, due to the existence of a capillar distribution network for industrial use since the late 50s and a traditionally high retail price for petrol. As of April 2012 there were about 1173 filling stations, mainly located in the northern regions,<ref>{{cite web | url = http://www.metanoauto.com/modules.php?name=Distributori | title = Distributori metano in Europa: Il primo elenco interattivo aggiornato in tempo reale, online da maggio 2006 |trans-title=Natural gas distributors in Europe: The first list is updated in real-time interactive, online since May 2006| publisher = metanoauto.com}}</ref> while the fleet reached 730,000 CNG vehicles at the end of 2010.<ref name=IANGV/>

====Ukraine====
Ukraine’s first compressed natural gas refueling station (CNGS) was commissioned in 1937. Today, there is a well-developed CNGS network across the country.<ref>{{cite web | url = http://www.apvgn.pt/documentacao/gnc_ucrania.pdf | title = Use of Compressed Natural Gas (CNG) as Motor Fuel in Ukraine, Prospects and Problems | date = 2006 | publisher = 23rd World Gas Conference, Amsterdam | authors = Igor Orlov and Volodymyr Kozak | access-date = 2014-01-06 | archive-url = https://web.archive.org/web/20140106040300/http://www.apvgn.pt/documentacao/gnc_ucrania.pdf | archive-date = 2014-01-06 | dead-url = yes | df = }}</ref> Many buses were converted to run on CNG during the 1990s, primarily for economic reasons. The retrofitted cylinders are often visible atop the vehicle's roof and/or underneath the body. Despite their age, these buses remain in service and continue to provide reliable public transport combined with the environmental benefits of CNG.

====United Kingdom====
CNG buses are beginning to be used in the UK, e.g. by [[Reading Buses]].

===North America===

With the recent increase in natural gas production due to widespread use of [[fracking]] technology, many countries, including the United States and Canada, now can be self-sufficient. Canada is a substantial net exporter of natural gas, though the United States still has a net import of natural gas.<ref>http://www.eia.gov/countries/country-data.cfm?fips=ca#ng</ref><ref>http://www.eia.gov/dnav/ng/hist/n9180us1m.htm</ref> Natural gas prices have decreased dramatically in the past few years and are likely to decrease further as additional production comes on line. However, the EIA predicts that natural gas prices will start increasing in a few years as the most profitable natural gas reserves are used up.<ref>{{Citation | url = http://www2.hmc.edu/~evans/AEO2012.pdf | title = Annual Energy Outlook 2012 | date = June 2012 | page = 91 }}{{Dead link|date=August 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Natural gas prices have decreased from $13 per mmbtu (USD) in 2008 to $3 per mmbtu (USD) in 2012.<ref>{{Cite web | url = http://www.infomine.com/investment/metal-prices/natural-gas/all/ | title = Historical Natural Gas Prices and Price Chart | publisher = InfoMine Inc. | accessdate = 24 November 2012}}</ref> It is likely therefore that natural gas-powered vehicles will be increasingly cheaper to run relative to gasoline-powered vehicles. The issue is how to finance the purchase and installation of conversion kits. Some support may be available through the Department of Energy. Private initiatives which essentially lease the conversion equipment in exchange for slightly higher natural gas refueling can be self-financing and offer considerable advantages to liquidity strapped consumers.{{citation needed|date=August 2012}}

====Canada====

[[File:Hamilton Street Railway 510213 wide.jpg|thumb|CNG-powered bus in [[Hamilton, Ontario]]]]

Natural Gas has been used as a motor fuel in Canada for over 20 years.<ref>{{Citation
| url = http://www.transportation.alberta.ca/Content/docType57/Production/NGVBrief.pdf | title = NATURAL GAS VEHICLES IN ALBERTA | first = Lawrence |last = Schmidt | first2=Jason |last2 = Politylo | first3=Sarah |last3 = Pinto | publisher = Government of Alberta, Infrastructure Policy and Planning | date = November 2005}}</ref> With assistance from federal and provincial research programs, demonstration projects, and NGV market deployment programs during the 1980s and 1990s, the population of light-duty NGVs grew to over 35,000 by the early 1990s. This assistance resulted in a significant adoption of natural gas transit buses as well.<ref name="iangv.org">{{citation|publisher=International Association for Natural Gas Vehicles |year=2010 |title=Natural Gas Vehicles Statistics |url=http://www.iangv.org/tools-resources/statistics.html |deadurl=yes |archiveurl=https://web.archive.org/web/20100110101111/http://www.iangv.org/tools-resources/statistics.html |archivedate=January 10, 2010 }}</ref> The NGV market started to decline after 1995, eventually reaching today’s vehicle population of about 12,000.<ref name="iangv.org"/>

This figure includes 150 urban transit buses, 45 school buses, 9,450 light-duty cars and trucks, and 2,400 forklifts and ice-resurfacers. The total fuel use in all NGV markets in Canada was 1.9 petajoules (PJs) in 2007 (or 54.6 million litres of gasoline litres equivalent), down from 2.6 PJs in 1997. Public CNG refuelling stations have declined in quantity from
134 in 1997 to 72 today. There are 22 in British Columbia, 12 in Alberta, 10 in Saskatchewan, 27 in
Ontario, and 1 in Québec. There are only 12 private fleet stations.<ref>{{citation | url = http://oee.nrcan.gc.ca/sites/oee.nrcan.gc.ca/files/pdf/transportation/alternative-fuels/resources/pdf/roadmap.pdf | title = Natural Gas Use in the Canadian Transportation Sector | author = Natural Gas Use in Transportation Roundtable | date = December 2010 | publisher = Canadian Natural Gas Vehicle Alliance}}</ref>

====United States====
[[File:Metrobus powered with CNG 5198 DCA 03 2009.jpg|thumb|Buses powered with [[Compressed natural gas|CNG]] are common in the United States ]]
As of December 2009, the U.S. had a fleet of 114,270 [[compressed natural gas]] (CNG) vehicles, 147,030 vehicles running on [[liquefied petroleum gas]] (LPG), and 3,176 vehicles running on [[liquefied natural gas]] (LNG).<ref name=USeDataBook>{{cite web|url=http://cta.ornl.gov/data/tedb30/Edition30_Full_Doc.pdf|title=Transportation Energy Data Book: Edition 30|author1=Stacy C. Davis|author2=Susan W. Diegel|author3=Robert G. Boundy|last-author-amp=yes|publisher=Office of Energy Efficiency and Renewable Energy, [[U.S. Department of Energy]]|date=June 2011|accessdate=2011-08-27|deadurl=yes|archiveurl=https://web.archive.org/web/20110928135644/http://cta.ornl.gov/data/tedb30/Edition30_Full_Doc.pdf|archivedate=2011-09-28|df=}} See Tables 6.1 and 6.5, pp. 6-3 and 6-8.</ref> The NGV fleet is made up mostly of transit buses but there are also some government fleet cars and vans, as well as increasing number of corporate trucks replacing diesel versions, most notably [[Waste Management, Inc]] and [[United Parcel Service|UPS]] trucks. As of 12-Dec-2013 Waste Management has a fleet of 2000 CNG Collection trucks; as of 12-Dec-2013 UPS has 2700 alternative fuel vehicles. As of February 2011, there were 873 CNG refueling sites, 2,589 LPG sites, and 40 LNG sites, led by [[California]] with 215 CNG refueling stations in operation, 228 LPG sites and 32 LNG sites. The number of refueling stations includes both public and private sites, and not all are available to the public.<ref name=USeDataBook/> As of December 2010, the U.S. ranked 6th in the world in terms of number of NGV stations.<ref name=IANGV/> Currently there are 160,000 NGVs operating in the country.

====Mexico====
The natural gas vehicle market is limited to fleet vehicles and other public use vehicles like minibuses in larger cities. However the state-owned bus company [[Red de Transporte de Pasajeros|RTP]] Of [[Mexico City]] has purchased 30 [[Hyundai]] Super Aero City CNG-Propelled buses to integrate with the existing fleet as well as to introduce new routes within the city.
[[File:Posto GNV 01 2009 485 CWB.jpg|thumb|CNG pumps at a Brazilian gasoline service station, [[Paraná (state)|Paraná state]].]]
[[File:SAO 09 2008 Fiat Siena TetraFuel 2 views v1.jpg|thumb|Popular among [[taxicab|taxi]] drivers, the Brazilian [[Fiat Siena|Fiat Siena Tetrafuel]] 1.4, is a [[multifuel]] car that runs as a [[flexible-fuel vehicle|flexible-fuel]] on pure [[gasoline]], or [[w:Common ethanol fuel mixtures#E20, E25|E20-E25 blend]], or pure ethanol ([[w:Common ethanol fuel mixtures#E100|E100]]); or runs as a [[bi-fuel vehicle|bi-fuel]] with [[Compressed natural gas|natural gas (CNG)]]. Below: the CNG storage tanks in the trunk.]]

===South America===

====Overview====
CNG vehicles are common in South America, with a 35% share of the worldwide NGV fleet,<ref name=IANGV/> where these vehicles are mainly used as [[taxicab]]s in main cities of Argentina and Brazil. Normally, standard gasoline vehicles are retrofitted in specialized shops, which involve installing the gas cylinder in the trunk and the CNG injection system and electronics.

As of 2009 Argentina had 1,807,186 NGV's with 1,851 refueling stations across the nation,<ref name=IANGV/> or 15% of all vehicles;<ref name="LatinGNV">{{cite web|url=http://www.ngvglobal.com/en/country-reports/latin-america-ngvs-an-update-report-02074.html |archive-url=https://archive.is/20081120221031/http://www.ngvglobal.com/en/country-reports/latin-america-ngvs-an-update-report-02074.html |dead-url=yes |archive-date=2008-11-20 |title=Latin America NGVs: An Update Report |author=R. Fernandes |publisher=International Association of Natural Gas Vehicles |date=2008-08-20 |accessdate=2008-10-11 }}</ref> and Brazil had 1,632,101 vehicles and 1,704 refueling stations,<ref name=IANGV/> with a higher concentration in the cities of [[Rio de Janeiro]] and [[São Paulo]].<ref name="GNVNews">{{cite web|url=http://www.bigas.com.br/sistema/?modulo=gnvnews&acao=abrir&id=22|title=Montadores Investem nos Carros á GNV|author=GNVNews|publisher=Institutio Brasileiro de Petroleo e Gas|date=November 2006|accessdate=2008-09-20|language=Portuguese|deadurl=yes|archiveurl=https://web.archive.org/web/20081211175309/http://www.bigas.com.br/sistema/?modulo=gnvnews&acao=abrir&id=22|archivedate=2008-12-11|df=}}</ref><ref name="LatinGNV"/>

Colombia had an NGV fleet of 300,000 vehicles, and 460 refueling stations as of 2009.<ref name=IANGV/> [[Bolivia]] has increased its fleet from 10,000 in 2003 to 121,908 units in 2009, with 128 refueling stations.<ref name=IANGV/>

Peru had 81,024 NGVs and 94 fueling stations as 2009,.<ref name=IANGV/> In Peru, several factory-built CNVs have the tanks installed under the body of the vehicle, leaving the trunk free. Among the models built with this feature are the [[Fiat Multipla]], the new [[Fiat Panda]], the [[Volkswagen Touran]] Ecofuel, the [[Volkswagen Caddy]] Ecofuel, and the Chevy Taxi. Right now, Peru has 224,035 NGVs.

Other countries with significant NGV fleets are [[Venezuela]] (226,100) as of 2017 and [[Chile]] (15,000) as of 2017.<ref name=IANGV/>

====Latest developments====
[[GM do Brasil]] introduced the MultiPower engine in August 2004 which was capable of using CNG, alcohol and gasoline as fuel. The GM engine has electronic fuel injection that automatically adjusts to any acceptable fuel configuration. This motor was used in the [[Opel Astra|Chevrolet Astra]] and was aimed at the taxi market.<ref name="GNVNews"/>

In 2006 the Brazilian subsidiary of [[Fiat]] introduced the [[Fiat Siena|Fiat Siena Tetra fuel]], a four-fuel car developed under [[Magneti Marelli]] of [[Fiat]] Brazil.<ref name="TreeH">{{cite web|url=http://www.treehugger.com/files/2006/08/Fiat_sienna_tetr.php|title= Fiat Siena Tetra Power: Your Choice of Four Fuels |publisher=Treehugger|author= Christine Lepisto|date=2006-08-27 |accessdate=2008-08-24|language= }}</ref><ref>{{cite web| url=http://news.caradisiac.com/Nouvelle-Fiat-Siena-2008-sans-complexe-359 |title=Nouvelle Fiat Siena 2008: sans complexe |publisher=Caradisiac | date=2007-11-01| accessdate=2008-08-31 | language=French }} {{fr icon}}</ref> This automobile can run on 100% ethanol ([[w:Common ethanol fuel mixtures#E100|E100]]), [[w:Common ethanol fuel mixtures#E20, E25|E20 to E25]] blend (Brazil's normal ethanol gasoline blend), pure gasoline (not available in Brazil), and natural gas, and switches from the gasoline-ethanol blend to CNG automatically, depending on the power required by road conditions.<ref>{{cite web |url=http://www.webmotors.com.br/wmpublicador/Noticias_Conteudo.vxlpub?hnid=36391 |author=Agência AutoInforme |title=Siena Tetrafuel vai custar R$ 41,9 mil |publisher=WebMotor |date=2006-06-19 |accessdate=2008-08-14 |language=Portuguese |deadurl=yes |archiveurl=https://web.archive.org/web/20081210211007/http://www.webmotors.com.br/wmpublicador/Noticias_Conteudo.vxlpub?hnid=36391 |archivedate=2008-12-10 |df= }} {{pt icon}}The article argues that even though Fiat called it tetra fuel, it actually runs on three fuels: natural gas, ethanol, and gasoline.</ref>

Since 2003 and with the commercial success of flex cars in Brazil, another existing option is to [[retrofit]] an ethanol [[flexible-fuel vehicle]] to add a natural gas tank and the corresponding injection system. Some [[taxicab]]s in [[São Paulo]] and [[Rio de Janeiro]], Brazil, run on this option, allowing the user to choose among three fuels (E25, E100 and CNG) according to current market prices at the pump. Vehicles with this adaptation are known in Brazil as '''tri-fuel''' cars.<ref>{{cite web|url=http://www.devanagari.com.br/taxinews.com.br/pag/noticia_02_resumos.asp?regn=36|title=Gás Natural Veicular|publisher=TDenavagari.com.br|author=TaxiNews|date=|accessdate=2008-08-24|language=Portuguese}}{{dead link|date=September 2017 |bot=InternetArchiveBot |fix-attempted=yes }} {{pt icon}}</ref>

===South Asia===

====Pakistan====
[[Pakistan]] was the country with the second largest fleet of NGV with a total of 2.85 million by the end of 2011.<ref>{{cite web | url = http://www.ngvc.org/about_ngv/index.html | title = About NGVs | publisher = Natural Gas Vehicles for America | accessdate = 24 November 2012}}</ref> Most of the public transportation fleet has been converted to CNG.<ref>{{cite news|url=http://www.thenews.com.pk/TodaysPrintDetail.aspx?ID=35323&Cat=5&dt=3/10/2011|title=CNG cylinders or moving bombs?|author=Shahab Ansari|work=International The News|date=2011-03-10|accessdate=2011-04-05}}</ref> Also, in Pakistan and India,<ref>{{cite news| url=http://www.hindu.com/2009/11/08/stories/2009110859560300.htm | location=Chennai, India | work=The Hindu | title=CNG shortage puts auto drivers in a fix | date=2009-11-08}}</ref><ref>{{cite news | url = http://www.rediff.com/news/slide-show/slide-show-1-gas-shortage-hits-mumbai/20110315.htm | title = Gas shortage hits Mumbai; Taxis, autos off roads | date = March 15, 2011 |publisher = Rediff.com}}</ref> there have been on-going (last several years now) series of CNG fuel shortages which periodically waxes and wanes, getting the fuel into a tank can be a major problem. In July 2011, petrol usage shot up 15% from the month before due to shortages.<ref>{{cite news | url = http://www.dailytimes.com.pk/default.asp?page=2011%5C08%5C12%5Cstory_12-8-2011_pg5_2 | newspaper = Daily Times | date = August 12, 2011 | title = Petrol sales at record high in July owing to CNG shortage | location = Karachi, Pakistan}}</ref> Pakistan also has reported that over 2,000 people have died in 2011 from CNG cylinder blasts, because of low quality of cylinders there.<ref>{{cite news | url = http://www.thenews.com.pk/Todays-News-4-102120-Over-2000-killed-in-CNG-cylinder-blasts-in-2011-report | location = Karachi, Pakistan | title = Over 2,000 killed in CNG cylinder blasts in 2011: report | first = M. Waqar | last = Bhatti | date = April 10, 2012 | newspaper = The News International}}</ref> In 2012, the Pakistani government took the decision to gradually phase out CNG sector altogether beginning by banning any new conversions to CNG and banning the manufacturing of new NGV's. In addition the government plans to close down all refueling stations in the next 3 years.<ref>{{cite news |url = http://tribune.com.pk/story/415090/time-is-up-government-to-wipe-out-cng-sector-gradually/ | title = Time is up: Government to wipe out CNG sector gradually | date = July 31, 2012 | newspaper = The Express Tribune | location = Lahore, Pakistan}}</ref><ref>{{cite news | url = http://www.nation.com.pk/pakistan-news-newspaper-daily-english-online/business/02-Oct-2012/govt-to-put-an-end-to-cng-industry-in-phases-asim | title = Govt to put an end to CNG industry in phases: Asim | first = Imran Ali | last = Kundi | date = October 2, 2012 | location = Islamabad, Pakistan | newspaper = The Nation | access-date = 2012-10-08 | archive-url = https://web.archive.org/web/20121009050329/http://www.nation.com.pk/pakistan-news-newspaper-daily-english-online/business/02-Oct-2012/govt-to-put-an-end-to-cng-industry-in-phases-asim | archive-date = 2012-10-09 | dead-url = yes | df = }}</ref>

====India====
[[File:CNG filling station, Delhi.JPG|thumb|A CNG powered car being filled in a filling station in Delhi]]
In 1993, CNG had become available in [[Delhi]], India's capital, though LPG is what really took off due to its inherently far lower capital costs. Compressed Natural Gas is a domestic energy produced in Western parts of India. In India, most CNG vehicles are dual fueled, which means they can run both on CNG and gasoline. This makes it very convenient and users can drive long distances without worrying about availability of natural gas (as long as gasoline is available). As of December 2010 India had 1,080,000 NGVs and 560 fueling stations, many of the older ones being LPG rather than CNG.<ref name=IANGV/> In addition, it is thought that more illegally converted LPG autos than legal ones ply the streets in India, some estimates are as high as 15 million "autos" (running the gamut of everything from LPG motored pedal bicycles to CNG buses)<ref>{{Cite web | url = http://info.bellperformance.com/blog/bid/48368/LPG-Fueled-Vehicles-Coming-Soon | work = Blog | title = LPG Fueled Vehicles Coming Soon |publisher = Bell Performance, Inc. |date = 22 February 2011}}</ref>

In 1995, a lawyer filed a case with the [[Supreme Court of India]] under the Public Interest Litigation rule, which is part of the Constitution of India and enables any citizen to address directly the Supreme Court. The lawyer’s case was about the health risks caused by air pollution emitted from road vehicles. The Supreme Court decided that cars put into circulation after 1995 would have to run on unleaded fuel. By 1998, India was converted to 100% of unleaded fuel after the government ruled that diesel cars in India were restricted to 10,000 ppm after 1995. At the beginning of 2005, 10,300 CNG busses, 55,000 CNG three-wheelers taxis, 5,000 CNG minibuses, 10,000 CNG taxis and 10,000 CNG cars run on India’s roads (1982-2008 Product-Life Institute, Geneva). The Delhi Transport Corporation currently operates the world's largest fleet of CNG buses for public transport.<ref>{{Citation | url = http://www.product-life.org/en/archive/cng-delhi | title = CNG Delhi – the world’s cleanest public bus system running on CNG: Interview with Anumita Roychaudhary, CES | publisher = Product-Life Institute, Geneva | date = |accessdate = 25 November 2012}}</ref> Currently India stands 3rd with 3.045 million NGVs.

====Iran====
By the end of 2015, Iran had the world's largest fleet of NGV at 3.5 million vehicles. The share of compressed natural gas in the national fuel basket is more than 23%. CNG consumption by Iran’s transportation sector is around 20 million cubic meters per day.<ref>http://financialtribune.com/articles/economy-auto/32408/iran-gas-vehicle-market-projections</ref> There are 2,335 CNG stations.<ref>http://financialtribune.com/articles/energy/44382/cng-stations-top-2380-march</ref> The growth of NGV market in Iran has in large part been due to Iranian government intervention to decrease the society's dependence on gasoline. This governmental plan was implemented to reduce the effect of sanctions on Iran and make the nation's domestic market less dependent on imported gasoline.<ref>{{citation | url = http://www.iags.org/iran121206.pdf | publisher = Institute for the Analysis of Global Security (IAGS) | title = Ahmadinejad’s Gas Revolution: A Plan to Defeat Economic Sanctions | first = Anne |last = Korin |first2= Gal |last2= Luft | date = December 2006}}</ref><ref>{{cite news | title = The New Iran Sanctions: Worse Than the Old Ones | first= Gal |last= Luft | date = 11 August 2009 | newspaper = Foreign Policy | url = https://foreignpolicy.com/articles/2009/08/11/the_new_iran_sanctions_worse_than_the_old_ones | publisher = The Foreign Policy Group, LLC.}}</ref><ref>{{citation | url = http://www.iea.org/publications/freepublications/publication/natural_gas_vehicles.pdf | title = The Contribution of Natural Gas Vehicles to Sustainable Transport | year = 2010 | publisher = International Energy Agency | first = Michiel |last = Nijboer}}</ref> Iran has been manufacturing its own NGV's through local manufacturing using [[IKCO EF Engines|dedicated CNG engines]] which use gasoline only as a back up fuel. Also by 2012, Iranian manufacturers had the capacity to build 1.5 million CNG cylinders per year and therefore Iranian government has banned their imports to support the local manufacturers.<ref>{{cite web | url = http://www.jomhourieslami.com/1391/13910129/13910129_18_jomhori_islami_eghtesadi_0011.html | first = Jomhuri | last = Eslami | date = 1391-01-29 | title = بازرسي مخازن سوخت خودروهاي گازسوز در سال 91، الزامي است | trans-title = NGV fuel tanks must be inspected in 91 | access-date = 2012-04-24 | archive-url = https://web.archive.org/web/20120422050753/http://jomhourieslami.com/1391/13910129/13910129_18_jomhori_islami_eghtesadi_0011.html | archive-date = 2012-04-22 | dead-url = yes | df = }}</ref> In addition CNG in Iran costs the least compared to the rest of the world.<ref>{{cite web | title = Prices of CNG | url = http://www.cngstations.com/prices-of-cng/ | publisher = CNGStations.com | year = 2010}}</ref> In 2012, the Iranian government announced a plan to replace the traditional CNG cylinders with [[Adsorption|Adsorbed]] Natural Gas (ANG) cylinders.<ref>{{Cite news | url = http://en.trend.az/regions/iran/2065382.html | title = Iran plans to produce ANG for vehicles |location = Baku, Azerbaijan |date = 14 September 2012 | first = S. |last = Isayev |first2= T. |last2= Jafarov | publisher = Trend News Agency}}</ref><ref>{{cite news | url = http://www.azernews.az/oil_and_gas/43683.html |title = Iran plans to substitute compressed gas with ANG in vehicles | date = 14 September 2012 |publisher = AzerNews}}</ref>

===Southeast Asia===
{{update section|date=December 2016}}
[[Image:No.39.jpg|thumb|A CNG powered [[Hino Motors|Hino RU1JSSL]] bus, operated by [[Bangkok Mass Transit Authority|BMTA]] in [[Thailand]].]]

====Thailand====
[[Thailand]] has for over a 15 years run [[autogas]] taxi cabs in Bangkok,<ref name="Thailand08">{{Cite news|url=http://www.ngvglobal.com/ptt-softens-loans-for-truck-operators-over-30-million-available-0819 |archive-url=https://web.archive.org/web/20121025032527/http://www.ngvglobal.com/ptt-softens-loans-for-truck-operators-over-30-million-available-0819 |dead-url=yes |archive-date=October 25, 2012 |title=PTT Softens Loans for Truck Operators – Over $30 Million Available |date=August 19, 2008 |location=Thailand, Bangkok |publisher=NGV Global News }}</ref> though autos and buses had erroneously labelled NGV stickers on them, when in fact, were LPG fuelled.

In view of a generous supply of natural gas but relying on imported oil, the Thailand government heavily promoted alternative fuels like LPG, natural gas and ethanol to replace gasoline beginning around 2003, yet NGV was very slow to take off due to cheaper LPG fuel, a pre-existing LPG fleet, and very low conversion cost of local LPG conversion shops as compared to factory installed CNG or conversion. A significant effort was taken when the state-controlled oil company [[PTT Public Company Limited|PTT PCL]] built a network of natural gas refueling stations. The cost of subsidy was estimated at US$150 million in 2008.

As price of oil climbed rapidly, it was estimated more than 40,000 new cars and trucks powered by natural-gas were purchased in six months in 2008, including many buses. That year, about half of the taxi fleet in Bangkok used LPG, and were prodded to convert to CNG, with little success. Since 2008, there has been a government arm-twisting to switch from LPG to CNG, with a rollout of CNG stations near Bangkok around 2007 and then upcountry in 2010, at times replacing LPG stations. Operators of used vehicles have balked at the massive conversion cost (up to quadruple that of LPG in Thailand), especially given Thailand's strong ultra-competitive domestic LPG conversion industry, as well as retail CNG fuel cost (one and a half times). Thailand had some 700,000 LPG fueled vehicles, and 300,000 CNG fueled, with 1,000 LPG stations and 600 CNG as of 2011.<ref>{{cite news | url = http://www.bangkokpost.com/business/economics/317341/motorists-unfazed-by-dearer-gas | newspaper = Bangkok Post | title = Motorists unfazed by dearer gas | date = 2012-10-17 | first = Yuthana |last = Praiwan}}</ref> Demand has increased 26% over 2011 for CNG in Thailand.<ref>http://www.bangkokpost.com/business/economics/324746/cng-price-likely-to-be-at-b13-28</ref> As of the end of 2012, Thailand has 1,014,000 LPG fueled vehicles, and consumed 606,000 tonnes in 2012 of LPG, while 483 stations serve up some 380,000 CNG vehicles.,<ref>http://www.bangkokpost.com/news/local/337380/lpg-vechicles-exceed-1-million</ref> showing that LPG conversion continues to enjoy heavy favor over NGVs despite massive government push for CNG. CNG vehicles are more likely to be bought factory installed while LPG is likely to be an aftermarket conversion. LNG vehicles in Thailand are almost non-existent except for lorries.

[[File:Taxi in Kuala Lumpur 04.JPG|thumb|NGV Proton Iswara taxi in Malaysia]]

====Malaysia====
In [[Malaysia]], the use of [[compressed natural gas]] was originally introduced for taxicabs and airport limousines during the late-1990s, when new taxis were launched with NGV engines while taxicab operators were encouraged to send in existing taxis for full engine conversions, reducing their costs of operation. Any vehicle converted to use CNG is labelled with white rhombus "NGV" (Natural Gas Vehicle) tags, lending to the common use of "NGV" when referring to road vehicles with CNG engine. The practice of using CNG remained largely confined to taxicabs predominantly in the [[Klang Valley]] and [[Penang]] due to a lack of interest. No incentives were offered for those besides taxicab owners to use CNG engines, while government subsidies on petrol and diesel made conventional road vehicles cheaper to use in the eyes of the consumers. [[Petronas]], Malaysia's state-owned oil company, also monopolises the provision of CNG to road users. {{As of|2008|July|df=US}}, Petronas only operates about 150 CNG refueling stations, most of which are concentrated in the Klang Valley. At the same time, another 50 was expected by the end of 2008.<ref name="MY CNG station no">{{cite web |url=http://thestar.com.my/metro/story.asp?file=/2008/6/13/central/21532536 |title=More natural gas stations needed, say motorists |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-13 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140522/http://thestar.com.my/metro/story.asp?file=%2F2008%2F6%2F13%2Fcentral%2F21532536 |archivedate=2011-05-21 |df= }}</ref>

As fuel subsidies were gradually removed in Malaysia starting June 5, 2008, the subsequent 41% price hike on petrol and diesel led to a 500% increase in the number of new CNG tanks installed.<ref name="MY rush 1">{{cite web |url=http://thestar.com.my/news/story.asp?file=/2008/6/8/focus/21482211 |title=Motorists rush to check out NGV system |author=Rashvinjeet S. Bedi |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-08 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140559/http://thestar.com.my/news/story.asp?file=%2F2008%2F6%2F8%2Ffocus%2F21482211 |archivedate=2011-05-21 |df= }}</ref><ref name="MY rush 2">{{cite web |url=http://thestar.com.my/metro/story.asp?file=/2008/6/25/north/21635112 |title=Long queue for NGV kits |author=Vinesh, Derrick |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-25 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140624/http://thestar.com.my/metro/story.asp?file=%2F2008%2F6%2F25%2Fnorth%2F21635112 |archivedate=2011-05-21 |df= }}</ref> National car maker [[Proton (carmaker)|Proton]] considered fitting its [[Proton Waja|Waja]], [[Proton Saga|Saga]] and [[Proton Persona|Persona]] models with CNG kits from Prins Autogassystemen by the end of 2008,<ref name="MY Potong CNG">{{cite web |url=http://thestar.com.my/news/story.asp?file=/2008/6/28/nation/21685753 |title=Proton cars to come with NGV kits |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-28 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140638/http://thestar.com.my/news/story.asp?file=%2F2008%2F6%2F28%2Fnation%2F21685753 |archivedate=2011-05-21 |df= }}</ref> while a local distributor of locally assembled [[Hyundai Motor Company|Hyundai]] cars offers new models with CNG kits.<ref name="MY Hyundai">{{cite web|url=http://biz.thestar.com.my/news/story.asp?file=/2008/7/7/business/21712982|title=Moving towards hybrid vehicles |author1=Elaine Ang |author2=Leong Hung Yee |lastauthoramp=yes |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-07-07 |accessdate=2008-08-04}}</ref> Conversion centres, which also benefited from the rush for lower running costs, also perform partial conversions to existing road vehicles, allowing them to run on both petrol or diesel and CNG with a cost varying between [[Malaysian ringgit|RM]]3,500 to RM5,000 for passenger cars.<ref name="MY rush 1"/><ref name="MY CNG conversion">{{cite web |url=http://thestar.com.my/metro/story.asp?file=/2008/6/13/central/21532553 |title=Rush to fit natural gas gadget |author=Perumal, Elan |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-13 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140707/http://thestar.com.my/metro/story.asp?file=%2F2008%2F6%2F13%2Fcentral%2F21532553 |archivedate=2011-05-21 |df= }}</ref>

[[Image:Volvo B10BLE SBS Transit SBS2988J.jpg|thumb|A CNG powered [[Volvo B10BLE]] bus, operated by [[SBS Transit]] in [[Singapore]].]]

====Singapore====
There were about 400 CNG-fueled vehicles in [[Singapore]] in mid-2007, of which about 110 are taxis operated by Smart Automobile. By February 2008, the number has risen 520 CNG vehicles, of which about half are taxis.<ref name=autogenerated1>{{Cite news | url = http://www.ngvglobal.com/en/market-developments/new-cng-fuelling-station-for-singapore.html | title = New CNG Fuelling Station for Singapore | date = February 17, 2008 |location = Singapore | publisher = NGV Global News}}</ref> All vehicles had to refuel at the sole CNG station operated by Sembcorp Gas and located on [[Jurong Island]] until the opening of the first publicly accessible CNG station at [[Mandai]] in 2008, operated by Smart Automobile.<ref>{{cite news | url = http://www.channelnewsasia.com/stories/singaporelocalnews/view/329584/1/.html | title = Singapore's largest CNG refuelling station opens at Mandai Link | author = Wong Mun Wai | date = 18 February 2008| publisher = Channel NewsAsia}}</ref> The company plans to build another four stations by 2011, by which time the company projects to operate 3,000 to 4,000 CNG taxis, and with 10,000 CNG public and commercial vehicles of other types on Singapore's roads.<ref>{{cite web |url= http://www.channelnewsasia.com/stories/singaporelocalnews/view/287780/1/.html |title=Singapore's first public CNG station to be ready by Jan 2008 |work=channelnewsasia.com |date=July 12, 2007 |author=Daryl Loo |accessdate=October 21, 2011}}</ref> Sembcorp Gas opened its second CNG station a week after the Mandai station at Jalan Buroh.<ref name=autogenerated1 />

====Indonesia====
CNG is almost unheard of as a transport fuel before 2010 in the archipelago except in [[Jakarta]], where a very relatively minor number of vehicles, most notably [[Transjakarta]] buses, use the fuel. However, since 2010 there has been a government emphasis to push usage of CNG not only for vehicle fuel, but also for domestic consumption over wood burning (which can produce deadly methanol) and kerosene.

===East Asia===

====China====
China had 450,000 NGV's and 870 refueling stations as of 2009.<ref name=IANGV/> China in 2012 has 1 million NGVs on the roads, 3 million forecast for 2015, with over 2000 stations (both CNG and LPG), with plans for 12,000 by 2020. Currently China leads the World with 5 million NGVs<ref>http://www.iangv.org/current-ngv-stats/</ref> China also has lot of vehicles running of Petrol blended with Methanol as M15 and M85.

====South Korea====
For the purpose of improving air quality in the metropolitan area of [[Seoul]], CNG buses were first introduced in July, 1997. By 2014, all [[Seoul buses]] were operating on CNG.{{citation needed|date=October 2016}} Hyundai motor developed a CNG hybrid bus with 34.5% more-fuel efficiency and 30% lower pollution compared to CNG buses.{{citation needed|date=October 2016}} As a result, Seoul city government plans to change to CNG hybrid buses for 2,235 low-bed disabled-friendly CNG bus in Seoul.{{citation needed|date=October 2016}}

CNG buses are operation in other major South Korean cities like Busan, Daegu, Daejeon, Gwangju and Incheon.{{citation needed|date=October 2016}}

====Motorsport====
{{Advert|section|date=September 2017}}
A new category of motorcar racing unites teams which compete with cars powered by natural gas, to demonstrate the effectiveness of natural gas as an alternative fuel. ECOMOTORI (magazine) Racing Team<ref>[http://www.ecomotori.net/_/ecomotori-racing-team/trionfo-di-ecomotori-al-7-ecorally-smarino-r3616 ECOMOTORI Racing Team]</ref> The magazine's team participates in the [[FIA Alternative Energies Cup]] and the talian [[:it:Campionato Italiano CSAI Energie Alternative|ACI/CSAI Alternative Energies Championship]]. In 2012, the team, led by [[Nicola Ventura]], competes with a Fiat 500 Abarth,<ref>[http://www.alvolante.it/news/abarth_500_metano-664611044 Fiat 500 Abarth]</ref> modified to run on natural gas with a Cavagna/Bigas fuel conversion kit and thus renamed "500 EcoAbarth". The driver is [[Massimo Liverani]] while in the role of navigator, alternate Valeria Strada, Alessandro Talmelli and [[Fulvio Ciervo]]. On October 14, 2012, at the end of the 7th Ecorally San Marino-Vatican with 3 wins and a second place (out of 4 races),<ref>[http://www.ecorally.eu/ Ecorally San Marino-Vatican]</ref> the Team also won the Italian CSAI Alternative Energy Pilots and Navigators titles. On 28 October 2012, after having raced in 7 European countries, collecting 3 wins, 2 second places and additional points, the team won the FIA Alternative Energies Drivers and Constructors world titles. For the first time ever, a car powered by methane won an FIA world title. In 2013, the team raced in the [[FIA Alternative Energies Cup]] and [[:it:Campionato Italiano CSAI Energie Alternative|CSAI]] Championships. The "500 EcoAbarth" of Ecomotori.net dominated the season, winning 5 of 5 titles. Thanks to the work of the team, the Abarth once again won a constructors' title since its last win 46 years ago.<ref>[http://www.lpgasmagazine.com/cavagna-bigas-traveling-to-world-lp-gas-forum-in-style/ Abarth]</ref>

==See also==
* [[Biogas|Biogas vehicle]]
* [[HCNG dispenser]]
* [[List of natural gas vehicles]]

==References==
{{Reflist|30em}}

== External links ==
{{Commons category|Compressed natural gas vehicles}}
* {{Citation|url=http://pleasebeinformed.com/publications/content/gas-powered-public-transport-how-it-began-part-1 |title=Gas Powered Public Transport - how it began |date = October 9, 2005 |website=Please Be Informed}}
* {{citation | url = http://www.afdc.energy.gov/afdc/vehicles/natural_gas_availability.html | publisher = [[U.S. Department of Energy]] | title = Natural Gas Vehicle Availability | date = November 18, 2015}}
* [http://www.greenercities.eu/ Greener Cities] – International project dedicated to the development of an ever-growing demand for environmentally friendly eco-sustainable vehicles, specifically to promote the use of cleaner fuels such as CNG and [[Biogas]]
* {{Cite web | url = http://naturalgasvehicles.com | title = Natural Gas Vehicles}}
* [http://www.metanoauto.com The Italian community of Natural Gas Vehicles ]– Forum, technical info, maps (also in English, German, and French)
* {{citation | url = http://www.energyquest.ca.gov/transportation/CNG.html | title = A Student's Guide to Alternative Fuel Vehicles: Compressed natural gas - natural gas under high pressure | publisher = California Energy Commission | date = April 22, 2002 | access-date = October 4, 2004 | archive-url = https://web.archive.org/web/20041013054711/http://www.energyquest.ca.gov/transportation/CNG.html | archive-date = October 13, 2004 | dead-url = yes | df = mdy-all }}
* {{citation|url=http://www.eere.energy.gov/cleancities/vbg/consumers/cng.shtml |publisher=U.S. Department of Energy |title=Consumers' Guide to Compressed Natural Gas |deadurl=yes |archiveurl=https://web.archive.org/web/20060429222452/http://www.eere.energy.gov/cleancities/vbg/consumers/cng.shtml |archivedate=April 29, 2006 }}
* {{cite news | url = http://www.msnbc.msn.com/id/5960905 |title = Boost for natural gas cars: Home fueling | year=2013 | publisher = NBCnews.com}}
* {{cite web | url = http://www.cngcalifornia.com/ | title = CNG California}}
* {{cite web | url=http://www.afdc.energy.gov/uploads/publication/ng_powered_bus_service.pdf |title=Developing a Natural GasPowered Bus Rapid Transit Service: A Case Study|first=George |last=Mitchell|work=[[National Renewable Energy Laboratory]]|date=November 2015}}
* [http://www.ngvjournal.com/worldwide-fuel-prices/ Worldwide fuel prices], 2010

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[[Category:Natural gas vehicles|*]]
[[Category:Green vehicles]]

Natural gas vehicle

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{{redirect|NGV|the art gallery in Melbourne, Australia|National Gallery of Victoria}}
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[[File:Guidetti cng truck.jpg|thumb|200px|Truck running with Guidetti CNG system]]
[[Image:FillingUpCNG.jpg|thumb|200px|Fueling ([[Fiat Multipla]])]]
[[Image:2009 Honda Civic NGV--DC.jpg|thumb|right|200px|2009 [[Honda Civic GX]] hooked up to Phill refueling system.]]

A '''natural gas vehicle''' ('''NGV''') is an [[alternative fuel vehicle]] that uses [[Compressed natural gas|compressed natural gas (CNG)]] or [[liquefied natural gas|liquefied natural gas (LNG)]]. Natural gas vehicles should not be confused with [[autogas|vehicles powered by LPG]] (mainly [[propane]]), which is a fuel with a fundamentally different composition.

In a natural gas powered vehicle, energy is released by combustion of essentially [[Methane]] gas (CH4) fuel with Oxygen (O2) from the air to CO2 and water vapor (H2O) in an [[internal combustion engine]]. Methane is the cleanest burning [[hydrocarbon]] and many contaminants present in [[natural gas]] are removed at source.

Safe, convenient and cost effective gas storage and fuelling is more of a challenge compared to petrol and diesel vehicles since the natural gas is pressurized and/or - in the case of LNG - the tank needs to be kept cold. This makes LNG unsuited for vehicles that are not in frequent use. The lower [[energy density]] of gases compared to liquid fuels is mitigated to a great extent by high compression or gas liquefaction, but requires a trade-off in terms of size/complexity/weight of the storage container, range of the vehicle between refueling stops, and time to refuel.

Although similar storage technologies may be used for and similar compromises would apply to a [[Hydrogen vehicle]] as part of a proposed new [[Hydrogen economy]], methane as a gaseous fuel is safer than hydrogen due to its [[flammability limit|lower flammability]], low corrosivity and better leak tightness due to larger [[molecular weight]]/ size, resulting in lower price hardware solutions based on proven technology and conversions. A key advantage of using natural gas is the existence, in principle, of most of the infrastructure and the supply chain, which is non-interchangeable with hydrogen. Methane today mostly comes from non-renewable sources but can be supplied or produced from [[renewable]] sources, offering net carbon neutral mobility. In many markets, especially the Americas, natural gas may trade at a discount to other [[fossil fuel]] products such as petrol, diesel or coal, or indeed be a less valuable by-product associated with their production that has to be disposed. Many countries also provide tax incentives for natural gas powered vehicles due to the environmental benefits to society. Lower operating costs and government incentives to reduce pollution from heavy vehicles in urban areas have driven the adoption of NGV for commercial and public uses, i.e. trucks and buses.

Many factors hold back NGV popularization for [[individual mobility]] applications, i.e. private vehicles, including: relatively price and environmentally insensitive but convenience seeking private individuals; good profits and taxes extractable from small batch sales of value-added, branded petrol and diesel fuels via established trade channels and oil refiners; resistance and safety concerns to increasing gas inventories in urban areas; dual-use of utility distribution networks originally built for home gas supply and allocation of network expansion costs; reluctance, effort and costs associated with switching; prestige and nostalgia associated with petroleum vehicles; fear of redundancy and disruption. A particular challenge may be the fact that refiners are currently set up to produce a certain fuels mix from crude oil. [[Aviation fuel]] is likely to remain the fuel of choice for aircraft due to their weight sensitivity for the foreseeable future.

Worldwide, there were 24.452 million NGVs by 2016, led by [[China]] (5.0 million), [[Iran]] (4.00 million), [[India]] (3.045 million), [[Pakistan]] (3.0 million), [[Argentina]] (2.295 million), [[Brazil]] (1.781 million), and [[Italy]] (1.001 million).<ref name=NGVJournal>{{cite web|url=http://www.iangv.org/current-ngv-stats/|title=Current Natural Gas Vehicle Statistics|publisher=IANGV}}</ref> The [[Asia-Pacific]] region leads the world with 6.8 million vehicles, followed by [[Latin America]] with 4.2 million.<ref name=IANGV>{{cite web |url=http://www.iangv.org/tools-resources/statistics.html |title=Natural Gas Vehicle Statistics: Summary Data 2010 |publisher=International Association for Natural Gas Vehicles |accessdate=2011-08-02 |deadurl=yes |archiveurl=https://web.archive.org/web/20100110101111/http://www.iangv.org/tools-resources/statistics.html |archivedate=2010-01-10 |df= }} ''Click on Summary Data (2010).''</ref> In Latin America, almost 90% of NGVs have [[bi-fuel engine]]s, allowing these vehicles to run on either gasoline or CNG.<ref>{{cite web|url=http://green.autoblog.com/2011/09/26/pike-research-predicts-68-jump-in-global-cng-vehicle-sales-by-2/#continued|title=Pike Research predicts 68% jump in global CNG vehicle sales by 2016|author=Pike Research|publisher=[[AutoblogGreen]] |date=2011-09-14|accessdate=2011-09-26}}</ref> In Pakistan, almost every vehicle converted to (or manufactured for) alternative fuel use typically retains the capability of running on gasoline.

As of 2016, the U.S. had a fleet of 160,000 NG vehicles, including 3,176 LNG vehicles. Other countries where natural gas-powered buses are popular include India, [[Australia]], Argentina, [[Germany]], and [[Greece]].<ref name="TwoBillion">{{Cite book |author1=Sperling, Daniel |author2=Deborah Gordon |lastauthoramp=yes | title = Two billion cars: driving toward sustainability | year = 2009 | pages= 93–94 | publisher = [[Oxford University Press]], New York| isbn = 978-0-19-537664-7}}</ref> In [[OECD]] countries, there are around 500,000 CNG vehicles.<ref name="SusTransp">{{Cite book |author1=Ryan, Lisa |author2=Turton, Hal | year = 2007 | title = Sustainable Automobile Transport| publisher = Edward Elgar Publishing Ltd, England| isbn = 978-1-84720-451-6| pages = 40–41}}</ref> Pakistan's market share of NGVs was 61.1% in 2010, follow by [[Armenia]] with more than 77% (2014), and [[Bolivia]] with 20%.<ref name=IANGV/> The number of NGV refueling stations has also increased, to 18,202 worldwide as of 2010, up 10.2% from the previous year.<ref name=IANGV/>

Existing gasoline-powered vehicles may be converted to run on CNG or LNG, and can be dedicated (running only on natural gas) or bi-fuel (running on either gasoline or natural gas). Diesel engines for heavy trucks and busses can also be converted and can be dedicated with the addition of new heads containing spark ignition systems, or can be run on a blend of diesel and natural gas, with the primary fuel being natural gas and a small amount of diesel fuel being used as an ignition source. It is also possible to generate energy in a small gas turbine and couple the gas engine or turbine with a small electric battery to create a hybrid electric motor driven vehicle. An increasing number of vehicles worldwide are being manufactured to run on CNG by major carmakers. Until recently, the [[Honda Civic GX]] was the only NGV commercially available in the US market. More recently, [[Ford]], [[General Motors]] and [[Ram Trucks]] have bi-fuel offerings in their vehicle lineup. In 2006, the Brazilian subsidiary of [[FIAT]] introduced the [[Fiat Siena|Fiat Siena Tetra fuel]], a four-fuel car that can run on natural gas (CNG).<ref name="TreeH"/>

NGV filling stations can be located anywhere that natural gas lines exist. Compressors (CNG) or liquifaction plants (LNG) are usually built on large scale but with CNG small home refueling stations are possible. A company called FuelMaker pioneered such a system called Phill Home Refueling Appliance (known as "Phill"), which they developed in partnership with [[Honda]] for the American GX model.<ref>{{Cite web |url=http://www.fuelmaker.com/Research/PhillQandA.htm |publisher=FuelMaker Corporation - World Leader in Convenient On-Site Refueling Systems |title=Phill: Questions and Answers |deadurl=yes |archiveurl=https://web.archive.org/web/20051016173628/http://www.fuelmaker.com/research/phillqanda.htm |archivedate=October 16, 2005 |df= }}</ref><ref>{{cite web | url = http://www.evworld.com/view.cfm?section=article&storyid=847 | publisher = EVWorld | title = FEATURE: Honda's Phill-way to Hydrogen | first= Bill |last = Moore | date = May 6, 2005 | work = Open Access}}</ref> Phill is now manufactured and sold by BRC FuelMaker, a division of Fuel Systems Solutions, Inc.<ref>{{Cite web|url=http://blogs.edmunds.com/greencaradvisor/2011/03/brc-fuelmaker-again-selling-phill-home-cng-fuel-station.html|title=BRC FuelMaker Again Selling Phill Home CNG Fuel Station|accessdate=2011-04-04|archive-url=https://web.archive.org/web/20110325155026/http://blogs.edmunds.com/greencaradvisor/2011/03/brc-fuelmaker-again-selling-phill-home-cng-fuel-station.html|archive-date=2011-03-25|dead-url=yes|df=}}</ref>

CNG may be generated and used for bulk storage and pipeline transport of renewable energy and also be mixed with [[biomethane]], itself derived from [[biogas]] from [[landfill]]s or [[anaerobic digestion]]. This would allow the use of CNG for mobility without increasing the concentration of carbon in the atmosphere. It would also allow continued use of CNG vehicles currently powered by non-renewable fossil fuels that do not become obsolete when stricter CO2 emissions regulations are mandated to combat global warming.

Despite its advantages, the use of natural gas vehicles faces several limitations, including fuel storage and infrastructure available for delivery and distribution at fueling stations. CNG must be stored in high pressure cylinders (3000psi to 3600psi operation pressure), and LNG must be stored in cryogenic cylinders (-260F to -200F). These cylinders take up more space than gasoline or diesel tanks that can be molded in intricate shapes to store more fuel and use less on-vehicle space. CNG tanks are usually located in the vehicle's trunk or pickup bed, reducing the space available for other cargo. This problem can be solved by installing the tanks under the body of the vehicle, or on the roof (typical for busses), leaving cargo areas free. As with other alternative fuels, other barriers for widespread use of NGVs are natural gas distribution to and at fueling stations as well as the low number of CNG and LNG stations.<ref name="SusTransp"/>

CNG-powered vehicles are considered to be safer than gasoline-powered vehicles.<ref>{{Cite web|url=http://ngvamerica.org/pdfs/TechBul2.pdf|title=How Safe are Natural Gas Vehicles?|publisher=Clean Vehicle Education Foundation|accessdate=2008-05-08|format=PDF}}</ref><ref>{{Cite web|url=http://alternativefuels.about.com/od/naturalgaspropane/a/safenaturalgas.htm|title=How Safe is Natural Gas?|accessdate=2008-05-08}}</ref><ref>{{cite web|url=http://www.firetrainingresources.net/items/CNGAutoFire-FIREFIGHTERNEARMISScompressedpics.pdf|title=Fighting CNG fires|accessdate=2008-05-08|format=PDF|deadurl=yes|archiveurl=https://web.archive.org/web/20080528041023/http://www.firetrainingresources.net/items/CNGAutoFire-FIREFIGHTERNEARMISScompressedpics.pdf|archivedate=2008-05-28|df=}}</ref>

==CNG/LNG as fuel for automobiles==

===Available production cars===
[[File:Meriva Flex GNV SAO 10 2009 7797 with logo flex.jpg|thumb|Brazilian [[flexible-fuel vehicle|flexible-fuel]] [[Taxicab|taxi]] retrofitted to run also as a NGV. The [[Compressed Natural Gas|compressed natural gas (CNG)]] tanks are located underneath the body in the rear.]]

Existing gasoline-powered vehicles may be converted to run on CNG or LNG, and can be dedicated (running only on natural gas) or bi-fuel (running on either gasoline or natural gas). However, an increasing number of vehicles worldwide are being manufactured to run on CNG.{{citation needed|date=October 2016}} Until recently, the now-discontinued [[Honda Civic GX]] was the only NGV commercially available in the US market.<ref>{{cite web |url=http://alternativefuels.about.com/od/2008ngvavailable/a/2008CNGvehicles.htm |title=2008 Natural Gas Vehicles (NGVs) Available |author1=Christine Gable |author2=Scott Gable |lastauthoramp=yes |publisher=About.com: Hybrid Cars & Alt Fuels |date= |accessdate=2008-10-18 |deadurl=yes |archiveurl=https://web.archive.org/web/20081011214336/http://alternativefuels.about.com/od/2008ngvavailable/a/2008CNGvehicles.htm |archivedate=2008-10-11 |df= }}</ref><ref>{{cite web|url=http://automobiles.honda.com/civic-gx/ |title=2009 Honda Civic GX Natural Gas Vehicle |publisher=Honda |date= |accessdate=2008-10-18}}</ref> More recently, [[Ford]], [[General Motors]] and [[Ram Trucks]] have bi-fuel offerings in their vehicle lineup.{{citation needed|date=October 2016}} Ford's approach is to offer a bi-fuel prep kit as a factory option, and then have the customer choose an authorized partner to install the natural gas equipment. Choosing GM's bi-fuel option sends the HD pickups with the 6.0L gasoline engine to IMPCO in Indiana to upfit the vehicle to run on CNG. Ram currently is the only pickup truck manufacturer with a truly CNG factory-installed bi-fuel system available in the U.S. market.{{citation needed|date=September 2014}}

Outside the U.S. [[General Motors do Brasil|GM do Brasil]] introduced the MultiPower engine in 2004, which was capable of using CNG, alcohol and gasoline ([[Common ethanol fuel mixtures#E20, E25|E20-E25 blend]]) as fuel, and it was used in the [[Opel Astra|Chevrolet Astra]] 2.0 model 2005, aimed at the taxi market.<ref name="GNVNews"/><ref>{{cite web|url=http://www.jornalexpress.com.br/noticias/detalhes.php?id_jornal=9095&id_noticia=1703|title=Astra é líder no segmento dos compactos em 2004: As versões do Chevrolet Astra 2005|publisher=Journal Express|date=2005-01-18|language=Portuguese|accessdate=2008-10-15}} {{pt icon}}</ref> In 2006, the Brazilian subsidiary of [[FIAT]] introduced the [[Fiat Siena|Fiat Siena Tetra fuel]], a four-fuel car developed under [[Magneti Marelli]] of [[Fiat]] Brazil. This automobile can run on natural gas (CNG); 100% ethanol ([[w:Common ethanol fuel mixtures#E100|E100]]); [[w:Common ethanol fuel mixtures#E20, E25|E20 to E25]] gasoline blend, Brazil's mandatory gasoline; and pure gasoline, though no longer available in Brazil it is used in neighboring countries.<ref name="TreeH"/><ref>{{cite web |url=http://www.webmotors.com.br/wmpublicador/Noticias_Conteudo.vxlpub?hnid=36391 |author=Agência AutoInforme |title=Siena Tetrafuel vai custar R$ 41,9 mil |publisher=WebMotor |date=2006-06-19 |accessdate=2008-08-14 |language=Portuguese |deadurl=yes |archiveurl=https://web.archive.org/web/20081210211007/http://www.webmotors.com.br/wmpublicador/Noticias_Conteudo.vxlpub?hnid=36391 |archivedate=2008-12-10 |df= }}{{pt icon}} The article argues that even though Fiat called it tetra fuel, it actually runs on three fuels: natural gas, ethanol, and gasoline, as Brazilian gasoline is an E20 to E25 blend.</ref>

In 2015, Honda announced its decision to phase out the commercialization of natural-gas powered vehicles to focus on the development of a new generation of [[electric vehicle|electrified vehicles]] such as [[hybrid electric vehicle|hybrids]], [[plug-in electric car]]s and hydrogen-powered [[fuel cell vehicle]]s. Since 2008, Honda sold about 16,000 natural-gas vehicles, mainly to taxi and commercial fleets.<ref>{{cite news | url=http://www.autonews.com/article/20150615/OEM05/150619915/honda-will-drop-cng-vehicles-to-focus-on-hybrids-evs | title=Honda will drop CNG vehicles to focus on hybrids, EVs | first=Neal E. | last=Boudette | work=[[Automotive News]] | date=2015-06-15 | accessdate=2016-05-28}}</ref>

===Differences between LNG and CNG fuels===
Though LNG and CNG are both considered NGVs, the technologies are vastly different. Refueling equipment, fuel cost, pumps, tanks, hazards, capital costs are all different.

One thing they share is that due to engines made for gasoline, computer controlled valves to control fuel mixtures are required for both of them, often being proprietary and specific to the manufacturer. The on-engine technology for fuel metering is the same for LNG and CNG.

===CNG as an auto fuel===
CNG, or compressed natural gas, is stored at high pressure, {{Convert|3000|to|3600|psi|MPa}}. The required tank is more massive and costly than a conventional fuel tank. Commercial on-demand refueling stations are more expensive to operate than LNG stations because of the energy required for compression, the compressor requires 100 times more electrical power, however, slow-fill (many hours) can be cost-effective with LNG stations [missing citation - the initial liquefaction of natural gas by cooling requires more energy than gas compression]. Time to fill a CNG tank varies greatly depending on the station. Home refuelers typically fill at about 0.4 [[Gasoline gallon equivalent|GGE]]/hr. "Fast-fill" stations may be able to refill a 10 GGE tank in 5–10 minutes. Also, because of the lower energy density, the range on CNG is limited by comparison to LNG. Gas composition and throughput allowing, it should be feasible to connect commercial CNG fueling stations to city gas networks, or enable home fueling of CNG vehicles directly using a gas compressor. Similar to a car battery, the CNG tank of a car could double as a home energy storage device and the compressor could be powered at times when there is excess/ free renewable electrical energy.

===LNG as an auto fuel===
LNG, or liquified natural gas, is natural gas that has been cooled to a point that it is a cryogenic liquid. In its liquid state, it is still more than 2 times as dense as CNG. LNG is usually dispensed from bulk storage tanks at LNG fuel stations at rates exceeding 20 [[Diesel gallon equivalent|DGE]]/min. Sometimes LNG is made locally from utility pipe. Because of its cryogenic nature, it is stored in specially designed insulated tanks. Generally speaking, these tanks operate at fairly low pressures (about 70-150 psi) when compared to CNG. A vaporizer is mounted in the fuel system that turns the LNG into a gas (which may simply be considered low pressure CNG). When comparing building a commercial LNG station with a CNG station, utility infrastructure, capital cost, and electricity heavily favor LNG over CNG. There are existing LCNG stations (both CNG and LNG), where fuel is stored as LNG, then vaporized to CNG on-demand. LCNG stations require less capital cost than fast-fill CNG stations alone, but more than LNG stations.

===Advantages over gasoline and diesel===
LNG – and especially CNG – tends to corrode and wear the parts of an engine less rapidly than gasoline. Thus it is quite common to find diesel-engine NGVs with high mileages (over 500,000 miles). CNG also emits 20-29% less CO2 than diesel and gasoline.<ref>{{Cite web|url=http://www.gas-south.com/business/compressed-natural-gas.aspx|title=Gas South Compressed Natural Gas|website=www.gas-south.com|access-date=2016-04-08}}</ref> Emissions are cleaner, with lower emissions of carbon and lower particulate emissions per equivalent distance traveled. There is generally less wasted fuel. However, cost (monetary, environmental, pre-existing infrastructure) of distribution, compression, cooling must be taken into account.

===Inherent advantages/disadvantages between autogas (LPG) power and NGV===
[[Autogas]], also known as LPG, has different chemical composition, but still a petroleum based gas, has a number of inherent advantages and disadvantages, as well as noninherent ones. The inherent advantage of autogas over CNG is that it requires far less compression (20% of CNG cost),<ref>{{cite web |url=http://www.energ2.com/home/applications/adsorbed-natural-gas.html |title=Archived copy |accessdate=2013-08-08 |deadurl=yes |archiveurl=https://web.archive.org/web/20131010015546/http://www.energ2.com/home/applications/adsorbed-natural-gas.html |archivedate=2013-10-10 |df= }}</ref> is denser as it is a liquid at room temperature, and thus requires far cheaper tanks (consumer) and fuel compressors (provider) than CNG. As compared to LNG, it requires no chilling (and thus less energy), or problems associated with extreme cold such as [[frostbite]]. Like NGV, it also has advantages over gasoline and diesel in cleaner emissions, along with less wear on engines over gasoline. The major drawback of LPG is its safety. The fuel is volatile and the fumes are heavier than air, which causes them to collect in a low spot in the event of a leak, making it far more hazardous to use and more care is needed in handling. Besides this, LPG (40% from Crude Oil refining) is more expensive than Natural Gas.

====Current advantages of LPG power over NGV====
In places like the US, Thailand, and India, there are five to ten times more stations thus making the fuel more accessible than NGV stations. Other countries like Poland, South Korea, and Turkey, LPG stations and autos are widespread while NGVs are not. In addition, in some countries such as Thailand, the retail LPG fuel is considerably cheaper in cost.

===Future possibilities===
Though ANG (adsorbed natural gas) has not yet been used in either providing stations nor consumer storage tanks, its low compression (500psi vs 3600 psi)<ref>http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/41_1_NEW%20ORLEANS_03-96_0246.pdf</ref> has the potential to drive down costs of NGV infrastructure and vehicle tanks.

==LNG fueled vehicles==

===Use of LNG to fuel large over-the-road trucks===
LNG is being evaluated and tested for over-the-road trucking,<ref>{{cite web| url=https://www.ngvamerica.org/vehicles/for-fleets/over-the-road/| title=Over the Road LNG vehicles in USA| accessdate=17 April 2015}}</ref> off-road,<ref>{{cite web| url=https://www.ngvamerica.org/vehicles/high-horsepower/| title= High horse power off-road LNG vehicles in USA| accessdate=17 April 2015}}</ref> marine, and railroad applications.<ref>{{cite web| url=https://af.reuters.com/article/commoditiesNews/idAFL6N0QI1Q920140812?sp=true| title=Next energy revolution will be on roads and railroads| accessdate=17 April 2015}}</ref> There are known problems with the fuel tanks and delivery of gas to the engine.<ref>{{cite web| url=http://www.cryogenicfuelsinc.com/tanks/systemAnalysis.cfm| title=LNG Tank System Analysis| accessdate=17 April 2015}}</ref>

China has been a leader in the use of LNG vehicles<ref>{{cite web|url= http://member.zeusintel.com/ZLFVR/news_details.aspx?newsid=31246| title=Development of LNG Fueling Stations in China vs. in U.S.| accessdate=17 April 2015}}</ref> with over 100,000 LNG powered vehicles on the road as of 2014.<ref>{{cite web| url=https://www.bloomberg.com/news/articles/2014-07-04/choking-smog-puts-chinese-driver-in-natural-gas-fast-lane| title=Choking Smog Puts Chinese Driver in Natural Gas Fast Lane| accessdate=17 April 2015}}</ref>

In the United States, there were 69 public truck LNG fuel centres as of February 2015.<ref>{{cite web| url=http://www.afdc.energy.gov/locator/stations/results?utf8=%E2%9C%93&location=&filtered=true&fuel=LNG&owner=all&payment=all&ev_level1=true&ev_level2=true&ev_dc_fast=true&radius_miles=5| title=Alternative Fueling Station Locator in USA| accessdate=17 April 2015}}</ref> The 2013 National Trucker's Directory lists approximately 7,000 truckstops,<ref>{{cite web| url=http://www.dieselboss.com/directory_DC.htm| title=The 2013 National Trucker's Directory| accessdate=17 April 2015}}</ref> thus approximately 1% of US truckstops have LNG available.

In 2013, Dillon Transport announced they were putting 25 LNG large trucks into service in Dallas Texas. They are refueling at a public LNG fuel center.<ref>{{cite web| url=http://www.fleetsandfuels.com/fuels/ngvs/2013/05/dillon-adding-25-lng-kenworth-t800s/| title=Dillon Adding 25 LNG Kenworth| accessdate=17 April 2015| archive-url=https://web.archive.org/web/20150410173419/http://www.fleetsandfuels.com/fuels/ngvs/2013/05/dillon-adding-25-lng-kenworth-t800s/| archive-date=2015-04-10| dead-url=yes| df=}}</ref> The same year Raven Transportation announced they were buying 36 LNG large trucks to be fueled by Clean Energy Fuels locations<ref>{{cite web|url= http://www.ngvjournal.com/clean-energy-commits-to-fueling-36-new-heavy-duty-lng-powered-trucks/|archive-url= https://web.archive.org/web/20160603031545/http://www.ngvjournal.com/clean-energy-commits-to-fueling-36-new-heavy-duty-lng-powered-trucks/|dead-url= yes|archive-date= 2016-06-03|title= Clean Energy commits to serving 36 new heavy-duty LNG-powered trucks}}</ref> and Lowe's finished converting one of its dedicated fleets to LNG fueled trucks.<ref>{{cite web| url=http://media.lowes.com/pr/2013/10/17/lowes-launches-natural-gas-powered-truck-fleet-at-texas-rdc/| title=Lowe’s Launches Natural Gas-Powered Truck Fleet At Texas RDC| accessdate=17 April 2015}}</ref>

UPS had over 1200 LNG fueled trucks on the roads in February 2015.<ref>{{cite web| url=http://www.ups.com/pressroom/us/press_releases/press_release/Press+Releases/Archive/2015/Q1/ci.Legislation+Introduced+by+Senators+Bennet+and+Burr+Would+End+the+Disparity+in+the+way+LNG+and+LPG+are+Taxed.syndication| title=Legislation Would End the Disparity in the way LNG and LPG are Taxed| accessdate=17 April 2015| archive-url=https://web.archive.org/web/20150402150742/http://www.ups.com/pressroom/us/press_releases/press_release/Press+Releases/Archive/2015/Q1/ci.Legislation+Introduced+by+Senators+Bennet+and+Burr+Would+End+the+Disparity+in+the+way+LNG+and+LPG+are+Taxed.syndication| archive-date=2 April 2015| dead-url=yes| df=dmy-all}}</ref> UPS has 16,000 tractor trucks in its fleet, and 60 of the new for 2014 large trucks will be placed in service in the Houston, Texas area, where UPS is building its own private LNG fuel center to avoid the lines at retail fuel centers.<ref>{{cite web| url=http://www.bizjournals.com/houston/blog/drilling-down/2014/06/new-lng-trucking-fleet-launches-in-houston.html?page=all| title=New LNG trucking fleet launches in Houston| accessdate=17 April 2015}}</ref> In Amarillo, Texas and Oklahoma City, Oklahoma, UPS is using public fuel centers.<ref>{{cite web|url= http://ttnews.com/articles/basetemplate.aspx?storyid=34594&t=Clean-Energy-Opens-Two-LNG-Highway-Stations| title=Clean Energy Opens Two LNG Highway Stations| accessdate=17 April 2015}}</ref>

Clean Energy Fuels has opened several public LNG Fuel Lanes along I-10 and claims that as of June 2014 LNG fueled trucks can use the route from Los Angeles, California to Houston, Texas by refueling exclusively at Clean Energy Fuels public facilities.<ref>{{cite web|url= http://investors.cleanenergyfuels.com/releasedetail.cfm?ReleaseID=854991| title=Clean Energy Opens Interstate 10 Highway Between Los Angeles and Houston to LNG Fueling| accessdate=17 April 2015}}</ref> In 2014 Shell and Travel Centers of America opened the first of a planned network of U.S. truck stop LNG stations in Ontario, California.<ref>{{cite web| url=http://www.fleetsandfuels.com/fuels/ngvs/2014/05/shell-opens-its-first-u-s-lng-lanes/| title=Shell, TA Open Their First U.S. LNG| accessdate=17 April 2015| archive-url=https://web.archive.org/web/20150410175127/http://www.fleetsandfuels.com/fuels/ngvs/2014/05/shell-opens-its-first-u-s-lng-lanes/| archive-date=2015-04-10| dead-url=yes| df=}}</ref> Per the alternative fuel fuelling centre tracking site there are 10 LNG capable public fuel stations in the greater Los Angeles area, making it the single most penetrated metro market. As of February 2015, Blu LNG has at least 23 operational LNG capable fuel centers across 8 states,<ref>{{cite web| url=http://www.blustations.com/| title=The Future of Fuel Starts Here| accessdate=17 April 2015| archive-url=https://web.archive.org/web/20150410213814/http://www.blustations.com/| archive-date=10 April 2015| dead-url=yes| df=dmy-all}}</ref> and Clean Energy had 39 operational public LNG facilities.<ref>{{cite web|url= http://www.cnglngstations.com/| title= LNG Station locator| accessdate=17 April 2015}}</ref>

As can be seen at the alternative fuel fueling center tracking site, as of early 2015 there is void of LNG fuel centers, public and private, from Illinois to the Rockies.<ref>{{cite web| url=http://www.afdc.energy.gov/locator/stations/results?utf8=%E2%9C%93&location=&fuel=LNG&private=false&private=true&planned=false&owner=all&payment=all&radius=false&radius_miles=5&lng_vehicle_class=all| title=Shell, TA Open Their First U.S. LNG| accessdate=17 April 2015}}</ref> A Noble Energy LNG production plant in northern Colorado was planned to go online in 1st quarter 2015<ref>{{cite web|url= http://www.lngworldnews.com/nobles-colorado-lng-facility-moving-forward/| title= Noble's LNG facility in Colorado remains on schedule| accessdate=17 April 2015}}</ref> and to have a capacity of 100,000 gallons of LNG per day for on-road, off-road, and drilling operations.<ref>{{cite web|url= http://www.lngworldnews.com/noble-energy-to-build-lng-plant-in-colorado-usa/| title=Noble Energy to Build LNG Plant in Colorado, USA| accessdate=17 April 2015}}</ref>

As of 2014, LNG fuel and NGV's had not achieved much usage in Europe.<ref>{{cite web|url= http://www.returnloads.net/news/lng-fuel-unlikely-fuel-of-choice-for-europe| title=LNG fuel unlikely to be fuel of choice for Europe| accessdate=17 April 2015}}</ref>

American Gas & Technology pioneered use of onsite liquefaction using van sized station to access Natural Gas from utility pipe and clean, liquefy, store and dispense it. Their stations make 300-5,000 gallons of LNG per day.

===Use of LNG to fuel high-horsepower/high-torque engines===

In internal combustion engines the volume of the cylinders is a common measure of the power of an engine. Thus a 2000cc engine would typically be more powerful than a 1800cc engine, but that assumes a similar air-fuel mixture is used.

If, via a turbocharger as an example, the 1800cc engine were using an air-fuel mixture that was significantly more energy dense, then it might be able to produce more power than a 2000cc engine burning a less energy dense air-fuel mixture. However, turbochargers are both complex and expensive. Thus it becomes clear for high-horsepower/high-torque engines a fuel that can inherently be used to create a more energy dense air-fuel mixture is preferred because a smaller and simpler engine can be used to produce the same power.

With traditional gasoline and diesel engines the energy density of the air-fuel mixture is limited because the liquid fuels do not mix well in the cylinder. Further, gasoline and diesel auto-ignite<ref>[[Autoignition temperature]]</ref> at temperatures and pressures relevant to engine design. An important part of traditional engine design is designing the cylinders, compression ratios, and fuel injectors such that pre-ignition is avoided,<ref>[[Engine knocking#Pre-ignition]]</ref> but at the same time as much fuel as possible can be injected, become well mixed, and still have time to complete the combustion process during the power stroke.

Natural gas does not auto-ignite at pressures and temperatures relevant to traditional gasoline and diesel engine design, thus providing more flexibility in the design of a natural gas engine. Methane, the main component of natural gas, has an autoignition temperature of 580C/1076F,<ref>{{cite web| url=http://www.engineeringtoolbox.com/fuels-ignition-temperatures-d_171.html| title=Fuels and Chemicals - Autoignition Temperatures| accessdate=17 April 2015}}</ref> whereas gasoline and diesel autoignite at approximately 250C and 210C respectively.

With a compressed natural gas (CNG) engine, the mixing of the fuel and the air is more effective since gases typically mix well in a short period of time, but at typical CNG compression pressures the fuel itself is less energy dense than gasoline or diesel thus the end result is a lower energy dense air-fuel mixture. Thus for the same cylinder displacement engine, a non turbocharged CNG powered engine is typically less powerful than a similarly sized gasoline or diesel engine. For that reason, turbochargers are popular on European CNG cars.<ref>{{cite web| url=http://wardsauto.com/ar/turbocharing_cng_europe_100308| title=Turbocharging Boosting Demand for CNG Vehicles in Europe| accessdate=17 April 2015}}</ref> Despite that limitation, the 12 liter Cummins Westport ISX12G engine<ref>{{cite web| url=http://www.cumminswestport.com/models/isx12-g| title=Cummins Westport ISX12 G natural gas engine| accessdate=17 April 2015}}</ref> is an example of a CNG capable engine designed to pull tractor/trailer loads up to 80,000 lbs showing CNG can be used in most if not all on-road truck applications. The original ISX G engines incorporated a turbocharger to enhance the air-fuel energy density.<ref>{{cite web| url=http://www.afdc.energy.gov/pdfs/36252.pdf| title=Development of the High-Pressure Direct-Injection ISX G Natural Gas Engine| accessdate=17 April 2015}}</ref>

LNG offers a unique advantage over CNG for more demanding high-horsepower applications by eliminating the need for a turbocharger. Because LNG boils at approximately -160C, using a simple heat exchanger a small amount of LNG can be converted to its gaseous form at extremely high pressure with the use of little or no mechanical energy. A properly designed high-horsepower engine can leverage this extremely high pressure energy dense gaseous fuel source to create a higher energy density air-fuel mixture than can be efficiently created with a CNG powered engine. The end result when compared to CNG engines is more overall efficiency in high-horsepower engine applications when high-pressure direct injection technology is used. The Westport HDMI2<ref>{{cite web| url=http://www.westport.com/is/core-technologies/hpdi-2| title=WESTPORT HPDI 2.0 LNG engine| accessdate=17 April 2015}}</ref> fuel system is an example of a high-pressure direct injection technology that does not require a turbocharger if teamed with appropriate LNG heat exchanger technology. The Volvo Trucks 13-liter LNG engine<ref>{{cite web| url=http://www.lngworldnews.com/volvo-trucks-north-america-to-launch-lng-engine/| title=Volvo Trucks North America to Launch LNG Engine| accessdate=17 April 2015}}</ref> is another example of a LNG engine leveraging advanced high pressure technology.

Westport recommends CNG for engines 7 liters or smaller and LNG with direct injection for engines between 20 and 150 liters. For engines between 7 and 20 liters either option is recommended. See slide 13 from their NGV BRUXELLES – INDUSTRY INNOVATION SESSION presentation<ref>{{cite web| url=http://www.ngvaeurope.eu/downloads/NGV_2014_BRUSSELS/1._Roberto_Defilippi.pdf| title=An innovative vision for LNG Fuel System for MD Diesel Dual Fuel Engine(DDF+LNG)| accessdate=17 April 2015}}</ref>

High horsepower engines in the oil drilling, mining, locomotive, and marine fields have been or are being developed. Paul Blomerous has written a paper<ref>{{cite web| url=http://www.gastechnology.org/Training/Documents/LNG17-proceedings/7-4-Paul_Blomerus.pdf| title=LNG AS A FUEL FOR DEMANDING HIGH HORSEPOWER ENGINE APPLICATIONS: TECHNOLOGY AND APPROACHES| accessdate=17 April 2015}}</ref> concluding as much as 40 million tonnes per annum of LNG (approximately 26.1 billion gallons/year or 71 million gallons/day) could be required just to meet the global needs of the high-horsepower engines by 2025 to 2030.

As of the end of 1st quarter 2015 Prometheus Energy Group Inc claims to have delivered over 100 million gallons of LNG within the previous 4 years into the industrial market,<ref>{{cite web| url=http://www.lngglobal.com/latest/prometheus-agreement-with-wpx-energy-to-supply-lng-and-equipment-for-drilling-operations.html| title=Prometheus agreement with WPX Energy to supply LNG and equipment for drilling operations| accessdate=17 April 2015| deadurl=yes| archiveurl=https://web.archive.org/web/20150926033722/http://www.lngglobal.com/latest/prometheus-agreement-with-wpx-energy-to-supply-lng-and-equipment-for-drilling-operations.html| archivedate=26 September 2015| df=}}</ref> and is continuing to add new customers.

===Ships===
The {{MV|Isla Bella}} is the world's first [[LNG]] powered [[container ship]].<ref name=Schuler>{{cite news|last1=Schuler|first1=Mike|title=Introducing ISLA BELLA – World’s First LNG-Powered Containership Launched at NASSCO|publisher=gCaptain|date=19 April 2015}}</ref> LNG carriers are sometimes powered by the boil-off of LNG from their storage tanks, although Diesel powered LNG carriers are also common to minimize loss of cargo and enable more versatile refueling.

===Aircraft===
[[Aviation fuel#LNG|Some airplanes]] use LNG to power their turbofans. Aircraft are particularly sensitive to weight and much of the weight of an aircraft goes into fuel carriage to allow the range. The low energy density of natural gas even in liquid form compared to conventional fuels give it a distinct disadvantage for flight applications.

== Chemical composition and energy content ==

=== Chemical composition ===

The primary component of [[natural gas]] is [[methane]] ([[carbon|C]][[hydrogen|H]]4), the shortest and lightest [[hydrocarbon]] molecule. It may also contain heavier gaseous hydrocarbons such as [[ethane]] ([[carbon|C]]2[[hydrogen|H]]6), [[propane]] ([[carbon|C]]3[[hydrogen|H]]8) and [[butane]] ([[carbon|C]]4[[hydrogen|H]]10), as well as other gases, in varying amounts. [[Hydrogen sulfide]] ([[hydrogen|H]]2[[sulfur|S]]) is a common contaminant, which must be removed prior to most uses.

===Energy content===

[[Combustion]] of one cubic meter yields 38 MJ (10.6 kWh). Natural gas has the highest energy/carbon ratio of any fossil fuel, and thus produces less carbon dioxide per unit of energy.

== Storage and transport ==

===Transport===

The major difficulty in the use of natural gas is [[transport]]ation. Natural gas [[pipeline transport|pipelines]] are economical and common on land and across medium-length stretches of water (like [[Langeled pipeline|Langeled]], [[Interconnector (North Sea)|Interconnector]] and [[Trans-Mediterranean Pipeline]]), but are impractical across large oceans. Liquefied natural gas ([[LNG]]) [[LNG carrier|tanker ships]], railway tankers, and [[tank truck]]s are also used.

===Storage===
[[File:Storage Density of Natural Gas.jpg|thumb|storage density of natural gas]]
CNG is typically stored in steel or [[composite overwrapped pressure vessel|composite containers]] at high pressure (3000 to 4000 psi, or 205 to 275 bar). These containers are not typically temperature controlled, but are allowed to stay at local ambient temperature. There are many standards for CNG cylinders, the most popular one is ISO 11439.<ref>{{cite web | url = http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=33298 | title = ISO 11439:2000, Gas cylinders -- High pressure cylinders for the on-board storage of natural gas as a fuel for automotive vehicles |publisher = ISO ([[International Organization for Standardization]])}}</ref><ref>{{cite web|url=http://www.iso11439.com |title=ISO 11439 Overview and FAQ |deadurl=yes |archiveurl=https://web.archive.org/web/20110713063142/http://www.iso11439.com/ |archivedate=July 13, 2011 }}</ref> For North America the standard is ANSI NGV-2.

LNG storage pressures are typically around 50-150 psi, or 3 to 10 bar. At atmospheric pressure, LNG is at a temperature of -260 °F (-162 °C), however, in a vehicle tank under pressure the temperature is slightly higher (see [[saturated fluid]]). Storage temperatures may vary due to varying composition and storage pressure. LNG is far denser than even the highly compressed state of CNG. As a consequence of the low temperatures, vacuum insulated storage tanks typically made of stainless steel are used to hold LNG.

CNG can be stored at lower pressure in a form known as an ANG ([[Adsorbed]] Natural Gas) tank at 35 bar (500 psi, the pressure of gas in natural gas pipelines) in various sponge like materials, such as [[activated carbon]]<ref>{{cite press release | date = February 16, 2007 | title = From Farm Waste to Fuel Tanks |url = https://www.nsf.gov/news/news_summ.jsp?cntn_id=108390 |publisher = US [[National Science Foundation]] (NSF)}}</ref> and [[metal-organic framework]]s (MOFs).<ref>{{cite journal | url = http://pubs.acs.org/doi/full/10.1021/ja0771639 | publisher = US [[National Science Foundation]] (NSF) | journal = Journal of the American Chemical Society | title = Metal-Organic Framework from an Anthracene Derivative Containing Nanoscopic Cages Exhibiting High Methane Uptake | author=Shengqian Ma |author2=Daofeng Sun |author3=Jason M. Simmons |author4=Christopher D. Collier |author5=Daqiang Yuan |author6=Hong-Cai Zhou | year = 2008 |volume = 130 |issue = 3 |pages = 1012–1016 | doi = 10.1021/ja0771639 | pmid=18163628}}</ref> The fuel is stored at similar or greater energy density than CNG. This means that vehicles can be refuelled from the natural gas network without extra gas compression, the fuel tanks can be slimmed down and made of lighter, less strong materials.

=== Conversion kits ===
Conversion kits for gasoline or diesel to LNG/CNG are available in many countries, along with the labor to install them. However, the range of prices and quality of conversion vary enormously.

Recently, regulations involving certification of installations in USA have been loosened to include certified private companies, those same kit installations for CNG have fallen to the $6,000+ range (depending on type of vehicle).{{Citation needed|date=February 2012}}

==Implementation==
{{Fancruft|section|date=September 2017|reason=This artilceis seriously bloated. Country-by-country breakdowns are one of the reasons this and many alternative fuel/electric vehicle articles are far too long.}}
{| style="float:right;" class="wikitable"
! colspan=6| '''Top ten countries with the largest NGV vehicle fleets - 2017<ref>http://www.ngvexpo.com/msg.php?id=1631</ref>''' (millions)
|-
!Rank||Country||Registered fleet ||Rank||Country|| Registered fleet
|-
|align=center| 1||China || style="text-align:right;"| 5.000||align=center| 6|| Brazil || style="text-align:right;"| 1.781
|-
|align=center| 2||Iran|| style="text-align:right;"| 4.000||align=center| 7|| Italy || style="text-align:right;"| 1.001
|-
|align=center| 3||India || style="text-align:right;"| 3.045||align=center| 8|| Colombia || style="text-align:right;"| 0.556
|-
|align=center| 4||Pakistan|| style="text-align:right;"| 3.000 ||align=center | 9|| Thailand || style="text-align:right;"| 0.474
|-
|align=center| 5||Argentina || style="text-align:right;"| 2.295||align=center| 10|| Uzbekistan || style="text-align:right;"| 0.450
|-
| align=center colspan=6| '''World Total = 24.452 million NGV vehicles'''
|}
===Overview===

Natural gas vehicles are popular in regions or countries where natural gas is abundant and where the government chooses to price CNG lower than gasoline.<ref name="TwoBillion"/> The use of natural gas began in the [[Po Valley|Po River Valley]] of [[Italy]] in the 1930s, followed by [[New Zealand]] in the 1980s, though its use has declined there. At the peak of New Zealand's natural gas use, 10% of the nation's cars were converted, around 110,000 vehicles.<ref name="TwoBillion"/> In the United States CNG powered buses are the favorite choice of several [[public transit]] agencies, with a fleet of more than 114,000 vehicles, mostly buses.<ref name="GreenCar">{{cite web|url=http://www.greencarcongress.com/2009/10/forecast-17m-natural-gas-vehicles-worldwide-by-2015.html#more|title=Forecast: 17M Natural Gas Vehicles Worldwide by 2015|author=Pike Research|date=2009-10-19|publisher=[[Green Car Congress]]|accessdate=2009-10-19}}</ref> India, Australia, Argentina, and Germany also have widespread use of natural gas-powered buses in their public transportation fleets.<ref name="TwoBillion"/>

===Europe===
[[File:Brescia Trasporti Iveco CityClass 632 via Sardegna 20120828.JPG|thumb|CNG-powered bus in Italy ]]
[[File:CNG-powered buses in Horlivka, Ukraine.tif|thumb|CNG-powered buses in [[Horlivka]], eastern Ukraine ]]

====Germany====
Germany hit the milestone of 900 CNG filling stations nationwide in December 2011. Gibgas, an independent consumer group, estimates that 21% of all CNG filling stations in the country offer a natural gas/[[biomethane]] mix to varying ratios, and 38 stations offer pure biomethane.<ref>{{cite web|url=http://www.ngvglobal.com/900th-cng-filling-station-for-germany-1221|title=900th CNG Filling Station for Germany|author=Gibgas|publisher=NGV Global News|date=2011-12-21|accessdate=2011-12-28}}</ref>

==== Greece ====
[[Greece]] uses natural gas buses for public transport in [[Athens]].
Also the Public Gas Company (DEPA) has a network of 11 stations (as of 2017), under brand "Fisikon", and plans more stations in next 5 years.

====Ireland====
[[Bus Éireann]] Introduced the first [[NGV]] on 17 July 2012. It will operate on the 216 city centre to Mount Oval, Rochestown, route until mid-August on a trial being undertaken in partnership with [[Ervia]]. The Eco-city bus is made by [[MAN SE|MAN]].<ref>{{cite news | url = http://www.irishexaminer.com/archives/2012/0717/ireland/natural-gas-bus-hits-the-streets-in-bid-to-cut-fuel-bill-201037.html| title = Natural gas bus hits the streets in bid to cut fuel bill | first = Eoin |last = English | date = July 17, 2012 | newspaper = Irish Examiner }}</ref>

====Italy====
Natural gas traction is quite popular in Italy, due to the existence of a capillar distribution network for industrial use since the late 50s and a traditionally high retail price for petrol. As of April 2012 there were about 1173 filling stations, mainly located in the northern regions,<ref>{{cite web | url = http://www.metanoauto.com/modules.php?name=Distributori | title = Distributori metano in Europa: Il primo elenco interattivo aggiornato in tempo reale, online da maggio 2006 |trans-title=Natural gas distributors in Europe: The first list is updated in real-time interactive, online since May 2006| publisher = metanoauto.com}}</ref> while the fleet reached 730,000 CNG vehicles at the end of 2010.<ref name=IANGV/>

====Ukraine====
Ukraine’s first compressed natural gas refueling station (CNGS) was commissioned in 1937. Today, there is a well-developed CNGS network across the country.<ref>{{cite web | url = http://www.apvgn.pt/documentacao/gnc_ucrania.pdf | title = Use of Compressed Natural Gas (CNG) as Motor Fuel in Ukraine, Prospects and Problems | date = 2006 | publisher = 23rd World Gas Conference, Amsterdam | authors = Igor Orlov and Volodymyr Kozak | access-date = 2014-01-06 | archive-url = https://web.archive.org/web/20140106040300/http://www.apvgn.pt/documentacao/gnc_ucrania.pdf | archive-date = 2014-01-06 | dead-url = yes | df = }}</ref> Many buses were converted to run on CNG during the 1990s, primarily for economic reasons. The retrofitted cylinders are often visible atop the vehicle's roof and/or underneath the body. Despite their age, these buses remain in service and continue to provide reliable public transport combined with the environmental benefits of CNG.

====United Kingdom====
CNG buses are beginning to be used in the UK, e.g. by [[Reading Buses]].

===North America===

With the recent increase in natural gas production due to widespread use of [[fracking]] technology, many countries, including the United States and Canada, now can be self-sufficient. Canada is a substantial net exporter of natural gas, though the United States still has a net import of natural gas.<ref>http://www.eia.gov/countries/country-data.cfm?fips=ca#ng</ref><ref>http://www.eia.gov/dnav/ng/hist/n9180us1m.htm</ref> Natural gas prices have decreased dramatically in the past few years and are likely to decrease further as additional production comes on line. However, the EIA predicts that natural gas prices will start increasing in a few years as the most profitable natural gas reserves are used up.<ref>{{Citation | url = http://www2.hmc.edu/~evans/AEO2012.pdf | title = Annual Energy Outlook 2012 | date = June 2012 | page = 91 }}{{Dead link|date=August 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Natural gas prices have decreased from $13 per mmbtu (USD) in 2008 to $3 per mmbtu (USD) in 2012.<ref>{{Cite web | url = http://www.infomine.com/investment/metal-prices/natural-gas/all/ | title = Historical Natural Gas Prices and Price Chart | publisher = InfoMine Inc. | accessdate = 24 November 2012}}</ref> It is likely therefore that natural gas-powered vehicles will be increasingly cheaper to run relative to gasoline-powered vehicles. The issue is how to finance the purchase and installation of conversion kits. Some support may be available through the Department of Energy. Private initiatives which essentially lease the conversion equipment in exchange for slightly higher natural gas refueling can be self-financing and offer considerable advantages to liquidity strapped consumers.{{citation needed|date=August 2012}}

====Canada====

[[File:Hamilton Street Railway 510213 wide.jpg|thumb|CNG-powered bus in [[Hamilton, Ontario]]]]

Natural Gas has been used as a motor fuel in Canada for over 20 years.<ref>{{Citation
| url = http://www.transportation.alberta.ca/Content/docType57/Production/NGVBrief.pdf | title = NATURAL GAS VEHICLES IN ALBERTA | first = Lawrence |last = Schmidt | first2=Jason |last2 = Politylo | first3=Sarah |last3 = Pinto | publisher = Government of Alberta, Infrastructure Policy and Planning | date = November 2005}}</ref> With assistance from federal and provincial research programs, demonstration projects, and NGV market deployment programs during the 1980s and 1990s, the population of light-duty NGVs grew to over 35,000 by the early 1990s. This assistance resulted in a significant adoption of natural gas transit buses as well.<ref name="iangv.org">{{citation|publisher=International Association for Natural Gas Vehicles |year=2010 |title=Natural Gas Vehicles Statistics |url=http://www.iangv.org/tools-resources/statistics.html |deadurl=yes |archiveurl=https://web.archive.org/web/20100110101111/http://www.iangv.org/tools-resources/statistics.html |archivedate=January 10, 2010 }}</ref> The NGV market started to decline after 1995, eventually reaching today’s vehicle population of about 12,000.<ref name="iangv.org"/>

This figure includes 150 urban transit buses, 45 school buses, 9,450 light-duty cars and trucks, and 2,400 forklifts and ice-resurfacers. The total fuel use in all NGV markets in Canada was 1.9 petajoules (PJs) in 2007 (or 54.6 million litres of gasoline litres equivalent), down from 2.6 PJs in 1997. Public CNG refuelling stations have declined in quantity from
134 in 1997 to 72 today. There are 22 in British Columbia, 12 in Alberta, 10 in Saskatchewan, 27 in
Ontario, and 1 in Québec. There are only 12 private fleet stations.<ref>{{citation | url = http://oee.nrcan.gc.ca/sites/oee.nrcan.gc.ca/files/pdf/transportation/alternative-fuels/resources/pdf/roadmap.pdf | title = Natural Gas Use in the Canadian Transportation Sector | author = Natural Gas Use in Transportation Roundtable | date = December 2010 | publisher = Canadian Natural Gas Vehicle Alliance}}</ref>

====United States====
[[File:Metrobus powered with CNG 5198 DCA 03 2009.jpg|thumb|Buses powered with [[Compressed natural gas|CNG]] are common in the United States ]]
As of December 2009, the U.S. had a fleet of 114,270 [[compressed natural gas]] (CNG) vehicles, 147,030 vehicles running on [[liquefied petroleum gas]] (LPG), and 3,176 vehicles running on [[liquefied natural gas]] (LNG).<ref name=USeDataBook>{{cite web|url=http://cta.ornl.gov/data/tedb30/Edition30_Full_Doc.pdf|title=Transportation Energy Data Book: Edition 30|author1=Stacy C. Davis|author2=Susan W. Diegel|author3=Robert G. Boundy|last-author-amp=yes|publisher=Office of Energy Efficiency and Renewable Energy, [[U.S. Department of Energy]]|date=June 2011|accessdate=2011-08-27|deadurl=yes|archiveurl=https://web.archive.org/web/20110928135644/http://cta.ornl.gov/data/tedb30/Edition30_Full_Doc.pdf|archivedate=2011-09-28|df=}} See Tables 6.1 and 6.5, pp. 6-3 and 6-8.</ref> The NGV fleet is made up mostly of transit buses but there are also some government fleet cars and vans, as well as increasing number of corporate trucks replacing diesel versions, most notably [[Waste Management, Inc]] and [[United Parcel Service|UPS]] trucks. As of 12-Dec-2013 Waste Management has a fleet of 2000 CNG Collection trucks; as of 12-Dec-2013 UPS has 2700 alternative fuel vehicles. As of February 2011, there were 873 CNG refueling sites, 2,589 LPG sites, and 40 LNG sites, led by [[California]] with 215 CNG refueling stations in operation, 228 LPG sites and 32 LNG sites. The number of refueling stations includes both public and private sites, and not all are available to the public.<ref name=USeDataBook/> As of December 2010, the U.S. ranked 6th in the world in terms of number of NGV stations.<ref name=IANGV/> Currently there are 160,000 NGVs operating in the country.

====Mexico====
The natural gas vehicle market is limited to fleet vehicles and other public use vehicles like minibuses in larger cities. However the state-owned bus company [[Red de Transporte de Pasajeros|RTP]] Of [[Mexico City]] has purchased 30 [[Hyundai]] Super Aero City CNG-Propelled buses to integrate with the existing fleet as well as to introduce new routes within the city.
[[File:Posto GNV 01 2009 485 CWB.jpg|thumb|CNG pumps at a Brazilian gasoline service station, [[Paraná (state)|Paraná state]].]]
[[File:SAO 09 2008 Fiat Siena TetraFuel 2 views v1.jpg|thumb|Popular among [[taxicab|taxi]] drivers, the Brazilian [[Fiat Siena|Fiat Siena Tetrafuel]] 1.4, is a [[multifuel]] car that runs as a [[flexible-fuel vehicle|flexible-fuel]] on pure [[gasoline]], or [[w:Common ethanol fuel mixtures#E20, E25|E20-E25 blend]], or pure ethanol ([[w:Common ethanol fuel mixtures#E100|E100]]); or runs as a [[bi-fuel vehicle|bi-fuel]] with [[Compressed natural gas|natural gas (CNG)]]. Below: the CNG storage tanks in the trunk.]]

===South America===

====Overview====
CNG vehicles are common in South America, with a 35% share of the worldwide NGV fleet,<ref name=IANGV/> where these vehicles are mainly used as [[taxicab]]s in main cities of Argentina and Brazil. Normally, standard gasoline vehicles are retrofitted in specialized shops, which involve installing the gas cylinder in the trunk and the CNG injection system and electronics.

As of 2009 Argentina had 1,807,186 NGV's with 1,851 refueling stations across the nation,<ref name=IANGV/> or 15% of all vehicles;<ref name="LatinGNV">{{cite web|url=http://www.ngvglobal.com/en/country-reports/latin-america-ngvs-an-update-report-02074.html |archive-url=https://archive.is/20081120221031/http://www.ngvglobal.com/en/country-reports/latin-america-ngvs-an-update-report-02074.html |dead-url=yes |archive-date=2008-11-20 |title=Latin America NGVs: An Update Report |author=R. Fernandes |publisher=International Association of Natural Gas Vehicles |date=2008-08-20 |accessdate=2008-10-11 }}</ref> and Brazil had 1,632,101 vehicles and 1,704 refueling stations,<ref name=IANGV/> with a higher concentration in the cities of [[Rio de Janeiro]] and [[São Paulo]].<ref name="GNVNews">{{cite web|url=http://www.bigas.com.br/sistema/?modulo=gnvnews&acao=abrir&id=22|title=Montadores Investem nos Carros á GNV|author=GNVNews|publisher=Institutio Brasileiro de Petroleo e Gas|date=November 2006|accessdate=2008-09-20|language=Portuguese|deadurl=yes|archiveurl=https://web.archive.org/web/20081211175309/http://www.bigas.com.br/sistema/?modulo=gnvnews&acao=abrir&id=22|archivedate=2008-12-11|df=}}</ref><ref name="LatinGNV"/>

Colombia had an NGV fleet of 300,000 vehicles, and 460 refueling stations as of 2009.<ref name=IANGV/> [[Bolivia]] has increased its fleet from 10,000 in 2003 to 121,908 units in 2009, with 128 refueling stations.<ref name=IANGV/>

Peru had 81,024 NGVs and 94 fueling stations as 2009,.<ref name=IANGV/> In Peru, several factory-built CNVs have the tanks installed under the body of the vehicle, leaving the trunk free. Among the models built with this feature are the [[Fiat Multipla]], the new [[Fiat Panda]], the [[Volkswagen Touran]] Ecofuel, the [[Volkswagen Caddy]] Ecofuel, and the Chevy Taxi. Right now, Peru has 224,035 NGVs.

Other countries with significant NGV fleets are [[Venezuela]] (226,100) as of 2017 and [[Chile]] (15,000) as of 2017.<ref name=IANGV/>

====Latest developments====
[[GM do Brasil]] introduced the MultiPower engine in August 2004 which was capable of using CNG, alcohol and gasoline as fuel. The GM engine has electronic fuel injection that automatically adjusts to any acceptable fuel configuration. This motor was used in the [[Opel Astra|Chevrolet Astra]] and was aimed at the taxi market.<ref name="GNVNews"/>

In 2006 the Brazilian subsidiary of [[Fiat]] introduced the [[Fiat Siena|Fiat Siena Tetra fuel]], a four-fuel car developed under [[Magneti Marelli]] of [[Fiat]] Brazil.<ref name="TreeH">{{cite web|url=http://www.treehugger.com/files/2006/08/Fiat_sienna_tetr.php|title= Fiat Siena Tetra Power: Your Choice of Four Fuels |publisher=Treehugger|author= Christine Lepisto|date=2006-08-27 |accessdate=2008-08-24|language= }}</ref><ref>{{cite web| url=http://news.caradisiac.com/Nouvelle-Fiat-Siena-2008-sans-complexe-359 |title=Nouvelle Fiat Siena 2008: sans complexe |publisher=Caradisiac | date=2007-11-01| accessdate=2008-08-31 | language=French }} {{fr icon}}</ref> This automobile can run on 100% ethanol ([[w:Common ethanol fuel mixtures#E100|E100]]), [[w:Common ethanol fuel mixtures#E20, E25|E20 to E25]] blend (Brazil's normal ethanol gasoline blend), pure gasoline (not available in Brazil), and natural gas, and switches from the gasoline-ethanol blend to CNG automatically, depending on the power required by road conditions.<ref>{{cite web |url=http://www.webmotors.com.br/wmpublicador/Noticias_Conteudo.vxlpub?hnid=36391 |author=Agência AutoInforme |title=Siena Tetrafuel vai custar R$ 41,9 mil |publisher=WebMotor |date=2006-06-19 |accessdate=2008-08-14 |language=Portuguese |deadurl=yes |archiveurl=https://web.archive.org/web/20081210211007/http://www.webmotors.com.br/wmpublicador/Noticias_Conteudo.vxlpub?hnid=36391 |archivedate=2008-12-10 |df= }} {{pt icon}}The article argues that even though Fiat called it tetra fuel, it actually runs on three fuels: natural gas, ethanol, and gasoline.</ref>

Since 2003 and with the commercial success of flex cars in Brazil, another existing option is to [[retrofit]] an ethanol [[flexible-fuel vehicle]] to add a natural gas tank and the corresponding injection system. Some [[taxicab]]s in [[São Paulo]] and [[Rio de Janeiro]], Brazil, run on this option, allowing the user to choose among three fuels (E25, E100 and CNG) according to current market prices at the pump. Vehicles with this adaptation are known in Brazil as '''tri-fuel''' cars.<ref>{{cite web|url=http://www.devanagari.com.br/taxinews.com.br/pag/noticia_02_resumos.asp?regn=36|title=Gás Natural Veicular|publisher=TDenavagari.com.br|author=TaxiNews|date=|accessdate=2008-08-24|language=Portuguese}}{{dead link|date=September 2017 |bot=InternetArchiveBot |fix-attempted=yes }} {{pt icon}}</ref>

===South Asia===

====Pakistan====
[[Pakistan]] was the country with the second largest fleet of NGV with a total of 2.85 million by the end of 2011.<ref>{{cite web | url = http://www.ngvc.org/about_ngv/index.html | title = About NGVs | publisher = Natural Gas Vehicles for America | accessdate = 24 November 2012}}</ref> Most of the public transportation fleet has been converted to CNG.<ref>{{cite news|url=http://www.thenews.com.pk/TodaysPrintDetail.aspx?ID=35323&Cat=5&dt=3/10/2011|title=CNG cylinders or moving bombs?|author=Shahab Ansari|work=International The News|date=2011-03-10|accessdate=2011-04-05}}</ref> Also, in Pakistan and India,<ref>{{cite news| url=http://www.hindu.com/2009/11/08/stories/2009110859560300.htm | location=Chennai, India | work=The Hindu | title=CNG shortage puts auto drivers in a fix | date=2009-11-08}}</ref><ref>{{cite news | url = http://www.rediff.com/news/slide-show/slide-show-1-gas-shortage-hits-mumbai/20110315.htm | title = Gas shortage hits Mumbai; Taxis, autos off roads | date = March 15, 2011 |publisher = Rediff.com}}</ref> there have been on-going (last several years now) series of CNG fuel shortages which periodically waxes and wanes, getting the fuel into a tank can be a major problem. In July 2011, petrol usage shot up 15% from the month before due to shortages.<ref>{{cite news | url = http://www.dailytimes.com.pk/default.asp?page=2011%5C08%5C12%5Cstory_12-8-2011_pg5_2 | newspaper = Daily Times | date = August 12, 2011 | title = Petrol sales at record high in July owing to CNG shortage | location = Karachi, Pakistan}}</ref> Pakistan also has reported that over 2,000 people have died in 2011 from CNG cylinder blasts, because of low quality of cylinders there.<ref>{{cite news | url = http://www.thenews.com.pk/Todays-News-4-102120-Over-2000-killed-in-CNG-cylinder-blasts-in-2011-report | location = Karachi, Pakistan | title = Over 2,000 killed in CNG cylinder blasts in 2011: report | first = M. Waqar | last = Bhatti | date = April 10, 2012 | newspaper = The News International}}</ref> In 2012, the Pakistani government took the decision to gradually phase out CNG sector altogether beginning by banning any new conversions to CNG and banning the manufacturing of new NGV's. In addition the government plans to close down all refueling stations in the next 3 years.<ref>{{cite news |url = http://tribune.com.pk/story/415090/time-is-up-government-to-wipe-out-cng-sector-gradually/ | title = Time is up: Government to wipe out CNG sector gradually | date = July 31, 2012 | newspaper = The Express Tribune | location = Lahore, Pakistan}}</ref><ref>{{cite news | url = http://www.nation.com.pk/pakistan-news-newspaper-daily-english-online/business/02-Oct-2012/govt-to-put-an-end-to-cng-industry-in-phases-asim | title = Govt to put an end to CNG industry in phases: Asim | first = Imran Ali | last = Kundi | date = October 2, 2012 | location = Islamabad, Pakistan | newspaper = The Nation | access-date = 2012-10-08 | archive-url = https://web.archive.org/web/20121009050329/http://www.nation.com.pk/pakistan-news-newspaper-daily-english-online/business/02-Oct-2012/govt-to-put-an-end-to-cng-industry-in-phases-asim | archive-date = 2012-10-09 | dead-url = yes | df = }}</ref>

====India====
[[File:CNG filling station, Delhi.JPG|thumb|A CNG powered car being filled in a filling station in Delhi]]
In 1993, CNG had become available in [[Delhi]], India's capital, though LPG is what really took off due to its inherently far lower capital costs. Compressed Natural Gas is a domestic energy produced in Western parts of India. In India, most CNG vehicles are dual fueled, which means they can run both on CNG and gasoline. This makes it very convenient and users can drive long distances without worrying about availability of natural gas (as long as gasoline is available). As of December 2010 India had 1,080,000 NGVs and 560 fueling stations, many of the older ones being LPG rather than CNG.<ref name=IANGV/> In addition, it is thought that more illegally converted LPG autos than legal ones ply the streets in India, some estimates are as high as 15 million "autos" (running the gamut of everything from LPG motored pedal bicycles to CNG buses)<ref>{{Cite web | url = http://info.bellperformance.com/blog/bid/48368/LPG-Fueled-Vehicles-Coming-Soon | work = Blog | title = LPG Fueled Vehicles Coming Soon |publisher = Bell Performance, Inc. |date = 22 February 2011}}</ref>

In 1995, a lawyer filed a case with the [[Supreme Court of India]] under the Public Interest Litigation rule, which is part of the Constitution of India and enables any citizen to address directly the Supreme Court. The lawyer’s case was about the health risks caused by air pollution emitted from road vehicles. The Supreme Court decided that cars put into circulation after 1995 would have to run on unleaded fuel. By 1998, India was converted to 100% of unleaded fuel after the government ruled that diesel cars in India were restricted to 10,000 ppm after 1995. At the beginning of 2005, 10,300 CNG busses, 55,000 CNG three-wheelers taxis, 5,000 CNG minibuses, 10,000 CNG taxis and 10,000 CNG cars run on India’s roads (1982-2008 Product-Life Institute, Geneva). The Delhi Transport Corporation currently operates the world's largest fleet of CNG buses for public transport.<ref>{{Citation | url = http://www.product-life.org/en/archive/cng-delhi | title = CNG Delhi – the world’s cleanest public bus system running on CNG: Interview with Anumita Roychaudhary, CES | publisher = Product-Life Institute, Geneva | date = |accessdate = 25 November 2012}}</ref> Currently India stands 3rd with 3.045 million NGVs.

====Iran====
By the end of 2015, Iran had the world's largest fleet of NGV at 3.5 million vehicles. The share of compressed natural gas in the national fuel basket is more than 23%. CNG consumption by Iran’s transportation sector is around 20 million cubic meters per day.<ref>http://financialtribune.com/articles/economy-auto/32408/iran-gas-vehicle-market-projections</ref> There are 2,335 CNG stations.<ref>http://financialtribune.com/articles/energy/44382/cng-stations-top-2380-march</ref> The growth of NGV market in Iran has in large part been due to Iranian government intervention to decrease the society's dependence on gasoline. This governmental plan was implemented to reduce the effect of sanctions on Iran and make the nation's domestic market less dependent on imported gasoline.<ref>{{citation | url = http://www.iags.org/iran121206.pdf | publisher = Institute for the Analysis of Global Security (IAGS) | title = Ahmadinejad’s Gas Revolution: A Plan to Defeat Economic Sanctions | first = Anne |last = Korin |first2= Gal |last2= Luft | date = December 2006}}</ref><ref>{{cite news | title = The New Iran Sanctions: Worse Than the Old Ones | first= Gal |last= Luft | date = 11 August 2009 | newspaper = Foreign Policy | url = https://foreignpolicy.com/articles/2009/08/11/the_new_iran_sanctions_worse_than_the_old_ones | publisher = The Foreign Policy Group, LLC.}}</ref><ref>{{citation | url = http://www.iea.org/publications/freepublications/publication/natural_gas_vehicles.pdf | title = The Contribution of Natural Gas Vehicles to Sustainable Transport | year = 2010 | publisher = International Energy Agency | first = Michiel |last = Nijboer}}</ref> Iran has been manufacturing its own NGV's through local manufacturing using [[IKCO EF Engines|dedicated CNG engines]] which use gasoline only as a back up fuel. Also by 2012, Iranian manufacturers had the capacity to build 1.5 million CNG cylinders per year and therefore Iranian government has banned their imports to support the local manufacturers.<ref>{{cite web | url = http://www.jomhourieslami.com/1391/13910129/13910129_18_jomhori_islami_eghtesadi_0011.html | first = Jomhuri | last = Eslami | date = 1391-01-29 | title = بازرسي مخازن سوخت خودروهاي گازسوز در سال 91، الزامي است | trans-title = NGV fuel tanks must be inspected in 91 | access-date = 2012-04-24 | archive-url = https://web.archive.org/web/20120422050753/http://jomhourieslami.com/1391/13910129/13910129_18_jomhori_islami_eghtesadi_0011.html | archive-date = 2012-04-22 | dead-url = yes | df = }}</ref> In addition CNG in Iran costs the least compared to the rest of the world.<ref>{{cite web | title = Prices of CNG | url = http://www.cngstations.com/prices-of-cng/ | publisher = CNGStations.com | year = 2010}}</ref> In 2012, the Iranian government announced a plan to replace the traditional CNG cylinders with [[Adsorption|Adsorbed]] Natural Gas (ANG) cylinders.<ref>{{Cite news | url = http://en.trend.az/regions/iran/2065382.html | title = Iran plans to produce ANG for vehicles |location = Baku, Azerbaijan |date = 14 September 2012 | first = S. |last = Isayev |first2= T. |last2= Jafarov | publisher = Trend News Agency}}</ref><ref>{{cite news | url = http://www.azernews.az/oil_and_gas/43683.html |title = Iran plans to substitute compressed gas with ANG in vehicles | date = 14 September 2012 |publisher = AzerNews}}</ref>

===Southeast Asia===
{{update section|date=December 2016}}
[[Image:No.39.jpg|thumb|A CNG powered [[Hino Motors|Hino RU1JSSL]] bus, operated by [[Bangkok Mass Transit Authority|BMTA]] in [[Thailand]].]]

====Thailand====
[[Thailand]] has for over a 15 years run [[autogas]] taxi cabs in Bangkok,<ref name="Thailand08">{{Cite news|url=http://www.ngvglobal.com/ptt-softens-loans-for-truck-operators-over-30-million-available-0819 |archive-url=https://web.archive.org/web/20121025032527/http://www.ngvglobal.com/ptt-softens-loans-for-truck-operators-over-30-million-available-0819 |dead-url=yes |archive-date=October 25, 2012 |title=PTT Softens Loans for Truck Operators – Over $30 Million Available |date=August 19, 2008 |location=Thailand, Bangkok |publisher=NGV Global News }}</ref> though autos and buses had erroneously labelled NGV stickers on them, when in fact, were LPG fuelled.

In view of a generous supply of natural gas but relying on imported oil, the Thailand government heavily promoted alternative fuels like LPG, natural gas and ethanol to replace gasoline beginning around 2003, yet NGV was very slow to take off due to cheaper LPG fuel, a pre-existing LPG fleet, and very low conversion cost of local LPG conversion shops as compared to factory installed CNG or conversion. A significant effort was taken when the state-controlled oil company [[PTT Public Company Limited|PTT PCL]] built a network of natural gas refueling stations. The cost of subsidy was estimated at US$150 million in 2008.

As price of oil climbed rapidly, it was estimated more than 40,000 new cars and trucks powered by natural-gas were purchased in six months in 2008, including many buses. That year, about half of the taxi fleet in Bangkok used LPG, and were prodded to convert to CNG, with little success. Since 2008, there has been a government arm-twisting to switch from LPG to CNG, with a rollout of CNG stations near Bangkok around 2007 and then upcountry in 2010, at times replacing LPG stations. Operators of used vehicles have balked at the massive conversion cost (up to quadruple that of LPG in Thailand), especially given Thailand's strong ultra-competitive domestic LPG conversion industry, as well as retail CNG fuel cost (one and a half times). Thailand had some 700,000 LPG fueled vehicles, and 300,000 CNG fueled, with 1,000 LPG stations and 600 CNG as of 2011.<ref>{{cite news | url = http://www.bangkokpost.com/business/economics/317341/motorists-unfazed-by-dearer-gas | newspaper = Bangkok Post | title = Motorists unfazed by dearer gas | date = 2012-10-17 | first = Yuthana |last = Praiwan}}</ref> Demand has increased 26% over 2011 for CNG in Thailand.<ref>http://www.bangkokpost.com/business/economics/324746/cng-price-likely-to-be-at-b13-28</ref> As of the end of 2012, Thailand has 1,014,000 LPG fueled vehicles, and consumed 606,000 tonnes in 2012 of LPG, while 483 stations serve up some 380,000 CNG vehicles.,<ref>http://www.bangkokpost.com/news/local/337380/lpg-vechicles-exceed-1-million</ref> showing that LPG conversion continues to enjoy heavy favor over NGVs despite massive government push for CNG. CNG vehicles are more likely to be bought factory installed while LPG is likely to be an aftermarket conversion. LNG vehicles in Thailand are almost non-existent except for lorries.

[[File:Taxi in Kuala Lumpur 04.JPG|thumb|NGV Proton Iswara taxi in Malaysia]]

====Malaysia====
In [[Malaysia]], the use of [[compressed natural gas]] was originally introduced for taxicabs and airport limousines during the late-1990s, when new taxis were launched with NGV engines while taxicab operators were encouraged to send in existing taxis for full engine conversions, reducing their costs of operation. Any vehicle converted to use CNG is labelled with white rhombus "NGV" (Natural Gas Vehicle) tags, lending to the common use of "NGV" when referring to road vehicles with CNG engine. The practice of using CNG remained largely confined to taxicabs predominantly in the [[Klang Valley]] and [[Penang]] due to a lack of interest. No incentives were offered for those besides taxicab owners to use CNG engines, while government subsidies on petrol and diesel made conventional road vehicles cheaper to use in the eyes of the consumers. [[Petronas]], Malaysia's state-owned oil company, also monopolises the provision of CNG to road users. {{As of|2008|July|df=US}}, Petronas only operates about 150 CNG refueling stations, most of which are concentrated in the Klang Valley. At the same time, another 50 was expected by the end of 2008.<ref name="MY CNG station no">{{cite web |url=http://thestar.com.my/metro/story.asp?file=/2008/6/13/central/21532536 |title=More natural gas stations needed, say motorists |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-13 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140522/http://thestar.com.my/metro/story.asp?file=%2F2008%2F6%2F13%2Fcentral%2F21532536 |archivedate=2011-05-21 |df= }}</ref>

As fuel subsidies were gradually removed in Malaysia starting June 5, 2008, the subsequent 41% price hike on petrol and diesel led to a 500% increase in the number of new CNG tanks installed.<ref name="MY rush 1">{{cite web |url=http://thestar.com.my/news/story.asp?file=/2008/6/8/focus/21482211 |title=Motorists rush to check out NGV system |author=Rashvinjeet S. Bedi |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-08 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140559/http://thestar.com.my/news/story.asp?file=%2F2008%2F6%2F8%2Ffocus%2F21482211 |archivedate=2011-05-21 |df= }}</ref><ref name="MY rush 2">{{cite web |url=http://thestar.com.my/metro/story.asp?file=/2008/6/25/north/21635112 |title=Long queue for NGV kits |author=Vinesh, Derrick |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-25 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140624/http://thestar.com.my/metro/story.asp?file=%2F2008%2F6%2F25%2Fnorth%2F21635112 |archivedate=2011-05-21 |df= }}</ref> National car maker [[Proton (carmaker)|Proton]] considered fitting its [[Proton Waja|Waja]], [[Proton Saga|Saga]] and [[Proton Persona|Persona]] models with CNG kits from Prins Autogassystemen by the end of 2008,<ref name="MY Potong CNG">{{cite web |url=http://thestar.com.my/news/story.asp?file=/2008/6/28/nation/21685753 |title=Proton cars to come with NGV kits |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-28 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140638/http://thestar.com.my/news/story.asp?file=%2F2008%2F6%2F28%2Fnation%2F21685753 |archivedate=2011-05-21 |df= }}</ref> while a local distributor of locally assembled [[Hyundai Motor Company|Hyundai]] cars offers new models with CNG kits.<ref name="MY Hyundai">{{cite web|url=http://biz.thestar.com.my/news/story.asp?file=/2008/7/7/business/21712982|title=Moving towards hybrid vehicles |author1=Elaine Ang |author2=Leong Hung Yee |lastauthoramp=yes |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-07-07 |accessdate=2008-08-04}}</ref> Conversion centres, which also benefited from the rush for lower running costs, also perform partial conversions to existing road vehicles, allowing them to run on both petrol or diesel and CNG with a cost varying between [[Malaysian ringgit|RM]]3,500 to RM5,000 for passenger cars.<ref name="MY rush 1"/><ref name="MY CNG conversion">{{cite web |url=http://thestar.com.my/metro/story.asp?file=/2008/6/13/central/21532553 |title=Rush to fit natural gas gadget |author=Perumal, Elan |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-13 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140707/http://thestar.com.my/metro/story.asp?file=%2F2008%2F6%2F13%2Fcentral%2F21532553 |archivedate=2011-05-21 |df= }}</ref>

[[Image:Volvo B10BLE SBS Transit SBS2988J.jpg|thumb|A CNG powered [[Volvo B10BLE]] bus, operated by [[SBS Transit]] in [[Singapore]].]]

====Singapore====
There were about 400 CNG-fueled vehicles in [[Singapore]] in mid-2007, of which about 110 are taxis operated by Smart Automobile. By February 2008, the number has risen 520 CNG vehicles, of which about half are taxis.<ref name=autogenerated1>{{Cite news | url = http://www.ngvglobal.com/en/market-developments/new-cng-fuelling-station-for-singapore.html | title = New CNG Fuelling Station for Singapore | date = February 17, 2008 |location = Singapore | publisher = NGV Global News}}</ref> All vehicles had to refuel at the sole CNG station operated by Sembcorp Gas and located on [[Jurong Island]] until the opening of the first publicly accessible CNG station at [[Mandai]] in 2008, operated by Smart Automobile.<ref>{{cite news | url = http://www.channelnewsasia.com/stories/singaporelocalnews/view/329584/1/.html | title = Singapore's largest CNG refuelling station opens at Mandai Link | author = Wong Mun Wai | date = 18 February 2008| publisher = Channel NewsAsia}}</ref> The company plans to build another four stations by 2011, by which time the company projects to operate 3,000 to 4,000 CNG taxis, and with 10,000 CNG public and commercial vehicles of other types on Singapore's roads.<ref>{{cite web |url= http://www.channelnewsasia.com/stories/singaporelocalnews/view/287780/1/.html |title=Singapore's first public CNG station to be ready by Jan 2008 |work=channelnewsasia.com |date=July 12, 2007 |author=Daryl Loo |accessdate=October 21, 2011}}</ref> Sembcorp Gas opened its second CNG station a week after the Mandai station at Jalan Buroh.<ref name=autogenerated1 />

====Indonesia====
CNG is almost unheard of as a transport fuel before 2010 in the archipelago except in [[Jakarta]], where a very relatively minor number of vehicles, most notably [[Transjakarta]] buses, use the fuel. However, since 2010 there has been a government emphasis to push usage of CNG not only for vehicle fuel, but also for domestic consumption over wood burning (which can produce deadly methanol) and kerosene.

===East Asia===

====China====
China had 450,000 NGV's and 870 refueling stations as of 2009.<ref name=IANGV/> China in 2012 has 1 million NGVs on the roads, 3 million forecast for 2015, with over 2000 stations (both CNG and LPG), with plans for 12,000 by 2020. Currently China leads the World with 5 million NGVs<ref>http://www.iangv.org/current-ngv-stats/</ref> China also has lot of vehicles running of Petrol blended with Methanol as M15 and M85.

====South Korea====
For the purpose of improving air quality in the metropolitan area of [[Seoul]], CNG buses were first introduced in July, 1997. By 2014, all [[Seoul buses]] were operating on CNG.{{citation needed|date=October 2016}} Hyundai motor developed a CNG hybrid bus with 34.5% more-fuel efficiency and 30% lower pollution compared to CNG buses.{{citation needed|date=October 2016}} As a result, Seoul city government plans to change to CNG hybrid buses for 2,235 low-bed disabled-friendly CNG bus in Seoul.{{citation needed|date=October 2016}}

CNG buses are operation in other major South Korean cities like Busan, Daegu, Daejeon, Gwangju and Incheon.{{citation needed|date=October 2016}}

====Motorsport====
{{Advert|section|date=September 2017}}
A new category of motorcar racing unites teams which compete with cars powered by natural gas, to demonstrate the effectiveness of natural gas as an alternative fuel. ECOMOTORI (magazine) Racing Team<ref>[http://www.ecomotori.net/_/ecomotori-racing-team/trionfo-di-ecomotori-al-7-ecorally-smarino-r3616 ECOMOTORI Racing Team]</ref> The magazine's team participates in the [[FIA Alternative Energies Cup]] and the talian [[:it:Campionato Italiano CSAI Energie Alternative|ACI/CSAI Alternative Energies Championship]]. In 2012, the team, led by [[Nicola Ventura]], competes with a Fiat 500 Abarth,<ref>[http://www.alvolante.it/news/abarth_500_metano-664611044 Fiat 500 Abarth]</ref> modified to run on natural gas with a Cavagna/Bigas fuel conversion kit and thus renamed "500 EcoAbarth". The driver is [[Massimo Liverani]] while in the role of navigator, alternate Valeria Strada, Alessandro Talmelli and [[Fulvio Ciervo]]. On October 14, 2012, at the end of the 7th Ecorally San Marino-Vatican with 3 wins and a second place (out of 4 races),<ref>[http://www.ecorally.eu/ Ecorally San Marino-Vatican]</ref> the Team also won the Italian CSAI Alternative Energy Pilots and Navigators titles. On 28 October 2012, after having raced in 7 European countries, collecting 3 wins, 2 second places and additional points, the team won the FIA Alternative Energies Drivers and Constructors world titles. For the first time ever, a car powered by methane won an FIA world title. In 2013, the team raced in the [[FIA Alternative Energies Cup]] and [[:it:Campionato Italiano CSAI Energie Alternative|CSAI]] Championships. The "500 EcoAbarth" of Ecomotori.net dominated the season, winning 5 of 5 titles. Thanks to the work of the team, the Abarth once again won a constructors' title since its last win 46 years ago.<ref>[http://www.lpgasmagazine.com/cavagna-bigas-traveling-to-world-lp-gas-forum-in-style/ Abarth]</ref>

==See also==
* [[Biogas|Biogas vehicle]]
* [[HCNG dispenser]]
* [[List of natural gas vehicles]]

==References==
{{Reflist|30em}}

== External links ==
{{Commons category|Compressed natural gas vehicles}}
* {{Citation|url=http://pleasebeinformed.com/publications/content/gas-powered-public-transport-how-it-began-part-1 |title=Gas Powered Public Transport - how it began |date = October 9, 2005 |website=Please Be Informed}}
* {{citation | url = http://www.afdc.energy.gov/afdc/vehicles/natural_gas_availability.html | publisher = [[U.S. Department of Energy]] | title = Natural Gas Vehicle Availability | date = November 18, 2015}}
* [http://www.greenercities.eu/ Greener Cities] – International project dedicated to the development of an ever-growing demand for environmentally friendly eco-sustainable vehicles, specifically to promote the use of cleaner fuels such as CNG and [[Biogas]]
* {{Cite web | url = http://naturalgasvehicles.com | title = Natural Gas Vehicles}}
* [http://www.metanoauto.com The Italian community of Natural Gas Vehicles ]– Forum, technical info, maps (also in English, German, and French)
* {{citation | url = http://www.energyquest.ca.gov/transportation/CNG.html | title = A Student's Guide to Alternative Fuel Vehicles: Compressed natural gas - natural gas under high pressure | publisher = California Energy Commission | date = April 22, 2002 | access-date = October 4, 2004 | archive-url = https://web.archive.org/web/20041013054711/http://www.energyquest.ca.gov/transportation/CNG.html | archive-date = October 13, 2004 | dead-url = yes | df = mdy-all }}
* {{citation|url=http://www.eere.energy.gov/cleancities/vbg/consumers/cng.shtml |publisher=U.S. Department of Energy |title=Consumers' Guide to Compressed Natural Gas |deadurl=yes |archiveurl=https://web.archive.org/web/20060429222452/http://www.eere.energy.gov/cleancities/vbg/consumers/cng.shtml |archivedate=April 29, 2006 }}
* {{cite news | url = http://www.msnbc.msn.com/id/5960905 |title = Boost for natural gas cars: Home fueling | year=2013 | publisher = NBCnews.com}}
* {{cite web | url = http://www.cngcalifornia.com/ | title = CNG California}}
* {{cite web | url=http://www.afdc.energy.gov/uploads/publication/ng_powered_bus_service.pdf |title=Developing a Natural GasPowered Bus Rapid Transit Service: A Case Study|first=George |last=Mitchell|work=[[National Renewable Energy Laboratory]]|date=November 2015}}
* [http://www.ngvjournal.com/worldwide-fuel-prices/ Worldwide fuel prices], 2010

{{Alternative propulsion}}

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[[Category:Natural gas vehicles|*]]
[[Category:Green vehicles]]

Natural gas vehicle

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{{redirect|NGV|the art gallery in Melbourne, Australia|National Gallery of Victoria}}
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[[File:Guidetti cng truck.jpg|thumb|200px|Truck running with Guidetti CNG system]]
[[Image:FillingUpCNG.jpg|thumb|200px|Fueling ([[Fiat Multipla]])]]
[[Image:2009 Honda Civic NGV--DC.jpg|thumb|right|200px|2009 [[Honda Civic GX]] hooked up to Phill refueling system.]]

A '''natural gas vehicle''' ('''NGV''') is an [[alternative fuel vehicle]] that uses [[Compressed natural gas|compressed natural gas (CNG)]] or [[liquefied natural gas|liquefied natural gas (LNG)]]. Natural gas vehicles should not be confused with [[autogas|vehicles powered by LPG]] (mainly [[propane]]), which is a fuel with a fundamentally different composition.

In a natural gas powered vehicle, energy is released by combustion of essentially [[Methane]] gas (CH4) fuel with Oxygen (O2) from the air to CO2 and water vapor (H2O) in an [[internal combustion engine]]. Methane is the cleanest burning [[hydrocarbon]] and many contaminants present in [[natural gas]] are removed at source.

Safe, convenient and cost effective gas storage and fuelling is more of a challenge compared to petrol and diesel vehicles since the natural gas is pressurized and/or - in the case of LNG - the tank needs to be kept cold. This makes LNG unsuited for vehicles that are not in frequent use. The lower [[energy density]] of gases compared to liquid fuels is mitigated to a great extent by high compression or gas liquefaction, but requires a trade-off in terms of size/complexity/weight of the storage container, range of the vehicle between refueling stops, and time to refuel.

Although similar storage technologies may be used for and similar compromises would apply to a [[Hydrogen vehicle]] as part of a proposed new [[Hydrogen economy]], Methane as a gaseous fuel is safer than Hydrogen due to its [[flammability limit|lower flammability]], low corrosivity and better leak tightness due to larger [[molecular weight]]/ size, resulting in lower price hardware solutions based on proven technology and conversions. A key advantage of using natural gas is the existence, in principle, of most of the infrastructure and the supply chain, which is non-interchangeable with Hydrogen. Methane today mostly comes from non-renewable sources but can be supplied or produced from [[renewable]] sources, offering net carbon neutral mobility. In many markets, especially the Americas, natural gas may trade at a discount to other [[fossil fuel]] products such as petrol, diesel or coal, or indeed be a less valuable by-product associated with their production that has to be disposed. Many countries also provide tax incentives for natural gas powered vehicles due to the environmental benefits to society. Lower operating costs and government incentives to reduce pollution from heavy vehicles in urban areas have driven the adoption of NGV for commercial and public uses, i.e. trucks and buses.

Many factors hold back NGV popularization for [[individual mobility]] applications, i.e. private vehicles, including: relatively price and environmentally insensitive but convenience seeking private individuals; good profits and taxes extractable from small batch sales of value-added, branded petrol and diesel fuels via established trade channels and oil refiners; resistance and safety concerns to increasing gas inventories in urban areas; dual-use of utility distribution networks originally built for home gas supply and allocation of network expansion costs; reluctance, effort and costs associated with switching; prestige and nostalgia associated with petroleum vehicles; fear of redundancy and disruption. A particular challenge may be the fact that refiners are currently set up to produce a certain fuels mix from crude oil. [[Aviation fuel]] is likely to remain the fuel of choice for aircraft due to their weight sensitivity for the foreseeable future.

Worldwide, there were 24.452 million NGVs by 2016, led by [[China]] (5.0 million), [[Iran]] (4.00 million), [[India]] (3.045 million), [[Pakistan]] (3.0 million), [[Argentina]] (2.295 million), [[Brazil]] (1.781 million), and [[Italy]] (1.001 million).<ref name=NGVJournal>{{cite web|url=http://www.iangv.org/current-ngv-stats/|title=Current Natural Gas Vehicle Statistics|publisher=IANGV}}</ref> The [[Asia-Pacific]] region leads the world with 6.8 million vehicles, followed by [[Latin America]] with 4.2 million.<ref name=IANGV>{{cite web |url=http://www.iangv.org/tools-resources/statistics.html |title=Natural Gas Vehicle Statistics: Summary Data 2010 |publisher=International Association for Natural Gas Vehicles |accessdate=2011-08-02 |deadurl=yes |archiveurl=https://web.archive.org/web/20100110101111/http://www.iangv.org/tools-resources/statistics.html |archivedate=2010-01-10 |df= }} ''Click on Summary Data (2010).''</ref> In Latin America, almost 90% of NGVs have [[bi-fuel engine]]s, allowing these vehicles to run on either gasoline or CNG.<ref>{{cite web|url=http://green.autoblog.com/2011/09/26/pike-research-predicts-68-jump-in-global-cng-vehicle-sales-by-2/#continued|title=Pike Research predicts 68% jump in global CNG vehicle sales by 2016|author=Pike Research|publisher=[[AutoblogGreen]] |date=2011-09-14|accessdate=2011-09-26}}</ref> In Pakistan, almost every vehicle converted to (or manufactured for) alternative fuel use typically retains the capability of running on gasoline.

As of 2016, the U.S. had a fleet of 160,000 NG vehicles, including 3,176 LNG vehicles. Other countries where natural gas-powered buses are popular include India, [[Australia]], Argentina, [[Germany]], and [[Greece]].<ref name="TwoBillion">{{Cite book |author1=Sperling, Daniel |author2=Deborah Gordon |lastauthoramp=yes | title = Two billion cars: driving toward sustainability | year = 2009 | pages= 93–94 | publisher = [[Oxford University Press]], New York| isbn = 978-0-19-537664-7}}</ref> In [[OECD]] countries, there are around 500,000 CNG vehicles.<ref name="SusTransp">{{Cite book |author1=Ryan, Lisa |author2=Turton, Hal | year = 2007 | title = Sustainable Automobile Transport| publisher = Edward Elgar Publishing Ltd, England| isbn = 978-1-84720-451-6| pages = 40–41}}</ref> Pakistan's market share of NGVs was 61.1% in 2010, follow by [[Armenia]] with more than 77% (2014), and [[Bolivia]] with 20%.<ref name=IANGV/> The number of NGV refueling stations has also increased, to 18,202 worldwide as of 2010, up 10.2% from the previous year.<ref name=IANGV/>

Existing gasoline-powered vehicles may be converted to run on CNG or LNG, and can be dedicated (running only on natural gas) or bi-fuel (running on either gasoline or natural gas). Diesel engines for heavy trucks and busses can also be converted and can be dedicated with the addition of new heads containing spark ignition systems, or can be run on a blend of diesel and natural gas, with the primary fuel being natural gas and a small amount of diesel fuel being used as an ignition source. It is also possible to generate energy in a small gas turbine and couple the gas engine or turbine with a small electric battery to create a hybrid electric motor driven vehicle. An increasing number of vehicles worldwide are being manufactured to run on CNG by major carmakers. Until recently, the [[Honda Civic GX]] was the only NGV commercially available in the US market. More recently, [[Ford]], [[General Motors]] and [[Ram Trucks]] have bi-fuel offerings in their vehicle lineup. In 2006, the Brazilian subsidiary of [[FIAT]] introduced the [[Fiat Siena|Fiat Siena Tetra fuel]], a four-fuel car that can run on natural gas (CNG).<ref name="TreeH"/>

NGV filling stations can be located anywhere that natural gas lines exist. Compressors (CNG) or liquifaction plants (LNG) are usually built on large scale but with CNG small home refueling stations are possible. A company called FuelMaker pioneered such a system called Phill Home Refueling Appliance (known as "Phill"), which they developed in partnership with [[Honda]] for the American GX model.<ref>{{Cite web |url=http://www.fuelmaker.com/Research/PhillQandA.htm |publisher=FuelMaker Corporation - World Leader in Convenient On-Site Refueling Systems |title=Phill: Questions and Answers |deadurl=yes |archiveurl=https://web.archive.org/web/20051016173628/http://www.fuelmaker.com/research/phillqanda.htm |archivedate=October 16, 2005 |df= }}</ref><ref>{{cite web | url = http://www.evworld.com/view.cfm?section=article&storyid=847 | publisher = EVWorld | title = FEATURE: Honda's Phill-way to Hydrogen | first= Bill |last = Moore | date = May 6, 2005 | work = Open Access}}</ref> Phill is now manufactured and sold by BRC FuelMaker, a division of Fuel Systems Solutions, Inc.<ref>{{Cite web|url=http://blogs.edmunds.com/greencaradvisor/2011/03/brc-fuelmaker-again-selling-phill-home-cng-fuel-station.html|title=BRC FuelMaker Again Selling Phill Home CNG Fuel Station|accessdate=2011-04-04|archive-url=https://web.archive.org/web/20110325155026/http://blogs.edmunds.com/greencaradvisor/2011/03/brc-fuelmaker-again-selling-phill-home-cng-fuel-station.html|archive-date=2011-03-25|dead-url=yes|df=}}</ref>

CNG may be generated and used for bulk storage and pipeline transport of renewable energy and also be mixed with [[biomethane]], itself derived from [[biogas]] from [[landfill]]s or [[anaerobic digestion]]. This would allow the use of CNG for mobility without increasing the concentration of carbon in the atmosphere. It would also allow continued use of CNG vehicles currently powered by non-renewable fossil fuels that do not become obsolete when stricter CO2 emissions regulations are mandated to combat global warming.

Despite its advantages, the use of natural gas vehicles faces several limitations, including fuel storage and infrastructure available for delivery and distribution at fueling stations. CNG must be stored in high pressure cylinders (3000psi to 3600psi operation pressure), and LNG must be stored in cryogenic cylinders (-260F to -200F). These cylinders take up more space than gasoline or diesel tanks that can be molded in intricate shapes to store more fuel and use less on-vehicle space. CNG tanks are usually located in the vehicle's trunk or pickup bed, reducing the space available for other cargo. This problem can be solved by installing the tanks under the body of the vehicle, or on the roof (typical for busses), leaving cargo areas free. As with other alternative fuels, other barriers for widespread use of NGVs are natural gas distribution to and at fueling stations as well as the low number of CNG and LNG stations.<ref name="SusTransp"/>

CNG-powered vehicles are considered to be safer than gasoline-powered vehicles.<ref>{{Cite web|url=http://ngvamerica.org/pdfs/TechBul2.pdf|title=How Safe are Natural Gas Vehicles?|publisher=Clean Vehicle Education Foundation|accessdate=2008-05-08|format=PDF}}</ref><ref>{{Cite web|url=http://alternativefuels.about.com/od/naturalgaspropane/a/safenaturalgas.htm|title=How Safe is Natural Gas?|accessdate=2008-05-08}}</ref><ref>{{cite web|url=http://www.firetrainingresources.net/items/CNGAutoFire-FIREFIGHTERNEARMISScompressedpics.pdf|title=Fighting CNG fires|accessdate=2008-05-08|format=PDF|deadurl=yes|archiveurl=https://web.archive.org/web/20080528041023/http://www.firetrainingresources.net/items/CNGAutoFire-FIREFIGHTERNEARMISScompressedpics.pdf|archivedate=2008-05-28|df=}}</ref>

==CNG/LNG as fuel for automobiles==

===Available production cars===
[[File:Meriva Flex GNV SAO 10 2009 7797 with logo flex.jpg|thumb|Brazilian [[flexible-fuel vehicle|flexible-fuel]] [[Taxicab|taxi]] retrofitted to run also as a NGV. The [[Compressed Natural Gas|compressed natural gas (CNG)]] tanks are located underneath the body in the rear.]]

Existing gasoline-powered vehicles may be converted to run on CNG or LNG, and can be dedicated (running only on natural gas) or bi-fuel (running on either gasoline or natural gas). However, an increasing number of vehicles worldwide are being manufactured to run on CNG.{{citation needed|date=October 2016}} Until recently, the now-discontinued [[Honda Civic GX]] was the only NGV commercially available in the US market.<ref>{{cite web |url=http://alternativefuels.about.com/od/2008ngvavailable/a/2008CNGvehicles.htm |title=2008 Natural Gas Vehicles (NGVs) Available |author1=Christine Gable |author2=Scott Gable |lastauthoramp=yes |publisher=About.com: Hybrid Cars & Alt Fuels |date= |accessdate=2008-10-18 |deadurl=yes |archiveurl=https://web.archive.org/web/20081011214336/http://alternativefuels.about.com/od/2008ngvavailable/a/2008CNGvehicles.htm |archivedate=2008-10-11 |df= }}</ref><ref>{{cite web|url=http://automobiles.honda.com/civic-gx/ |title=2009 Honda Civic GX Natural Gas Vehicle |publisher=Honda |date= |accessdate=2008-10-18}}</ref> More recently, [[Ford]], [[General Motors]] and [[Ram Trucks]] have bi-fuel offerings in their vehicle lineup.{{citation needed|date=October 2016}} Ford's approach is to offer a bi-fuel prep kit as a factory option, and then have the customer choose an authorized partner to install the natural gas equipment. Choosing GM's bi-fuel option sends the HD pickups with the 6.0L gasoline engine to IMPCO in Indiana to upfit the vehicle to run on CNG. Ram currently is the only pickup truck manufacturer with a truly CNG factory-installed bi-fuel system available in the U.S. market.{{citation needed|date=September 2014}}

Outside the U.S. [[General Motors do Brasil|GM do Brasil]] introduced the MultiPower engine in 2004, which was capable of using CNG, alcohol and gasoline ([[Common ethanol fuel mixtures#E20, E25|E20-E25 blend]]) as fuel, and it was used in the [[Opel Astra|Chevrolet Astra]] 2.0 model 2005, aimed at the taxi market.<ref name="GNVNews"/><ref>{{cite web|url=http://www.jornalexpress.com.br/noticias/detalhes.php?id_jornal=9095&id_noticia=1703|title=Astra é líder no segmento dos compactos em 2004: As versões do Chevrolet Astra 2005|publisher=Journal Express|date=2005-01-18|language=Portuguese|accessdate=2008-10-15}} {{pt icon}}</ref> In 2006, the Brazilian subsidiary of [[FIAT]] introduced the [[Fiat Siena|Fiat Siena Tetra fuel]], a four-fuel car developed under [[Magneti Marelli]] of [[Fiat]] Brazil. This automobile can run on natural gas (CNG); 100% ethanol ([[w:Common ethanol fuel mixtures#E100|E100]]); [[w:Common ethanol fuel mixtures#E20, E25|E20 to E25]] gasoline blend, Brazil's mandatory gasoline; and pure gasoline, though no longer available in Brazil it is used in neighboring countries.<ref name="TreeH"/><ref>{{cite web |url=http://www.webmotors.com.br/wmpublicador/Noticias_Conteudo.vxlpub?hnid=36391 |author=Agência AutoInforme |title=Siena Tetrafuel vai custar R$ 41,9 mil |publisher=WebMotor |date=2006-06-19 |accessdate=2008-08-14 |language=Portuguese |deadurl=yes |archiveurl=https://web.archive.org/web/20081210211007/http://www.webmotors.com.br/wmpublicador/Noticias_Conteudo.vxlpub?hnid=36391 |archivedate=2008-12-10 |df= }}{{pt icon}} The article argues that even though Fiat called it tetra fuel, it actually runs on three fuels: natural gas, ethanol, and gasoline, as Brazilian gasoline is an E20 to E25 blend.</ref>

In 2015, Honda announced its decision to phase out the commercialization of natural-gas powered vehicles to focus on the development of a new generation of [[electric vehicle|electrified vehicles]] such as [[hybrid electric vehicle|hybrids]], [[plug-in electric car]]s and hydrogen-powered [[fuel cell vehicle]]s. Since 2008, Honda sold about 16,000 natural-gas vehicles, mainly to taxi and commercial fleets.<ref>{{cite news | url=http://www.autonews.com/article/20150615/OEM05/150619915/honda-will-drop-cng-vehicles-to-focus-on-hybrids-evs | title=Honda will drop CNG vehicles to focus on hybrids, EVs | first=Neal E. | last=Boudette | work=[[Automotive News]] | date=2015-06-15 | accessdate=2016-05-28}}</ref>

===Differences between LNG and CNG fuels===
Though LNG and CNG are both considered NGVs, the technologies are vastly different. Refueling equipment, fuel cost, pumps, tanks, hazards, capital costs are all different.

One thing they share is that due to engines made for gasoline, computer controlled valves to control fuel mixtures are required for both of them, often being proprietary and specific to the manufacturer. The on-engine technology for fuel metering is the same for LNG and CNG.

===CNG as an auto fuel===
CNG, or compressed natural gas, is stored at high pressure, {{Convert|3000|to|3600|psi|MPa}}. The required tank is more massive and costly than a conventional fuel tank. Commercial on-demand refueling stations are more expensive to operate than LNG stations because of the energy required for compression, the compressor requires 100 times more electrical power, however, slow-fill (many hours) can be cost-effective with LNG stations [missing citation - the initial liquefaction of natural gas by cooling requires more energy than gas compression]. Time to fill a CNG tank varies greatly depending on the station. Home refuelers typically fill at about 0.4 [[Gasoline gallon equivalent|GGE]]/hr. "Fast-fill" stations may be able to refill a 10 GGE tank in 5–10 minutes. Also, because of the lower energy density, the range on CNG is limited by comparison to LNG. Gas composition and throughput allowing, it should be feasible to connect commercial CNG fueling stations to city gas networks, or enable home fueling of CNG vehicles directly using a gas compressor. Similar to a car battery, the CNG tank of a car could double as a home energy storage device and the compressor could be powered at times when there is excess/ free renewable electrical energy.

===LNG as an auto fuel===
LNG, or liquified natural gas, is natural gas that has been cooled to a point that it is a cryogenic liquid. In its liquid state, it is still more than 2 times as dense as CNG. LNG is usually dispensed from bulk storage tanks at LNG fuel stations at rates exceeding 20 [[Diesel gallon equivalent|DGE]]/min. Sometimes LNG is made locally from utility pipe. Because of its cryogenic nature, it is stored in specially designed insulated tanks. Generally speaking, these tanks operate at fairly low pressures (about 70-150 psi) when compared to CNG. A vaporizer is mounted in the fuel system that turns the LNG into a gas (which may simply be considered low pressure CNG). When comparing building a commercial LNG station with a CNG station, utility infrastructure, capital cost, and electricity heavily favor LNG over CNG. There are existing LCNG stations (both CNG and LNG), where fuel is stored as LNG, then vaporized to CNG on-demand. LCNG stations require less capital cost than fast-fill CNG stations alone, but more than LNG stations.

===Advantages over gasoline and diesel===
LNG – and especially CNG – tends to corrode and wear the parts of an engine less rapidly than gasoline. Thus it is quite common to find diesel-engine NGVs with high mileages (over 500,000 miles). CNG also emits 20-29% less CO2 than diesel and gasoline.<ref>{{Cite web|url=http://www.gas-south.com/business/compressed-natural-gas.aspx|title=Gas South Compressed Natural Gas|website=www.gas-south.com|access-date=2016-04-08}}</ref> Emissions are cleaner, with lower emissions of carbon and lower particulate emissions per equivalent distance traveled. There is generally less wasted fuel. However, cost (monetary, environmental, pre-existing infrastructure) of distribution, compression, cooling must be taken into account.

===Inherent advantages/disadvantages between autogas (LPG) power and NGV===
[[Autogas]], also known as LPG, has different chemical composition, but still a petroleum based gas, has a number of inherent advantages and disadvantages, as well as noninherent ones. The inherent advantage of autogas over CNG is that it requires far less compression (20% of CNG cost),<ref>{{cite web |url=http://www.energ2.com/home/applications/adsorbed-natural-gas.html |title=Archived copy |accessdate=2013-08-08 |deadurl=yes |archiveurl=https://web.archive.org/web/20131010015546/http://www.energ2.com/home/applications/adsorbed-natural-gas.html |archivedate=2013-10-10 |df= }}</ref> is denser as it is a liquid at room temperature, and thus requires far cheaper tanks (consumer) and fuel compressors (provider) than CNG. As compared to LNG, it requires no chilling (and thus less energy), or problems associated with extreme cold such as [[frostbite]]. Like NGV, it also has advantages over gasoline and diesel in cleaner emissions, along with less wear on engines over gasoline. The major drawback of LPG is its safety. The fuel is volatile and the fumes are heavier than air, which causes them to collect in a low spot in the event of a leak, making it far more hazardous to use and more care is needed in handling. Besides this, LPG (40% from Crude Oil refining) is more expensive than Natural Gas.

====Current advantages of LPG power over NGV====
In places like the US, Thailand, and India, there are five to ten times more stations thus making the fuel more accessible than NGV stations. Other countries like Poland, South Korea, and Turkey, LPG stations and autos are widespread while NGVs are not. In addition, in some countries such as Thailand, the retail LPG fuel is considerably cheaper in cost.

===Future possibilities===
Though ANG (adsorbed natural gas) has not yet been used in either providing stations nor consumer storage tanks, its low compression (500psi vs 3600 psi)<ref>http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/41_1_NEW%20ORLEANS_03-96_0246.pdf</ref> has the potential to drive down costs of NGV infrastructure and vehicle tanks.

==LNG fueled vehicles==

===Use of LNG to fuel large over-the-road trucks===
LNG is being evaluated and tested for over-the-road trucking,<ref>{{cite web| url=https://www.ngvamerica.org/vehicles/for-fleets/over-the-road/| title=Over the Road LNG vehicles in USA| accessdate=17 April 2015}}</ref> off-road,<ref>{{cite web| url=https://www.ngvamerica.org/vehicles/high-horsepower/| title= High horse power off-road LNG vehicles in USA| accessdate=17 April 2015}}</ref> marine, and railroad applications.<ref>{{cite web| url=https://af.reuters.com/article/commoditiesNews/idAFL6N0QI1Q920140812?sp=true| title=Next energy revolution will be on roads and railroads| accessdate=17 April 2015}}</ref> There are known problems with the fuel tanks and delivery of gas to the engine.<ref>{{cite web| url=http://www.cryogenicfuelsinc.com/tanks/systemAnalysis.cfm| title=LNG Tank System Analysis| accessdate=17 April 2015}}</ref>

China has been a leader in the use of LNG vehicles<ref>{{cite web|url= http://member.zeusintel.com/ZLFVR/news_details.aspx?newsid=31246| title=Development of LNG Fueling Stations in China vs. in U.S.| accessdate=17 April 2015}}</ref> with over 100,000 LNG powered vehicles on the road as of 2014.<ref>{{cite web| url=https://www.bloomberg.com/news/articles/2014-07-04/choking-smog-puts-chinese-driver-in-natural-gas-fast-lane| title=Choking Smog Puts Chinese Driver in Natural Gas Fast Lane| accessdate=17 April 2015}}</ref>

In the United States, there were 69 public truck LNG fuel centres as of February 2015.<ref>{{cite web| url=http://www.afdc.energy.gov/locator/stations/results?utf8=%E2%9C%93&location=&filtered=true&fuel=LNG&owner=all&payment=all&ev_level1=true&ev_level2=true&ev_dc_fast=true&radius_miles=5| title=Alternative Fueling Station Locator in USA| accessdate=17 April 2015}}</ref> The 2013 National Trucker's Directory lists approximately 7,000 truckstops,<ref>{{cite web| url=http://www.dieselboss.com/directory_DC.htm| title=The 2013 National Trucker's Directory| accessdate=17 April 2015}}</ref> thus approximately 1% of US truckstops have LNG available.

In 2013, Dillon Transport announced they were putting 25 LNG large trucks into service in Dallas Texas. They are refueling at a public LNG fuel center.<ref>{{cite web| url=http://www.fleetsandfuels.com/fuels/ngvs/2013/05/dillon-adding-25-lng-kenworth-t800s/| title=Dillon Adding 25 LNG Kenworth| accessdate=17 April 2015| archive-url=https://web.archive.org/web/20150410173419/http://www.fleetsandfuels.com/fuels/ngvs/2013/05/dillon-adding-25-lng-kenworth-t800s/| archive-date=2015-04-10| dead-url=yes| df=}}</ref> The same year Raven Transportation announced they were buying 36 LNG large trucks to be fueled by Clean Energy Fuels locations<ref>{{cite web|url= http://www.ngvjournal.com/clean-energy-commits-to-fueling-36-new-heavy-duty-lng-powered-trucks/|archive-url= https://web.archive.org/web/20160603031545/http://www.ngvjournal.com/clean-energy-commits-to-fueling-36-new-heavy-duty-lng-powered-trucks/|dead-url= yes|archive-date= 2016-06-03|title= Clean Energy commits to serving 36 new heavy-duty LNG-powered trucks}}</ref> and Lowe's finished converting one of its dedicated fleets to LNG fueled trucks.<ref>{{cite web| url=http://media.lowes.com/pr/2013/10/17/lowes-launches-natural-gas-powered-truck-fleet-at-texas-rdc/| title=Lowe’s Launches Natural Gas-Powered Truck Fleet At Texas RDC| accessdate=17 April 2015}}</ref>

UPS had over 1200 LNG fueled trucks on the roads in February 2015.<ref>{{cite web| url=http://www.ups.com/pressroom/us/press_releases/press_release/Press+Releases/Archive/2015/Q1/ci.Legislation+Introduced+by+Senators+Bennet+and+Burr+Would+End+the+Disparity+in+the+way+LNG+and+LPG+are+Taxed.syndication| title=Legislation Would End the Disparity in the way LNG and LPG are Taxed| accessdate=17 April 2015| archive-url=https://web.archive.org/web/20150402150742/http://www.ups.com/pressroom/us/press_releases/press_release/Press+Releases/Archive/2015/Q1/ci.Legislation+Introduced+by+Senators+Bennet+and+Burr+Would+End+the+Disparity+in+the+way+LNG+and+LPG+are+Taxed.syndication| archive-date=2 April 2015| dead-url=yes| df=dmy-all}}</ref> UPS has 16,000 tractor trucks in its fleet, and 60 of the new for 2014 large trucks will be placed in service in the Houston, Texas area, where UPS is building its own private LNG fuel center to avoid the lines at retail fuel centers.<ref>{{cite web| url=http://www.bizjournals.com/houston/blog/drilling-down/2014/06/new-lng-trucking-fleet-launches-in-houston.html?page=all| title=New LNG trucking fleet launches in Houston| accessdate=17 April 2015}}</ref> In Amarillo, Texas and Oklahoma City, Oklahoma, UPS is using public fuel centers.<ref>{{cite web|url= http://ttnews.com/articles/basetemplate.aspx?storyid=34594&t=Clean-Energy-Opens-Two-LNG-Highway-Stations| title=Clean Energy Opens Two LNG Highway Stations| accessdate=17 April 2015}}</ref>

Clean Energy Fuels has opened several public LNG Fuel Lanes along I-10 and claims that as of June 2014 LNG fueled trucks can use the route from Los Angeles, California to Houston, Texas by refueling exclusively at Clean Energy Fuels public facilities.<ref>{{cite web|url= http://investors.cleanenergyfuels.com/releasedetail.cfm?ReleaseID=854991| title=Clean Energy Opens Interstate 10 Highway Between Los Angeles and Houston to LNG Fueling| accessdate=17 April 2015}}</ref> In 2014 Shell and Travel Centers of America opened the first of a planned network of U.S. truck stop LNG stations in Ontario, California.<ref>{{cite web| url=http://www.fleetsandfuels.com/fuels/ngvs/2014/05/shell-opens-its-first-u-s-lng-lanes/| title=Shell, TA Open Their First U.S. LNG| accessdate=17 April 2015| archive-url=https://web.archive.org/web/20150410175127/http://www.fleetsandfuels.com/fuels/ngvs/2014/05/shell-opens-its-first-u-s-lng-lanes/| archive-date=2015-04-10| dead-url=yes| df=}}</ref> Per the alternative fuel fuelling centre tracking site there are 10 LNG capable public fuel stations in the greater Los Angeles area, making it the single most penetrated metro market. As of February 2015, Blu LNG has at least 23 operational LNG capable fuel centers across 8 states,<ref>{{cite web| url=http://www.blustations.com/| title=The Future of Fuel Starts Here| accessdate=17 April 2015| archive-url=https://web.archive.org/web/20150410213814/http://www.blustations.com/| archive-date=10 April 2015| dead-url=yes| df=dmy-all}}</ref> and Clean Energy had 39 operational public LNG facilities.<ref>{{cite web|url= http://www.cnglngstations.com/| title= LNG Station locator| accessdate=17 April 2015}}</ref>

As can be seen at the alternative fuel fueling center tracking site, as of early 2015 there is void of LNG fuel centers, public and private, from Illinois to the Rockies.<ref>{{cite web| url=http://www.afdc.energy.gov/locator/stations/results?utf8=%E2%9C%93&location=&fuel=LNG&private=false&private=true&planned=false&owner=all&payment=all&radius=false&radius_miles=5&lng_vehicle_class=all| title=Shell, TA Open Their First U.S. LNG| accessdate=17 April 2015}}</ref> A Noble Energy LNG production plant in northern Colorado was planned to go online in 1st quarter 2015<ref>{{cite web|url= http://www.lngworldnews.com/nobles-colorado-lng-facility-moving-forward/| title= Noble's LNG facility in Colorado remains on schedule| accessdate=17 April 2015}}</ref> and to have a capacity of 100,000 gallons of LNG per day for on-road, off-road, and drilling operations.<ref>{{cite web|url= http://www.lngworldnews.com/noble-energy-to-build-lng-plant-in-colorado-usa/| title=Noble Energy to Build LNG Plant in Colorado, USA| accessdate=17 April 2015}}</ref>

As of 2014, LNG fuel and NGV's had not achieved much usage in Europe.<ref>{{cite web|url= http://www.returnloads.net/news/lng-fuel-unlikely-fuel-of-choice-for-europe| title=LNG fuel unlikely to be fuel of choice for Europe| accessdate=17 April 2015}}</ref>

American Gas & Technology pioneered use of onsite liquefaction using van sized station to access Natural Gas from utility pipe and clean, liquefy, store and dispense it. Their stations make 300-5,000 gallons of LNG per day.

===Use of LNG to fuel high-horsepower/high-torque engines===

In internal combustion engines the volume of the cylinders is a common measure of the power of an engine. Thus a 2000cc engine would typically be more powerful than a 1800cc engine, but that assumes a similar air-fuel mixture is used.

If, via a turbocharger as an example, the 1800cc engine were using an air-fuel mixture that was significantly more energy dense, then it might be able to produce more power than a 2000cc engine burning a less energy dense air-fuel mixture. However, turbochargers are both complex and expensive. Thus it becomes clear for high-horsepower/high-torque engines a fuel that can inherently be used to create a more energy dense air-fuel mixture is preferred because a smaller and simpler engine can be used to produce the same power.

With traditional gasoline and diesel engines the energy density of the air-fuel mixture is limited because the liquid fuels do not mix well in the cylinder. Further, gasoline and diesel auto-ignite<ref>[[Autoignition temperature]]</ref> at temperatures and pressures relevant to engine design. An important part of traditional engine design is designing the cylinders, compression ratios, and fuel injectors such that pre-ignition is avoided,<ref>[[Engine knocking#Pre-ignition]]</ref> but at the same time as much fuel as possible can be injected, become well mixed, and still have time to complete the combustion process during the power stroke.

Natural gas does not auto-ignite at pressures and temperatures relevant to traditional gasoline and diesel engine design, thus providing more flexibility in the design of a natural gas engine. Methane, the main component of natural gas, has an autoignition temperature of 580C/1076F,<ref>{{cite web| url=http://www.engineeringtoolbox.com/fuels-ignition-temperatures-d_171.html| title=Fuels and Chemicals - Autoignition Temperatures| accessdate=17 April 2015}}</ref> whereas gasoline and diesel autoignite at approximately 250C and 210C respectively.

With a compressed natural gas (CNG) engine, the mixing of the fuel and the air is more effective since gases typically mix well in a short period of time, but at typical CNG compression pressures the fuel itself is less energy dense than gasoline or diesel thus the end result is a lower energy dense air-fuel mixture. Thus for the same cylinder displacement engine, a non turbocharged CNG powered engine is typically less powerful than a similarly sized gasoline or diesel engine. For that reason, turbochargers are popular on European CNG cars.<ref>{{cite web| url=http://wardsauto.com/ar/turbocharing_cng_europe_100308| title=Turbocharging Boosting Demand for CNG Vehicles in Europe| accessdate=17 April 2015}}</ref> Despite that limitation, the 12 liter Cummins Westport ISX12G engine<ref>{{cite web| url=http://www.cumminswestport.com/models/isx12-g| title=Cummins Westport ISX12 G natural gas engine| accessdate=17 April 2015}}</ref> is an example of a CNG capable engine designed to pull tractor/trailer loads up to 80,000 lbs showing CNG can be used in most if not all on-road truck applications. The original ISX G engines incorporated a turbocharger to enhance the air-fuel energy density.<ref>{{cite web| url=http://www.afdc.energy.gov/pdfs/36252.pdf| title=Development of the High-Pressure Direct-Injection ISX G Natural Gas Engine| accessdate=17 April 2015}}</ref>

LNG offers a unique advantage over CNG for more demanding high-horsepower applications by eliminating the need for a turbocharger. Because LNG boils at approximately -160C, using a simple heat exchanger a small amount of LNG can be converted to its gaseous form at extremely high pressure with the use of little or no mechanical energy. A properly designed high-horsepower engine can leverage this extremely high pressure energy dense gaseous fuel source to create a higher energy density air-fuel mixture than can be efficiently created with a CNG powered engine. The end result when compared to CNG engines is more overall efficiency in high-horsepower engine applications when high-pressure direct injection technology is used. The Westport HDMI2<ref>{{cite web| url=http://www.westport.com/is/core-technologies/hpdi-2| title=WESTPORT HPDI 2.0 LNG engine| accessdate=17 April 2015}}</ref> fuel system is an example of a high-pressure direct injection technology that does not require a turbocharger if teamed with appropriate LNG heat exchanger technology. The Volvo Trucks 13-liter LNG engine<ref>{{cite web| url=http://www.lngworldnews.com/volvo-trucks-north-america-to-launch-lng-engine/| title=Volvo Trucks North America to Launch LNG Engine| accessdate=17 April 2015}}</ref> is another example of a LNG engine leveraging advanced high pressure technology.

Westport recommends CNG for engines 7 liters or smaller and LNG with direct injection for engines between 20 and 150 liters. For engines between 7 and 20 liters either option is recommended. See slide 13 from their NGV BRUXELLES – INDUSTRY INNOVATION SESSION presentation<ref>{{cite web| url=http://www.ngvaeurope.eu/downloads/NGV_2014_BRUSSELS/1._Roberto_Defilippi.pdf| title=An innovative vision for LNG Fuel System for MD Diesel Dual Fuel Engine(DDF+LNG)| accessdate=17 April 2015}}</ref>

High horsepower engines in the oil drilling, mining, locomotive, and marine fields have been or are being developed. Paul Blomerous has written a paper<ref>{{cite web| url=http://www.gastechnology.org/Training/Documents/LNG17-proceedings/7-4-Paul_Blomerus.pdf| title=LNG AS A FUEL FOR DEMANDING HIGH HORSEPOWER ENGINE APPLICATIONS: TECHNOLOGY AND APPROACHES| accessdate=17 April 2015}}</ref> concluding as much as 40 million tonnes per annum of LNG (approximately 26.1 billion gallons/year or 71 million gallons/day) could be required just to meet the global needs of the high-horsepower engines by 2025 to 2030.

As of the end of 1st quarter 2015 Prometheus Energy Group Inc claims to have delivered over 100 million gallons of LNG within the previous 4 years into the industrial market,<ref>{{cite web| url=http://www.lngglobal.com/latest/prometheus-agreement-with-wpx-energy-to-supply-lng-and-equipment-for-drilling-operations.html| title=Prometheus agreement with WPX Energy to supply LNG and equipment for drilling operations| accessdate=17 April 2015| deadurl=yes| archiveurl=https://web.archive.org/web/20150926033722/http://www.lngglobal.com/latest/prometheus-agreement-with-wpx-energy-to-supply-lng-and-equipment-for-drilling-operations.html| archivedate=26 September 2015| df=}}</ref> and is continuing to add new customers.

===Ships===
The {{MV|Isla Bella}} is the world's first [[LNG]] powered [[container ship]].<ref name=Schuler>{{cite news|last1=Schuler|first1=Mike|title=Introducing ISLA BELLA – World’s First LNG-Powered Containership Launched at NASSCO|publisher=gCaptain|date=19 April 2015}}</ref> LNG carriers are sometimes powered by the boil-off of LNG from their storage tanks, although Diesel powered LNG carriers are also common to minimize loss of cargo and enable more versatile refueling.

===Aircraft===
[[Aviation fuel#LNG|Some airplanes]] use LNG to power their turbofans. Aircraft are particularly sensitive to weight and much of the weight of an aircraft goes into fuel carriage to allow the range. The low energy density of natural gas even in liquid form compared to conventional fuels give it a distinct disadvantage for flight applications.

== Chemical composition and energy content ==

=== Chemical composition ===

The primary component of [[natural gas]] is [[methane]] ([[carbon|C]][[hydrogen|H]]4), the shortest and lightest [[hydrocarbon]] molecule. It may also contain heavier gaseous hydrocarbons such as [[ethane]] ([[carbon|C]]2[[hydrogen|H]]6), [[propane]] ([[carbon|C]]3[[hydrogen|H]]8) and [[butane]] ([[carbon|C]]4[[hydrogen|H]]10), as well as other gases, in varying amounts. [[Hydrogen sulfide]] ([[hydrogen|H]]2[[sulfur|S]]) is a common contaminant, which must be removed prior to most uses.

===Energy content===

[[Combustion]] of one cubic meter yields 38 MJ (10.6 kWh). Natural gas has the highest energy/carbon ratio of any fossil fuel, and thus produces less carbon dioxide per unit of energy.

== Storage and transport ==

===Transport===

The major difficulty in the use of natural gas is [[transport]]ation. Natural gas [[pipeline transport|pipelines]] are economical and common on land and across medium-length stretches of water (like [[Langeled pipeline|Langeled]], [[Interconnector (North Sea)|Interconnector]] and [[Trans-Mediterranean Pipeline]]), but are impractical across large oceans. Liquefied natural gas ([[LNG]]) [[LNG carrier|tanker ships]], railway tankers, and [[tank truck]]s are also used.

===Storage===
[[File:Storage Density of Natural Gas.jpg|thumb|storage density of natural gas]]
CNG is typically stored in steel or [[composite overwrapped pressure vessel|composite containers]] at high pressure (3000 to 4000 psi, or 205 to 275 bar). These containers are not typically temperature controlled, but are allowed to stay at local ambient temperature. There are many standards for CNG cylinders, the most popular one is ISO 11439.<ref>{{cite web | url = http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=33298 | title = ISO 11439:2000, Gas cylinders -- High pressure cylinders for the on-board storage of natural gas as a fuel for automotive vehicles |publisher = ISO ([[International Organization for Standardization]])}}</ref><ref>{{cite web|url=http://www.iso11439.com |title=ISO 11439 Overview and FAQ |deadurl=yes |archiveurl=https://web.archive.org/web/20110713063142/http://www.iso11439.com/ |archivedate=July 13, 2011 }}</ref> For North America the standard is ANSI NGV-2.

LNG storage pressures are typically around 50-150 psi, or 3 to 10 bar. At atmospheric pressure, LNG is at a temperature of -260 °F (-162 °C), however, in a vehicle tank under pressure the temperature is slightly higher (see [[saturated fluid]]). Storage temperatures may vary due to varying composition and storage pressure. LNG is far denser than even the highly compressed state of CNG. As a consequence of the low temperatures, vacuum insulated storage tanks typically made of stainless steel are used to hold LNG.

CNG can be stored at lower pressure in a form known as an ANG ([[Adsorbed]] Natural Gas) tank at 35 bar (500 psi, the pressure of gas in natural gas pipelines) in various sponge like materials, such as [[activated carbon]]<ref>{{cite press release | date = February 16, 2007 | title = From Farm Waste to Fuel Tanks |url = https://www.nsf.gov/news/news_summ.jsp?cntn_id=108390 |publisher = US [[National Science Foundation]] (NSF)}}</ref> and [[metal-organic framework]]s (MOFs).<ref>{{cite journal | url = http://pubs.acs.org/doi/full/10.1021/ja0771639 | publisher = US [[National Science Foundation]] (NSF) | journal = Journal of the American Chemical Society | title = Metal-Organic Framework from an Anthracene Derivative Containing Nanoscopic Cages Exhibiting High Methane Uptake | author=Shengqian Ma |author2=Daofeng Sun |author3=Jason M. Simmons |author4=Christopher D. Collier |author5=Daqiang Yuan |author6=Hong-Cai Zhou | year = 2008 |volume = 130 |issue = 3 |pages = 1012–1016 | doi = 10.1021/ja0771639 | pmid=18163628}}</ref> The fuel is stored at similar or greater energy density than CNG. This means that vehicles can be refuelled from the natural gas network without extra gas compression, the fuel tanks can be slimmed down and made of lighter, less strong materials.

=== Conversion kits ===
Conversion kits for gasoline or diesel to LNG/CNG are available in many countries, along with the labor to install them. However, the range of prices and quality of conversion vary enormously.

Recently, regulations involving certification of installations in USA have been loosened to include certified private companies, those same kit installations for CNG have fallen to the $6,000+ range (depending on type of vehicle).{{Citation needed|date=February 2012}}

==Implementation==
{{Fancruft|section|date=September 2017|reason=This artilceis seriously bloated. Country-by-country breakdowns are one of the reasons this and many alternative fuel/electric vehicle articles are far too long.}}
{| style="float:right;" class="wikitable"
! colspan=6| '''Top ten countries with the largest NGV vehicle fleets - 2017<ref>http://www.ngvexpo.com/msg.php?id=1631</ref>''' (millions)
|-
!Rank||Country||Registered fleet ||Rank||Country|| Registered fleet
|-
|align=center| 1||China || style="text-align:right;"| 5.000||align=center| 6|| Brazil || style="text-align:right;"| 1.781
|-
|align=center| 2||Iran|| style="text-align:right;"| 4.000||align=center| 7|| Italy || style="text-align:right;"| 1.001
|-
|align=center| 3||India || style="text-align:right;"| 3.045||align=center| 8|| Colombia || style="text-align:right;"| 0.556
|-
|align=center| 4||Pakistan|| style="text-align:right;"| 3.000 ||align=center | 9|| Thailand || style="text-align:right;"| 0.474
|-
|align=center| 5||Argentina || style="text-align:right;"| 2.295||align=center| 10|| Uzbekistan || style="text-align:right;"| 0.450
|-
| align=center colspan=6| '''World Total = 24.452 million NGV vehicles'''
|}
===Overview===

Natural gas vehicles are popular in regions or countries where natural gas is abundant and where the government chooses to price CNG lower than gasoline.<ref name="TwoBillion"/> The use of natural gas began in the [[Po Valley|Po River Valley]] of [[Italy]] in the 1930s, followed by [[New Zealand]] in the 1980s, though its use has declined there. At the peak of New Zealand's natural gas use, 10% of the nation's cars were converted, around 110,000 vehicles.<ref name="TwoBillion"/> In the United States CNG powered buses are the favorite choice of several [[public transit]] agencies, with a fleet of more than 114,000 vehicles, mostly buses.<ref name="GreenCar">{{cite web|url=http://www.greencarcongress.com/2009/10/forecast-17m-natural-gas-vehicles-worldwide-by-2015.html#more|title=Forecast: 17M Natural Gas Vehicles Worldwide by 2015|author=Pike Research|date=2009-10-19|publisher=[[Green Car Congress]]|accessdate=2009-10-19}}</ref> India, Australia, Argentina, and Germany also have widespread use of natural gas-powered buses in their public transportation fleets.<ref name="TwoBillion"/>

===Europe===
[[File:Brescia Trasporti Iveco CityClass 632 via Sardegna 20120828.JPG|thumb|CNG-powered bus in Italy ]]
[[File:CNG-powered buses in Horlivka, Ukraine.tif|thumb|CNG-powered buses in [[Horlivka]], eastern Ukraine ]]

====Germany====
Germany hit the milestone of 900 CNG filling stations nationwide in December 2011. Gibgas, an independent consumer group, estimates that 21% of all CNG filling stations in the country offer a natural gas/[[biomethane]] mix to varying ratios, and 38 stations offer pure biomethane.<ref>{{cite web|url=http://www.ngvglobal.com/900th-cng-filling-station-for-germany-1221|title=900th CNG Filling Station for Germany|author=Gibgas|publisher=NGV Global News|date=2011-12-21|accessdate=2011-12-28}}</ref>

==== Greece ====
[[Greece]] uses natural gas buses for public transport in [[Athens]].
Also the Public Gas Company (DEPA) has a network of 11 stations (as of 2017), under brand "Fisikon", and plans more stations in next 5 years.

====Ireland====
[[Bus Éireann]] Introduced the first [[NGV]] on 17 July 2012. It will operate on the 216 city centre to Mount Oval, Rochestown, route until mid-August on a trial being undertaken in partnership with [[Ervia]]. The Eco-city bus is made by [[MAN SE|MAN]].<ref>{{cite news | url = http://www.irishexaminer.com/archives/2012/0717/ireland/natural-gas-bus-hits-the-streets-in-bid-to-cut-fuel-bill-201037.html| title = Natural gas bus hits the streets in bid to cut fuel bill | first = Eoin |last = English | date = July 17, 2012 | newspaper = Irish Examiner }}</ref>

====Italy====
Natural gas traction is quite popular in Italy, due to the existence of a capillar distribution network for industrial use since the late 50s and a traditionally high retail price for petrol. As of April 2012 there were about 1173 filling stations, mainly located in the northern regions,<ref>{{cite web | url = http://www.metanoauto.com/modules.php?name=Distributori | title = Distributori metano in Europa: Il primo elenco interattivo aggiornato in tempo reale, online da maggio 2006 |trans-title=Natural gas distributors in Europe: The first list is updated in real-time interactive, online since May 2006| publisher = metanoauto.com}}</ref> while the fleet reached 730,000 CNG vehicles at the end of 2010.<ref name=IANGV/>

====Ukraine====
Ukraine’s first compressed natural gas refueling station (CNGS) was commissioned in 1937. Today, there is a well-developed CNGS network across the country.<ref>{{cite web | url = http://www.apvgn.pt/documentacao/gnc_ucrania.pdf | title = Use of Compressed Natural Gas (CNG) as Motor Fuel in Ukraine, Prospects and Problems | date = 2006 | publisher = 23rd World Gas Conference, Amsterdam | authors = Igor Orlov and Volodymyr Kozak | access-date = 2014-01-06 | archive-url = https://web.archive.org/web/20140106040300/http://www.apvgn.pt/documentacao/gnc_ucrania.pdf | archive-date = 2014-01-06 | dead-url = yes | df = }}</ref> Many buses were converted to run on CNG during the 1990s, primarily for economic reasons. The retrofitted cylinders are often visible atop the vehicle's roof and/or underneath the body. Despite their age, these buses remain in service and continue to provide reliable public transport combined with the environmental benefits of CNG.

====United Kingdom====
CNG buses are beginning to be used in the UK, e.g. by [[Reading Buses]].

===North America===

With the recent increase in natural gas production due to widespread use of [[fracking]] technology, many countries, including the United States and Canada, now can be self-sufficient. Canada is a substantial net exporter of natural gas, though the United States still has a net import of natural gas.<ref>http://www.eia.gov/countries/country-data.cfm?fips=ca#ng</ref><ref>http://www.eia.gov/dnav/ng/hist/n9180us1m.htm</ref> Natural gas prices have decreased dramatically in the past few years and are likely to decrease further as additional production comes on line. However, the EIA predicts that natural gas prices will start increasing in a few years as the most profitable natural gas reserves are used up.<ref>{{Citation | url = http://www2.hmc.edu/~evans/AEO2012.pdf | title = Annual Energy Outlook 2012 | date = June 2012 | page = 91 }}{{Dead link|date=August 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Natural gas prices have decreased from $13 per mmbtu (USD) in 2008 to $3 per mmbtu (USD) in 2012.<ref>{{Cite web | url = http://www.infomine.com/investment/metal-prices/natural-gas/all/ | title = Historical Natural Gas Prices and Price Chart | publisher = InfoMine Inc. | accessdate = 24 November 2012}}</ref> It is likely therefore that natural gas-powered vehicles will be increasingly cheaper to run relative to gasoline-powered vehicles. The issue is how to finance the purchase and installation of conversion kits. Some support may be available through the Department of Energy. Private initiatives which essentially lease the conversion equipment in exchange for slightly higher natural gas refueling can be self-financing and offer considerable advantages to liquidity strapped consumers.{{citation needed|date=August 2012}}

====Canada====

[[File:Hamilton Street Railway 510213 wide.jpg|thumb|CNG-powered bus in [[Hamilton, Ontario]]]]

Natural Gas has been used as a motor fuel in Canada for over 20 years.<ref>{{Citation
| url = http://www.transportation.alberta.ca/Content/docType57/Production/NGVBrief.pdf | title = NATURAL GAS VEHICLES IN ALBERTA | first = Lawrence |last = Schmidt | first2=Jason |last2 = Politylo | first3=Sarah |last3 = Pinto | publisher = Government of Alberta, Infrastructure Policy and Planning | date = November 2005}}</ref> With assistance from federal and provincial research programs, demonstration projects, and NGV market deployment programs during the 1980s and 1990s, the population of light-duty NGVs grew to over 35,000 by the early 1990s. This assistance resulted in a significant adoption of natural gas transit buses as well.<ref name="iangv.org">{{citation|publisher=International Association for Natural Gas Vehicles |year=2010 |title=Natural Gas Vehicles Statistics |url=http://www.iangv.org/tools-resources/statistics.html |deadurl=yes |archiveurl=https://web.archive.org/web/20100110101111/http://www.iangv.org/tools-resources/statistics.html |archivedate=January 10, 2010 }}</ref> The NGV market started to decline after 1995, eventually reaching today’s vehicle population of about 12,000.<ref name="iangv.org"/>

This figure includes 150 urban transit buses, 45 school buses, 9,450 light-duty cars and trucks, and 2,400 forklifts and ice-resurfacers. The total fuel use in all NGV markets in Canada was 1.9 petajoules (PJs) in 2007 (or 54.6 million litres of gasoline litres equivalent), down from 2.6 PJs in 1997. Public CNG refuelling stations have declined in quantity from
134 in 1997 to 72 today. There are 22 in British Columbia, 12 in Alberta, 10 in Saskatchewan, 27 in
Ontario, and 1 in Québec. There are only 12 private fleet stations.<ref>{{citation | url = http://oee.nrcan.gc.ca/sites/oee.nrcan.gc.ca/files/pdf/transportation/alternative-fuels/resources/pdf/roadmap.pdf | title = Natural Gas Use in the Canadian Transportation Sector | author = Natural Gas Use in Transportation Roundtable | date = December 2010 | publisher = Canadian Natural Gas Vehicle Alliance}}</ref>

====United States====
[[File:Metrobus powered with CNG 5198 DCA 03 2009.jpg|thumb|Buses powered with [[Compressed natural gas|CNG]] are common in the United States ]]
As of December 2009, the U.S. had a fleet of 114,270 [[compressed natural gas]] (CNG) vehicles, 147,030 vehicles running on [[liquefied petroleum gas]] (LPG), and 3,176 vehicles running on [[liquefied natural gas]] (LNG).<ref name=USeDataBook>{{cite web|url=http://cta.ornl.gov/data/tedb30/Edition30_Full_Doc.pdf|title=Transportation Energy Data Book: Edition 30|author1=Stacy C. Davis|author2=Susan W. Diegel|author3=Robert G. Boundy|last-author-amp=yes|publisher=Office of Energy Efficiency and Renewable Energy, [[U.S. Department of Energy]]|date=June 2011|accessdate=2011-08-27|deadurl=yes|archiveurl=https://web.archive.org/web/20110928135644/http://cta.ornl.gov/data/tedb30/Edition30_Full_Doc.pdf|archivedate=2011-09-28|df=}} See Tables 6.1 and 6.5, pp. 6-3 and 6-8.</ref> The NGV fleet is made up mostly of transit buses but there are also some government fleet cars and vans, as well as increasing number of corporate trucks replacing diesel versions, most notably [[Waste Management, Inc]] and [[United Parcel Service|UPS]] trucks. As of 12-Dec-2013 Waste Management has a fleet of 2000 CNG Collection trucks; as of 12-Dec-2013 UPS has 2700 alternative fuel vehicles. As of February 2011, there were 873 CNG refueling sites, 2,589 LPG sites, and 40 LNG sites, led by [[California]] with 215 CNG refueling stations in operation, 228 LPG sites and 32 LNG sites. The number of refueling stations includes both public and private sites, and not all are available to the public.<ref name=USeDataBook/> As of December 2010, the U.S. ranked 6th in the world in terms of number of NGV stations.<ref name=IANGV/> Currently there are 160,000 NGVs operating in the country.

====Mexico====
The natural gas vehicle market is limited to fleet vehicles and other public use vehicles like minibuses in larger cities. However the state-owned bus company [[Red de Transporte de Pasajeros|RTP]] Of [[Mexico City]] has purchased 30 [[Hyundai]] Super Aero City CNG-Propelled buses to integrate with the existing fleet as well as to introduce new routes within the city.
[[File:Posto GNV 01 2009 485 CWB.jpg|thumb|CNG pumps at a Brazilian gasoline service station, [[Paraná (state)|Paraná state]].]]
[[File:SAO 09 2008 Fiat Siena TetraFuel 2 views v1.jpg|thumb|Popular among [[taxicab|taxi]] drivers, the Brazilian [[Fiat Siena|Fiat Siena Tetrafuel]] 1.4, is a [[multifuel]] car that runs as a [[flexible-fuel vehicle|flexible-fuel]] on pure [[gasoline]], or [[w:Common ethanol fuel mixtures#E20, E25|E20-E25 blend]], or pure ethanol ([[w:Common ethanol fuel mixtures#E100|E100]]); or runs as a [[bi-fuel vehicle|bi-fuel]] with [[Compressed natural gas|natural gas (CNG)]]. Below: the CNG storage tanks in the trunk.]]

===South America===

====Overview====
CNG vehicles are common in South America, with a 35% share of the worldwide NGV fleet,<ref name=IANGV/> where these vehicles are mainly used as [[taxicab]]s in main cities of Argentina and Brazil. Normally, standard gasoline vehicles are retrofitted in specialized shops, which involve installing the gas cylinder in the trunk and the CNG injection system and electronics.

As of 2009 Argentina had 1,807,186 NGV's with 1,851 refueling stations across the nation,<ref name=IANGV/> or 15% of all vehicles;<ref name="LatinGNV">{{cite web|url=http://www.ngvglobal.com/en/country-reports/latin-america-ngvs-an-update-report-02074.html |archive-url=https://archive.is/20081120221031/http://www.ngvglobal.com/en/country-reports/latin-america-ngvs-an-update-report-02074.html |dead-url=yes |archive-date=2008-11-20 |title=Latin America NGVs: An Update Report |author=R. Fernandes |publisher=International Association of Natural Gas Vehicles |date=2008-08-20 |accessdate=2008-10-11 }}</ref> and Brazil had 1,632,101 vehicles and 1,704 refueling stations,<ref name=IANGV/> with a higher concentration in the cities of [[Rio de Janeiro]] and [[São Paulo]].<ref name="GNVNews">{{cite web|url=http://www.bigas.com.br/sistema/?modulo=gnvnews&acao=abrir&id=22|title=Montadores Investem nos Carros á GNV|author=GNVNews|publisher=Institutio Brasileiro de Petroleo e Gas|date=November 2006|accessdate=2008-09-20|language=Portuguese|deadurl=yes|archiveurl=https://web.archive.org/web/20081211175309/http://www.bigas.com.br/sistema/?modulo=gnvnews&acao=abrir&id=22|archivedate=2008-12-11|df=}}</ref><ref name="LatinGNV"/>

Colombia had an NGV fleet of 300,000 vehicles, and 460 refueling stations as of 2009.<ref name=IANGV/> [[Bolivia]] has increased its fleet from 10,000 in 2003 to 121,908 units in 2009, with 128 refueling stations.<ref name=IANGV/>

Peru had 81,024 NGVs and 94 fueling stations as 2009,.<ref name=IANGV/> In Peru, several factory-built CNVs have the tanks installed under the body of the vehicle, leaving the trunk free. Among the models built with this feature are the [[Fiat Multipla]], the new [[Fiat Panda]], the [[Volkswagen Touran]] Ecofuel, the [[Volkswagen Caddy]] Ecofuel, and the Chevy Taxi. Right now, Peru has 224,035 NGVs.

Other countries with significant NGV fleets are [[Venezuela]] (226,100) as of 2017 and [[Chile]] (15,000) as of 2017.<ref name=IANGV/>

====Latest developments====
[[GM do Brasil]] introduced the MultiPower engine in August 2004 which was capable of using CNG, alcohol and gasoline as fuel. The GM engine has electronic fuel injection that automatically adjusts to any acceptable fuel configuration. This motor was used in the [[Opel Astra|Chevrolet Astra]] and was aimed at the taxi market.<ref name="GNVNews"/>

In 2006 the Brazilian subsidiary of [[Fiat]] introduced the [[Fiat Siena|Fiat Siena Tetra fuel]], a four-fuel car developed under [[Magneti Marelli]] of [[Fiat]] Brazil.<ref name="TreeH">{{cite web|url=http://www.treehugger.com/files/2006/08/Fiat_sienna_tetr.php|title= Fiat Siena Tetra Power: Your Choice of Four Fuels |publisher=Treehugger|author= Christine Lepisto|date=2006-08-27 |accessdate=2008-08-24|language= }}</ref><ref>{{cite web| url=http://news.caradisiac.com/Nouvelle-Fiat-Siena-2008-sans-complexe-359 |title=Nouvelle Fiat Siena 2008: sans complexe |publisher=Caradisiac | date=2007-11-01| accessdate=2008-08-31 | language=French }} {{fr icon}}</ref> This automobile can run on 100% ethanol ([[w:Common ethanol fuel mixtures#E100|E100]]), [[w:Common ethanol fuel mixtures#E20, E25|E20 to E25]] blend (Brazil's normal ethanol gasoline blend), pure gasoline (not available in Brazil), and natural gas, and switches from the gasoline-ethanol blend to CNG automatically, depending on the power required by road conditions.<ref>{{cite web |url=http://www.webmotors.com.br/wmpublicador/Noticias_Conteudo.vxlpub?hnid=36391 |author=Agência AutoInforme |title=Siena Tetrafuel vai custar R$ 41,9 mil |publisher=WebMotor |date=2006-06-19 |accessdate=2008-08-14 |language=Portuguese |deadurl=yes |archiveurl=https://web.archive.org/web/20081210211007/http://www.webmotors.com.br/wmpublicador/Noticias_Conteudo.vxlpub?hnid=36391 |archivedate=2008-12-10 |df= }} {{pt icon}}The article argues that even though Fiat called it tetra fuel, it actually runs on three fuels: natural gas, ethanol, and gasoline.</ref>

Since 2003 and with the commercial success of flex cars in Brazil, another existing option is to [[retrofit]] an ethanol [[flexible-fuel vehicle]] to add a natural gas tank and the corresponding injection system. Some [[taxicab]]s in [[São Paulo]] and [[Rio de Janeiro]], Brazil, run on this option, allowing the user to choose among three fuels (E25, E100 and CNG) according to current market prices at the pump. Vehicles with this adaptation are known in Brazil as '''tri-fuel''' cars.<ref>{{cite web|url=http://www.devanagari.com.br/taxinews.com.br/pag/noticia_02_resumos.asp?regn=36|title=Gás Natural Veicular|publisher=TDenavagari.com.br|author=TaxiNews|date=|accessdate=2008-08-24|language=Portuguese}}{{dead link|date=September 2017 |bot=InternetArchiveBot |fix-attempted=yes }} {{pt icon}}</ref>

===South Asia===

====Pakistan====
[[Pakistan]] was the country with the second largest fleet of NGV with a total of 2.85 million by the end of 2011.<ref>{{cite web | url = http://www.ngvc.org/about_ngv/index.html | title = About NGVs | publisher = Natural Gas Vehicles for America | accessdate = 24 November 2012}}</ref> Most of the public transportation fleet has been converted to CNG.<ref>{{cite news|url=http://www.thenews.com.pk/TodaysPrintDetail.aspx?ID=35323&Cat=5&dt=3/10/2011|title=CNG cylinders or moving bombs?|author=Shahab Ansari|work=International The News|date=2011-03-10|accessdate=2011-04-05}}</ref> Also, in Pakistan and India,<ref>{{cite news| url=http://www.hindu.com/2009/11/08/stories/2009110859560300.htm | location=Chennai, India | work=The Hindu | title=CNG shortage puts auto drivers in a fix | date=2009-11-08}}</ref><ref>{{cite news | url = http://www.rediff.com/news/slide-show/slide-show-1-gas-shortage-hits-mumbai/20110315.htm | title = Gas shortage hits Mumbai; Taxis, autos off roads | date = March 15, 2011 |publisher = Rediff.com}}</ref> there have been on-going (last several years now) series of CNG fuel shortages which periodically waxes and wanes, getting the fuel into a tank can be a major problem. In July 2011, petrol usage shot up 15% from the month before due to shortages.<ref>{{cite news | url = http://www.dailytimes.com.pk/default.asp?page=2011%5C08%5C12%5Cstory_12-8-2011_pg5_2 | newspaper = Daily Times | date = August 12, 2011 | title = Petrol sales at record high in July owing to CNG shortage | location = Karachi, Pakistan}}</ref> Pakistan also has reported that over 2,000 people have died in 2011 from CNG cylinder blasts, because of low quality of cylinders there.<ref>{{cite news | url = http://www.thenews.com.pk/Todays-News-4-102120-Over-2000-killed-in-CNG-cylinder-blasts-in-2011-report | location = Karachi, Pakistan | title = Over 2,000 killed in CNG cylinder blasts in 2011: report | first = M. Waqar | last = Bhatti | date = April 10, 2012 | newspaper = The News International}}</ref> In 2012, the Pakistani government took the decision to gradually phase out CNG sector altogether beginning by banning any new conversions to CNG and banning the manufacturing of new NGV's. In addition the government plans to close down all refueling stations in the next 3 years.<ref>{{cite news |url = http://tribune.com.pk/story/415090/time-is-up-government-to-wipe-out-cng-sector-gradually/ | title = Time is up: Government to wipe out CNG sector gradually | date = July 31, 2012 | newspaper = The Express Tribune | location = Lahore, Pakistan}}</ref><ref>{{cite news | url = http://www.nation.com.pk/pakistan-news-newspaper-daily-english-online/business/02-Oct-2012/govt-to-put-an-end-to-cng-industry-in-phases-asim | title = Govt to put an end to CNG industry in phases: Asim | first = Imran Ali | last = Kundi | date = October 2, 2012 | location = Islamabad, Pakistan | newspaper = The Nation | access-date = 2012-10-08 | archive-url = https://web.archive.org/web/20121009050329/http://www.nation.com.pk/pakistan-news-newspaper-daily-english-online/business/02-Oct-2012/govt-to-put-an-end-to-cng-industry-in-phases-asim | archive-date = 2012-10-09 | dead-url = yes | df = }}</ref>

====India====
[[File:CNG filling station, Delhi.JPG|thumb|A CNG powered car being filled in a filling station in Delhi]]
In 1993, CNG had become available in [[Delhi]], India's capital, though LPG is what really took off due to its inherently far lower capital costs. Compressed Natural Gas is a domestic energy produced in Western parts of India. In India, most CNG vehicles are dual fueled, which means they can run both on CNG and gasoline. This makes it very convenient and users can drive long distances without worrying about availability of natural gas (as long as gasoline is available). As of December 2010 India had 1,080,000 NGVs and 560 fueling stations, many of the older ones being LPG rather than CNG.<ref name=IANGV/> In addition, it is thought that more illegally converted LPG autos than legal ones ply the streets in India, some estimates are as high as 15 million "autos" (running the gamut of everything from LPG motored pedal bicycles to CNG buses)<ref>{{Cite web | url = http://info.bellperformance.com/blog/bid/48368/LPG-Fueled-Vehicles-Coming-Soon | work = Blog | title = LPG Fueled Vehicles Coming Soon |publisher = Bell Performance, Inc. |date = 22 February 2011}}</ref>

In 1995, a lawyer filed a case with the [[Supreme Court of India]] under the Public Interest Litigation rule, which is part of the Constitution of India and enables any citizen to address directly the Supreme Court. The lawyer’s case was about the health risks caused by air pollution emitted from road vehicles. The Supreme Court decided that cars put into circulation after 1995 would have to run on unleaded fuel. By 1998, India was converted to 100% of unleaded fuel after the government ruled that diesel cars in India were restricted to 10,000 ppm after 1995. At the beginning of 2005, 10,300 CNG busses, 55,000 CNG three-wheelers taxis, 5,000 CNG minibuses, 10,000 CNG taxis and 10,000 CNG cars run on India’s roads (1982-2008 Product-Life Institute, Geneva). The Delhi Transport Corporation currently operates the world's largest fleet of CNG buses for public transport.<ref>{{Citation | url = http://www.product-life.org/en/archive/cng-delhi | title = CNG Delhi – the world’s cleanest public bus system running on CNG: Interview with Anumita Roychaudhary, CES | publisher = Product-Life Institute, Geneva | date = |accessdate = 25 November 2012}}</ref> Currently India stands 3rd with 3.045 million NGVs.

====Iran====
By the end of 2015, Iran had the world's largest fleet of NGV at 3.5 million vehicles. The share of compressed natural gas in the national fuel basket is more than 23%. CNG consumption by Iran’s transportation sector is around 20 million cubic meters per day.<ref>http://financialtribune.com/articles/economy-auto/32408/iran-gas-vehicle-market-projections</ref> There are 2,335 CNG stations.<ref>http://financialtribune.com/articles/energy/44382/cng-stations-top-2380-march</ref> The growth of NGV market in Iran has in large part been due to Iranian government intervention to decrease the society's dependence on gasoline. This governmental plan was implemented to reduce the effect of sanctions on Iran and make the nation's domestic market less dependent on imported gasoline.<ref>{{citation | url = http://www.iags.org/iran121206.pdf | publisher = Institute for the Analysis of Global Security (IAGS) | title = Ahmadinejad’s Gas Revolution: A Plan to Defeat Economic Sanctions | first = Anne |last = Korin |first2= Gal |last2= Luft | date = December 2006}}</ref><ref>{{cite news | title = The New Iran Sanctions: Worse Than the Old Ones | first= Gal |last= Luft | date = 11 August 2009 | newspaper = Foreign Policy | url = https://foreignpolicy.com/articles/2009/08/11/the_new_iran_sanctions_worse_than_the_old_ones | publisher = The Foreign Policy Group, LLC.}}</ref><ref>{{citation | url = http://www.iea.org/publications/freepublications/publication/natural_gas_vehicles.pdf | title = The Contribution of Natural Gas Vehicles to Sustainable Transport | year = 2010 | publisher = International Energy Agency | first = Michiel |last = Nijboer}}</ref> Iran has been manufacturing its own NGV's through local manufacturing using [[IKCO EF Engines|dedicated CNG engines]] which use gasoline only as a back up fuel. Also by 2012, Iranian manufacturers had the capacity to build 1.5 million CNG cylinders per year and therefore Iranian government has banned their imports to support the local manufacturers.<ref>{{cite web | url = http://www.jomhourieslami.com/1391/13910129/13910129_18_jomhori_islami_eghtesadi_0011.html | first = Jomhuri | last = Eslami | date = 1391-01-29 | title = بازرسي مخازن سوخت خودروهاي گازسوز در سال 91، الزامي است | trans-title = NGV fuel tanks must be inspected in 91 | access-date = 2012-04-24 | archive-url = https://web.archive.org/web/20120422050753/http://jomhourieslami.com/1391/13910129/13910129_18_jomhori_islami_eghtesadi_0011.html | archive-date = 2012-04-22 | dead-url = yes | df = }}</ref> In addition CNG in Iran costs the least compared to the rest of the world.<ref>{{cite web | title = Prices of CNG | url = http://www.cngstations.com/prices-of-cng/ | publisher = CNGStations.com | year = 2010}}</ref> In 2012, the Iranian government announced a plan to replace the traditional CNG cylinders with [[Adsorption|Adsorbed]] Natural Gas (ANG) cylinders.<ref>{{Cite news | url = http://en.trend.az/regions/iran/2065382.html | title = Iran plans to produce ANG for vehicles |location = Baku, Azerbaijan |date = 14 September 2012 | first = S. |last = Isayev |first2= T. |last2= Jafarov | publisher = Trend News Agency}}</ref><ref>{{cite news | url = http://www.azernews.az/oil_and_gas/43683.html |title = Iran plans to substitute compressed gas with ANG in vehicles | date = 14 September 2012 |publisher = AzerNews}}</ref>

===Southeast Asia===
{{update section|date=December 2016}}
[[Image:No.39.jpg|thumb|A CNG powered [[Hino Motors|Hino RU1JSSL]] bus, operated by [[Bangkok Mass Transit Authority|BMTA]] in [[Thailand]].]]

====Thailand====
[[Thailand]] has for over a 15 years run [[autogas]] taxi cabs in Bangkok,<ref name="Thailand08">{{Cite news|url=http://www.ngvglobal.com/ptt-softens-loans-for-truck-operators-over-30-million-available-0819 |archive-url=https://web.archive.org/web/20121025032527/http://www.ngvglobal.com/ptt-softens-loans-for-truck-operators-over-30-million-available-0819 |dead-url=yes |archive-date=October 25, 2012 |title=PTT Softens Loans for Truck Operators – Over $30 Million Available |date=August 19, 2008 |location=Thailand, Bangkok |publisher=NGV Global News }}</ref> though autos and buses had erroneously labelled NGV stickers on them, when in fact, were LPG fuelled.

In view of a generous supply of natural gas but relying on imported oil, the Thailand government heavily promoted alternative fuels like LPG, natural gas and ethanol to replace gasoline beginning around 2003, yet NGV was very slow to take off due to cheaper LPG fuel, a pre-existing LPG fleet, and very low conversion cost of local LPG conversion shops as compared to factory installed CNG or conversion. A significant effort was taken when the state-controlled oil company [[PTT Public Company Limited|PTT PCL]] built a network of natural gas refueling stations. The cost of subsidy was estimated at US$150 million in 2008.

As price of oil climbed rapidly, it was estimated more than 40,000 new cars and trucks powered by natural-gas were purchased in six months in 2008, including many buses. That year, about half of the taxi fleet in Bangkok used LPG, and were prodded to convert to CNG, with little success. Since 2008, there has been a government arm-twisting to switch from LPG to CNG, with a rollout of CNG stations near Bangkok around 2007 and then upcountry in 2010, at times replacing LPG stations. Operators of used vehicles have balked at the massive conversion cost (up to quadruple that of LPG in Thailand), especially given Thailand's strong ultra-competitive domestic LPG conversion industry, as well as retail CNG fuel cost (one and a half times). Thailand had some 700,000 LPG fueled vehicles, and 300,000 CNG fueled, with 1,000 LPG stations and 600 CNG as of 2011.<ref>{{cite news | url = http://www.bangkokpost.com/business/economics/317341/motorists-unfazed-by-dearer-gas | newspaper = Bangkok Post | title = Motorists unfazed by dearer gas | date = 2012-10-17 | first = Yuthana |last = Praiwan}}</ref> Demand has increased 26% over 2011 for CNG in Thailand.<ref>http://www.bangkokpost.com/business/economics/324746/cng-price-likely-to-be-at-b13-28</ref> As of the end of 2012, Thailand has 1,014,000 LPG fueled vehicles, and consumed 606,000 tonnes in 2012 of LPG, while 483 stations serve up some 380,000 CNG vehicles.,<ref>http://www.bangkokpost.com/news/local/337380/lpg-vechicles-exceed-1-million</ref> showing that LPG conversion continues to enjoy heavy favor over NGVs despite massive government push for CNG. CNG vehicles are more likely to be bought factory installed while LPG is likely to be an aftermarket conversion. LNG vehicles in Thailand are almost non-existent except for lorries.

[[File:Taxi in Kuala Lumpur 04.JPG|thumb|NGV Proton Iswara taxi in Malaysia]]

====Malaysia====
In [[Malaysia]], the use of [[compressed natural gas]] was originally introduced for taxicabs and airport limousines during the late-1990s, when new taxis were launched with NGV engines while taxicab operators were encouraged to send in existing taxis for full engine conversions, reducing their costs of operation. Any vehicle converted to use CNG is labelled with white rhombus "NGV" (Natural Gas Vehicle) tags, lending to the common use of "NGV" when referring to road vehicles with CNG engine. The practice of using CNG remained largely confined to taxicabs predominantly in the [[Klang Valley]] and [[Penang]] due to a lack of interest. No incentives were offered for those besides taxicab owners to use CNG engines, while government subsidies on petrol and diesel made conventional road vehicles cheaper to use in the eyes of the consumers. [[Petronas]], Malaysia's state-owned oil company, also monopolises the provision of CNG to road users. {{As of|2008|July|df=US}}, Petronas only operates about 150 CNG refueling stations, most of which are concentrated in the Klang Valley. At the same time, another 50 was expected by the end of 2008.<ref name="MY CNG station no">{{cite web |url=http://thestar.com.my/metro/story.asp?file=/2008/6/13/central/21532536 |title=More natural gas stations needed, say motorists |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-13 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140522/http://thestar.com.my/metro/story.asp?file=%2F2008%2F6%2F13%2Fcentral%2F21532536 |archivedate=2011-05-21 |df= }}</ref>

As fuel subsidies were gradually removed in Malaysia starting June 5, 2008, the subsequent 41% price hike on petrol and diesel led to a 500% increase in the number of new CNG tanks installed.<ref name="MY rush 1">{{cite web |url=http://thestar.com.my/news/story.asp?file=/2008/6/8/focus/21482211 |title=Motorists rush to check out NGV system |author=Rashvinjeet S. Bedi |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-08 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140559/http://thestar.com.my/news/story.asp?file=%2F2008%2F6%2F8%2Ffocus%2F21482211 |archivedate=2011-05-21 |df= }}</ref><ref name="MY rush 2">{{cite web |url=http://thestar.com.my/metro/story.asp?file=/2008/6/25/north/21635112 |title=Long queue for NGV kits |author=Vinesh, Derrick |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-25 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140624/http://thestar.com.my/metro/story.asp?file=%2F2008%2F6%2F25%2Fnorth%2F21635112 |archivedate=2011-05-21 |df= }}</ref> National car maker [[Proton (carmaker)|Proton]] considered fitting its [[Proton Waja|Waja]], [[Proton Saga|Saga]] and [[Proton Persona|Persona]] models with CNG kits from Prins Autogassystemen by the end of 2008,<ref name="MY Potong CNG">{{cite web |url=http://thestar.com.my/news/story.asp?file=/2008/6/28/nation/21685753 |title=Proton cars to come with NGV kits |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-28 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140638/http://thestar.com.my/news/story.asp?file=%2F2008%2F6%2F28%2Fnation%2F21685753 |archivedate=2011-05-21 |df= }}</ref> while a local distributor of locally assembled [[Hyundai Motor Company|Hyundai]] cars offers new models with CNG kits.<ref name="MY Hyundai">{{cite web|url=http://biz.thestar.com.my/news/story.asp?file=/2008/7/7/business/21712982|title=Moving towards hybrid vehicles |author1=Elaine Ang |author2=Leong Hung Yee |lastauthoramp=yes |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-07-07 |accessdate=2008-08-04}}</ref> Conversion centres, which also benefited from the rush for lower running costs, also perform partial conversions to existing road vehicles, allowing them to run on both petrol or diesel and CNG with a cost varying between [[Malaysian ringgit|RM]]3,500 to RM5,000 for passenger cars.<ref name="MY rush 1"/><ref name="MY CNG conversion">{{cite web |url=http://thestar.com.my/metro/story.asp?file=/2008/6/13/central/21532553 |title=Rush to fit natural gas gadget |author=Perumal, Elan |publisher=[[The Star (Malaysia)|''The Star'' Online]] |date=2008-06-13 |accessdate=2008-08-04 |deadurl=yes |archiveurl=https://web.archive.org/web/20110521140707/http://thestar.com.my/metro/story.asp?file=%2F2008%2F6%2F13%2Fcentral%2F21532553 |archivedate=2011-05-21 |df= }}</ref>

[[Image:Volvo B10BLE SBS Transit SBS2988J.jpg|thumb|A CNG powered [[Volvo B10BLE]] bus, operated by [[SBS Transit]] in [[Singapore]].]]

====Singapore====
There were about 400 CNG-fueled vehicles in [[Singapore]] in mid-2007, of which about 110 are taxis operated by Smart Automobile. By February 2008, the number has risen 520 CNG vehicles, of which about half are taxis.<ref name=autogenerated1>{{Cite news | url = http://www.ngvglobal.com/en/market-developments/new-cng-fuelling-station-for-singapore.html | title = New CNG Fuelling Station for Singapore | date = February 17, 2008 |location = Singapore | publisher = NGV Global News}}</ref> All vehicles had to refuel at the sole CNG station operated by Sembcorp Gas and located on [[Jurong Island]] until the opening of the first publicly accessible CNG station at [[Mandai]] in 2008, operated by Smart Automobile.<ref>{{cite news | url = http://www.channelnewsasia.com/stories/singaporelocalnews/view/329584/1/.html | title = Singapore's largest CNG refuelling station opens at Mandai Link | author = Wong Mun Wai | date = 18 February 2008| publisher = Channel NewsAsia}}</ref> The company plans to build another four stations by 2011, by which time the company projects to operate 3,000 to 4,000 CNG taxis, and with 10,000 CNG public and commercial vehicles of other types on Singapore's roads.<ref>{{cite web |url= http://www.channelnewsasia.com/stories/singaporelocalnews/view/287780/1/.html |title=Singapore's first public CNG station to be ready by Jan 2008 |work=channelnewsasia.com |date=July 12, 2007 |author=Daryl Loo |accessdate=October 21, 2011}}</ref> Sembcorp Gas opened its second CNG station a week after the Mandai station at Jalan Buroh.<ref name=autogenerated1 />

====Indonesia====
CNG is almost unheard of as a transport fuel before 2010 in the archipelago except in [[Jakarta]], where a very relatively minor number of vehicles, most notably [[Transjakarta]] buses, use the fuel. However, since 2010 there has been a government emphasis to push usage of CNG not only for vehicle fuel, but also for domestic consumption over wood burning (which can produce deadly methanol) and kerosene.

===East Asia===

====China====
China had 450,000 NGV's and 870 refueling stations as of 2009.<ref name=IANGV/> China in 2012 has 1 million NGVs on the roads, 3 million forecast for 2015, with over 2000 stations (both CNG and LPG), with plans for 12,000 by 2020. Currently China leads the World with 5 million NGVs<ref>http://www.iangv.org/current-ngv-stats/</ref> China also has lot of vehicles running of Petrol blended with Methanol as M15 and M85.

====South Korea====
For the purpose of improving air quality in the metropolitan area of [[Seoul]], CNG buses were first introduced in July, 1997. By 2014, all [[Seoul buses]] were operating on CNG.{{citation needed|date=October 2016}} Hyundai motor developed a CNG hybrid bus with 34.5% more-fuel efficiency and 30% lower pollution compared to CNG buses.{{citation needed|date=October 2016}} As a result, Seoul city government plans to change to CNG hybrid buses for 2,235 low-bed disabled-friendly CNG bus in Seoul.{{citation needed|date=October 2016}}

CNG buses are operation in other major South Korean cities like Busan, Daegu, Daejeon, Gwangju and Incheon.{{citation needed|date=October 2016}}

====Motorsport====
{{Advert|section|date=September 2017}}
A new category of motorcar racing unites teams which compete with cars powered by natural gas, to demonstrate the effectiveness of natural gas as an alternative fuel. ECOMOTORI (magazine) Racing Team<ref>[http://www.ecomotori.net/_/ecomotori-racing-team/trionfo-di-ecomotori-al-7-ecorally-smarino-r3616 ECOMOTORI Racing Team]</ref> The magazine's team participates in the [[FIA Alternative Energies Cup]] and the talian [[:it:Campionato Italiano CSAI Energie Alternative|ACI/CSAI Alternative Energies Championship]]. In 2012, the team, led by [[Nicola Ventura]], competes with a Fiat 500 Abarth,<ref>[http://www.alvolante.it/news/abarth_500_metano-664611044 Fiat 500 Abarth]</ref> modified to run on natural gas with a Cavagna/Bigas fuel conversion kit and thus renamed "500 EcoAbarth". The driver is [[Massimo Liverani]] while in the role of navigator, alternate Valeria Strada, Alessandro Talmelli and [[Fulvio Ciervo]]. On October 14, 2012, at the end of the 7th Ecorally San Marino-Vatican with 3 wins and a second place (out of 4 races),<ref>[http://www.ecorally.eu/ Ecorally San Marino-Vatican]</ref> the Team also won the Italian CSAI Alternative Energy Pilots and Navigators titles. On 28 October 2012, after having raced in 7 European countries, collecting 3 wins, 2 second places and additional points, the team won the FIA Alternative Energies Drivers and Constructors world titles. For the first time ever, a car powered by methane won an FIA world title. In 2013, the team raced in the [[FIA Alternative Energies Cup]] and [[:it:Campionato Italiano CSAI Energie Alternative|CSAI]] Championships. The "500 EcoAbarth" of Ecomotori.net dominated the season, winning 5 of 5 titles. Thanks to the work of the team, the Abarth once again won a constructors' title since its last win 46 years ago.<ref>[http://www.lpgasmagazine.com/cavagna-bigas-traveling-to-world-lp-gas-forum-in-style/ Abarth]</ref>

==See also==
* [[Biogas|Biogas vehicle]]
* [[HCNG dispenser]]
* [[List of natural gas vehicles]]

==References==
{{Reflist|30em}}

== External links ==
{{Commons category|Compressed natural gas vehicles}}
* {{Citation|url=http://pleasebeinformed.com/publications/content/gas-powered-public-transport-how-it-began-part-1 |title=Gas Powered Public Transport - how it began |date = October 9, 2005 |website=Please Be Informed}}
* {{citation | url = http://www.afdc.energy.gov/afdc/vehicles/natural_gas_availability.html | publisher = [[U.S. Department of Energy]] | title = Natural Gas Vehicle Availability | date = November 18, 2015}}
* [http://www.greenercities.eu/ Greener Cities] – International project dedicated to the development of an ever-growing demand for environmentally friendly eco-sustainable vehicles, specifically to promote the use of cleaner fuels such as CNG and [[Biogas]]
* {{Cite web | url = http://naturalgasvehicles.com | title = Natural Gas Vehicles}}
* [http://www.metanoauto.com The Italian community of Natural Gas Vehicles ]– Forum, technical info, maps (also in English, German, and French)
* {{citation | url = http://www.energyquest.ca.gov/transportation/CNG.html | title = A Student's Guide to Alternative Fuel Vehicles: Compressed natural gas - natural gas under high pressure | publisher = California Energy Commission | date = April 22, 2002 | access-date = October 4, 2004 | archive-url = https://web.archive.org/web/20041013054711/http://www.energyquest.ca.gov/transportation/CNG.html | archive-date = October 13, 2004 | dead-url = yes | df = mdy-all }}
* {{citation|url=http://www.eere.energy.gov/cleancities/vbg/consumers/cng.shtml |publisher=U.S. Department of Energy |title=Consumers' Guide to Compressed Natural Gas |deadurl=yes |archiveurl=https://web.archive.org/web/20060429222452/http://www.eere.energy.gov/cleancities/vbg/consumers/cng.shtml |archivedate=April 29, 2006 }}
* {{cite news | url = http://www.msnbc.msn.com/id/5960905 |title = Boost for natural gas cars: Home fueling | year=2013 | publisher = NBCnews.com}}
* {{cite web | url = http://www.cngcalifornia.com/ | title = CNG California}}
* {{cite web | url=http://www.afdc.energy.gov/uploads/publication/ng_powered_bus_service.pdf |title=Developing a Natural GasPowered Bus Rapid Transit Service: A Case Study|first=George |last=Mitchell|work=[[National Renewable Energy Laboratory]]|date=November 2015}}
* [http://www.ngvjournal.com/worldwide-fuel-prices/ Worldwide fuel prices], 2010

{{Alternative propulsion}}

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{{DEFAULTSORT:Natural Gas Vehicle}}
[[Category:Natural gas vehicles|*]]
[[Category:Green vehicles]]

Monaco

2018-10-02T16:25:43Z

173.165.237.1: /* Climate */

{{about|the city-state}}
{{Use dmy dates|date=December 2017}}

{{Infobox country
| conventional_long_name = Principality of Monaco
| common_name = Monaco
| native_name = {{native name|fr|Principauté de Monaco|nbsp=omit}}{{efn|name=a|In other languages of Monaco:
*{{lang-it|Principato di Monaco}}
*[[Monégasque dialect|Monégasque]]: ''Principatu de Múnegu''
*{{lang-oc|Principat de Mónegue}}}}
| image_flag = Flag of Monaco.svg
| image_coat = Coat of Arms of Monaco.svg
| national_motto = {{native phrase|la|"Deo Juvante"|italics=off}} ({{Lang-en|"With God's Help"}})
| national_anthem = "[[Hymne Monégasque]]" ({{Lang-en|"Hymn of Monaco"}})
<div style="display:inline-block;margin-top:0.4em;">[[File:Monaco National Anthem.ogg]]</div>
| image_map = Location Monaco Europe.png
| map_caption = {{map caption |location_color=green |region=Europe |region_color=green & dark grey }}
| image_map2 =
| map2_width =
| capital = Monaco ([[city-state]]){{ref label|infoboxa|a|}}<ref>{{cite web |url=http://data.un.org/CountryProfile.aspx?crName=Monaco |title=United-Nations data, country profile |date= |accessdate=29 October 2013}}</ref><ref>{{cite web |url=http://en.gouv.mc/Government-Institutions/Institutions/Constitution-of-the-Principality#eztoc1036069_10 |title=Constitution of Monaco (art. 78): ''The territory of the Principality forms a single commune.'' |date= |accessdate=29 October 2013}}</ref>
| coordinates = {{Coord|43|44|N|7|25|E|type:city}}
| largest_settlement = [[Monte Carlo]]
| largest_settlement_type = ''Quartier''
| official_languages = [[French language|French]]<ref>{{cite web |accessdate=22 May 2008 |url=http://www.gouv.mc/devwww/wwwnew.nsf/1909$/036c62fe5f92f2efc1256f5b0054fa42gb?OpenDocument&3Gb |archiveurl=https://web.archive.org/web/20110722170607/http://www.gouv.mc/devwww/wwwnew.nsf/1909$/036c62fe5f92f2efc1256f5b0054fa42gb?OpenDocument&3Gb |archivedate=22 July 2011 |title=Constitution de la Principauté |publisher=[[Council of Government (Monaco)|Council of Government]] |deadurl=yes |df=dmy }}</ref>
| languages_type = [[Lingua franca|Common languages]]
| languages = {{unbulleted list |[[Monégasque dialect|Monégasque]] |[[Italian language|Italian]] |[[Occitan language|Occitan]]|[[English language|English]]}}
| ethnic_groups = {{unbulleted list |[[Monégasque people|Monégasques]] |[[Italian people|Italians]] | [[French people|French]], [[Occitans]]}}
| demonym = {{unbulleted list |Monégasque |Monacan{{ref label|infoboxc|c|}}}}
| government_type = [[Unitary state|Unitary]] [[parliamentary system|parliamentary]] [[constitutional monarchy]]
| leader_title1 = [[Monarchy of Monaco|Monarch]]
| leader_name1 = [[Albert II, Prince of Monaco|Albert II]]
| leader_title2 = [[Minister of State (Monaco)|Minister of State]]
| leader_name2 = [[Serge Telle]]
| legislature = [[National Council (Monaco)|National Council]]
| sovereignty_type = [[Independence]]
| established_event1 = [[House of Grimaldi]] (under the sovereignty of the [[Republic of Genoa]])
| established_date1 = 1297
| established_event2 = from the [[Alpes-Maritimes|French Empire]]
| established_date2 = 17 May 1814
| established_event3 = from occupation of the [[Sixth Coalition]]
| established_date3 = 17 June 1814
| established_event4 = [[Franco-Monegasque Treaty]]
| established_date4 = 1861
| established_event5 = [[Constitution of Monaco|Constitution]]
| established_date5 = 1911
| area_km2 = 2.020
| area_rank = 194th 
| area_sq_mi = 1.26 
| percent_water = negligible<ref name="monacodata">{{cite web|url=http://www.gouv.mc/devwww/wwwnew.nsf/e89a6190e96cbd1fc1256f7f005dbe6e/e1201ddb4e532285c125702a004775bc/$FILE/Pocket%202009.pdf |title=Monaco en Chiffres |accessdate=15 November 2009 |deadurl=bot: unknown |archiveurl=https://web.archive.org/web/20091115210931/http://www.gouv.mc/devwww/wwwnew.nsf/e89a6190e96cbd1fc1256f7f005dbe6e/e1201ddb4e532285c125702a004775bc/$FILE/Pocket%202009.pdf |archivedate=15 November 2009 |df=dmy }}, Principauté de Monaco. Retrieved 7 June 2010.</ref>
| population_estimate = 38,400<ref name="imsee.mc">{{cite web |url=http://www.monacostatistics.mc/IMSEE/Publications/monaco-statistics-pocket|title=Monaco Statistics / IMSEE — Monaco IMSEE |language= fr |publisher=Imsee.mc |date= |accessdate= 3 August 2016}}</ref>
| population_census = 37,308<ref name="monacodata"/>
| population_estimate_year = 2015
| population_estimate_rank = 217th
| population_census_year = 2016
| population_density_km2 = 18,713
| population_density_sq_mi = 48,462 
| population_density_rank = 1st 
| GDP_nominal = $6.5 billion<ref name="unsd">{{cite web |url=http://unstats.un.org/unsd/snaama/selCountry.asp |title=National Accounts Main Aggregates Database |publisher=[[United Nations Statistics Division]] |accessdate=8 October 2012}}</ref>
| GDP_nominal_year = 2016{{ref label|infoboxb|b|}}
| GDP_nominal_rank = 148th
| GDP_nominal_per_capita = $168,000<ref>{{cite web|url=http://data.un.org/CountryProfile.aspx?crName=Monaco|title=UNdata - country profile - Monaco|website=data.un.org}}</ref>
| GDP_nominal_per_capita_rank = 1st
| Gini = 
| Gini_year =
| Gini_change = 
| Gini_ref =
| Gini_rank =
| currency = [[Euro]] ([[Euro sign|€]])
| currency_code = EUR
| time_zone = [[Central European Time|CET]]
| utc_offset = +1
| utc_offset_DST = +2
| time_zone_DST = [[Central European Summer Time|CEST]]
| drives_on = [[Driving side|right]]<ref>{{cite web |url=http://whatsideoftheroad.com/ |title=What side of the road do people drive on? |publisher=Whatsideoftheroad.com |date= |accessdate=28 May 2012}}</ref>
| calling_code = [[Telephone numbers in Monaco|+377]]
| cctld = [[.mc]]
| footnote_a = {{note|infoboxa}} Government offices are however, located in the ''Quartier'' of [[Monaco-Ville]].
| footnote_b = {{note|infoboxb}} GDP per capita calculations include non-resident workers from France and Italy.
| footnote_c = {{note|infoboxc}} ''Monacan'' is the term for residents.
| map2_caption =
| religion = [[Roman Catholicism]] (official)<ref>{{cite web |url=http://en.gouv.mc/Gouvernement-et-Institutions/Les-Institutions/La-Constitution-de-la-Principaute#eztoc1036069_2 |title=Monaco Constitution Chapter 1, Article 9 |date= |accessdate=18 July 2017}}</ref>
| area_magnitude = 1 G6|
}}

'''Monaco''' ({{IPAc-en|audio=En-us-Monaco.ogg|ˈ|m|ɒ|n|ə|k|oʊ}}; {{IPA-fr|mɔnako}}), officially the '''Principality of Monaco''' ({{lang-fr|Principauté de Monaco}}),{{efn|name=a}} is a sovereign [[city-state]], [[country]] and [[microstate]] on the [[French Riviera]] in [[Western Europe]]. [[France]] borders the country on three sides while the other side borders the [[Mediterranean Sea]]. Monaco is also located close to [[Italy]], although it has no direct border.

Monaco has an area of {{convert|2.020|km²|abbr=on}}, making it the [[List of countries and dependencies by area|second-smallest]] state in the world after the [[Vatican City|Vatican]]. Its population was about 38,400 based on the last census of 2016.<ref name="imsee.mc" /> With 19,009 inhabitants per km², it is the [[List of countries by population density|most densely-populated]] [[sovereign state]] in the world. Monaco has a land border of {{convert|5.47|km|abbr=on}},<ref name="imsee.mc" /> a coastline of {{convert|3.83|km|abbr=on}}, and a width that varies between {{convert|1700|and|349|m|abbr=on|yd}}. The highest point in the country is a narrow pathway named [[Chemin des Révoires]] on the slopes of [[Mont Agel]], in the [[Les Révoires]] ''Ward'', which is {{convert|161|m|ft|abbr=off}} [[Above mean sea level|above sea level]]. Monaco's most populous ''Quartier'' is [[Monte Carlo]] and the most populous ''Ward'' is [[Larvotto|Larvotto/Bas Moulins]]. Through [[land reclamation]], Monaco's land mass has [[Land reclamation in Monaco|expanded by 20 percent]]; in 2005, it had an area of only {{convert|1.974|km²|abbr=on}}. Monaco is known as a playground for the rich and famous, due to its tax laws. In 2014, it was noted about 30% of the population was made up of millionaires, more than in [[Zürich]] or [[Geneva]].<ref>{{cite web|url=http://profit.ndtv.com/news/global-economy/article-one-in-three-is-a-millionaire-in-monaco-study-650514|title=One in Three is a Millionaire in Monaco: Study|work=ndtv.com}}</ref>

Monaco is a [[principality]] governed under a form of [[constitutional monarchy]], with [[Albert II, Prince of Monaco|Prince Albert II]] as [[head of state]]. Although Prince Albert II is a constitutional monarch, he wields immense political power. The [[House of Grimaldi]] have ruled Monaco, with brief interruptions, since 1297.<ref>In fact [[François Grimaldi|Francesco Grimaldi]], who captured [[Monaco-Ville|the Rock]] on the night of 8 January 1297, was forced to flee Monaco only four years after the fabled raid, never to come back. The Grimaldi family was not able to permanently secure their holding until 1419 when they purchased Monaco, along with two neighbouring villages, [[Menton]] and [[Roquebrune-Cap-Martin|Roquebrune]]. Source: {{cite book|last=Edwards|first=Anne|authorlink=Anne Edwards|title=The Grimaldis of Monaco: The Centuries of Scandal – The Years of Grace|year=1992|publisher=[[William Morrow and Company|William Morrow]]|location=|isbn=978-0-688-08837-8}}</ref> The official language is French, but [[Monégasque dialect|Monégasque]], Italian, and English are widely spoken and understood.{{efn|For further information, see [[languages of Monaco]].}} The state's sovereignty was officially recognized by the [[Franco-Monegasque Treaty|Franco-Monegasque Treaty of 1861]], with Monaco becoming a full [[United Nations]] voting member in 1993. Despite Monaco's independence and separate foreign policy, its defense is the responsibility of France. However, Monaco does maintain two small [[Military of Monaco|military units]].

Economic development was spurred in the late 19th century with the opening of the country's first casino, [[Monte Carlo Casino|Monte Carlo]], and a railway connection to Paris.<ref>{{cite web |url=http://www.montecarlolegend.com/monte-carlo-the-birth-of-a-legend/|title=Monte Carlo : The Birth of a Legend|publisher=SBM Group |date=|accessdate=23 August 2013}}</ref> Since then, Monaco's mild climate, scenery, and gambling facilities have contributed to the principality's status as a tourist destination and recreation centre for the rich. In more recent years, Monaco has become a major [[banking centre]] and has sought to diversify its economy into the services sector and small, [[High value products|high-value-added]], non-polluting industries. The state has no [[income tax]], [[Tax rates around the world|low business taxes]], and is well known for being a [[tax haven]]. It is also the host of the annual street circuit motor race [[Monaco Grand Prix]], one of the original Grands Prix of [[Formula One]]. The principality has a club football team; [[AS Monaco]], who have become [[List of French football champions|French]] champions on multiple occasions.

Monaco is not formally a part of the [[European Union]] (EU), but it [[Monaco–European Union relations|participates in certain EU policies]], including customs and border controls. Through its relationship with France, Monaco uses the [[euro]] as its sole currency (prior to this it used the [[Monégasque franc]]). Monaco joined the [[Council of Europe]] in 2004. It is a member of the [[Organisation Internationale de la Francophonie]] (OIF).

== History ==
{{Main|History of Monaco}}
[[File:Meyers b9 s0067b.jpg|thumb|Monaco in Roman [[Liguria]] in [[Italy]], 1st century BC]]

Monaco's name comes from the nearby 6th-century BC [[Phocaea]]n [[Ancient Greece|Greek]] colony. Referred to by the [[Liguria]]ns as ''Monoikos'', from the [[Greek language|Greek]] "μόνοικος", "single house", from "μόνος" (''monos'') "alone, single"<ref>{{cite web|url=http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dmo%2Fnos |title=μόνος |accessdate=29 June 2011 |deadurl=bot: unknown |archiveurl=https://web.archive.org/web/20110629164313/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dmo%2Fnos |archivedate=29 June 2011 |df=dmy }}, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus Digital Library</ref> + "οἶκος" (''oikos'') "house",<ref>{{cite web|url=http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Doi%29%3Dkos1 |title=οἶκος |accessdate=29 June 2011 |deadurl=bot: unknown |archiveurl=https://web.archive.org/web/20110629164225/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Doi%29%3Dkos1 |archivedate=29 June 2011 |df=dmy }}, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus Digital Library</ref> which bears the sense of a people either settled in a "single habitation" or of "living apart" from others. According to an ancient myth, [[Hercules]] passed through the Monaco area and turned away the previous gods.<ref>{{cite web |url=http://www.monaco-montecarlo.com/index-history_monaco-en.html |title=History of Monaco |publisher=Monaco-montecarlo.com |date=|accessdate=28 May 2012}}</ref> As a result, a temple was constructed there, the temple of Hercules Monoikos. Because the only temple of this area was the "House" of Hercules, the city was called Monoikos.<ref>''Strabo, Geography, Gaul, 4.6.3'' [http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Strabo/4F*.html at LacusCurtious]</ref><ref>{{cite web|url=http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dmo%2Fnoikos |title=μόνοικος |accessdate=29 June 2011 |deadurl=bot: unknown |archiveurl=https://web.archive.org/web/20110629164248/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dmo%2Fnoikos |archivedate=29 June 2011 |df=dmy }}, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus Digital Library</ref> It ended up in the hands of the [[Holy Roman Empire]], which gave it to the Genoese. An ousted branch of a Genoese family, the [[House of Grimaldi|Grimaldi]], contested it for a hundred years before actually gaining control. Though the [[Republic of Genoa]] would last until the 19th century, they allowed the Grimaldi family to keep Monaco, and, likewise, both France and [[Spain]] left it alone for hundreds of years. France did not annex it until the [[French Revolution]], but after the defeat of [[Napoleon]] it was put under the care of the [[Kingdom of Sardinia]]. In the 19th century, when [[Sardinia]] became a part of [[Italy]], the region came under French influence again but France allowed it to remain independent. Like France, Monaco was overrun by the [[Axis powers]] during the [[World War II|Second World War]] and for a short time was administered by Italy, then the [[Nazi Germany|Third Reich]], before finally being liberated. Although the occupation lasted for just a short time, it meant the deportation of the [[Jews|Jewish]] population and execution of several [[French Resistance|resistance]] members from Monaco. Since then Monaco has been independent. It has taken some steps towards [[Microstates and the European Union|integration with the European Union]].

===Arrival of the Grimaldi family===
[[File:Raniero I de Mónaco.jpg|thumb|left|upright|Rainier I of Grimaldi, victor of the naval battle at [[Battle of Zierikzee|Zierikzee]] and first sovereign Grimaldi ruler of Monaco]]
Following a land grant from Emperor [[Henry VI, Holy Roman Emperor|Henry VI]] in 1191, Monaco was refounded in 1215 as a colony of Genoa.<ref name="state1">{{cite web |url=https://www.state.gov/r/pa/ei/bgn/3397.htm |title=Monaco |publisher=State.gov |date=16 November 2011 |accessdate=28 May 2012}}</ref><ref>{{cite web |url=http://www.monacolife.net/?content=articles&action=show&id=28 |title=Monaco Life |publisher=Monaco Life |date=26 July 2011 |accessdate=28 May 2012}}</ref> Monaco was first ruled by a member of the House of Grimaldi in 1297, when [[François Grimaldi|Francesco Grimaldi]], known as "''Il Malizia''" (translated from Italian either as "The Malicious One" or "The Cunning One"), and his men captured the fortress protecting the [[Rock of Monaco]] while dressed as [[Franciscan]] [[monk]]s—a ''monaco'' in Italian, although this is a coincidence as the area was already known by this name.<ref>{{cite web |url=http://www.visitmonaco.com/us/About-Monaco/History |title=Monaco history |publisher=Visitmonaco.com |date=|accessdate=28 May 2012}}</ref> Francesco, however, was evicted only a few years afterwards by the Genoese forces, and the struggle over "the Rock" continued for another century.<ref>{{cite web |url=http://fr.montecarlosbm.com/sejour-luxe-monaco/monte-carlo/histoire/ |title=Histoire de Monaco, famille Grimaldi | Monte-Carlo SBM |publisher=Fr.montecarlosbm.com |date=|accessdate=28 May 2012}}</ref> The Grimaldi family was Genoese and the struggle was something of a family feud. However, the Genoese became engaged in other conflicts, and in the late 1300s Genoa became involved in a conflict with the [[Crown of Aragon]] over [[Corsica]].<ref name="explorethemed.com">{{cite web|url=http://explorethemed.com/AragonMed.asp?c=1|title=The Mediterranean Empire of the Crown of Aragon|website=explorethemed.com}}</ref> The Crown of Aragon eventually became a part of Spain through marriage (see modern day [[Aragon]]) and other parts drifted into various pieces of other kingdoms and nations.<ref name="explorethemed.com"/>

===1400–1800===
[[File:Italia 1494-it.svg|thumb|Monaco in 1494]]
In 1419, the Grimaldi family purchased Monaco from the Crown of Aragon and became the official and undisputed rulers of "the Rock of Monaco". In 1612 [[Honoré II]] began to style himself "Prince" of Monaco.<ref>{{cite web |url=http://monaco.me/ |title=Monaco – The Principality of Monaco |publisher=Monaco.me |date=|accessdate=28 May 2012}}</ref> In the 1630s, he sought French protection against the Spanish forces and, in 1642, was received at the court of [[Louis XIII]] "Duc et Pair Etranger".<ref name="monacoangebote.de">{{cite web |url=http://www.monacoangebote.de/index.php?q=en/history |title=The History Of Monaco |publisher=Monacoangebote.de |date=|accessdate=28 May 2012}}</ref> The princes of Monaco thus became vassals of the French kings while at the same time remaining sovereign princes.<ref>with the title [[Duc de Valentinois]] and other lesser French titles, to most of which the House of Grimaldi still lays claim,</ref> Though successive princes and their families spent most of their lives in [[Paris]], and intermarried with French and Italian nobilities, the House of Grimaldi is Italian. The principality continued its existence as a protectorate of France until the [[French Revolution]].<ref>{{cite web |url=http://www3.monaco.mc/monaco/info/history1.html |title=Monaco: History |publisher=.monaco.mc |date=|accessdate=28 May 2012}}</ref>

In 1793, Revolutionary forces captured Monaco and it remained under direct French control until 1814, when the Grimaldi family returned to the throne.<ref name="monacoangebote.de"/><ref name="Monte-carlo.mc">{{cite web |url=http://www.monte-carlo.mc/en/general/important-dates/ |title=Important dates – Monaco Monte-Carlo |publisher=Monte-carlo.mc |date=|accessdate=28 May 2012}}</ref>

===19th century===
[[File:County of nice.svg|thumb|French annexation in 1860]]
Between 1793 and 1814 Monaco was occupied by the French (in this period much of Europe had been overrun by the French under command of Napoleon).<ref name="monacoangebote.de"/><ref name="Monte-carlo.mc"/>
The principality was reestablished in 1814 only to be designated a protectorate of the [[Kingdom of Sardinia]] by the [[Congress of Vienna]] in 1815.<ref name="Monte-carlo.mc"/> Monaco remained in this position until 1860 when, by the [[Treaty of Turin (1860)|Treaty of Turin]], the Sardinian forces pulled out of the principality and the surrounding county of [[Nice]] (as well as [[Savoy]]) was ceded to France.<ref name="infoplease1">{{cite web |url=http://www.infoplease.com/ce6/world/A0859729.html |title=24 X 7 |publisher=Infoplease.com |date=|accessdate=28 May 2012}}</ref> Monaco became a French protectorate once again. Before this time there was unrest in [[Menton]] and [[Roquebrune-Cap-Martin|Roquebrune]], where the townspeople had become weary of heavy taxation by the Grimaldi family. They declared their independence, hoping for annexation by Sardinia. France protested. The unrest continued until [[Charles III of Monaco|Charles III]] gave up his claim to the two mainland towns (some 95% of the principality at the time) that had been ruled by the Grimaldi family for over 500 years.<ref>{{cite web |url=http://www.accesspropertiesmonaco.com/en/histoire |title=History of the Principality of Monaco – Access Properties Monaco – Real-estate Agency Monaco |publisher=Access Properties Monaco |date=|accessdate=28 May 2012}}</ref> These were ceded to France in return for 4,100,000 francs.<ref>{{cite web |url=http://monacodc.org/monhistory.html |title=History of Monaco |publisher=Monacodc.org |date=|accessdate=28 May 2012}}</ref> The transfer and Monaco's sovereignty were recognized by the [[Franco-Monegasque Treaty|Franco-Monegasque Treaty of 1861]]. In 1869, the principality stopped collecting income tax from its residents—an indulgence the Grimaldi family could afford to entertain thanks solely to the extraordinary success of the casino.<ref>{{cite web |url=http://www.monaco-mairie.mc/principaute-monaco-monte-carlo/ |title=Histoire de la Principauté – Monaco – Mairie de Monaco – Ma ville au quotidien – Site officiel de la Mairie de Monaco |publisher=Monaco-mairie.mc |date= |accessdate=28 May 2012 |archive-url=https://web.archive.org/web/20120603055329/http://www.monaco-mairie.mc/principaute-monaco-monte-carlo |archive-date=3 June 2012 |dead-url=yes |df=dmy-all }}</ref> This made Monaco not only a playground for the rich, but a favored place for them to live.<ref>{{cite web |url=http://www.tlfq.ulaval.ca/axl/europe/monaco.htm |title=MONACO |publisher=Tlfq.ulaval.ca |date=|accessdate=28 May 2012}}</ref>

=== 20th century ===
[[File:Monegasque Revolution.jpg|thumb|left|Mayor of Monaco announcing concessions ending absolute monarchy of [[Prince Albert I]] in 1910]]
Until the [[Monegasque Revolution]] of 1910 forced the adoption of the [[Constitution of Monaco|1911 constitution]], the [[List of rulers of Monaco|princes of Monaco]] were [[Absolute monarchy|absolute rulers]].<ref>{{cite news|url=http://news.bbc.co.uk/2/hi/europe/country_profiles/2530539.stm |title=Monaco timeline |publisher=BBC News |date=28 March 2012 |accessdate=28 May 2012}}</ref> The new constitution, however, barely reduced the autocratic rule of the Grimaldi family and [[Prince Albert I]] soon suspended it during the [[First World War]].

In July 1918, the [[Franco-Monegasque Treaty]] was signed, providing for limited French protection over Monaco. The treaty, endorsed in 1919 by the [[Treaty of Versailles]], established that Monegasque international policy would be aligned with French political, military, and economic interests, and resolved the [[Monaco Succession Crisis of 1918|Monaco Succession Crisis]].<ref>{{cite web |url=http://www.nationsencyclopedia.com/economies/Europe/Monaco-POLITICS-GOVERNMENT-AND-TAXATION.html |title=Monaco Politics, government, and taxation|publisher=Nationsencyclopedia.com |date= |accessdate=28 May 2012}}</ref>

[[File:Prince Rainier III and Princess Grace.jpg|thumb|right|The marriage of [[Grace Kelly]] to [[Prince Rainier III]] brought attention to the principality.]]

In 1943, the [[Italian Army]] invaded and occupied Monaco, forming a [[Fascism|fascist]] administration.<ref name="monaco.alloexpat.com">{{cite web |url=http://www.monaco.alloexpat.com/monaco_information/history_of_monaco.php |title=Monaco History, History of Monaco – Allo' Expat Monaco |publisher=Monaco.alloexpat.com |date= |accessdate=28 May 2012 |deadurl=yes |archiveurl=https://web.archive.org/web/20120527162437/http://www.monaco.alloexpat.com/monaco_information/history_of_monaco.php |archivedate=27 May 2012 |df=dmy-all }}</ref> Shortly thereafter, following the collapse of [[Benito Mussolini|Mussolini]], the German [[Wehrmacht]] occupied Monaco and the [[Nazism|Nazi]] deportation of the Jewish population began. [[René Blum (ballet)|René Blum]], the prominent French Jew who founded the Ballet de l'Opera in Monte Carlo, was arrested in his [[Paris]] home and held in the [[Drancy internment camp|Drancy]] deportation camp outside the French capital before being transported to the [[Auschwitz concentration camp]], where he was later killed.<ref>Abramovici P. ''[https://www.amazon.com/rocher-bien-occupé-pendant-1939-1945/dp/2020372118 Un rocher bien occupé : Monaco pendant la guerre 1939–1945]'' Editions Seuil, Paris 2001, {{ISBN|2-02-037211-8}}</ref> Blum's colleague [[Raoul Gunsbourg]], the director of the [[Opéra de Monte-Carlo]], helped by the [[French Resistance]], escaped arrest and fled to [[Switzerland]].<ref>{{cite web |url=http://tmeheust.free.fr/monacohistoire2.html |title=Monaco histoire |publisher=Tmeheust.free.fr |date=|accessdate=28 May 2012}}</ref> In August 1944, the Germans executed René Borghini, Joseph-Henri Lajoux and Esther Poggio, who were Resistance leaders.

[[Rainier III, Prince of Monaco|Rainier III]], who ruled until 2005, succeeded to the throne following the death of his grandfather, Prince [[Louis II, Prince of Monaco|Louis II]], in 1949. On 19 April 1956, Prince Rainier married the American actress [[Grace Kelly]]; the event was widely televised and covered in the popular press, focusing the world's attention on the tiny principality.<ref>{{cite web |url=http://www.nationsonline.org/oneworld/monaco.htm |title=Monaco – Principality of Monaco – Principauté de Monaco – French Riviera Travel and Tourism |publisher=Nationsonline.org |date=|accessdate=28 May 2012}}</ref>

A 1962 amendment to the constitution abolished capital punishment, provided for [[women's suffrage]], and established a [[Supreme Court of Monaco]] to guarantee fundamental liberties.

In 1963, a crisis developed when [[Charles de Gaulle]] blockaded Monaco, angered by its status as a tax haven for wealthy French. The 2014 film ''[[Grace of Monaco (film)|Grace of Monaco]]'' is loosely based on this crisis.<ref>{{cite web|url=http://pagesix.com/2014/04/02/monaco-royals-will-not-be-at-cannes-grace-of-monaco-premiere/?_ga=1.162783800.562580333.1395152845|title=Monaco royals will not be at Cannes ‘Grace of Monaco’ premiere – Page Six|work=Page Six}}</ref>

In 1993, the Principality of Monaco became a member of the [[United Nations]], with full voting rights.<ref name="infoplease1"/><ref name="cia">{{cite web |url=https://www.cia.gov/library/publications/the-world-factbook/geos/mn.html |title=CIA – The World Factbook |publisher=Cia.gov |date=|accessdate=22 March 2012}}</ref>

===21st century===
[[File:Vista de Mónaco, 2016-06-23, DD 13.jpg|thumb|View of Monaco in 2016]]
In 2002, a new treaty between France and Monaco specified that, should there be no heirs to carry on the Grimaldi dynasty, the principality would still remain an independent nation rather than revert to France. Monaco's military defence, however, is still the responsibility of France.<ref>{{cite web |url=http://www.europe-cities.com/en/657/monaco/history/chronology/ |title=History of Monaco. Monaco chronology |publisher=Europe-cities.com |date= |accessdate=28 May 2012 |archive-url=https://web.archive.org/web/20130116210452/http://www.europe-cities.com/en/657/monaco/history/chronology/ |archive-date=16 January 2013 |dead-url=yes |df=dmy-all }}</ref><ref>{{cite web |url=http://www.theodora.com/wfbcurrent/monaco/monaco_military.html |title=Monaco Military 2012, CIA World Factbook |publisher=Theodora.com |date=|accessdate=28 May 2012}}</ref>

On 31 March 2005, Rainier III, who was too ill to exercise his duties, relinquished them to his only son and heir, Albert.<ref>{{cite web |url=http://www.yourmonaco.com/royal |title=Monaco Royal Family |publisher=Yourmonaco.com |date=|accessdate=28 May 2012}}</ref> He died six days later, after a reign of 56 years, with his son succeeding him as [[Albert II, Prince of Monaco|Albert II]], [[Sovereign Prince of Monaco]].

Following a period of official mourning, Prince Albert II formally assumed the princely crown on 12 July 2005,<ref>{{cite web |url=http://www.palais.mc/monaco/palais-princier/english/h.s.h.-prince-albert-ii/biography/biography.391.html |title=Biography – Prince's Palace of Monaco |publisher=Palais.mc |date=|accessdate=28 May 2012}}</ref> in a celebration that began with a solemn [[Mass (liturgy)|Mass]] at [[Saint Nicholas Cathedral, Monaco|Saint Nicholas Cathedral]], where his father had been buried three months earlier. His accession to the Monégasque throne was a two-step event with a further ceremony, drawing heads of state for an elaborate reception, held on 18 November 2005, at the historic [[Prince's Palace of Monaco|Prince's Palace]] in [[Monaco-Ville]].<ref>{{cite web |url=http://www.montecarlosbm.com/luxury-trip-monaco/visit-monaco/monaco-history/ |title=History of Monaco, Grimaldi family |publisher=Monte-Carlo SBM |date=|accessdate=28 May 2012}}</ref>

On 27 August 2015, Albert II apologized for Monaco's role during [[World War II]] in facilitating the deportation of a total of 90 Jews and resistance fighters, of whom only nine survived. "We committed the irreparable in handing over to the neighbouring authorities women, men and a child who had taken refuge with us to escape the persecutions they had suffered in France," Albert said at a ceremony in which a monument to the victims was unveiled at the Monaco cemetery. "In distress, they came specifically to take shelter with us, thinking they would find neutrality."<ref>{{cite news|last=Williams|first=Carol J.|title=More than seven decades later, Monaco apologises for deporting Jews|url=http://www.latimes.com/world/europe/la-fg-monaco-jews-deportation-apology-20150827-story.html|work=[[Los Angeles Times]]|date=27 August 2015|accessdate=31 August 2015}}</ref>

In 2015, Monaco unanimously approved a modest [[Land reclamation in Monaco|land reclamation]] expansion intended primarily for some desperately needed housing and a small green/park area.<ref name="rivieratimes.com">{{cite web|url=http://www.rivieratimes.com/index.php/monaco-article/items/monaco-land-reclamation-project-gets-green-light.html|title=Monaco land reclamation project gets green light|work=rivieratimes.com|access-date=8 August 2015|archive-url=https://web.archive.org/web/20150904002030/http://www.rivieratimes.com/index.php/monaco-article/items/monaco-land-reclamation-project-gets-green-light.html|archive-date=4 September 2015|dead-url=yes|df=dmy-all}}</ref> Monaco had previously considered an expansion in 2008, but called it off.<ref name="rivieratimes.com"/> The plan is for about six [[hectare]]s of apartment buildings, parks, shops and offices for about 1 billion euros for the land.<ref name="thenational.ae">{{cite web|url=http://www.thenational.ae/business/industry-insights/property/monaco-1-billion-reclamation-plan-for-luxury-homes-district|title=Monaco €1 billion reclamation plan for luxury homes district|author=Colin Randall|work=thenational.ae}}</ref> The development will be adjacent to the [[Larvotto]] district and also will include a small marina.<ref name="thenational.ae"/><ref name="mooringspot.com">{{cite web|url=http://www.mooringspot.com/anse-portier-marina-monaco-monte-carlo-new-berths|title=Monaco’s New Marina, in 10 Years from now|work=mooringspot.com}}</ref> There were four main proposals, and the final mix of use will be finalised as the development progresses.<ref>{{cite web|url=https://www.forbes.com/sites/jimdobson/2015/06/25/the-future-of-monaco-man-made-island-and-floating-formula-one-race-track/|title=Forbes Life|work=forbes.com}}</ref> The name for the new district is [[Le Portier|Anse du Portier]].<ref name="mooringspot.com"/>
[[File:PW0018.jpg|thumb|center|upright=2.75|<center>Panoramic view of Monaco from the [[Tête de Chien]] in 2017</center>]]

== Government ==
{{Main|Politics of Monaco}}
[[File:The Prince of Monaco in 2013.jpg|thumb|right|[[Albert II, Prince of Monaco]]]]
Monaco has been governed under a [[constitutional monarchy]] since 1911, with the [[Prince of Monaco|Sovereign Prince of Monaco]] as [[head of state]].<ref>{{cite web |url=https://www.state.gov/r/pa/ei/bgn/3397.htm |title=Monaco |publisher=State.gov |date=16 November 2011 |accessdate=22 March 2012}}</ref> The [[Executive (government)|executive branch]] consists of a [[Minister of State (Monaco)|Minister of State]] as the [[head of government]], who presides over a five-member [[Council of Government]].<ref>{{cite web |url=http://www.monaco-iq.com/politics |title=Politics |publisher=Monaco-IQ |date=|accessdate=28 May 2012}}</ref> Until 2002, the Minister of State was a French citizen appointed by the prince from among candidates proposed by the French government; since a constitutional amendment in 2002, the Minister of State can be French or Monegasque.<ref name="state1"/> However, Prince Albert II appointed, on 3 March 2010, the Frenchman [[Michel Roger]] as Minister of State.<ref name="monaco-consulate1">{{cite web |url=http://www.monaco-consulate.com/index.php/about/history/ |title=History « Consulate General of Monaco |publisher=Monaco-consulate.com |date= |accessdate=28 May 2012 |archive-url=https://web.archive.org/web/20120610201643/http://www.monaco-consulate.com/index.php/about/history/ |archive-date=10 June 2012 |dead-url=yes |df=dmy-all }}</ref>

Under the 1962 constitution, the prince shares his [[veto power]] with the [[Unicameralism|unicameral]] [[National Council of Monaco|National Council]].<ref>{{cite web |url=http://globaledge.msu.edu/Countries/Monaco/government |title=Monaco: Government |publisher=Globaledge.msu.edu |date=4 October 2004 |accessdate=28 May 2012}}</ref> The 24 members of the National Council are elected for five-year terms; 16 are chosen through a majority electoral system and 8 by proportional representation.<ref name="freedomhouse1">{{cite web |url=http://www.freedomhouse.org/report/freedom-world/2011/monaco |title=Monaco |publisher=Freedom House |date=|accessdate=28 May 2012}}</ref> All legislation requires the approval of the National Council, which is currently dominated by the conservative [[National and Democratic Union|Rally and Issues for Monaco]] (REM) party which holds 20 seats.<ref name="freedomhouse1"/> [[Union Monégasque]] holds three seats<ref name="freedomhouse1"/> while [[Renaissance (Monaco)|Renaissance]] holds one seat. The principality's city affairs are directed by the [[Communal Council of Monaco|Communal Council]],<ref name=autogenerated3>{{cite web|url=http://www.monacohebdo.mc/4786-deux-listes-pour-une-mairie|title=Deux listes pour une mairie|work=Monaco Hebdo}}</ref> which consists of 14 elected members and is presided over by a mayor.<ref>{{cite web|url=http://www.monaco-mairie.mc/elus-monaco/|title=Les élus|author=Mairie de Monaco|work=La Mairie de Monaco|access-date=15 April 2013|archive-url=https://web.archive.org/web/20130515063156/http://www.monaco-mairie.mc/elus-monaco/|archive-date=15 May 2013|dead-url=yes|df=dmy-all}}</ref> Unlike the National Council, councillors are elected for four-year terms,<ref>{{cite web|url=http://www.monaco-mairie.mc/mairie-monaco/le-conseil-communal/|title=Le Conseil Communal – Mairie de Monaco|work=La Mairie de Monaco|access-date=15 April 2013|archive-url=https://web.archive.org/web/20130116232740/http://www.monaco-mairie.mc/mairie-monaco/le-conseil-communal/|archive-date=16 January 2013|dead-url=yes|df=dmy-all}}</ref> and are strictly [[non-partisan]]; however, [[Opposition (politics)|oppositions]] inside the council frequently form.<ref name=autogenerated3/><ref>{{cite web|url=http://www.nicematin.com/article/actualites/elections-communales-a-monaco-vingt-quatre-candidats-en-lice.460784.html|title=Élections communales à Monaco: vingt-quatre candidats en lice|work=nicematin.com}}</ref>

=== Administrative divisions ===
{{Update|section|date=July 2015|reason=wards were re-organized in 2013. See [[:fr:Monaco#Organisation territoriale|Monaco#Organisation territoriale (fr)]]}}
[[File:MonacoLibreDeDroits.jpg|thumb|In the center is [[La Condamine]]. At the right with the smaller harbor is [[Fontvieille, Monaco|Fontvieille]], with [[Rock of Monaco|The Rock]] (the old town, fortress, and Palace) jutting out between the two harbors. At the left are the high-rise buildings of [[Saint Roman (community)|La Rousse/Saint Roman]].]]
Monaco is the [[list of sovereign states and dependencies by area|second-smallest country by area]] in the [[world]]; only [[Vatican City]] is smaller.<ref>{{cite web|last=Robertson |first=Alex |url=http://www.gadling.com/2012/02/01/the-10-smallest-countries-in-the-world/ |title=The 10 smallest countries in the world |publisher=Gadling.com |date=1 February 2012 |accessdate=28 May 2012}}</ref> Monaco is also the world's second-smallest monarchy,<ref>{{cite web |url=http://www.worldmarineguide.com/country/monaco |title=Marinas, Ports & Anchorages in Monaco |publisher=Worldmarineguide.com |date= |accessdate=28 May 2012 |archive-url=https://web.archive.org/web/20111224013637/http://www.worldmarineguide.com/country/monaco |archive-date=24 December 2011 |dead-url=yes |df=dmy-all }}</ref> and is the most [[list of countries and territories by population density|densely populated]] country in the world.<ref>{{cite web |url=http://geography.about.com/od/populationgeography/a/popdensity.htm |title=Population Density |publisher=Geography.about.com |date=|accessdate=28 May 2012}}</ref> The state consists of only one [[municipality]] (''commune''), the [[Municipality of Monaco]]. There is no geographical distinction between the State and City of Monaco, although responsibilities of the government (state-level) and of the municipality (city-level) are different.<ref name="monaco-consulate1"/> According to the constitution of 1911, the [[principality]] was subdivided into three municipalities:<ref>{{cite web |url=http://www.jci-ec2013.com/en/about/monaco-monte-carlo/general-presentation.html |title=About Monaco |publisher=JCI EC 2013 |date=3 March 2010 |accessdate=28 May 2012}}</ref>

* [[Monaco-Ville]], the old city on a rocky promontory extending into the Mediterranean, known as the [[Rock of Monaco]], or simply "The Rock";
* [[Monte Carlo]], the principal residential and resort area with the [[Monte Carlo Casino]] in the east and northeast;
* [[La Condamine]], the southwestern section including the port area, [[Port Hercules]].

The municipalities were merged into one in 1917, after accusations that the government was acting according to the motto "divide and conquer," and they were accorded the status of ''[[Ward (electoral subdivision)|Wards]]'' or ''Quartiers'' thereafter.

* [[Fontvieille, Monaco|Fontvieille]] was added as a fourth ward, a newly constructed area claimed from the sea in the 1970s;
* [[Moneghetti]] became the fifth ward, created from part of La Condamine;
* [[Larvotto]] became the sixth ward, created from part of Monte Carlo;
* [[Saint Roman (community)|La Rousse/Saint Roman]] (including Le Ténao) became the seventh ward, also created from part of Monte Carlo.

Subsequently, three additional wards were created:

* [[Saint Michel, Monaco|Saint Michel]], created from part of Monte Carlo;
* [[La Colle, Monaco|La Colle]], created from part of La Condamine;
* [[Les Révoires]], also created from part of La Condamine.

An additional ward was planned by new land reclamation to be settled beginning in 2014<ref>{{cite web |url=http://www.west8.nl/projects/landscape/cape_grace_monaco/ |title=West 8 Urban Design & Landscape Architecture / projects / Cape Grace, Monaco |publisher=West8.nl |date=|accessdate=28 May 2012}}</ref> but Prince Albert II announced in his 2009 New Year Speech that he had ended plans due to the current economic climate.<ref>{{cite web |url=http://www.cityoutmonaco.com/monaco-property/articles/tourodeon2 |title=The new Monaco skyline |publisher=CityOut Monaco |date=17 March 2010 |accessdate=28 May 2012 |archive-url=https://web.archive.org/web/20111011020551/http://cityoutmonaco.com/monaco-property/articles/tourodeon2 |archive-date=11 October 2011 |dead-url=yes |df=dmy-all }}</ref> However, Prince Albert II in mid-2010 firmly restarted the program.<ref>{{cite news|last=Samuel |first=Henry |url=https://www.telegraph.co.uk/news/worldnews/europe/monaco/6894991/Monaco-to-build-into-the-sea-to-create-more-space.html |title=Monaco to build into the sea to create more space |work=The Daily Telegraph |date=28 December 2009 |accessdate=28 May 2012 |location=London}}</ref><ref name="cityoutmonaco.com">{{cite web |url=http://www.cityoutmonaco.com/monaco-property/articles/monacoprince |title=Prince speaks of future developments |publisher=CityOut Monaco |date=29 December 2009 |accessdate=28 May 2012 |archive-url=https://web.archive.org/web/20111011043404/http://cityoutmonaco.com/monaco-property/articles/monacoprince |archive-date=11 October 2011 |dead-url=yes |df=dmy-all }}</ref> In 2015, a new development called [[Le Portier|Anse du Portier]] was announced.<ref name="mooringspot.com"/>

==== Traditional quarters and modern geographic areas ====
The four traditional ''Quartiers'' of Monaco are [[Monaco-Ville]], [[La Condamine]], [[Monte Carlo]] and [[Fontvieille, Monaco|Fontvieille]].<ref>{{cite web |url=http://www.nationsencyclopedia.com/economies/Europe/Monaco.html |title=Monaco – Location and size |publisher=Nationsencyclopedia.com |date=2 July 2011 |accessdate=28 May 2012}}</ref><ref>{{cite web |url=http://www.websters-online-dictionary.org/definitions/Larvotto |title=Dictionary – Definition of Larvotto |publisher=Websters-online-dictionary.org |date=1 March 2008 |accessdate=28 May 2012 |archive-url=https://web.archive.org/web/20130530230643/http://www.websters-online-dictionary.org/definitions/Larvotto |archive-date=30 May 2013 |dead-url=yes |df=dmy-all }}</ref> However, the [[suburb]] of [[Moneghetti]], the high-level part of La Condamine, is generally seen today as an effective fifth ''Quartier'' of the Monaco, having a very distinct atmosphere and topography when compared with low-level La Condamine.<ref>{{cite web |url=http://www.visitmonaco.com/index.cfm?fuseaction=Page.viewPage&pageId=16 |title=Tourist Board official website |publisher=Visitmonaco.com |date=|accessdate=28 May 2012}}</ref>

==== Wards ====
{{Update|section|date=July 2015|reason=wards were re-organized in 2013 (see [[:fr:Monaco#Organisation territoriale|Monaco#Organisation territoriale]].}}
[[File:Monaco5.png|thumb|[[Ward (electoral subdivision)|Wards]] of Monaco]]
Currently Monaco is subdivided into ten [[ward (electoral subdivision)|wards]], with their official numbers; either Fontvieille II or Le Portier would become the effective eleventh ward, if built:<ref name="cityoutmonaco.com"/><ref name="autogenerated2">{{cite web|author=Nom (obligatoire) |url=http://www.monacohebdo.mc/9156-extension-en-mer-fontvieille-ou-larvotto |title=Extension en mer: Fontvieille ou Larvotto ? |publisher=Monacohebdo.mc |date=|accessdate=12 March 2013}}</ref><ref>{{cite web |url=http://statoids.com/umc.html |title=Monaco Commune |publisher=Statoids.com |date=|accessdate=28 May 2012}}</ref>

{| class="wikitable"
|-
! [[Ward (electoral subdivision)|Ward]] || Area (km²) || Population (Census of 2008) || Density (km²)||[[City block|City]] [[City block|Blocks]] ''(îlots)''||Remarks
|-
| colspan="7" style="text-align:center; background:#efefef;"| '''Former municipality of [[Monaco-Ville|Monaco]]'''
|-
| [[Monaco-Ville]] || style="text-align:right;"| 0.19 || style="text-align:right;"| 1,034|| style="text-align:right;"| 5,442 || style="text-align:right;"| 19 || Old City
|-
| colspan="7" style="text-align:center; background:#efefef;"| '''Former municipality of [[Monte Carlo]]'''
|-
| [[Monte Carlo|Monte Carlo/Spélugues]] (''Bd. Des Moulins-Av. de la Madone'')|| style="text-align:right;"| 0.30 || style="text-align:right;"| 3,834 || style="text-align:right;"| 12,780|| style="text-align:right;"| 20|| Casino and resort area
|-
| [[Saint Roman (community)|La Rousse/Saint Roman]] (''Annonciade-Château Périgord'')|| style="text-align:right;"| 0.13 || style="text-align:right;"| 3,223 || style="text-align:right;"| 24,792|| style="text-align:right;"| 17|| Northeast area, includes [[Le Ténao]]
|-
| [[Larvotto|Larvotto/Bas Moulins]] (''Larvotto-Bd Psse Grace'')|| style="text-align:right;"| 0.34 || style="text-align:right;"| 5,443 || style="text-align:right;"| 16,009|| style="text-align:right;"| 17|| Eastern beach area
|-
| [[Saint Michel, Monaco|Saint Michel]] (''Psse Charlotte-Park Palace'')|| style="text-align:right;"| 0.16 || style="text-align:right;"| 3,907 || style="text-align:right;"| 24,419|| style="text-align:right;"| 24|| Central residential area
|-
| colspan="7" style="text-align:center; background:#efefef;"| '''Former municipality of [[La Condamine]]'''
|-
| [[La Condamine]] || style="text-align:right;"| 0.28 || style="text-align:right;"| 3,947 || style="text-align:right;"| 14,096|| style="text-align:right;"| 28|| Northwest port area
|-
| [[La Colle, Monaco|La Colle]] (''Plati-Pasteur-Bd Charles III'')|| style="text-align:right;"| 0.11 || style="text-align:right;"| 2,829 || style="text-align:right;"| 25,718|| style="text-align:right;"| 15|| On the western border with [[Cap-d'Ail|Cap d'Ail]]
|-
| [[Les Révoires]] (''Hector Otto-Honoré Labande'')|| style="text-align:right;"| 0.09 || style="text-align:right;"| 2,545 || style="text-align:right;"| 28,278|| style="text-align:right;"| 11|| Contains the [[Jardin Exotique de Monaco]]
|-
| [[Moneghetti|Moneghetti/ Bd de Belgique]] (''Bd Rainier III-Bd de Belgique'') || style="text-align:right;"| 0.10 || style="text-align:right;"| 3,003 || style="text-align:right;"| 30,030 || style="text-align:right;"| 17|| Central-north residential area
|-
| colspan="7" style="text-align:center; background:#efefef;"| '''[[Land reclamation|New land reclaimed from the sea]]'''
|-
| [[Fontvieille, Monaco|Fontvieille]] || style="text-align:right;"| 0.35 || style="text-align:right;"| 3,901 || style="text-align:right;"| 11,146|| style="text-align:right;"| 10|| Started 1981
|- style="background: #CCC;"
| Monaco<ref name="Recensement"/><ref>{{cite web |url=http://www.gouv.mc/Action-Gouvernementale/L-Economie/Analyses-et-Statistiques/Publications/Monaco-Statistiques-Pocket |title=Monaco Statistiques Pocket |language= fr |publisher=Gouv.mc |date=|accessdate=6 September 2012}}</ref> || style="text-align:right;"| 2.05 || style="text-align:right;"| 33,666 || style="text-align:right;"| 16,422|| style="text-align:right;"| 178||  
|-
| colspan="7" style="background:#fff;"|(1) Not included in the total, as it is only proposed
|}

''Note: for statistical purposes, the Wards of Monaco are further subdivided into 178 [[city block]]s (îlots), which are comparable to the [[census block]]s in the United States''.<ref name="Recensement"/>

* Other possible expansions are [[Le Portier]], a project relaunched in 2012<ref>{{cite web |url=http://www.nicematin.com/economie/monaco-une-extension-en-mer-au-larvotto-de-nouveau-a-letude.898376.html |title=Monaco: une extension en mer au Larvotto de nouveau à l'étude |publisher=Nice-Matin |date=13 June 2012 |accessdate=12 March 2013 |deadurl=yes |archiveurl=https://web.archive.org/web/20130116210451/http://www.nicematin.com/economie/monaco-une-extension-en-mer-au-larvotto-de-nouveau-a-letude.898376.html |archivedate=16 January 2013 |df=dmy-all }}</ref>
* Another possibility was [[Fontvieille II]] Development to commence in 2013<ref name=autogenerated2/><ref>{{cite web|url=https://books.google.com/books?id=UORSzFBv1tAC&pg=PA51&lpg=PA51&dq=%22Fontvieille+II%22&source=bl&ots=c-FRAIekSk&sig=689bX3QqLtD4tmea3B-O-CBC5C0&hl=en&sa=X&ved=0CFwQ6AEwDWoVChMIjI2X6OaZxwIVwZYeCh2qrwCc#v=onepage&q=%22Fontvieille%20II%22&f=false|title=Seizing the Future|work=google.com}}</ref>

[[File:Monaco depuis since 1861.png|thumb|center|upright=3.2|<center>Land reclamation in Monaco since 1861</center>]]

=== Security ===
{{See also|Law enforcement in Monaco|Military of Monaco}}
[[File:Fuerstenpalast Wache.jpg|thumb|left|Palace guard in Monaco]]
The wider defence of the nation is provided by France. Monaco has no navy or air force, but on both a per-capita and per-area basis, Monaco has one of the largest police forces (515 police officers for about 36,000 people) and police presences in the world.<ref>{{cite web |url=http://www.monte-carlo.mc/en/information/safety/ |title=Security in Monaco |publisher=Monte-carlo.mc |date=13 May 2012 |accessdate=28 May 2012}}</ref> Its police includes a special unit which operates patrol and surveillance boats.<ref>{{cite web |url=http://www.gouv.mc/Gouvernement-et-Institutions/Le-Gouvernement/Departement-de-l-Interieur/Direction-de-la-Surete-Publique/Division-de-Police-Maritime-et-Aeroportuaire |title=Division de Police Maritime et Aéroportuaire |language= fr |publisher=Gouv.mc |date=16 August 1960 |accessdate=28 May 2012}}</ref>

There is also a small [[Military of Monaco|military force]]. This consists of a bodyguard unit for the Prince and the palace in [[Monaco-Ville]] called the [[Compagnie des Carabiniers du Prince]] (Prince's Company of Carabiniers), which is equipped with weapons such as [[M16A2 rifle]]s and 9 mm pistols (Glock 17),<ref>{{cite web |url=http://www.palais.mc/monaco/palais-princier/english/sovereign-house/the-palace-guards/the-palace-guards.453.html |title=The Palace Guards – Prince's Palace of Monaco |publisher=Palais.mc |date=27 January 2011 |accessdate=28 May 2012 |deadurl=yes |archiveurl=https://web.archive.org/web/20120423061945/http://www.palais.mc/monaco/palais-princier/english/sovereign-house/the-palace-guards/the-palace-guards.453.html |archivedate=23 April 2012 |df=dmy-all }}</ref> and which together with the militarized, armed fire and civil defence Corps (Sapeurs-Pompiers) forms Monaco's total public forces.<ref>{{cite web|url=http://www.pompiers.gouv.mc/321/wwwnew.nsf/1909!/x1Fr?OpenDocument%261Fr |title=Archived copy |accessdate=22 May 2012 |deadurl=yes |archiveurl=https://web.archive.org/web/20131206010807/http://www.pompiers.gouv.mc/321/wwwnew.nsf/1909!/x1Fr?OpenDocument&1Fr |archivedate=6 December 2013 |df=dmy }}</ref> The ''Compagnie des Carabiniers du Prince'' was created by Prince [[Honoré IV, Prince of Monaco|Honoré IV]] in 1817 for the protection of the principality and the Princely family. The company numbers exactly 116 officers and men; while the [[non-commissioned officer|NCOs]] and soldiers are local, the officers have generally served in the [[French Army]]. In addition to their guard duties as described, the Carabiniers patrol the principality's beaches and coastal waters.<ref>{{cite web|url=http://www.gouv.mc/Gouvernement-et-Institutions/Le-Gouvernement/Departement-de-l-Interieur/Compagnie-des-Carabiniers-du-Prince |title=Compagnie des Carabiniers du Prince |language= fr |publisher=Gouv.mc |date=|accessdate=12 March 2013}}</ref>

== Geography ==
{{See also|Land reclamation in Monaco}}
[[File:Monaco satellite map.png|thumb|Satellite view of Monaco, with the Monégasque-French border shown in yellow]]
Monaco is a sovereign [[city state]], with five ''quartiers'' and ten wards,<ref>{{cite web |url=http://monaco.me/monaco/monaco-districts/ |title=Monaco Districts |publisher=Monaco.me |date=|accessdate=22 March 2012}}</ref> located on the [[French Riviera]] in [[Western Europe]]. It is bordered by [[France]]'s [[Alpes-Maritimes]] ''département'' on three sides, with one side bordering the [[Mediterranean Sea]]. Its center is about {{convert|16|km|abbr=on}} from [[Italy]] and only {{convert|13|km|abbr=on}} northeast of [[Nice, France]].<ref name="cia"/> It has an area of {{convert|2.02|km²|abbr=on}}, or {{convert|202|ha|acre|abbr=off}}, and a population of 38,400,<ref name="auto">{{cite web|url=http://www.monacostatistics.mc/IMSEE/Publications/monaco-statistics-pocket|title="monaco statistics pocket" / Publications / IMSEE - Monaco IMSEE|first=Government of|last=Monaco|website=Monacostatistics.mc}}</ref> making Monaco the [[List of countries and dependencies by area|second-smallest]] and the most [[List of countries by population density|densely populated country in the world]].<ref name="cia"/> The country has a [[land border]] of only {{convert|5.47|km|abbr=on}},<ref name="auto"/> a [[coastline]] of {{convert|3.83|km|abbr=on}}, a [[Maritime boundary|maritime claim]] that extends {{Convert|22.2|km|mi|1}}, and a width that varies between {{convert|1700|and|349|m|abbr=on}}.<ref name="about">{{cite web|url=http://mapofeurope.com/monaco/ |title=Geography and Map of Monaco |publisher=mapofeurope.com |date=|accessdate=11 September 2014}}</ref><ref name="visitmonaco">{{cite web|url=http://visitmonaco.com/us/About-Monaco/Geography/Monaco%27s-Areas |title=Monaco's Areas / Monaco Official Site |publisher=Visitmonaco.com |date=|accessdate=12 March 2013}}</ref>

The highest point in the country is at the access to the ''Patio Palace'' residential building on the [[Chemin des Révoires]] (ward [[Les Révoires]]) from the D6007 (''Moyenne Corniche'' street) at {{convert|164.4|m|ft|abbr=off}} [[Above mean sea level|above sea level]].<ref>''Highest point at ground level (Access to Patio Palace on D6007)'' {{cite web|url=http://www.gouv.mc/content/download/175997/2030403/file/monaco%20statistics%20pocket%202014.pdf|publisher=Monaco Statistics – Principality of Monaco|title=Monaco Statistics pocket – Edition 2014|format=PDF}}</ref> The lowest point in the country is the Mediterranean Sea.<ref>{{cite web |url=http://www.worldatlas.com/aatlas/infopage/highlow.htm |title=Highest and lowest points in countries islands oceans of the world |publisher=Worldatlas.com |date=|accessdate=6 September 2012}}</ref>

[[Saint-Jean brook|Saint-Jean]] is the longest flowing body of water, around {{convert|0.19|km|m mi ft|abbr=in}} in length, and [[Fontvieille lake|Fontvieille]] is the largest lake, approximately {{convert|0.5|ha|m2 acre ft2|2|abbr=on}} in area.<ref>{{cite web|url=https://maps.google.com/maps?hl=en&cp=5&gs_id=28&xhr=t&q=monaco&safe=off&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&biw=1366&bih=704&um=1&ie=UTF-8&sa=N&tab=wl |title=Monaco |publisher=Google Maps|date=|accessdate=6 September 2012}}</ref> Monaco's most populated ''quartier'' is [[Monte Carlo]], and the most populated ward is [[Larvotto|Larvotto/Bas Moulins]].<ref name="Recensement"/>

After a recent expansion of [[Port Hercules]],<ref name="Extension"/> Monaco's total area grew to {{convert|2.02|km²|abbr=on}} or {{convert|202|ha|acre|abbr=off}};<ref name="Recensement"/> consequently, new plans have been approved to extend the district of Fontvieille by {{convert|0.08|km²|abbr=on}} or {{convert|8|ha|acre|abbr=off}}, with land [[Reclaimed land|reclaimed]] from the Mediterranean Sea. Current land reclamation projects include extending the district of Fontvieille.<ref name="telegraph">{{cite news|last=Samuel|first=Henry |url=https://www.telegraph.co.uk/news/worldnews/europe/monaco/6894991/Monaco-to-build-into-the-sea-to-create-more-space.html |title=Monaco to build into the sea to create more space |work=The Daily Telegraph |date=28 December 2009 |accessdate=22 March 2012 |location=London}}</ref><ref name="OpenDoc">{{cite web| author=Robert Bouhnik|url=http://cloud.gouv.mc/devwww/wwwnew.nsf/1909$/3952ae296ac3807cc1256f73002bd426gb?OpenDocument&6Gb&Count=10000 |title=Home > Files and Reports > Public works(Gb) |publisher=Cloud.gouv.mc |date=19 October 2010 |accessdate=22 March 2012}}</ref><ref>{{cite web |url=http://royalopinions.proboards.com/index.cgi?action=display&board=currentmonaco&thread=192&page=5 |title=Royal Opinions – Social, Political, & Economical Affairs of Monaco |publisher=Royalopinions.proboards.com |date=|accessdate=22 March 2012}}</ref><ref name="Extension">{{cite web |author=Robert BOUHNIK |url=http://cloud.gouv.mc/devwww/wwwnew.nsf/1909$/1ddf179c1910b5fbc1256fc60036dcc6gb?OpenDocument&Count=10000&InfoChap=%20Files%20and%20Reports&InfoSujet=2002%20Archives%20-%20Extension%20of%20%22La%20Condamine%20Port%22&6Gb |title=Home > Files and Reports > Public works > 2002 Archives — Extension of "La Condamine Port"(Gb) |publisher=Cloud.gouv.mc |date=19 October 2010 |accessdate=22 March 2012 }}{{Dead link|date=August 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref>{{cite web |url=http://www.econostrum.info/Monaco-remet-sur-le-tapis-le-projet-d-extension-en-mer_a9166.html |title=Monaco remet sur le tapis le projet d'extension en mer |publisher=Econostrum.info |date=|accessdate=22 March 2012}}</ref> There are two [[port]]s in Monaco, Port Hercules and Port Fontvieille.<ref name="Presentation">{{cite web |url=http://www.ports-monaco.com/lang-en.html |title=Presentation |publisher=Ports-monaco.com |date=1 January 2006 |accessdate=22 March 2012 |archive-url=https://web.archive.org/web/20120620235447/http://www.ports-monaco.com/lang-en.html |archive-date=20 June 2012 |dead-url=yes |df=dmy-all }}</ref> Monaco's only [[natural resource]] is [[fishing]];<ref>{{cite web| author=|url=//www.youtube.com/watch?v=nyIYViMSlOE |title=Prince Albert of Monaco interview on fishing issues |publisher=YouTube |date=30 June 2011 |accessdate=22 March 2012}}</ref> with almost the entire country being an [[urban area]], Monaco lacks any sort of commercial [[agriculture|agriculture industry]]. There is a neighboring French port called [[Cap d'Ail]] that is near Monaco.<ref name="Presentation"/>

[[File:Monaco_City_001.jpg|thumb|center|1000px|upright=3.2|<center>Panoramic view of [[La Condamine]] and [[Monte Carlo]]</center>]]

===Architecture===
{{See also|Monaco villas}}
Monaco exhibits a wide range of architecture, but the principality's signature style, particularly in Monte Carlo, is that of the [[Belle Epoque]]. It finds its most florid expression in the 1878–9 [[Monte Carlo Casino|Casino]] and the [[Opéra de Monte-Carlo|Salle Garnier]] created by [[Charles Garnier (architect)|Charles Garnier]] and Jules Dutrou. Decorative elements including turrets, balconies, pinnacles, multi-coloured ceramics and caryatids and borrowed and blended to create a picturesque fantasy of pleasure and luxury, and an alluring expression of how Monaco sought, and still seeks, to portray itself.<ref>Novella, René; Sassi, Luca ''Monaco : eight centuries of art and architecture', Epi Communication, 2015</ref> This [[Capriccio (art)|capriccio]] of French, Italian and Spanish elements was incorporated into hacienda villas and apartments. Following major development in the 1970s, [[Rainier III, Prince of Monaco|Prince Rainier III]] banned high-rise development in the principality. However, his successor, [[Albert II, Prince of Monaco|Prince Albert II]], overturned this Sovereign Order.<ref name="Fair">{{Cite web|url=http://www.vanityfair.fr/actualites/france/articles/monaco-la-tour-odeon-un-chantier-malheureux/23582|title=La tour Odéon, l'histoire d'un chantier dont les malheurs ont atteint des sommets|last=Fair|first=Vanity|access-date=7 August 2016}}</ref> In recent years the accelerating demolition of Monaco's architectural heritage, including its single-family villas, has created dismay.<ref>Lyall, Sarah; Baume, Maïa de la ''Development Blitz Provokes a Murmur of Dissent in Monaco'', New York Times, 11 December 2013; https://www.nytimes.com/2013/12/12/world/europe/development-blitz-provokes-a-murmur-of-dissent-in-monaco.html</ref> The principality currently has no heritage protection legislation.<ref name="lobservateurdemonaco.mc">''Monaco's Heritage In Danger?'', L'Observateur de Monaco, No141, April 2015, pp60-67;http://www.lobservateurdemonaco.mc/wp-content/uploads/2015/09/Obs141.pdf</ref>

=== Climate ===
Monaco has a [[hot-summer Mediterranean climate]] ([[Köppen climate classification]]: Csa), which is influenced by [[oceanic climate]] and [[humid subtropical climate]]. As a result, it has warm, dry summers and mild, rainy winters.<ref>{{cite web |url=http://www.worldtravelguide.net/monaco/weather-climate-geography |title=Monaco weather, climate and geography |publisher=Worldtravelguide.net |date=|accessdate=6 September 2012}}</ref> Cool and rainy interludes can interrupt the dry summer season, the average length of which is also shorter. Summer afternoons are infrequently hot (indeed, temperatures greater than {{convert|30|°C|°F|disp=or}} are rare) as the atmosphere is temperate because of constant sea breezes. On the other hand, the nights are very mild, due to the fairly high temperature of the sea in summer. Generally, temperatures do not drop below {{convert|20|°C}} in this season. In the winter, frosts and snowfalls are extremely rare and generally occur once or twice every ten years.<ref>{{cite web|url=http://www.montecarlodailyphoto.com/2009/12/snow-in-casino-square.html |title=Snow in Casino Square! |publisher=Monte Carlo Daily Photo |date=19 December 2009 |accessdate=6 September 2012}}</ref><ref>{{cite web |url=http://www.visitmonaco.com/us/About-Monaco/Weather |title=Monaco – Weather / Monaco Official Site |publisher=Visitmonaco.com |date=|accessdate=6 September 2012}}</ref>

{{Weather box
|location = Monaco (1981–2010 averages, extremes 1966–present)
|metric first = yes
|single line = yes
|Jan record high C = 19.9
|Feb record high C = 23.2
|Mar record high C = 25.6
|Apr record high C = 26.2
|May record high C = 30.3
|Jun record high C = 32.5
|Jul record high C = 34.4
|Aug record high C = 34.5
|Sep record high C = 33.1
|Oct record high C = 29.0
|Nov record high C = 25.0
|Dec record high C = 22.3
|year record high C = 34.5
|Jan high C = 13.0
|Feb high C = 13.0
|Mar high C = 14.9
|Apr high C = 16.7
|May high C = 20.4
|Jun high C = 23.7
|Jul high C = 26.6
|Aug high C = 26.9
|Sep high C = 24.0
|Oct high C = 20.6
|Nov high C = 16.5
|Dec high C = 13.9
|year high C = 19.2
|Jan mean C = 10.2
|Feb mean C = 10.2
|Mar mean C = 12.0
|Apr mean C = 13.8
|May mean C = 17.5
|Jun mean C = 20.9
|Jul mean C = 23.8
|Aug mean C = 24.2
|Sep mean C = 21.1
|Oct mean C = 17.9
|Nov mean C = 13.8
|Dec mean C = 11.2
|year mean C = 16.4
|Jan low C = 7.4
|Feb low C = 7.4
|Mar low C = 9.1
|Apr low C = 10.9
|May low C = 14.6
|Jun low C = 18.0
|Jul low C = 21.0
|Aug low C = 21.4
|Sep low C = 18.3
|Oct low C = 15.2
|Nov low C = 11.2
|Dec low C = 8.5
|year low C = 13.6
|Jan record low C = -3.1
|Feb record low C = -5.2
|Mar record low C = -3.1
|Apr record low C = 3.8
|May record low C = 7.5
|Jun record low C = 9.0
|Jul record low C = 10.5
|Aug record low C = 12.4
|Sep record low C = 10.5
|Oct record low C = 6.5
|Nov record low C = 1.6
|Dec record low C = -1.0
|year record low C = -5.2
|Jan precipitation mm = 67.7
|Feb precipitation mm = 48.4
|Mar precipitation mm = 41.2
|Apr precipitation mm = 71.3
|May precipitation mm = 49.0
|Jun precipitation mm = 32.6
|Jul precipitation mm = 13.7
|Aug precipitation mm = 26.5
|Sep precipitation mm = 72.5
|Oct precipitation mm = 128.7
|Nov precipitation mm = 103.2
|Dec precipitation mm = 88.8
|year precipitation mm = 743.6
|unit precipitation days = 1.0 mm
|Jan precipitation days = 6.0
|Feb precipitation days = 4.9
|Mar precipitation days = 4.5
|Apr precipitation days = 7.3
|May precipitation days = 5.5
|Jun precipitation days = 4.1
|Jul precipitation days = 1.7
|Aug precipitation days = 2.5
|Sep precipitation days = 5.1
|Oct precipitation days = 7.3
|Nov precipitation days = 7.1
|Dec precipitation days = 6.5
|year precipitation days = 62.4
|Jan sun = 149.8
|Feb sun = 158.9
|Mar sun = 185.5
|Apr sun = 210.0
|May sun = 248.1
|Jun sun = 281.1
|Jul sun = 329.3
|Aug sun = 296.7
|Sep sun = 224.7
|Oct sun = 199.0
|Nov sun = 155.2
|Dec sun = 136.5
|year sun = 2574.7
|source 1 = [[Météo France]]<ref>{{cite web
| archiveurl = https://web.archive.org/web/20180227004241/https://donneespubliques.meteofrance.fr/FichesClim/FICHECLIM_99138001.pdf
| archivedate = 27 February 2018
| url = https://donneespubliques.meteofrance.fr/FichesClim/FICHECLIM_99138001.pdf
| title = Monaco (99)
| work = Fiche Climatologique: Statistiques 1981–2010 et records
| publisher = Meteo France
| language = French
| accessdate = 26 February 2018}}</ref>
|source 2 = Monaco website (sun only)<ref>{{cite web
| archiveurl = https://web.archive.org/web/20180302082530/http://www.visitmonaco.com/fr/Pratique/Climat
| archivedate = 2 March 2018
| url = http://www.visitmonaco.com/fr/Monaco-Pratique/Climat
| title = Climatological information for Monaco
| publisher = Monaco Tourist Authority
| language = French
| accessdate = 2 March 2018}}</ref>
|date=September 2010
}}

{|style="width:90%;text-align:center;font-size:90%;line-height:1.2em;margin-left:auto;margin-right:auto" class="wikitable"
|-
!Colspan=14|Climate data for Monaco
|-
!Month
!Jan
!Feb
!Mar
!Apr
!May
!Jun
!Jul
!Aug
!Sep
!Oct
!Nov
!Dec
!style="border-left-width:medium"|Year
|-
!Average sea temperature °C (°F)
|style="background:#C9C9FF;color:#000000;"|13.4 (56.2)
|style="background:#C3C3FF;color:#000000;"|13.0 (55.5)
|style="background:#C9C9FF;color:#000000;"|13.4 (56.1)
|style="background:#DBDBFF;color:#000000;"|14.6 (58.4)
|style="background:#FFEBAA;color:#000000;"|18.0 (64.3)
|style="background:#FFA000;color:#000000;"|21.8 (71.3)
|style="background:#FF8700;color:#000000;"|23.1 (73.6)
|style="background:#FF7D00;color:#000000;"|23.6 (74.4)
|style="background:#FF9900;color:#000000;"|22.2 (71.9)
|style="background:#FFCB21;color:#000000;"|19.6 (67.2)
|style="background:#FFF7DD;color:#000000;"|17.4 (63.3)
|style="background:#DFDFFF;color:#000000;"|14.9 (58.9)
|style="background:#FFEDB1;color:#000000;border-left-width:medium"|17.9 (64.3)
|-
!Colspan=14 style="background:#f8f9fa;font-weight:normal;font-size:95%;"|Source: Weather Atlas<ref name="Weather Atlas">{{cite web |url=http://www.weather-atlas.com/en/monaco/monaco-climate |title=Monaco, Monaco – Climate data |publisher=Weather Atlas |access-date=15 March 2017 }}</ref>
|}

== Economy ==
{{Main|Economy of Monaco}}
[[File:Monaco004.jpg|thumb|[[Fontvieille, Monaco|Fontvieille]] and its new harbour]]
Monaco has the world's second-highest [[List of countries by GDP (nominal) per capita|GDP nominal per capita]] at US$153,177, [[List of countries by GDP (PPP) per capita|GDP PPP per capita]] at $132,571 and [[List of countries by GNI (nominal, Atlas method) per capita|GNI per capita]] at $183,150.<ref name="unsd"/><ref>[https://web.archive.org/web/20120402032202/http://databank.worldbank.org/databank/download/GNIPC.pdf Gross national income per capita 2010, Atlas method and PPP]. World Bank</ref><ref>{{cite web |url=http://monacodc.org/economy.html |title=Business And Economy |publisher=Monacodc.org |date=|accessdate=22 March 2012}}</ref> It also has an [[List of countries by unemployment rate|unemployment rate]] of 2%,<ref>{{cite web |url=https://www.cia.gov/library/publications/the-world-factbook/fields/2129.html |title=Central Intelligence Agency |publisher=Cia.gov |date=|accessdate=22 March 2012}}</ref> with over 48,000 workers who commute from France and Italy each day.<ref name="Recensement">{{cite web |url=http://cloud.gouv.mc/devwww/wwwnew.nsf/e89a6190e96cbd1fc1256f7f005dbe6e/64a1643c86f9f661c12575ae004cc473/$FILE/ATTW9ZI8/Recensement2008_p8-9.pdf |title=Plan General De La Principaute De Monaco |format=PDF |date= |accessdate=28 May 2012 }}{{Dead link|date=August 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> According to the [[CIA World Factbook]], Monaco has the world's [[List of countries by poverty|lowest poverty rate]]<ref name="theodora"/> and the highest number of millionaires and billionaires per capita in the world.<ref>{{cite news|last=Alleyne |first=Richard |url=https://www.telegraph.co.uk/news/uknews/1565068/Prince-Albert-We-want-more-for-Monaco.html |title=Prince Albert: We want more for Monaco |work=The Daily Telegraph |date=4 October 2007 |accessdate=22 March 2012 |location=London}}</ref><ref name="dailymail1">{{cite news|url=http://www.dailymail.co.uk/news/article-1132957/Piers-Morgans-Monte-The-tax-haven-jewels-real-orgasms-fake.html |title=Piers Morgan's full Monte! The tax haven where the jewels are real and the orgasms are fake |work=Daily Mail |date=31 January 2009 |accessdate=28 May 2012 |location=London}}</ref> For the fourth year in a row, Monaco in 2012 had the world's most expensive real estate market, at $58,300 per square metre.<ref>{{cite web| author=Katya Wachtel |url=https://www.privatebank.citibank.com/pdf/wealthReport2012_lowRes.pdf |title=The Wealth Report 2012|publisher=Citi Private Bank |date=28 March 2012 |accessdate=6 March 2013}}</ref><ref>{{cite web| author=Robert Frank |url=https://blogs.wsj.com/wealth/2012/03/28/the-most-expensive-real-estate-in-the-world/ |title=The Most Expensive Real-Estate in the World |work=The Wall Street Journal |date=28 March 2012 |accessdate=6 March 2013}}</ref><ref>{{cite web| author=Julie Zeveloff| url=http://www.businessinsider.com/most-expensive-real-estate-markets-2013-3 |title=Here Are The World's Most Expensive Real Estate Markets |work=Business Insider |date=7 March 2013 |accessdate=7 March 2013}}</ref>

One of Monaco's main sources of income is tourism. Each year many foreigners are attracted to its casino and pleasant climate.<ref name="visitmonaco"/><ref>{{cite web |url=http://globaledge.msu.edu/Countries/Monaco/economy |title=Monaco: Economy >> globalEDGE: Your source for Global Business Knowledge |publisher=Globaledge.msu.edu |date=|accessdate=22 March 2012}}</ref> It has also become a major [[banking center]], holding over [[Euro|€]]100 billion worth of funds.<ref>{{cite web |author=Robert BOUHNIK |url=http://cloud.gouv.mc/devwww/wwwnew.nsf/1909$/607f54a31a14184fc1256a130075eb71gb?OpenDocument&6Gb |archive-url=https://archive.is/20120711135421/http://cloud.gouv.mc/devwww/wwwnew.nsf/1909$/607f54a31a14184fc1256a130075eb71gb?OpenDocument&6Gb |dead-url=yes |archive-date=11 July 2012 |title=Home > Files and Reports > Economy(Gb) |publisher=Cloud.gouv.mc |date=19 December 2011 |accessdate=22 March 2012 }}</ref> Banks in Monaco specialize in providing private banking, asset and wealth management services.<ref name="thebanks">{{cite web|url=https://thebanks.eu/articles/banks-in-Monaco | title=Banks in Monaco}}</ref> The principality has successfully sought to diversify its economic base into services and small, high-value-added, non-polluting industries, such as cosmetics and biothermics.<ref name="theodora">{{cite web |url=http://www.theodora.com/wfbcurrent/monaco/monaco_economy.html |title=Monaco Economy 2012, CIA World Factbook |publisher=Theodora.com |date=|accessdate=28 May 2012}}</ref>

The state retains [[Monopoly|monopolies]] in numerous sectors, including tobacco and the postal service. The telephone network ([[Monaco Telecom]]) used to be fully owned by the state; it now owns only 45%, while the remaining 55% is owned by both [[Cable & Wireless Communications]] (49%) and [[Compagnie Monégasque de Banque]] (6%). It is still, however, a monopoly. Living standards are high, roughly comparable to those in prosperous French metropolitan areas.<ref>{{cite web |url=https://www.cia.gov/library/publications/the-world-factbook/geos/mn.html |title=CIA – The World Factbook |publisher=Cia.gov |date=|accessdate=28 May 2012}}</ref>

Monaco is not a member of the [[European Union]]. However, it is very closely linked via a customs union with France and, as such, its currency is the same as that of France, the [[euro]]. Before 2002, Monaco minted its own coins, the [[Monegasque franc]]. Monaco has acquired the right to mint [[euro coins]] with [[Monegasque euro coins|Monegasque designs]] on its national side.

=== Gambling industry ===
[[File:Le casino de Monte-Carlo.JPG|thumb|[[Monte Carlo Casino]]]]
The plan for casino gambling was drafted during the reign of [[Florestan I, Prince of Monaco|Florestan I]] in 1846. Under Louis-Philippe's [[Petite bourgeoisie|petite-bourgeois]] regime, however, a dignitary such as the [[Prince of Monaco]] was not allowed to operate a gambling house.<ref name="state1"/> All this changed in the dissolute [[Second French Empire]] under [[Napoleon III]]. The [[House of Grimaldi]] was in dire need of money. The towns of [[Menton, France|Menton]] and [[Roquebrune-Cap-Martin|Roquebrune]], which had been the main sources of income for the Grimaldi family for centuries, were now accustomed to a much improved standard of living and lenient taxation thanks to Sardinian intervention and clamored for financial and political concession, even for separation. The Grimaldi family hoped the newly legal industry would help alleviate the difficulties they faced, above all the crushing debt the family had incurred, but Monaco's first casino would not be ready to operate until after [[Charles III, Prince of Monaco|Charles III]] assumed the throne in 1856.

The grantee of the princely concession (licence) was unable to attract enough business to sustain the operation and, after relocating the casino several times, sold the concession to French casino magnates [[François Blanc|François]] and [[Louis Blanc (businessman)|Louis Blanc]] for 1.7 million francs. The Blancs had already set up a highly successful casino (in fact the largest in Europe) in Bad-Homburg in the Grand Duchy of Hesse-Homburg, a small German principality comparable to Monaco, and quickly petitioned Charles III to rename a depressed seaside area known as "Les Spelegures (Den of Thieves)" to "Monte Carlo (Mount Charles)."<ref name="Craps">{{cite web |url=http://www.crapsdicecontrol.com/monte_carlo.htm|title=History of Monte Carlo Casino|publisher=Craps Dice Control|accessdate=28 April 2012}}</ref> They then constructed their casino in the newly dubbed "Monte Carlo" and cleared out the area's less-than-savory elements to make the neighborhood surrounding the establishment more conducive to tourism.

The Blancs opened [[Le Grand Casino de Monte Carlo]] in 1858 and the casino benefited from the tourist traffic the newly built French railway system created.<ref>{{cite web|url=http://www.iptv.org/series.cfm/9038/rick_steves_europe/ep:504|title=Rick Steves' Europe: Little Europe: San Marino, Monaco, Vatican City, Liechtenstein, and Andorra|publisher=|access-date=27 April 2012|archive-url=https://web.archive.org/web/20121114170925/http://www.iptv.org/series.cfm/9038/rick_steves_europe/ep:504|archive-date=14 November 2012|dead-url=yes|df=dmy-all}}</ref> Due to the combination of the casino and the railroads, Monaco finally recovered from the previous half-century of economic slump and the principality's success attracted other businesses.<ref>{{cite web |url=http://www.ricksteves.com/tvr/littleeurope504_scr.htm |title=Rick Steves Europe: Little Europe: Five Microcountries |publisher=Ricksteves.com |date=|accessdate=28 May 2012}}</ref> In the years following the casino's opening, Monaco founded its [[Oceanographic Museum]] and the [[Monte Carlo Opera House]], 46 hotels were built and the number of jewelers operating in Monaco increased by nearly five-fold. In an apparent effort to not overtax citizens, it was decreed that the Monégasque citizens were prohibited from entering the casino unless they were employees.<ref>{{cite web| author=Keremcan| url=https://www.gamblingherald.com/why-do-monaco-laws-forbid-locals-from-gambling/| title=Why Do Monaco Laws Forbid Locals from Gambling?| work=Gambling Herald |date=23 August 2016| accessdate=7 December 2017}}</ref> By 1869, the casino was making such a vast sum of money that the principality could afford to end tax collection from the Monegasques—a master stroke that was to attract affluent residents from all over Europe in a policy that still exists today.

Today, [[Société des bains de mer de Monaco]], which owns Le Grand Casino, still operates in the original building that the Blancs constructed and has since been joined by several other casinos, including the [[Le Casino Café de Paris]], the [[Monte Carlo Sporting Club & Casino]] and the [[Sun Casino]]. The most recent addition in Monte Carlo is the [[Monte-Carlo Bay Hotel & Resort|Monte Carlo Bay Casino]], which sits on 4 hectares of the Mediterranean Sea and, among other things, offers 145 slot machines, all equipped with "[[ticket-in, ticket-out]]" (TITO); it is the first Mediterranean casino to use this technology.<ref name="Porter">{{cite book | year=2006 | title=Frommer's Provence and the Riviera (Fifth. ed.) | author=Porter, D. | author2=D. Prince | publisher=Wiley Publishing Inc.}}</ref>

=== Taxes ===
Monaco has high social-insurance taxes, payable by both employers and employees. The employers' contributions are between 28% and 40% (averaging 35%) of gross salary, including benefits, and employees pay a further 10% to 14% (averaging 13%).<ref>{{cite web |url=http://www.lowtax.net/lowtax/html/jmcpetx.html|title=Monaco Personal Taxation | accessdate=28 May 2010}}</ref>

[[File:Monaco-Ville-ruelle.jpg|thumb|left|upright|Residential area in Monaco]]
Monaco has never levied [[income tax]] on [[individual]]s,<ref name=telegraph/> and foreigners are thus able to use it as a "[[tax haven]]" from their own country's taxes, because as an independent country, Monaco is not obligated to pay taxes to other countries.<ref>{{cite news|url=https://www.telegraph.co.uk/finance/globalbusiness/7243401/Monaco-might-not-charge-residents-income-tax-but-its-no-tax-haven.html |title=Monaco might not charge residents income tax, but it's no tax haven |work=The Daily Telegraph |date=16 February 2010|accessdate=28 May 2012 |location=London}}</ref><ref>{{cite web |url=http://www.lowtax.net/lowtax/html/jmccfir.html |title=Monaco Country and Foreign Investment Regime |publisher=Lowtax.net |date=|accessdate=22 March 2012}}</ref> The absence of a personal income tax in the principality has attracted to it a considerable number of wealthy "tax refugee" residents from European countries who derive the majority of their income from activity outside Monaco; [[Celebrity|celebrities]] such as [[Formula One]] drivers attract most of the attention, but the vast majority of them are lesser-known business people.<ref name="dailymail1"/><ref>{{cite news|author=David Leigh |url=https://www.theguardian.com/business/2006/jul/10/frontpagenews.uknews |title=The tax haven that today's super rich City commuters call home |work=The Guardian |date=10 July 2006|accessdate=28 May 2012 |location=London}}</ref> However, due to a bilateral treaty with France, French citizens are still required to pay applicable income and wealth taxes to the French state even if they are resident in Monaco,<ref name="state.gov">{{cite web|url=https://www.state.gov/e/eb/rls/othr/ics/2015/241564.htm|title=France and Monaco|work=U.S. Department of State}}</ref> and the principality also actively discourages the registration of foreign corporations, charging a 33 per cent [[Corporate tax|corporation tax]] on profits unless it can be shown that at least three-quarters of the turnover has been generated within its borders. Unlike classic tax havens, it does not offer offshore financial services.<ref name=telegraph>Evelyne Genta, [https://www.telegraph.co.uk/finance/globalbusiness/7243401/Monaco-might-not-charge-residents-income-tax-but-its-no-tax-haven.html Monaco might not charge residents income tax, but it's no tax haven] in ''[[The Daily Telegraph]]'' online dated 6 January 2018, accessed 11 January 2018</ref>

In 1998 the [[Centre for Tax Policy and Administration]], part of the [[Organisation for Economic Co-operation and Development]] (OECD), issued a first report on the consequences of the financial systems of known [[tax haven]]s.<ref>{{cite web |url=http://www.escapeartist.com/OREQ24/Offshore_Tax_Havens.html |title=Obscure Tax Havens |publisher=Escapeartist.com |date=|accessdate=28 May 2012}}</ref> Monaco did not appear in the list of these territories until 2004, when the OECD became indignant regarding the Monegasque situation and denounced it in a report, as well as [[Andorra]], [[Liechtenstein]], [[Liberia]], and the [[Marshall Islands]], underlining its lack of co-operation regarding financial information disclosure and availability.<ref>''Declaration of 18 April 2004, by the representative of the [[Organisation for Economic Co-operation and Development|OECD]] Centre for Tax Policy and Administration Gabriel Makhlouf regarding the list of alleged [[tax haven]]s non-cooperatives countries comparable''</ref><ref>''Stage Report 2004: Project of [[Organisation for Economic Co-operation and Development|OECD]] on the detrimental tax practices, [[Organisation for Economic Co-operation and Development|OECD]], Paris, 2004''</ref> However, Monaco went on to overcome the objections of the OECD and was thus removed from its "grey list" of unco-operative jurisdictions. In 2009 it went a step farther and secured a place on its "white list", after signing twelve information exchange treaties with other jurisdictions.<ref name=telegraph/>

In 2000, the [[Financial Action Task Force on Money Laundering]] (FATF) stated: "The anti-money laundering system in Monaco is comprehensive. However, difficulties have been encountered with Monaco by countries in international investigations on serious crimes that appear to be linked also with tax matters. In addition, the FIU of Monaco (SICCFIN) suffers a great lack of adequate resources. The authorities of Monaco have stated that they will provide additional resources to SICCFIN."<ref>{{cite web|url=http://www.fatf-gafi.org/dataoecd/56/43/33921824.pdf |archiveurl=https://web.archive.org/web/20110726051252/http://www.fatf-gafi.org/dataoecd/56/43/33921824.pdf |archivedate=26 July 2011 |title=Review to Identify Non-Cooperative Countries or Territories: Increasing the Worldwide Effectiveness of Anti-Money Laundering Measures |publisher=Financial Action Task Force on Money Laundering |date=22 June 2000 |location=Paris |page=8 |accessdate=23 May 2009 |deadurl=no |df=dmy }}</ref> Also in 2000, a report by the [[National Assembly of France|French parliamentarians]] [[Arnaud Montebourg]] and [[Vincent Peillon]] stated that Monaco had relaxed policies with respect to money laundering, including within its casino, and that the government of Monaco had been placing political pressure on the judiciary, so that alleged crimes were not being properly investigated.<ref>{{cite web |url=http://www.assemblee-nationale.fr/11/rap-info/i2311-2.asp |title=Assemblee-Nationale report |publisher=Assemblee-nationale.fr |date=27 July 1987 |accessdate=28 August 2010}}</ref> In its Progress Report of 2005, the [[International Monetary Fund]] (IMF) identified Monaco, along with 36 other territories, as a [[tax haven]],<ref>''Financial Centres with Significant Offshore Activities in Offshore Financial Centres. The Assessment Program. A Progress Report Supplementary Information, IMF, Washington, 2005''</ref> but in its [[Financial Action Task Force on Money Laundering|FATF]] report of the same year it took a positive view of Monaco's measures against money-laundering.<ref>''Review to Identify Non-Cooperative Countries or Territories: Increasing the Worldwide Effectiveness of Anti-Money Laundering Measures, [[Financial Action Task Force on Money Laundering|FATF]], Paris, 2005''</ref><ref>''Review to Identify Non-Cooperative Countries or Territories: Increasing the Worldwide Effectiveness of Anti-Money Laundering Measures, FATF, Paris, 2006''</ref>

The [[Council of Europe]] also decided to issue reports naming tax havens. Twenty-two territories, including Monaco, were thus evaluated between 1998 and 2000 on a first round. Monaco was the only territory that refused to perform the second round, between 2001 and 2003, whereas the 21 other territories had planned implementing the third and final round, planned between 2005 and 2007.<ref>''First Mutual Evaluation Report on the Principality of Monaco, Moneyval, Strasbourg, 2003''</ref>

=== Numismatics ===
{{Main|Monégasque franc|Monégasque euro coins|Euro gold and silver commemorative coins (Monaco)}}
[[File:1FrancMonaco1978face.jpg|thumb|left|1978 [[Monégasque franc]] coin with an effigy of Rainier III]]
Of interest to [[numismatists]], in Monaco the euro was introduced in 2002, having been preceded by the [[Monégasque franc]].<ref>{{cite web |url=http://www.eurocoins.co.uk/monaco.html |title=Monaco Euro Coins |publisher=Eurocoins.co.uk |date=1 January 2002 |accessdate=11 May 2017}}</ref> In preparation for this date, the minting of the new euro coins started as early as 2001. Like Belgium, Finland, France, the Netherlands, and Spain, Monaco decided to put the minting date on its coins. This is why the first euro coins from Monaco have the year 2001 on them, instead of 2002, like the other countries of the [[Eurozone]] that decided to put the year of first circulation (2002) on their coins.<ref>{{cite web |url=http://www.ecb.int/euro/coins/html/mo.en.html |title=ECB: Monaco |publisher=Ecb.int |date=|accessdate=22 March 2012}}</ref><ref>{{cite web |url=http://monaco.me/monaco-coins/ |title=Monaco Coins |publisher=Monaco.me |date=1 January 2002 |accessdate=22 March 2012}}</ref> Three different designs were selected for the Monégasque coins.<ref name="visitmonaco1">{{cite web |url=http://www.visitmonaco.com/en/Places-to-visit/Museums/The-Museum-of-Stamps-and-Coins |title=Monaco – The Museum of Stamps and Coins |publisher=Visitmonaco.com |date=|accessdate=22 March 2012}}</ref> However, in 2006, the design was changed after the death of ruling Prince Rainier to have the effigy of Prince Albert.<ref name="visitmonaco1"/><ref>{{cite web |url=http://www.taxfreegold.co.uk/monaco.html |title=Monegasque Gold Coins – Monaco |publisher=Taxfreegold.co.uk |date=|accessdate=22 March 2012}}</ref>

Monaco also has a rich and valuable collection of collectors' coins, with face value ranging from €5 to €100.<ref>{{cite web|author=Siam Internet Co., Ltd. |url=http://www.euro-coins.tv/monaco-euro-coins.php |title=Monaco Euro Coins – daily updated collectors value for every single coin |publisher=euro-coins.tv |date=|accessdate=22 March 2012}}</ref> These coins are a legacy of an old national practice of minting silver and gold [[commemorative coins]].<ref>{{cite web |url=http://www.monacorarecoins.com/rare-gold-coins/ |title=Buy Gold Coins – Rare Gold Coins |publisher=Monacorarecoins.com |date=|accessdate=22 March 2012}}</ref><ref>{{cite web |url=http://www.williamyoungerman.com/world_gold_coins/monaco_gold_coins.htm |archiveurl=https://web.archive.org/web/20090224123645/http://williamyoungerman.com/world_gold_coins/monaco_gold_coins.htm |archivedate=24 February 2009 |title=Monaco Gold Coins -World Gold Coins |publisher=Williamyoungerman.com |date= |accessdate=22 March 2012 |deadurl=yes |df=dmy-all }}</ref> Unlike normal issues, these coins are not [[legal tender]] in all the Eurozone.<ref>{{cite web |url=http://www.sheppardsoftware.com/Europeweb/factfile/Unique-facts-Europe16.htm |title=Unique Facts About Europe: Euro |publisher=Sheppardsoftware.com |date=|accessdate=28 May 2012}}</ref> The same practice concerning commemorative coins is exercised by all eurozone countries.
{{clear}}

== Population ==
=== Demographics ===
{{Main|Demographics of Monaco}}

{{Pie chart
|thumb = right
|caption = Monaco's Population
|label1 = [[French People|French]]
|value1 = 28.4
|color1 = #141464
|label2 = [[Monegasques]]
|value2 = 21.6
|color2 = #649678
|label3 = [[Italians]]
|value3 = 18.7
|color3 = #5AD282
|label4 = [[British People|British]]
|value4 = 7.5
|color4 = #DC64DC
|label5 = [[Belgians]]
|value5 = 2.8
|color5 = #BE5A14
|label6 = [[Germans]]
|value6 = 2.5
|color6 = #5A3C3C
|label7 = [[Swiss people|Swiss]]
|value7 = 2.5
|color7 = #325050
|label8 = [[Americans]]
|color8 = #414181
|value8 = 1.2
|label9 = Other
|color9 = LightYellow
|value9 = 14.8
}}
Monaco's total population was 38,400 in 2015.<ref>{{cite web|url=http://www.monacostatistics.mc/IMSEE/Publications/monaco-statistics-pocket |title=Monaco Statistics office|website=Monacostatistics.mc|accessdate=3 August 2017}}</ref> Monaco's population is unusual in that the native Monégasques are a minority in their own country: the largest group are French nationals at 28.4%, followed by Monégasque (21.6%), Italian (18.7%), British (7.5%), Belgian (2.8%), German (2.5%), Swiss (2.5%) and U.S. nationals (1.2%).<ref name="2008census">{{cite web |title=General Population Census 2008: Population Recensee et Population Estimee |url=http://www.gouv.mc/devwww/wwwnew.nsf/e89a6190e96cbd1fc1256f7f005dbe6e/64a1643c86f9f661c12575ae004cc473/$FILE/Recensement2008_Ch1.pdf |archiveurl=https://web.archive.org/web/20110614212422/http://www.gouv.mc/devwww/wwwnew.nsf/e89a6190e96cbd1fc1256f7f005dbe6e/64a1643c86f9f661c12575ae004cc473/$FILE/Recensement2008_Ch1.pdf |archivedate=14 June 2011 |publisher=Government of the Principality of Monaco |accessdate=7 October 2011 |language=French |year=2008 |deadurl=yes |df=dmy }}</ref>

Citizens of Monaco, whether born in the country or naturalized, are called ''Monégasque''.<ref>{{cite web |url=http://www.everyculture.com/Ma-Ni/Monaco.html |title=Culture of Monaco |publisher=Everyculture.com |date=|accessdate=6 September 2012}}</ref> Monaco has the world's highest [[List of countries by life expectancy|life expectancy]] at nearly 90 years.<ref>{{cite web |url=https://www.cia.gov/library/publications/the-world-factbook/geos/mn.html |title=CIA World Factbook, Monaco |publisher=Cia.gov |date=|accessdate=28 May 2012}}</ref><ref>{{cite web |url=https://theodora.com/wfbcurrent/monaco/monaco_international_rankings_2018.html |title=International Rankings of Monaco - 2018 |publisher=Theodora.com |date=|accessdate=4 July 2018}}</ref>

=== Language ===
{{Main|Languages of Monaco}}
The official language of Monaco is [[French language|French]], while [[Italian language|Italian]] is spoken by the principality's sizeable community from Italy. Thus, French and Italian supplants Monegasque, the vernacular language of the Monegasques, which is not recognized as an official language; English is used by [[Americans|American]], [[British people|British]], Anglo-[[Canadians|Canadian]], and [[Irish people|Irish]] residents.

The [[Grimaldi Family|Grimaldi]], [[princes of Monaco]], have Ligurian origin, thus, the traditional national language is [[Monégasque language|Monégasque]], a variety of [[Ligurian (Romance language)|Ligurian]], now spoken by only a minority of residents and as a common second language by many native residents. In [[Monaco-Ville]], street signs are printed in both French and Monégasque.<ref>{{cite web |url=http://www.monaco-iq.com/society |title=Society |publisher=Monaco-IQ |date= |accessdate=6 September 2012}}</ref><ref>{{cite web |url=http://www.monte-carlo.mc/en/general/principality-of-monaco/ |title=Principality of Monaco – Monaco Monte-Carlo |publisher=Monte-carlo.mc |date= |accessdate=6 September 2012}}</ref>

=== Religion ===
{{Bar box
| title=Religion in Monaco (2012)<ref name="joshuaproject.net">{{cite web|author=Joshua Project |url=http://www.joshuaproject.net/countries.php?rog3=MN |title=Ethnic People Groups of Monaco |publisher=Joshua Project |date= |accessdate=12 March 2013}}</ref>{{efn|Percentage based on a 35,000 person population.}}
| titlebar=#ddd
| float=left
| bars=
{{Bar percent|[[Christianity]]|blue|83.2}}
{{Bar percent|No Religion|red|12.9}}
{{Bar percent|[[Judaism]]|purple|2.9}}
{{Bar percent|[[Islam]]|green|0.8}}
{{Bar percent|Others/[[unspecified]]|grey|0.5}}
}}
{{clear}}

==== Catholic Church ====
[[File:Monaco BW 2011-06-07 16-07-20.jpg|thumb|[[Saint Nicholas Cathedral, Monaco]]]]
{{Main|Catholic Church in Monaco}}
The official religion is the Catholic Church, with freedom of other religions guaranteed by the constitution.<ref name="joshuaproject.net"/> There are five Catholic parish churches in Monaco and one cathedral, which is the seat of the [[archbishop of Monaco]].

The diocese, which has existed since the mid-19th century, was raised to a non-metropolitan archbishopric in 1981 as the [[Roman Catholic Archdiocese of Monaco|Archdiocese of Monaco]] and remains exempt (i.e. immediately subject to the Holy See). The [[patron saint]] is [[Saint Devota]].

Christians comprise a total of 83.2% of Monaco's population.<ref name="joshuaproject.net"/>

==== Protestantism ====
According to Monaco 2012 International Religious Freedom Report, Protestants are the second-largest group after Roman Catholics. There are various [[Evangelical Protestant]] communities that gather periodically. The report states that there are two Protestant churches, including the local Anglican church and a [[Reformed]] church.

==== Anglicanism ====
There is one [[Anglican Communion|Anglican]] church ([[Saint Paul|St. Paul's]] Church), located in the Avenue de Grande Bretagne in Monte Carlo. In 2007 this had a formal membership of 135 Anglicans resident in the principality, but was also serving a considerably larger number of Anglicans temporarily in the country, mostly as tourists. The church site also accommodates an English-language library of over 3,000 books.<ref>{{cite web|url=http://www.stpaulsmonaco.com/|title=Saint Paul's Church, Monte-Carlo|work=stpaulsmonaco.com}}</ref> The church is part of the Anglican [[Diocese in Europe]].

==== Greek Orthodoxy ====
Monaco's 2012 International Religious Freedom Report states that there is one [[Greek Orthodox Church|Greek Orthodox]] Church in Monaco.

==== Judaism ====

The Association Culturelle Israélite de Monaco (founded in 1948) is a converted house containing a synagogue, a community Hebrew school, and a [[Kashrut|kosher]] food shop, located in Monte Carlo.<ref>{{cite web |url=http://www.mavensearch.com/synagogues/C3414Y41808RX |title=Synagogues in Monte Carlo – Shuls in Monte Carlo – Jewish Temples in Monte Carlo |publisher=Mavensearch.com |date=6 July 2007 |accessdate=28 May 2012}}</ref> The community mainly consists of retirees from Britain (40%) and [[North Africa]]. Two-thirds of the Jewish population is [[Sephardi Jews|Sephardic]], mainly from [[North Africa]], while the other third is [[Ashkenazi Jews|Ashkenazi]].<ref>Details at [https://www.jewishvirtuallibrary.org/jsource/vjw/monaco.html Jewish Virtual Library]</ref>

==== Islam ====
The [[Muslim]] population of Monaco consists of about 280 people, most of whom are exclusively residents, not citizens.<ref>{{cite web|url=https://www.theguardian.com/news/datablog/2011/jan/28/muslim-population-country-projection-2030|title=Muslim populations by country: how big will each Muslim population be by 2030?|author=Simon Rogers|work=the Guardian}}</ref> The majority of the Muslim population of Monaco are [[Arabs]], though there are smaller [[Turkish people|Turkish]] minorities as well.<ref>{{cite web|url=http://www.muslimpopulation.com/Europe/MONACO/Islam%20in%20Monaco.php|title=Islam in Monaco|work=muslimpopulation.com}}</ref> Monaco does not have any official [[mosque]]s.<ref>{{cite web|url=http://www.islamicpopulation.com/Europe/MONACO/Islam%20in%20Monaco.htm|title=Islam in Monaco|work=islamicpopulation.com}}</ref> There is a Muslim mosque in nearby [[Beausoleil, France]], within easy walking distance of Monaco.

== Sports ==
=== Formula One ===
{{Main|Monaco Grand Prix}}
[[File:Grand Prix Monaco96 131954710.jpg|thumb|Formation lap for the [[1996 Monaco Grand Prix]]]]
Since 1929, the [[Monaco Grand Prix]] has been held annually in the streets of Monaco.<ref name="autogenerated1">{{cite web|url=http://www.monaco-grand-prix-ticket.com/Monaco-Grand-Prix.aspx|title=Monaco Grand Prix|date=3 March 2012|publisher=|deadurl=yes|archiveurl=https://web.archive.org/web/20120303200854/http://www.monaco-grand-prix-ticket.com/Monaco-Grand-Prix.aspx|archivedate=3 March 2012|df=dmy-all}}</ref> It is widely considered to be one of the most prestigious automobile races in the world. The erection of the [[Circuit de Monaco]] takes six weeks to complete and the removal after the race takes another three weeks.<ref name="autogenerated1"/> The circuit is incredibly narrow and tight and its tunnel, tight corners and many elevation changes make it perhaps the most demanding [[Formula One]] track.<ref>{{cite web|author=liam mcmurray, lesley kazan-pinfield |url=http://www.monaco-f1grandprix.com/course.html |title=Monaco Formula One Grand Prix |publisher=Monaco-f1grandprix.com |date=|accessdate=6 September 2012}}</ref> Driver [[Nelson Piquet]] compared driving the circuit to "riding a bicycle around your living room".

Despite the challenging nature of the course it has only had one fatality, [[Lorenzo Bandini]], who crashed, burned and died three days later from his injuries in 1967.<ref name=SheboyganPressMay8>"Hulme Wins Monte Carlo; Bandini Hurt", ''[[Sheboygan Press]]'', 8 May 1967, Page 13.</ref> Two other drivers had lucky escapes after they crashed into the harbour, the most famous being [[Alberto Ascari]] in the [[1955 Monaco Grand Prix]] and [[Paul Hawkins (racing driver)|Paul Hawkins]], during the [[1965 Monaco Grand Prix|1965 race]].<ref name="autogenerated1"/>

=== Monte Carlo Rally ===
Since 1911 part of the [[Monte Carlo Rally]] has been held in the principality, originally held at the behest of [[Albert I, Prince of Monaco|Prince Albert I]]. Like the Grand Prix, the rally is organized by [[Automobile Club de Monaco]]. It has long been considered to be one of the toughest and most prestigious events in [[rallying]] and from 1973 to 2008 was the opening round of the [[World Rally Championship]] (WRC).<ref>{{cite web |author=Federall |url=http://www.acm.mc/page-tab-histo.php?id_menu=5&id_sousmenu=27 |title=ACM – Automobile Club de Monaco |publisher=Acm.mc |date= |accessdate=6 September 2012 |archive-url=https://web.archive.org/web/20121109144441/http://www.acm.mc/page-tab-histo.php?id_menu=5&id_sousmenu=27 |archive-date=9 November 2012 |dead-url=yes |df=dmy-all }}</ref> From 2009 until 2011, the rally served as the opening round of the [[Intercontinental Rally Challenge]].<ref>{{cite news |url=https://www.telegraph.co.uk/motoring/motorsport/8238574/Rallye-Monte-Carlo-Historique.html |title=Rallye Monte Carlo Historique |work=The Daily Telegraph |location=London |date=|accessdate=6 September 2012}}</ref> The rally returned to the WRC calendar in 2012 and has been held annually since.<ref>{{cite web |url=http://www.wrc.com/news/2012-world-rally-championship-events-announced/?fid=14515 |title=2012 World Rally Championship events announced |publisher=wrc.com |date=27 April 2012 |accessdate=28 May 2012}}</ref> Due to Monaco's limited size, all but the ending of the rally is held on French territory.

=== Football ===
[[File:Stadion von Monaco Seitenansicht.jpg|thumb|left|upright|[[Stade Louis II]], home of [[AS Monaco FC]]]]
Monaco hosts two major football teams in the principality: the men's football club, [[AS Monaco FC]], and the women's football club, OS Monaco. AS Monaco plays at the [[Stade Louis II]] and competes in [[Ligue 1]] the first division of [[French football]]. The club is historically one of the most successful clubs in the French league, having won Ligue 1 eight times (most recently in 2016–17) and competed at the top level for all but six seasons since 1953. The club reached the [[2004 UEFA Champions League Final]], with a team that included [[Dado Pršo]], [[Fernando Morientes]], [[Jérôme Rothen]], [[Akis Zikos]] and [[Ludovic Giuly]], but lost 3–0 to Portuguese team [[FC Porto]]. Many international stars have played for the club, such as French World Cup-winners [[Thierry Henry]], [[Fabien Barthez]], [[David Trezeguet]], and [[Kylian Mbappe]]. The Stade Louis II also played host to the annual [[UEFA Super Cup]] (1998–2012) between the winners of the [[UEFA Champions League]] and the [[UEFA Europa League]].

The women's team, OS Monaco, competes in the women's [[French football league system]]. The club currently plays in the local regional league, deep down in the league system. It once played in the [[Division 1 Féminine]], in the 1994–95 season, but was quickly relegated. Current [[France women's national football team|French women's international]] goalkeeper [[Sarah Bouhaddi]] had a short stint at the club before going to the [[INF Clairefontaine]] academy.

The [[Monaco national football team]] represents the nation in [[association football]] and is controlled by the [[Monégasque Football Federation]], the governing body for [[football in Monaco]]. However, Monaco is one of only three sovereign states in Europe (along with the [[United Kingdom]] and [[Vatican City]]) that is not a member of [[UEFA]] and so does not take part in any [[UEFA European Football Championship]] or [[FIFA World Cup]] competitions. The team plays its home matches in the Stade Louis II.

=== Rugby ===
{{Main|Rugby union in Monaco}}
[[Monaco national rugby union team|Monaco's national rugby team]], as of October 2013, is 91st in the [[International Rugby Board]] rankings.<ref>{{cite web |url=http://www.irb.com/rankings/full.html |title=International Rugby Board – World Rankings |publisher=Irb.com |date= |accessdate=28 May 2012 |deadurl=yes |archiveurl=https://web.archive.org/web/20110810042746/http://www.irb.com/rankings/full.html |archivedate=10 August 2011 |df=dmy-all }}</ref>

=== Other sports ===
[[File:2011 Monaco Porsche Supercup.jpg|thumb|left|A view of the 2011 Monaco Porsche Supercup. Motor racing is very popular, with one course encompassing almost the whole country.]]

The [[Monte-Carlo Masters]] is held annually in neighbouring [[Roquebrune-Cap-Martin]], France, as a professional tournament for men as part of tennis's [[ATP World Tour Masters 1000|ATP Masters Series]].<ref>{{cite web |url=http://www.monte-carlorolexmasters.com/About/Tournament-Fact-Sheet.aspx |title=Tennis – Tournament Fact Sheet |publisher=Monte-Carlo Rolex Masters |date=30 September 2011 |accessdate=28 May 2012}}</ref> The tournament has been held since 1897. Golf's [[Monte Carlo Open (golf)|Monte Carlo Open]] was also held at the Monte Carlo Golf Club at Mont Agel in France between 1984 and 1992. Monaco has also [[Monaco at the Olympics|competed]] in the Olympic Games, although, no athlete from Monaco has ever won an Olympic medal.

The [[2009 Tour de France]], the world's premier cycle race, started from Monaco with a {{convert|15|km|0|adj=mid}} closed-circuit individual time trial starting and finishing there on the first day, and the {{convert|182|km|0|adj=mid}} second leg starting there on the following day and ending in [[Brignoles]], France.<ref>{{cite web |url=http://www.letour.com/2008/TDF/COURSE/us/grand_depart_2009.html |title=Tour de France 2008 – Grand start 2009 |publisher=Letour.com |date= |accessdate=28 May 2012 |archive-url=https://web.archive.org/web/20130116210455/http://www.letour.com/2008/TDF/COURSE/us/grand_depart_2009.html |archive-date=16 January 2013 |dead-url=yes |df=dmy-all }}</ref>

Monaco also stage part of the [[Global Champions Tour]] (International Show-jumping). Acknowledged as the most glamorous of the series, Monaco will be hosting the world's most celebrated riders, including Monaco's own [[Charlotte Casiraghi]], in a setting facing out over the world's most beautiful yachts, and framed by the Port Hercules and Prince's palace.<ref>{{cite web |url=http://www.globalchampionstour.com/events/2012/monte-carlo/ |title=Monte-Carlo |publisher=Global Champions Tour |date=|accessdate=6 September 2012}}</ref> In 2009, the Monaco stage of the Global Champions tour took place between 25–27 June.

The [[Monaco Marathon]] is the only marathon in the world to pass through three separate countries, those of Monaco, France and Italy, before the finish at the [[Stade Louis II]].

The Monaco Ironman 70.3 triathlon race is an annual event with over 1,000 athletes competing and attracts top professional athletes from around the world. The race includes a {{convert|1.9|km|1|adj=mid|abbr=off}} swim, {{convert|90|km|0|adj=mid|abbr=off}} bike ride and {{convert|21.1|km|1|adj=mid|abbr=off}} run.

Since 1993, the headquarters of the [[International Association of Athletics Federations]],<ref>{{cite web |url=http://www.iaaf.org/aboutiaaf/headquarter/index.html |title=Headquarters |publisher=iaaf.org |date=10 June 1994 |accessdate=28 May 2012 |archive-url=https://web.archive.org/web/20120605031229/http://www.iaaf.org/aboutiaaf/headquarter/index.html |archive-date=5 June 2012 |dead-url=yes |df=dmy-all }}</ref> the world governing body of [[athletics (sport)|athletics]], is located in Monaco.<ref>{{cite web |url=http://www.iaaf.org/aboutiaaf/index.html |title=Inside IAAF Intro |publisher=iaaf.org |date= |accessdate=28 May 2012 |archive-url=https://web.archive.org/web/20120604054507/http://www.iaaf.org/aboutiaaf/index.html |archive-date=4 June 2012 |dead-url=yes |df=dmy-all }}</ref> An IAAF Diamond League meet is annually held at Stade Louis II.<ref>{{cite web |url=http://www.diamondleague-monaco.com/en/Home/ |title=Usain BOLT and Yelena ISINBAEVA for Herculis |publisher=Diamondleague-monaco.com |date=30 April 2012 |accessdate=28 May 2012}}</ref>

A municipal sports complex, the [[Rainier III Nautical Stadium]] in the [[Port Hercules]] district consists of a heated saltwater [[Olympic-size swimming pool]], diving boards and a slide.<ref name="Mon">{{cite web|title=Rainer III Nautical Stadium|url=http://www.monaco-mairie.mc/en/langues-etrangeres/events-entertainment/rainier-iii-nautical-stadium/|work=Marie de Monaco – Rainier III Nautical Stadium|publisher=Marie de Monaco|accessdate=25 May 2013|deadurl=yes|archiveurl=https://web.archive.org/web/20130517044436/http://www.monaco-mairie.mc/en/langues-etrangeres/events-entertainment/rainier-iii-nautical-stadium/|archivedate=17 May 2013|df=dmy-all}}</ref> The pool is converted into an [[ice rink]] from December to March.<ref name="Mon"/>

From 10–12 July 2014 Monaco inaugurated the Solar1 Monte Carlo Cup, a series of ocean races exclusively for solar-powered boats.<ref>The Riviera Times, Issue 148, July 2014</ref>,<ref>{{cite web|url=http://www.solar1races.com/wp-content/uploads/Solar1Magazine.pdf|format=PDF|title=Monte-Carlo Cup|website=Solar1races.com|accessdate=3 August 2017}}</ref>

== Culture ==
=== Music ===
{{Main|Music of Monaco}}
[[File:Monaco opera 034.jpg|thumb|Seaside façade of the Salle Garnier, home of the [[Opéra de Monte-Carlo]]]]
Monaco has an [[Opéra de Monte-Carlo|opera house]], a [[Monte-Carlo Philharmonic Orchestra|symphony orchestra]] and a [[Les Ballets de Monte Carlo|classical ballet company]].<ref name="auto2">{{cite web|url=http://www.everyculture.com/Ma-Ni/Monaco.html|title=Culture of Monaco |work=everyculture.com}}</ref>

===Visual arts===
Monaco has a national museum of contemporary visual art at the [[New National Museum of Monaco]]. The country also has numerous works of public art, statues,museums, and memorials (see [[list of public art in Monaco]]).

===Museums in Monaco===
{{Main|List of museums in Monaco}}
[[File:Monaco BW 2011-06-07 17-50-43.jpg|thumb|[[Oceanographic Museum]], Monaco]]
* [[Monaco Top Cars Collection]]
* [[Napoleon Museum (Monaco)]]
* [[Oceanographic Museum]]

=== Events, festivals and shows ===
The Principality of Monaco hosts major international events such as :
* [[International Circus Festival of Monte-Carlo]]
* [[Mondial du Théâtre]]
* [[Monte-Carlo Television Festival]]

== Education ==
=== Primary and secondary schools ===
[[File:Le Lycée Albert 1er de Monaco.jpg|thumb|[[Lycée Albert Premier]] of Monaco]]
Monaco has ten state-operated schools, including: seven [[Nursery school|nursery]] and [[primary school]]s; one [[secondary school]], Collège Charles III;<ref>{{cite web|url=http://www.college-charles3.mc/ |archiveurl=https://web.archive.org/web/20110511103100/http://www.college-charles3.mc/ |archivedate=11 May 2011 |title=Collège Charles III |publisher=College-charles3.mc |accessdate=28 August 2010 |deadurl=no |df=dmy }}</ref> one [[Secondary education in France|''lycée'']] that provides general and technological training, [[Lycee Albert Premier|Lycée Albert 1er]];<ref>{{cite web|url=http://www.lycee-albert1er.mc/ |archiveurl=https://web.archive.org/web/20110722170522/http://www.lycee-albert1er.mc/ |archivedate=22 July 2011 |title=Lycée Albert 1er |publisher=Lycee-albert1er.mc |accessdate=28 August 2010 |deadurl=no |df=dmy }}</ref> and one lycée that provides vocational and hotel training, Lycée technique et hôtelier de Monte-Carlo.<ref>{{cite web|title=Lycée technique et hôtelier de Monte-Carlo |url=http://www.lycee-technique.mc/ |archiveurl=https://web.archive.org/web/20110722170522/http://www.lycee-technique.mc/ |archivedate=22 July 2011 |location=Monaco |language=French |accessdate=23 May 2009 |deadurl=no |df=dmy }}</ref> There are also two grant-aided denominational private schools, Institution François d'Assise Nicolas Barré and Ecole des Sœurs Dominicaines, and one [[international school]], the [[International School of Monaco]],<ref>{{cite web|url=http://www.ismonaco.org/|title=The International School Of Monaco|work=ismonaco.org}}</ref><ref>{{cite web|title=Education System|url=http://www.monaco-consulate-uk.gouv.mc/315UK/wwwnew.nsf/1909$/e72b5e7946917f37c1257339004c433dgb?OpenDocument&2Gb#EDUCATION%20SYSTEM|accessdate=15 February 2013}}</ref> founded in 1994.<ref>{{cite web|title=School Website|url=https://www.ismonaco.org/history-ism|accessdate=19 April 2017}}</ref>

=== Colleges and universities ===
There is one university located in Monaco, namely the [[International University of Monaco]] (IUM), an English-language school specializing in business education and operated by the ''Institut des hautes études économiques et commerciales'' (INSEEC) group of schools.

== Flag ==
[[File:Coat of arms and flag of Monaco.jpg|thumb|right|Monaco's flag and [[Coat of arms]]]]
{{Main|Flag of Monaco}}
The flag of Monaco is one of the world's oldest national flag designs.<ref>{{cite web|url=http://www.worldflags101.com/m/monaco-flag.aspx|title=Monaco Flag - World Flags 101 - Monacan Flags|website=Worldflags101.com}}</ref> The flag of Monaco, which Monaco adopted in April 4, 1881, is almost identical to the [[flag of Indonesia]] (adopted by Indonesia in August 17, 1945) except for the ratio of height to width.<ref>{{cite web |url=http://www.worldflags101.com/m/monaco-flag.aspx |title=Monaco Flag |publisher=Worldflags101.com |accessdate=2 July 2011}}</ref>

== Transport ==
{{Main|Transport in Monaco}}
{{further|Rail transport in Monaco}}
The [[Rail transport in Monaco|Monaco-Monte Carlo station]] is served by the [[SNCF]], the French national rail system. The [[Monaco Heliport]] provides helicopter service to the closest airport, [[Nice Côte d'Azur Airport|Côte d'Azur Airport]] in Nice, France.

The Monaco bus company (CAM) covers all the tourist attractions, museums, [[Jardin Exotique de Monaco|Exotic garden]], business centres, and the Casino or the Louis II Stadium.<ref>{{cite web|title=Monaco Bus Line|url=http://www.visitmonaco.com/en/Practical/Bus-Line}}</ref>

==Relations with other countries==
{{main|Foreign relations of Monaco}}
[[File:Monacoc1890.jpg|thumb|left|''Le Rocher'' in 1890]]
Monaco is so old that it has outlived many of the nations and institutions that it has had relations with. The [[Crown of Aragon]] and [[Republic of Genoa]] became a part of other countries, as did the [[Kingdom of Sardinia]]. [[Honoré II, Prince of Monaco]] secured recognition of his independent [[sovereignty]] from [[Spain]] in 1633, and then from [[Louis XIII]] of France by the [[Treaty of Péronne (1641)]].

Monaco made a special agreement with France in 1963 in which French customs laws apply in Monaco and its territorial waters.<ref name="state.gov"/> Monaco uses the [[euro]] but is not a member of the European Union.<ref name="state.gov"/> Monaco shares a {{convert|6|km|mi|adj=mid|abbr=off}} border with France but also has about {{convert|2|km|mi|1|adj=mid|abbr=off}} of coastline with the Mediterranean sea.<ref name="Monaco">{{cite web|url=https://www.cia.gov/library/publications/the-world-factbook/geos/mn.html|title=The World Factbook|work=cia.gov}}</ref> Two important agreements that support Monaco's independence from France include the [[Franco-Monegasque Treaty]] of 1861 and the [[Monaco succession crisis of 1918#French Treaty of 1918|French Treaty of 1918]] (see also [[Kingdom of Sardinia]]). The United States CIA Factbook records 1419 as the year of Monaco's independence.<ref name="Monaco"/>

*[[France–Monaco relations|France-Monaco relations]]
*[[Monaco–United States relations]]
*[[Monaco–Russia relations]]

There are two embassies in Monaco: those of France and Italy.<ref name="embassypages.com">{{cite web|url=http://www.embassypages.com/monaco|title=Monaco – Embassies and Consulates|work=embassypages.com}}</ref> There are about another 30 or so [[consulates]].<ref name="embassypages.com"/> By the 21st century Monaco maintained embassies in Belgium (Brussels), France (Paris), Germany (Berlin), the Vatican, Italy (Rome), Spain (Madrid), Switzerland (Bern), United Kingdom (London) and the United States (Washington).<ref name="embassypages.com"/>

In the year 2000 nearly two-thirds of the residents of Monaco were foreigners<ref>{{cite web|url=http://www.encyclopedia.com/topic/Monaco.aspx|title=Monaco|work=encyclopedia.com}}</ref> In 2015 the immigrant population was estimated at 60%<ref name="Monaco"/> However, it is reported to be difficult to gain citizenship in Monaco, or at least in relative number there is not many people who do so.<ref name="auto2"/> In 2015 an immigration rate of about 4 people per 1,000 was noted, which works out to something like 100–150 people a year.<ref>{{cite web|url=https://www.cia.gov/library/publications/the-world-factbook/fields/2112.html|title=The World Factbook|work=cia.gov}}</ref> The population of Monaco went from 35,000 in 2008 to 36,000 in 2013, and of that about 20 percent were native Monegasque<ref>{{cite web|url=http://www.populationfun.com/monaco-population/|title=Monaco|work=populationfun.com}}</ref> (see also [[Nationality law of Monaco]]).

A recurring issue Monaco encounters with other countries is the attempt by foreign nationals to use Monaco to avoid paying taxes in their own country.<ref name="Monaco"/> Monaco actually collects a number of taxes including a 20% VAT and 33% on companies unless they make over 75% of their income inside Monaco.<ref name="Monaco"/> Monaco does not allow dual citizenship, but does have multiple paths to citizenship including by declaration and naturalization.<ref name="Residency">{{cite web|url=http://flagtheory.com/monaco-residency/|title=Principality of Monaco|work=flagtheory.com}}</ref> In many cases the key issue for obtaining citizenship, rather than attaining residency in Monaco, is the person’s ties to their departure country.<ref name="Residency"/> For example, French citizens must still pay taxes to France even if they live full-time in Monaco unless they resided in the country before 1962 for at least 5 years.<ref name="Residency"/> In the early 1960s there was some tension between France and Monaco over taxation.<ref>{{cite web|url=http://www.finance-watch.org/hot-topics/blog/1074-lesson-from-history-monaco-crisis|title=Lessons from history – The Monaco crisis from 1962–1963 and the emancipation of tax havens |author=Charlotte Geiger|work=finance-watch.org}}</ref>

There are no border formalities entering or leaving to France. For visitors a souvenir [[passport]] stamp is available on request at Monaco's tourist office. This is located on the far side of the gardens that face the Casino.

{|class="wikitable" style="font-size:90%;line-height:1.2"
|-valign="bottom"
! Microstate
! [[European Union Association Agreement|Association Agreement]]
! [[Eurozone]]<ref>{{cite web|title=The euro outside the euro area |publisher=[[Europa (web portal)]] |url=http://ec.europa.eu/economy_finance/euro/world/outside_euro_area/index_en.htm |accessdate=26 February 2011}}</ref>
! [[Schengen Area]]
! [[Internal Market|EU single market]]
! [[European Union Customs Union|EU customs territory]]<ref>{{cite web|url=http://exporthelp.europa.eu/thdapp/display.htm?page=rt/rt_EUCustomsUnion.html&docType=main&languageId=EN|title=EU Customs Union|accessdate=18 June 2015|publisher=[[European Commission]]}}</ref>
! [[European Union Value Added Tax Area|EU VAT area]]<ref name="VAT">{{cite web|url=http://ec.europa.eu/taxation_customs/common/travellers/within_eu/faq_1179_en.htm|title=Taxation and Customs Union – Within the EU|accessdate=9 September 2012|publisher=[[European Commission]]|deadurl=yes|archiveurl=https://web.archive.org/web/20121111165632/http://ec.europa.eu/taxation_customs/common/travellers/within_eu/faq_1179_en.htm|archivedate=11 November 2012|df=dmy-all}}</ref>
! [[Dublin Regulation]]
|-
|{{MCO}} ([[Monaco–European Union relations|relations]])
|{{No|Negotiating}}<ref name=AANEG>{{cite web|url=http://ec.europa.eu/avservices/video/player.cfm?ref=I100473|title=RECORDED HRVP Federica MOGHERINI host the ceremony on the occasion of the launching of the Association Agreement(s) negotiations with the Principality of Andorra, the Principality of Monaco and the Republic of San Marino|date=18 March 2015|accessdate=18 March 2015|publisher=[[European Commission]]}}</ref>
|{{Yes|[[Monegasque euro coins|Yes]]}}{{efn|[[International status and usage of the euro#Sovereign states|Monetary agreement with the EU]] to issue euros.|name=euros}}
|{{Partial|de facto}}{{efn|Although not a contracting party to the [[Schengen Agreement]], has an [[Schengen Area#Status of the European microstates|open border with France]] and Schengen laws are administered as if it were a part of France.<ref name=obstacles>{{cite web|url=http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=SWD:2012:0388:FIN:EN:HTML|title=Obstacles to access by Andorra, Monaco and San Marino to the EU's Internal Market and Cooperation in other Areas|date=2012|accessdate=30 March 2013}}</ref><ref>{{cite journal|url=http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:41998D0019:EN:HTML|title= The Schengen acquis – Decision of the Executive Committee of 23 June 1998 on Monegasque residence permits|date=22 September 2000|accessdate=9 September 2012|journal=[[Official Journal of the European Union]]}}</ref>}}
|{{Partial}}{{efn|Through an agreement with France.<ref>[http://register.consilium.europa.eu/pdf/en/11/st11/st11466.en11.pdf EU relations with the Principality of Andorra, the Republic of San Marino and the Principality of Monaco]: "If France adopts internal legislation transposing EU directives in certain areas covered by bilateral Agreements with Monaco, the Principality directly applies the French legislation in certain areas"</ref>}}
|{{Yes}}{{efn|Through an [[Franco-Monegasque Treaty|agreement]] with France. Part of the EU Customs territory, administered as part of France.<ref name=obstacles/><ref>{{cite web|url=http://ec.europa.eu/taxation_customs/common/faq/faq_1178_en.htm|title=Taxation and Customs – FAQ|publisher=[[European Commission]]|accessdate=12 September 2012|deadurl=yes|archiveurl=https://web.archive.org/web/20120608000239/http://ec.europa.eu/taxation_customs/common/faq/faq_1178_en.htm|archivedate=8 June 2012|df=dmy-all}}</ref><ref>{{cite journal|url=http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:1992:302:0001:0050:EN:PDF|title=Council Regulation (EEC) No 2913/92 of 12 October 1992 establishing the Community Customs Code|journal=[[Official Journal of the European Union]]|date=19 October 1992|accessdate=12 September 2012}}</ref><ref name=euterritory/>|name=france}}
|{{Yes}}{{efn|Also part of the EU excise territory.<ref name=euterritory>{{cite web|url=http://ec.europa.eu/taxation_customs/resources/documents/customs/procedural_aspects/general/sad/guide/1619-08annexi_en.pdf|title=Annex 1: Overview of European Union countries|publisher=[[European Commission]]|deadurl=yes|archiveurl=https://web.archive.org/web/20140504214400/http://ec.europa.eu/taxation_customs/resources/documents/customs/procedural_aspects/general/sad/guide/1619-08annexi_en.pdf|archivedate=4 May 2014|df=dmy-all}}</ref>}}{{efn|Through an agreement with France. Administered as a part of France for taxation purposes.<ref name="VAT"/><ref name=obstacles/><ref name=euterritory/><ref name="excise">{{cite journal|url=http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:009:0012:0030:EN:PDF|title=COUNCIL DIRECTIVE 2008/118/EC of 16 December 2008 concerning the general arrangements for excise duty and repealing Directive 92/12/EEC|date=14 January 2009|accessdate=10 September 2012|journal=[[Official Journal of the European Union]]}}</ref>}}
|{{No}}
|-
|}

== See also ==
{{portal|Geography|Europe|Mediterranean}}
* [[Outline of Monaco]]
* [[List of sovereign states and dependent territories by population density]]
* [[Foreign relations of Monaco]]
* [[List of rulers of Monaco]]
* [[Japanese Garden, Monaco]]
* [[Telecommunications in Monaco]]
* [[Microstates and the European Union]]
* [[List of diplomatic missions in Monaco]]
* [[List of diplomatic missions of Monaco]]
* [[Monaco–European Union relations]]
{{clear}}

== Notes ==
{{notelist|25em}}

== References ==
{{Reflist}}

== External links ==
{{Sister project links|voy=Monaco}}
; Government
* [http://www.gouv.mc/ Official Government Portal]
* [http://www.palais.mc/ Official website of the Prince's Palace of Monaco]
* [https://www.cia.gov/library/publications/world-leaders-1/MN.html Chief of State and Cabinet Members]
* [http://www.gouv.mc/content/download/175997/2030403/file/monaco%20statistics%20pocket%202014.pdf Monaco Statistics Pocket – Edition 2014]

; General information
* {{CIA World Factbook link|mn|Monaco}}
* [https://web.archive.org/web/20080607085244/http://ucblibraries.colorado.edu/govpubs/for/monaco.htm Monaco] from ''UCB Libraries GovPubs''
* {{dmoz|Regional/Europe/Monaco}}
* [https://www.bbc.co.uk/news/world-europe-17615784 Monaco] from the [[BBC News]]
* [http://www.monaco.me/ Monaco] information about Monaco
* [http://eudocs.lib.byu.edu/index.php/History_of_Monaco:_Primary_Documents History of Monaco: Primary documents]
* {{Wikiatlas|Monaco}}
* {{osmrelation-inline|1124039}}

; Travel
* [http://www.visitmonaco.com/ Official website for Tourism]
* [http://www.yourmonaco.com/ Your Monaco] Monaco travel guide
* [http://www.petitmonegasque.fr/ Discovery of Monaco]

; Work
* [http://www.work-monaco.com/ Monaco Job Portal]

; Other
*[http://www.ordremedecins.mc/ Order of the doctors of Monaco] {{fr icon}}
*[http://www.monaco-prestige.info/ French Monaco Web portail] {{fr icon}}
*[http://glomed.free.fr/laprincipauté.html/ La Principauté – Le premier journal d'actualité de Monaco]{{Dead link|date=August 2018 |bot=InternetArchiveBot |fix-attempted=yes }}
*Monaco Today, a daily newsletter in English, [http://www.monacolife.net/ Monacolife.net]
*[http://www.monacolife.net/ Monacolife.net] English news portal
*[http://www.monacotimes.com/ The Monaco Times] – a regular feature in The Riviera Times is the English language newspaper for the French – Italian Riviera and the Principality of Monaco provides monthly local news and information about business, art and culture, people and lifestyle, events and also the real estate market.
*[http://www.monaco-iq.com/ Monaco-IQ] Monaco information and news aggregator
*[http://www.ilprincipato.com/ Monte-Carlo] Italian Monte-Carlo unofficial portal
*[https://www.ismonaco.org/ International School of Monaco]

{{Monaco topics}}
{{Navboxes
|title = Geographic locale
|list =
{{Administrative divisions of Monaco}}
{{Geography of Europe}}
{{Sovereign states of Europe}}
{{List of European capitals by region}}
{{Countries and territories bordering the Mediterranean Sea}}
{{Europe topic|Climate of}}
}}
{{Navboxes
|title = International organizations
|list =
{{Council of Europe members}}
}}
{{Navboxes
|title = Other information
|list =
{{Monarchies}}
}}

{{Population country lists}}
{{Authority control}}

{{Coord|43|44|N|7|25|E|type:city(31000)|display=title}}

[[Category:Monaco| ]]
[[Category:Capitals in Europe]]
[[Category:City-states]]
[[Category:French-speaking countries and territories]]
[[Category:Italian-speaking countries and territories]]
[[Category:Massalian colonies]]
[[Category:Member states of the Council of Europe]]
[[Category:Member states of the Organisation internationale de la Francophonie]]
[[Category:Member states of the Union for the Mediterranean]]
[[Category:Member states of the United Nations]]
[[Category:Port cities of the Mediterranean Sea]]
[[Category:Principalities]]
[[Category:Romance countries and territories]]
[[Category:States and territories established in 1297]]
[[Category:Countries in Europe]]
[[Category:Christian states]]
[[Category:Western European countries]]
[[Category:Axis powers]]

Spinning drop method

2018-09-12T18:17:20Z

173.165.237.1: /* Comparison with other methods */

The '''spinning drop method''' (rotating drop method) is one of the methods used to measure [[Surface tension|interfacial tension]]. Measurements are carried out in a rotating horizontal tube which contains a dense fluid. A drop of a less dense liquid or a gas bubble is placed inside the fluid. Since the rotation of the horizontal tube creates a [[centrifugal force]] towards the tube walls, the liquid drop will start to deform into an elongated shape; this elongation stops when the interfacial tension and centrifugal forces are balanced. The surface tension between the two liquids (for bubbles: between the fluid and the gas) can then be derived from the shape of the drop at this [[equilibrium point]]. A device used for such measurements is called a “spinning drop tensiometer”.

The spinning drop method is usually preferred for the accurate measurements of surface tensions below 10−2 mN/m. It refers to either using the fluids with low interfacial tension or working at very high angular velocities. This method is widely used in many different applications such as measuring the interfacial tension of polymer blends<ref name=hujoseph>{{cite journal|author1=H.H. Hu |author2=D.D. Joseph |journal= J. Colloid Interface Sci.|volume= 162 |year=1994|pages= 331–339|doi=10.1006/jcis.1994.1047|title=Evolution of a Liquid Drop ''in a'' spinning Drop Tensiometer|issue=2}}</ref> and copolymers.<ref>{{cite journal|author1=C. Verdier |author2=H.T.M. Vinagre |author3=M. Piau |author4=D.D. Joseph |journal= Polymer |volume=41|year=2000|pages= 6683–6689|doi=10.1016/S0032-3861(00)00059-8|title=High temperature interfacial tension measurements of PA6/PP interfaces compatibilized with copolymers ''using a'' spinning drop tensiometer|issue=17}}</ref>

== Theory ==
An approximate theory was developed by Bernard Vonnegut<ref>{{cite journal|author=B. Vonnegut|journal= Rev. Sci. Instrum.|volume= 13 |issue=6 |year=1942|pages= 6–9|doi=10.1063/1.1769937|title=Rotating Bubble Method for the Determination of Surface and Interfacial Tensions}}</ref> in 1942 to measure the surface tension of the fluids, which is based on the principle that the interfacial tension and centrifugal forces are balanced at [[mechanical equilibrium]]. This theory assumes that the droplet's length L is much greater than its radius R, so that it may be approximated as a straight circular cylinder.

[[Image:Mine1.JPG]]

The relation between the surface tension and [[angular velocity]] of a droplet can be obtained in different ways. One of them involves considering the total mechanical energy of the droplet as the summation of its [[kinetic energy]] and its surface energy:

:<math> E=E_k +\gamma_s </math>

The kinetic energy of a cylinder of length L and radius R rotating about its central axis is given by

:<math> E_k=\frac{1}{2}I\omega^2=\frac{1}{4}mR^2\omega^2 </math>

in which

:<math> I=\frac{1}{2}mR^2 </math>

is the [[moment of inertia]] of a cylinder rotating about its central axis and ''ω'' is its angular velocity.
The surface energy of the droplet is given by

:<math> \gamma_s=2\pi LR\sigma=\frac{2V}{R}\sigma </math>

in which V is the constant volume of the droplet and ''σ'' is the interfacial tension.
Then the total mechanical energy of the droplet is

:<math> E=E_k +\gamma_s=\frac{1}{4}\Delta\rho VR^2\omega^2+\frac{2V}{R}\sigma </math>

in which Δ''ρ'' is the difference between the densities of the droplet and of the surrounding fluid.
At mechanical equilibrium, the mechanical energy is minimized, and thus

:<math>\frac{dE}{dR}=0=\frac{1}{2}\Delta\rho VR\omega^2-\frac{2V}{R^2}\sigma</math>

Substituting in

:<math> V=\pi LR^2 </math>

for a cylinder and then solving this relation for interfacial tension yields

:<math> \sigma=\frac{\Delta\rho\omega^2}{4}R^3 </math>

This equation is known as Vonnegut’s expression. Interfacial tension of any liquid that gives a shape very close to a cylinder at steady state, can be estimated using this equation. The straight cylindrical shape will always develop for sufficiently high ω; this typically happens for ''L''/''R'' > 4.<ref name=hujoseph /> Once this shape has developed, further increasing ω will decrease ''R'' while increasing ''L'' keeping ''LR2'' fixed to meet conservation of volume.

== New developments after 1942 ==
The full mathematical analysis on the shape of spinning drops was done by Princen and others.<ref>{{cite journal|author=|title=Measurement of Interfacial Tension from the Shape of a Rotating Drop|journal= Journal of Colloid and Interface Science|doi=10.1016/0021-9797(67)90090-2|year=1967|last1=Princen|first1=H|last2=Zia|first2=I|last3=Mason|first3=S|volume=23|pages=99}}</ref> Progress in numerical algorithms and available computing resources turned solving the non linear implicit parameter equations to a pretty much 'common' task, which has been tackled by various authors and companies. The results are proving the Vonnegut restriction is no longer valid for the spinning drop method.

== Comparison with other methods ==
The spinning drop method is convenient compared to other widely used methods for obtaining interfacial tension, because contact angle measurement is not required. Another advantage of the spinning drop method is that it is not necessary to estimate the curvature at the interface, which entails complexities associated with shape of the fluid drop.

On the other hand, this theory suggested by Vonnegut, is restricted with the [[Rotational speed|rotational velocity]]. The spinning drop method is not expected to give accurate results for high surface tension measurements, since the centrifugal force that is required to maintain the drop in a cylindrical shape is much higher in the case of liquids that have high interfacial tensions.

==References==
{{reflist}}

[[Category:Fluid mechanics]]

{{Expert needed|fluid dynamics|talk=|reason=The explanation of the "Vonnegut restriction" as well as the two bottom paragraphs would need a bit of a clean-up.|date=October 2016}}

Steam distillation

2018-09-10T17:52:57Z

173.165.237.1:

[[Image:Steam dist.svg|thumb|alt=Steam Distillation Apparatus|Steam distillation apparatus in a lab.]]
[[File:Steam distilation.jpg|thumb|Steam distillation apparatus, showing [[aniline]] steam distillation]]

'''Steam distillation''' is a special type of [[distillation]] (a [[separation processes|separation process]]) for ''temperature sensitive'' materials like natural [[aromaticity|aromatic]] compounds. It once was a popular laboratory method for purification of organic compounds, but has become less common due to the proliferation of [[vacuum distillation]]. Steam distillation remains important in certain industrial sectors.<ref name=Ullmann>{{cite book |doi=10.1002/14356007.a11_141 |chapter=Flavors and Fragrances |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2003 |last1=Fahlbusch |first1=Karl-Georg |last2=Hammerschmidt |first2=Franz-Josef |last3=Panten |first3=Johannes |last4=Pickenhagen |first4=Wilhelm |last5=Schatkowski |first5=Dietmar |last6=Bauer |first6=Kurt |last7=Garbe |first7=Dorothea |last8=Surburg |first8=Horst |isbn=3-527-30673-0 }}</ref>

Many [[organic compound]]s tend to [[Chemical decomposition|decompose]] at high sustained temperatures. Separation by distillation at the normal (1 atmosphere) boiling points is not an option, so water or [[steam]] is introduced into the distillation apparatus. The water vapor carries small amounts of the vaporized compounds to the condensation flask, where the condensed liquid phase separates, allowing easy collection. This process effectively enables distillation at lower temperatures, reducing the deterioration of the desired products. If the substances to be distilled are very sensitive to heat, steam distillation may be applied under reduced pressure, thereby reducing the operating temperature further.

After distillation the vapors are condensed. Usually the immediate product is a two-[[phase (matter)|phase system]] of water and the organic distillate, allowing separation of the components by [[decantation]], [[Partition coefficient|partitioning]] or other suitable methods.

==Principle==
[[File:Steam Distillation Diagram.jpg|alt=steam-distillation-diagram-koch|thumb|Diagram of how to economically clean up plant wastewater streams. Steam is use as a stripping gas to remove hydrocarbons from the waste water. This method is effective when the [[volatile organic compound]]s (i.e. chlorine) have lower boiling points than water or have limited solubility in water.]]
When a mixture of two practically [[miscibility|immiscible]] liquids is heated while being agitated to expose the surface of each liquid to the vapor phase, each constituent independently exerts its own [[vapor pressure]] as a function of temperature as if the other constituent were not present. Consequently, the vapor pressure of the whole system increases. Boiling begins when the sum of the [[vapour pressure]]s of the two immiscible liquids just exceeds the [[atmospheric pressure]] (approximately 101 [[Pascal (unit)|kPa]] at sea level). In this way, many organic compounds insoluble in water can be purified at a temperature well below the point at which decomposition occurs. For example, the boiling point of [[bromobenzene]] is 156 [[Celsius|°C]] and the boiling point of water is 100 °C, but a mixture of the two boils at 95 °C. Thus, bromobenzene can be easily distilled at a temperature 61 °C below its normal boiling point.<ref>Martin's Physical Pharmacy & Pharmaceutical sciences, fifth edition, {{ISBN|0-7817-6426-2}}, Lippincott williams & wilkins</ref>

== Applications ==
[[File:Steam water distiller.JPG|thumb|A boiling water distiller. Boiling tank on top and holding tank on the bottom.]]
Steam distillation is employed in the isolation of [[essential oil]]s, for use in [[perfumes]], for example. In this method, steam is passed through the plant material containing the desired oils. [[Eucalyptus oil]] and [[orange oil]] are obtained by this method on an industrial scale. Steam distillation is also sometimes used to separate intermediate or final products during the synthesis of complex organic compounds.<ref name=Ullmann/>

Steam distillation is also widely used in [[Oil refinery|petroleum refineries]] and [[petrochemical]] plants where it is commonly referred to as "steam stripping".<ref>Beychok, M.R., ''The Design of Sour Water Strippers'', Individual Paper 61, Proceedings of Seventh World Petroleum Congress, Mexico City, April 1967</ref><ref name=Kister>{{cite book|author=Kister, Henry Z.|title= [[Distillation Design]]|edition=1st |publisher=McGraw-Hill|year=1992|isbn=0-07-034909-6}}</ref>

Steam distillation also is an important means of separating fatty acids from mixtures and for treating crude products such as [[tall oil]]s to extract and separate [[fatty acid]]s, [[soap]]s and other commercially valuable organic compounds.<ref name="Chakrabarty2003">{{cite book|author=M.M. Chakrabarty|title=Chemistry and Technology of Oils & Fats|url=https://books.google.com/books?id=zIq9UBNQOskC&pg=PA12|date=9 November 2003|publisher=Allied Publishers|isbn=978-81-7764-495-1|pages=12–}}</ref>

== Equipment ==
[[File:Hydrodistillation using the Clevenger-type apparatus - N. Sadgrove and G. Jones, Agriculture 2015, 5(1), 48-102.png|thumb|Hydrodistillation using the Steam distillation apparatus, Clevenger-type apparatus.
(A) Power regulator;
(B) Heating mantle with round bottom flask containing water and aromatic leaves;
(C) Clevenger-type apparatus which returns the hydrosol to the still and maintains the essential oil phase, but only for essential oils that are less dense than water and therefore float;
(D) The condenser.]]
On a lab scale, steam distillations are carried out using steam generated outside the system and piped through macerated biomass or steam generated in-situ using a Clevenger-type apparatus.<ref>Walton & Brown, Chemicals From Plants, Imperial College Press, 1999.</ref>

==See also==
* [[Azeotropic distillation]]
* [[Batch distillation]]
* [[Distillation]]
* [[Extractive distillation]]
* [[Fractional distillation]]
* [[Heteroazeotrope]]
* [[Herbal distillates]]
* [[wikt:hydrodistillation|Hydrodistillation]]
* [[Laboratory equipment]]
* [[Steam engine]]
* [[Supercritical fluid extraction]]
* [[Theoretical plate]]

==References==
{{Reflist}}

{{Distillation}}

{{Authority control}}

{{DEFAULTSORT:Steam Distillation}}
[[Category:Distillation]]

2005 United Kingdom snow events

2018-08-24T17:49:44Z

173.165.237.1: /* January */

The year 2005 saw 25 heavy [[snowfall]] days, which is the joint snowiest year with 1876 across the [[United Kingdom]], between the years 1861-2005.

== January ==

The first event occurred on the [[Workweek|weekend]] of '''Saturday 1st and Sunday 2 January'''. Belts of [[rain]] sweeping west to east across the UK turned to [[snow]] on the leading edge over parts of [[Scotland]] and [[Northern England]], particularly the [[Scottish Highlands]] on the 2nd. The snow caused some [[travel]] disruption with some roads being forced to close. The snow was accompanied by [[gale]]-force winds, peaking at 70 mph during the period.<ref>{{cite news |title=BBC website: 'Gales and snowy conditions ease' |url= http://news.bbc.co.uk/1/hi/uk/4140729.stm|accessdate=2008-09-03 | date=2005-01-02 |work=BBC News}}</ref>

Snow showers continued to affect Highland Scotland on '''Wednesday 12 January''', with [[blizzard]]s caused by 100 mph winds. Snow showers also affected parts of Southern Scotland, [[Northeast England]] and the [[English Midlands|Midlands]].

After a brief spell of [[settled]] weather, a series of Atlantic depressions affected all of the [[United Kingdom]] on '''Monday 17th and Tuesday 18 January'''. Rainbands pushed eastwards across the country, turning to [[snow]] across [[Scotland]], and also [[Northern Ireland]] and [[Northern England]] on the 18th. All of the schools on the [[Western Isles]] were closed on the 18th as up to 25 cm (9 inches) of snow fell in central and eastern regions of Scotland.<ref>{{cite news |title=BBC website: ‘Scotland braced for more storms’ |url= http://news.bbc.co.uk/1/hi/scotland/4180365.stm|accessdate=2008-09-03 | date=2005-01-18 |work=BBC News}}</ref> Several roads were forced to close.<ref>{{cite news |title=BBC website: ‘Heavy snow causes traffic chaos’ |url= http://news.bbc.co.uk/1/hi/uk/4183957.stm|accessdate=2008-09-03 | date=2005-01-18 |work=BBC News}}</ref>

As an [[anticyclone]] dominated the [[weather]] between '''Sunday 23rd and Thursday 27th''', cold northerly winds plagued eastern coasts of both [[Scotland]] and [[England]]. Frequent heavy snow [[shower]]s affect Eastern and Northern Scotland, Eastern England and also Central Southern England. County Durham received 29 cm (11.5 inches) of lying snow on the 23rd, whilst 4 cm (1.5 inches) was reported in Dover and Folkestone, [[Kent]], on the 25th<ref>{{cite news |title=BBC website: ‘UK Caught in Topsy Turvy freeze’ |url= http://news.bbc.co.uk/1/hi/uk/4204707.stm|accessdate=2008-09-03 | date=2005-01-26 |work=BBC News}}</ref> and some minor snowfalls also affected the [[English Midlands|Midlands]] and the higher ground of [[Southwest England]].

== February ==

After a relatively mild but unsettled first half of February, [[Arctic]] air flooded southwards behind a [[cold front]] on the 18th. Snow showers affected the Midlands, Northern England, [[Southeast England]] and Northern Scotland between '''Sunday 20th and Monday 28th'''. North Yorkshire received 8 cm (3 inches) of lying snow on the 21st, whilst blizzards and 13 cm (5 inches)of lying snow forced more than 30 schools to close in [[Aberdeenshire]]. [[Temperature]]s also struggled to climb above [[freezing]], with Buxton, Derbyshire, only reaching 0.8 °C as a maximum temperature on the 22nd. By the 25th, 30 cm (12 inches) of snow lay over the [[Pennines]], with drifts of 1.5 metres (5 feet) reported, 50 cm (19 inches) of snow lay in [[County Durham]] and 7 cm (about 3 inches) in the [[Dover]] area of [[Kent]].

The cold, arctic weather continued right to the end of February, with further frequent snow showers in eastern regions. 54 flights were cancelled from [[Heathrow]] and hundreds of schools across the southeast were forced to shut as 27 cm (11 inches) of snow fell across [[Kent]].

50 cm (19 inch) snow drifts were reported in Kent and [[East Sussex]] on the 27th, causing several road [[accidents]].

== March ==

Snow continued to fall across Scotland and Eastern England into March, with 30 vehicles involved in an accident on the M8 between Glasgow and Edinburgh, on the 1st. The snow caused more than 140 schools in [[Fife]] and 30 schools in [[Aberdeenshire]] to close or partially close, along with 20 schools and nurseries in [[Angus, Scotland|Angus]].

The heaviest March snowfall for 10 years occurred across Kent on the 2nd. 30 cm (12 inch) drifts on the [[North Downs]] caused the closure of 400+ schools and the M2 and Operation Stack was implemented on the M20 motorway. 200 homes also lost their electricity supply in [[Kent]], [[Surrey]] and [[East Sussex]]. Snow continued to fall in these regions on the 3rd and 4th, temporarily closing [[Luton]] and [[Stansted]] airports. Meanwhile, further snow affected Northeast Scotland and Northeast England, with significant accumulations reported and hundreds of school closures.

However, milder weather made a return across the UK, however as showers pushed eastwards they turned to snow across Northern Scotland during the night of the '''13th and 14 March'''. March continued and ended on a relatively mild but unsettled note.

== April ==

Typically, a showery start to April was replaced with a return to cold, northerly winds as a weak cold front passed eastwards on '''7 and 8 April'''. This brought a period of heavy snow to the Scottish Highlands, blocking many high level routes in the area.

Showers also turned briefly to snow as far south as the [[Derbyshire]] Peaks on the night of the '''15th'''. This was the last snow event of the season.

== November ==

As two cold fronts pushed eastwards on the '''24th''', squally showers turned to [[Ice storm|sleet]] and snow across [[East Anglia]], [[Wales]] and Southwest England. Up to 30 cm of snow was reported in Devon and Cornwall on the '''25th''', with 2 metre drifts. The snowfall trapped approximately 1000 people on the A30 near Kennards House, across [[Bodmin Moor]], Cornwall, after several snow related accidents blocked the road. The snow caused a six-mile tailback and people were advised by the police to remain in their vehicles. A [[Royal Marine]] and two [[RAF]] and [[Navy]] helicopters, and a convoy of four-wheel drive vehicles, organised by [[Devon]] and [[Cornwall]] police, took stranded drivers to leisure centres and emergency shelters for the night. 68 schools across [[Cornwall]] were forced to close because of the bad weather.

Blizzards also affected Northern Scotland and Northern Ireland, where four men were stranded on the [[Cairngorms]].
Heavy snow showers continued to fall over the [[Grampian]]s and the [[Scottish Highlands|Highlands]] on the '''28th''', and snow showers also reported in [[Manchester]], over the [[Pennines]] and [[North York Moors]]. These also pushed southwards into the [[English Midlands|Midlands]] and [[Lincolnshire]] during the afternoon, before affecting [[Gloucestershire]] during the evening, especially between 17:00-20:00GMT. Approximately 400 cars were abandoned on the A417 between Gloucester and Cirencester due to snowy conditions, and the A57 [[Snake Pass]] in the [[Peak District]] was closed for a time.

== December ==

A brief northerly blast mid-month brought frequent [[hail]] and snow showers down the east coast, where a covering of snow was reported in [[Norfolk]] on the '''17th'''.

Then, after a quiet and relatively settled [[Christmas]] period, showers over [[Essex]] and [[Kent]] turned increasingly wintry on [[Boxing day]] night as cold air arrived from the east. Here the snow settled, and frequent snow showers in Southeast England and East Anglia on '''27 and 28 December''' gave a covering of 30 cm across the Downs in Kent, causing some roads and the [[Channel Tunnel]] terminal to close for two hours. By the '''28th''', the snow showers began to affect other northern regions, including Norfolk, Lincolnshire, [[West Yorkshire]] and [[Northeast England]]. [[North Yorkshire]] received 20 cm of snow over high ground, whilst the snow caused huge tailbacks on the [[A1 road (Great Britain)|A1]] between [[Alnwick]] and [[Berwick-upon-Tweed|Berwick]]. The snow showers petered later on the '''29th''' as outbreaks of rain, sleet and hill snow moved into western areas.

On Friday 30 December, a band of heavy rain pushed eastwards, with heavy snow on the leading edge. This brought several hours of snow followed by rain, where 20 cm fell in some parts of [[Yorkshire]], with snowdrifts of 1 metre reported. The snow caused hundreds of drivers to be stranded on the A1079 during the late morning at Arras Hill in the East Riding of Yorkshire. There was a marked temperature difference on the 30th, with [[Redesdale]], [[Northumberland]], only reaching 0.4 °C as a maximum, whilst some places reached 12 °C in Southwest England.

== References ==
{{reflist|2}}

{{portalbar|Weather|United Kingdom}}

{{DEFAULTSORT:2005 United Kingdom Snow Events}}
[[Category:2005 disasters in the United Kingdom|Snow events]]
[[Category:2005 meteorology|United Kingdom snow events]]
[[Category:Snow in the United Kingdom]]

2005 United Kingdom snow events

2018-08-24T17:47:34Z

173.165.237.1: /* March */

The year 2005 saw 25 heavy [[snowfall]] days, which is the joint snowiest year with 1876 across the [[United Kingdom]], between the years 1861-2005.

== January ==

The first event occurred on the [[Workweek|weekend]] of '''Saturday 1st and Sunday 2 January'''. Belts of [[rain]] sweeping west to east across the UK turned to [[snow]] on the leading edge over parts of [[Scotland]] and [[Northern England]], particularly the [[Scottish Highlands]] on the 2nd. The snow caused some [[travel]] disruption with some roads being forced to close. The snow was accompanied by [[gale]]-force winds, peaking at 70 mph during the period.<ref>{{cite news |title=BBC website: 'Gales and snowy conditions ease' |url= http://news.bbc.co.uk/1/hi/uk/4140729.stm|accessdate=2008-09-03 | date=2005-01-02 |work=BBC News}}</ref>

Snow showers continued to affect Highland Scotland on '''Wednesday 12 January''', with [[blizzard]]s caused by 100 mph winds. Snow showers also affected parts of Southern Scotland, [[Northeast England]] and the [[English Midlands|Midlands]].

After a brief spell of [[settled]] weather, a series of Atlantic depressions affected all of the [[United Kingdom]] on '''Monday 17th and Tuesday 18 January'''. Rainbands pushed eastwards across the country, turning to [[snow]] across [[Scotland]], and also [[Northern Ireland]] and [[Northern England]] on the 18th. All of the schools on the [[Western Isles]] were closed on the 18th as up to 25 cm of snow fell in central and eastern regions of Scotland.<ref>{{cite news |title=BBC website: ‘Scotland braced for more storms’ |url= http://news.bbc.co.uk/1/hi/scotland/4180365.stm|accessdate=2008-09-03 | date=2005-01-18 |work=BBC News}}</ref> Several roads were forced to close.<ref>{{cite news |title=BBC website: ‘Heavy snow causes traffic chaos’ |url= http://news.bbc.co.uk/1/hi/uk/4183957.stm|accessdate=2008-09-03 | date=2005-01-18 |work=BBC News}}</ref>

As an [[anticyclone]] dominated the [[weather]] between '''Sunday 23rd and Thursday 27th''', cold northerly winds plagued eastern coasts of both [[Scotland]] and [[England]]. Frequent heavy snow [[shower]]s affect Eastern and Northern Scotland, Eastern England and also Central Southern England. County Durham received 29 cm of lying snow on the 23rd, whilst 4 cm was reported in Dover and Folkestone, [[Kent]], on the 25th<ref>{{cite news |title=BBC website: ‘UK Caught in Topsy Turvy freeze’ |url= http://news.bbc.co.uk/1/hi/uk/4204707.stm|accessdate=2008-09-03 | date=2005-01-26 |work=BBC News}}</ref> and some minor snowfalls also affected the [[English Midlands|Midlands]] and the higher ground of [[Southwest England]].

== February ==

After a relatively mild but unsettled first half of February, [[Arctic]] air flooded southwards behind a [[cold front]] on the 18th. Snow showers affected the Midlands, Northern England, [[Southeast England]] and Northern Scotland between '''Sunday 20th and Monday 28th'''. North Yorkshire received 8 cm (3 inches) of lying snow on the 21st, whilst blizzards and 13 cm (5 inches)of lying snow forced more than 30 schools to close in [[Aberdeenshire]]. [[Temperature]]s also struggled to climb above [[freezing]], with Buxton, Derbyshire, only reaching 0.8 °C as a maximum temperature on the 22nd. By the 25th, 30 cm (12 inches) of snow lay over the [[Pennines]], with drifts of 1.5 metres (5 feet) reported, 50 cm (19 inches) of snow lay in [[County Durham]] and 7 cm (about 3 inches) in the [[Dover]] area of [[Kent]].

The cold, arctic weather continued right to the end of February, with further frequent snow showers in eastern regions. 54 flights were cancelled from [[Heathrow]] and hundreds of schools across the southeast were forced to shut as 27 cm (11 inches) of snow fell across [[Kent]].

50 cm (19 inch) snow drifts were reported in Kent and [[East Sussex]] on the 27th, causing several road [[accidents]].

== March ==

Snow continued to fall across Scotland and Eastern England into March, with 30 vehicles involved in an accident on the M8 between Glasgow and Edinburgh, on the 1st. The snow caused more than 140 schools in [[Fife]] and 30 schools in [[Aberdeenshire]] to close or partially close, along with 20 schools and nurseries in [[Angus, Scotland|Angus]].

The heaviest March snowfall for 10 years occurred across Kent on the 2nd. 30 cm (12 inch) drifts on the [[North Downs]] caused the closure of 400+ schools and the M2 and Operation Stack was implemented on the M20 motorway. 200 homes also lost their electricity supply in [[Kent]], [[Surrey]] and [[East Sussex]]. Snow continued to fall in these regions on the 3rd and 4th, temporarily closing [[Luton]] and [[Stansted]] airports. Meanwhile, further snow affected Northeast Scotland and Northeast England, with significant accumulations reported and hundreds of school closures.

However, milder weather made a return across the UK, however as showers pushed eastwards they turned to snow across Northern Scotland during the night of the '''13th and 14 March'''. March continued and ended on a relatively mild but unsettled note.

== April ==

Typically, a showery start to April was replaced with a return to cold, northerly winds as a weak cold front passed eastwards on '''7 and 8 April'''. This brought a period of heavy snow to the Scottish Highlands, blocking many high level routes in the area.

Showers also turned briefly to snow as far south as the [[Derbyshire]] Peaks on the night of the '''15th'''. This was the last snow event of the season.

== November ==

As two cold fronts pushed eastwards on the '''24th''', squally showers turned to [[Ice storm|sleet]] and snow across [[East Anglia]], [[Wales]] and Southwest England. Up to 30 cm of snow was reported in Devon and Cornwall on the '''25th''', with 2 metre drifts. The snowfall trapped approximately 1000 people on the A30 near Kennards House, across [[Bodmin Moor]], Cornwall, after several snow related accidents blocked the road. The snow caused a six-mile tailback and people were advised by the police to remain in their vehicles. A [[Royal Marine]] and two [[RAF]] and [[Navy]] helicopters, and a convoy of four-wheel drive vehicles, organised by [[Devon]] and [[Cornwall]] police, took stranded drivers to leisure centres and emergency shelters for the night. 68 schools across [[Cornwall]] were forced to close because of the bad weather.

Blizzards also affected Northern Scotland and Northern Ireland, where four men were stranded on the [[Cairngorms]].
Heavy snow showers continued to fall over the [[Grampian]]s and the [[Scottish Highlands|Highlands]] on the '''28th''', and snow showers also reported in [[Manchester]], over the [[Pennines]] and [[North York Moors]]. These also pushed southwards into the [[English Midlands|Midlands]] and [[Lincolnshire]] during the afternoon, before affecting [[Gloucestershire]] during the evening, especially between 17:00-20:00GMT. Approximately 400 cars were abandoned on the A417 between Gloucester and Cirencester due to snowy conditions, and the A57 [[Snake Pass]] in the [[Peak District]] was closed for a time.

== December ==

A brief northerly blast mid-month brought frequent [[hail]] and snow showers down the east coast, where a covering of snow was reported in [[Norfolk]] on the '''17th'''.

Then, after a quiet and relatively settled [[Christmas]] period, showers over [[Essex]] and [[Kent]] turned increasingly wintry on [[Boxing day]] night as cold air arrived from the east. Here the snow settled, and frequent snow showers in Southeast England and East Anglia on '''27 and 28 December''' gave a covering of 30 cm across the Downs in Kent, causing some roads and the [[Channel Tunnel]] terminal to close for two hours. By the '''28th''', the snow showers began to affect other northern regions, including Norfolk, Lincolnshire, [[West Yorkshire]] and [[Northeast England]]. [[North Yorkshire]] received 20 cm of snow over high ground, whilst the snow caused huge tailbacks on the [[A1 road (Great Britain)|A1]] between [[Alnwick]] and [[Berwick-upon-Tweed|Berwick]]. The snow showers petered later on the '''29th''' as outbreaks of rain, sleet and hill snow moved into western areas.

On Friday 30 December, a band of heavy rain pushed eastwards, with heavy snow on the leading edge. This brought several hours of snow followed by rain, where 20 cm fell in some parts of [[Yorkshire]], with snowdrifts of 1 metre reported. The snow caused hundreds of drivers to be stranded on the A1079 during the late morning at Arras Hill in the East Riding of Yorkshire. There was a marked temperature difference on the 30th, with [[Redesdale]], [[Northumberland]], only reaching 0.4 °C as a maximum, whilst some places reached 12 °C in Southwest England.

== References ==
{{reflist|2}}

{{portalbar|Weather|United Kingdom}}

{{DEFAULTSORT:2005 United Kingdom Snow Events}}
[[Category:2005 disasters in the United Kingdom|Snow events]]
[[Category:2005 meteorology|United Kingdom snow events]]
[[Category:Snow in the United Kingdom]]

2005 United Kingdom snow events

2018-08-24T17:46:50Z

173.165.237.1: /* February */

The year 2005 saw 25 heavy [[snowfall]] days, which is the joint snowiest year with 1876 across the [[United Kingdom]], between the years 1861-2005.

== January ==

The first event occurred on the [[Workweek|weekend]] of '''Saturday 1st and Sunday 2 January'''. Belts of [[rain]] sweeping west to east across the UK turned to [[snow]] on the leading edge over parts of [[Scotland]] and [[Northern England]], particularly the [[Scottish Highlands]] on the 2nd. The snow caused some [[travel]] disruption with some roads being forced to close. The snow was accompanied by [[gale]]-force winds, peaking at 70 mph during the period.<ref>{{cite news |title=BBC website: 'Gales and snowy conditions ease' |url= http://news.bbc.co.uk/1/hi/uk/4140729.stm|accessdate=2008-09-03 | date=2005-01-02 |work=BBC News}}</ref>

Snow showers continued to affect Highland Scotland on '''Wednesday 12 January''', with [[blizzard]]s caused by 100 mph winds. Snow showers also affected parts of Southern Scotland, [[Northeast England]] and the [[English Midlands|Midlands]].

After a brief spell of [[settled]] weather, a series of Atlantic depressions affected all of the [[United Kingdom]] on '''Monday 17th and Tuesday 18 January'''. Rainbands pushed eastwards across the country, turning to [[snow]] across [[Scotland]], and also [[Northern Ireland]] and [[Northern England]] on the 18th. All of the schools on the [[Western Isles]] were closed on the 18th as up to 25 cm of snow fell in central and eastern regions of Scotland.<ref>{{cite news |title=BBC website: ‘Scotland braced for more storms’ |url= http://news.bbc.co.uk/1/hi/scotland/4180365.stm|accessdate=2008-09-03 | date=2005-01-18 |work=BBC News}}</ref> Several roads were forced to close.<ref>{{cite news |title=BBC website: ‘Heavy snow causes traffic chaos’ |url= http://news.bbc.co.uk/1/hi/uk/4183957.stm|accessdate=2008-09-03 | date=2005-01-18 |work=BBC News}}</ref>

As an [[anticyclone]] dominated the [[weather]] between '''Sunday 23rd and Thursday 27th''', cold northerly winds plagued eastern coasts of both [[Scotland]] and [[England]]. Frequent heavy snow [[shower]]s affect Eastern and Northern Scotland, Eastern England and also Central Southern England. County Durham received 29 cm of lying snow on the 23rd, whilst 4 cm was reported in Dover and Folkestone, [[Kent]], on the 25th<ref>{{cite news |title=BBC website: ‘UK Caught in Topsy Turvy freeze’ |url= http://news.bbc.co.uk/1/hi/uk/4204707.stm|accessdate=2008-09-03 | date=2005-01-26 |work=BBC News}}</ref> and some minor snowfalls also affected the [[English Midlands|Midlands]] and the higher ground of [[Southwest England]].

== February ==

After a relatively mild but unsettled first half of February, [[Arctic]] air flooded southwards behind a [[cold front]] on the 18th. Snow showers affected the Midlands, Northern England, [[Southeast England]] and Northern Scotland between '''Sunday 20th and Monday 28th'''. North Yorkshire received 8 cm (3 inches) of lying snow on the 21st, whilst blizzards and 13 cm (5 inches)of lying snow forced more than 30 schools to close in [[Aberdeenshire]]. [[Temperature]]s also struggled to climb above [[freezing]], with Buxton, Derbyshire, only reaching 0.8 °C as a maximum temperature on the 22nd. By the 25th, 30 cm (12 inches) of snow lay over the [[Pennines]], with drifts of 1.5 metres (5 feet) reported, 50 cm (19 inches) of snow lay in [[County Durham]] and 7 cm (about 3 inches) in the [[Dover]] area of [[Kent]].

The cold, arctic weather continued right to the end of February, with further frequent snow showers in eastern regions. 54 flights were cancelled from [[Heathrow]] and hundreds of schools across the southeast were forced to shut as 27 cm (11 inches) of snow fell across [[Kent]].

50 cm (19 inch) snow drifts were reported in Kent and [[East Sussex]] on the 27th, causing several road [[accidents]].

== March ==

Snow continued to fall across Scotland and Eastern England into March, with 30 vehicles involved in an accident on the M8 between Glasgow and Edinburgh, on the 1st. The snow caused more than 140 schools in [[Fife]] and 30 schools in [[Aberdeenshire]] to close or partially close, along with 20 schools and nurseries in [[Angus, Scotland|Angus]].

The heaviest March snowfall for 10 years occurred across Kent on the 2nd. 30 cm drifts on the [[North Downs]] caused the closure of 400+ schools and the M2 and Operation Stack was implemented on the M20 motorway. 200 homes also lost their electricity supply in [[Kent]], [[Surrey]] and [[East Sussex]]. Snow continued to fall in these regions on the 3rd and 4th, temporarily closing [[Luton]] and [[Stansted]] airports. Meanwhile, further snow affected Northeast Scotland and Northeast England, with significant accumulations reported and hundreds of school closures.

However, milder weather made a return across the UK, however as showers pushed eastwards they turned to snow across Northern Scotland during the night of the '''13th and 14 March'''. March continued and ended on a relatively mild but unsettled note.

== April ==

Typically, a showery start to April was replaced with a return to cold, northerly winds as a weak cold front passed eastwards on '''7 and 8 April'''. This brought a period of heavy snow to the Scottish Highlands, blocking many high level routes in the area.

Showers also turned briefly to snow as far south as the [[Derbyshire]] Peaks on the night of the '''15th'''. This was the last snow event of the season.

== November ==

As two cold fronts pushed eastwards on the '''24th''', squally showers turned to [[Ice storm|sleet]] and snow across [[East Anglia]], [[Wales]] and Southwest England. Up to 30 cm of snow was reported in Devon and Cornwall on the '''25th''', with 2 metre drifts. The snowfall trapped approximately 1000 people on the A30 near Kennards House, across [[Bodmin Moor]], Cornwall, after several snow related accidents blocked the road. The snow caused a six-mile tailback and people were advised by the police to remain in their vehicles. A [[Royal Marine]] and two [[RAF]] and [[Navy]] helicopters, and a convoy of four-wheel drive vehicles, organised by [[Devon]] and [[Cornwall]] police, took stranded drivers to leisure centres and emergency shelters for the night. 68 schools across [[Cornwall]] were forced to close because of the bad weather.

Blizzards also affected Northern Scotland and Northern Ireland, where four men were stranded on the [[Cairngorms]].
Heavy snow showers continued to fall over the [[Grampian]]s and the [[Scottish Highlands|Highlands]] on the '''28th''', and snow showers also reported in [[Manchester]], over the [[Pennines]] and [[North York Moors]]. These also pushed southwards into the [[English Midlands|Midlands]] and [[Lincolnshire]] during the afternoon, before affecting [[Gloucestershire]] during the evening, especially between 17:00-20:00GMT. Approximately 400 cars were abandoned on the A417 between Gloucester and Cirencester due to snowy conditions, and the A57 [[Snake Pass]] in the [[Peak District]] was closed for a time.

== December ==

A brief northerly blast mid-month brought frequent [[hail]] and snow showers down the east coast, where a covering of snow was reported in [[Norfolk]] on the '''17th'''.

Then, after a quiet and relatively settled [[Christmas]] period, showers over [[Essex]] and [[Kent]] turned increasingly wintry on [[Boxing day]] night as cold air arrived from the east. Here the snow settled, and frequent snow showers in Southeast England and East Anglia on '''27 and 28 December''' gave a covering of 30 cm across the Downs in Kent, causing some roads and the [[Channel Tunnel]] terminal to close for two hours. By the '''28th''', the snow showers began to affect other northern regions, including Norfolk, Lincolnshire, [[West Yorkshire]] and [[Northeast England]]. [[North Yorkshire]] received 20 cm of snow over high ground, whilst the snow caused huge tailbacks on the [[A1 road (Great Britain)|A1]] between [[Alnwick]] and [[Berwick-upon-Tweed|Berwick]]. The snow showers petered later on the '''29th''' as outbreaks of rain, sleet and hill snow moved into western areas.

On Friday 30 December, a band of heavy rain pushed eastwards, with heavy snow on the leading edge. This brought several hours of snow followed by rain, where 20 cm fell in some parts of [[Yorkshire]], with snowdrifts of 1 metre reported. The snow caused hundreds of drivers to be stranded on the A1079 during the late morning at Arras Hill in the East Riding of Yorkshire. There was a marked temperature difference on the 30th, with [[Redesdale]], [[Northumberland]], only reaching 0.4 °C as a maximum, whilst some places reached 12 °C in Southwest England.

== References ==
{{reflist|2}}

{{portalbar|Weather|United Kingdom}}

{{DEFAULTSORT:2005 United Kingdom Snow Events}}
[[Category:2005 disasters in the United Kingdom|Snow events]]
[[Category:2005 meteorology|United Kingdom snow events]]
[[Category:Snow in the United Kingdom]]

Plastic extrusion

2018-08-13T18:38:35Z

173.165.237.1: /* Screw design */

{{More citations needed|date=October 2009}}
{{Use American English|date=April 2014}}
[[File:Extruder with sheet die.jpg|400px|thumb|right|Cross-section of a plastic extruder to show the screw]]

'''Plastics extrusion''' is a high-volume manufacturing process in which raw [[plastic]] is melted and formed into a continuous profile. Extrusion produces items such as pipe/tubing, [[weatherstripping]], fencing, [[deck railing]]s, [[window|window frames]], [[plastic film]]s and sheeting, [[thermoplastic]] coatings, and wire insulation.

This process starts by feeding plastic material (pellets, granules, flakes or powders) from a hopper into the barrel of the extruder. The material is gradually melted by the mechanical energy generated by turning screws and by heaters arranged along the barrel. The molten polymer is then forced into a die, which shapes the polymer into a shape that hardens during cooling.<ref>{{Cite web|url = http://www.teppfa.eu/production-processes/|title = Production Processes|date = |accessdate = |website = |publisher = |last = TEPPFA, The European Plastic Pipes and Fittings Association|first = }}</ref>

==History==
[[File:Production processes.png|thumb|Pipe extrusion]]
The first precursors to the modern extruder were developed in the early 19th century. In 1820, Thomas Hancock invented a rubber "masticator" designed to reclaim processed rubber scraps, and in 1836 Edwin Chaffee developed a two-roller machine to mix additives into [[rubber]].<ref>Tadmor and Gogos (2006). ‘’Principles of Polymer Processing’’. John Wiley and Sons. {{ISBN|978-0-471-38770-1}}</ref> The first thermoplastic extrusion was in 1935 by Paul Troester and his wife Ashley Gershoff in [[Hamburg]], Germany. Shortly after, Roberto Colombo of LMP developed the first twin screw extruders in Italy.<ref>{{Citation | last = Rauwendaal | first = Chris | title = Polymer Extrusion, 4th ed | page = | publisher = Hanser | year = 2001 | isbn = 3-446-21774-6}}.</ref>

==Process==
In the extrusion of plastics, the raw compound material is commonly in the form of nurdles (small beads, often called resin) that are gravity fed from a top mounted [[:wikt:hopper|hopper]] into the barrel of the extruder. Additives such as colorants and UV inhibitors (in either liquid or pellet form) are often used and can be mixed into the resin prior to arriving at the hopper. The process has much in common with [[injection molding|plastic injection molding]] from the point of the extruder technology, although it differs in that it is usually a continuous process. While [[pultrusion]] can offer many similar profiles in continuous lengths, usually with added reinforcing, this is achieved by pulling the finished product out of a die instead of extruding the polymer melt through a die.

The material enters through the feed throat (an opening near the rear of the barrel) and comes into contact with the screw. The rotating screw (normally turning at e.g. 120 rpm) forces the plastic beads forward into the heated barrel. The desired extrusion temperature is rarely equal to the set temperature of the barrel due to viscous heating and other effects. In most processes, a heating profile is set for the barrel in which three or more independent [[PID controller|PID]]-controlled heater zones gradually increase the temperature of the barrel from the rear (where the plastic enters) to the front. This allows the plastic beads to melt gradually as they are pushed through the barrel and lowers the risk of overheating which may cause degradation in the polymer.

Extra heat is contributed by the intense pressure and friction taking place inside the barrel. In fact, if an extrusion line is running certain materials fast enough, the heaters can be shut off and the melt temperature maintained by pressure and friction alone inside the barrel. In most extruders, cooling fans are present to keep the temperature below a set value if too much heat is generated. If forced air cooling proves insufficient then cast-in cooling jackets are employed.

[[File:Extruder section.jpg|450px|thumb|left|Plastic extruder cut in half to show the components]]

At the front of the barrel, the [[wikt:molten|molten]] plastic leaves the screw and travels through a screen pack to remove any contaminants in the melt. The screens are reinforced by a breaker plate (a thick metal puck with many holes drilled through it) since the pressure at this point can exceed 5,000 [[Pound-force per square inch|psi]] (34 [[MPa]]). The screen pack/breaker plate assembly also serves to create [[back pressure]] in the barrel. Back pressure is required for uniform melting and proper mixing of the polymer, and how much pressure is generated can be "tweaked" by varying screen pack composition (the number of screens, their wire weave size, and other parameters). This breaker plate and screen pack combination also eliminates the "rotational memory" of the molten plastic and creates instead, "longitudinal memory".

After passing through the breaker plate molten plastic enters the die. The die is what gives the final product its profile and must be designed so that the molten plastic evenly flows from a cylindrical profile, to the product's profile shape. Uneven flow at this stage can produce a product with unwanted residual stresses at certain points in the profile which can cause warping upon cooling. A wide variety of shapes can be created, restricted to continuous profiles.

The product must now be cooled and this is usually achieved by pulling the extrudate through a water bath. Plastics are very good thermal insulators and are therefore difficult to cool quickly. Compared to [[steel]], plastic conducts its heat away 2,000 times more slowly. In a tube or pipe extrusion line, a sealed water bath is acted upon by a carefully controlled vacuum to keep the newly formed and still molten tube or pipe from collapsing. For products such as plastic sheeting, the cooling is achieved by pulling through a set of cooling rolls. For films and very thin sheeting, air cooling can be effective as an initial cooling stage, as in blown film extrusion.

Plastic extruders are also extensively used to reprocess recycled [[plastic pollution|plastic waste]] or other raw materials after cleaning, sorting and/or blending. This material is commonly extruded into filaments suitable for chopping into the bead or pellet stock to use as a precursor for further processing.

==Screw design==
There are five possible zones in a thermoplastic screw. Since terminology is not standardized in the industry, different names may refer to these zones. Different types of polymer will have differing screw designs, some not incorporating all of the possible zones.

[[File:Plastic extruder screw.jpg|600px|thumb|centre|A simple plastic extrusion screw]]

[[File:Extruder Screws From Boston Matthews.jpg|thumb|Extruder screws From Boston Matthews]]

Most screws have these three zones:
* Feed zone (also called the solids conveying zone): this zone feeds the resin into the extruder, and the channel depth is usually the same throughout the zone.
* Melting zone (also called the transition or compression zone): most of the polymer is melted in this section, and the channel depth gets progressively smaller.
* Metering zone (also called the melt conveying zone): this zone melts the last particles and mixes to a uniform temperature and composition. Like the feed zone, the channel depth is constant throughout this zone.
In addition, a vented (two-stage) screw has:
* Decompression zone. In this zone, about two-thirds down the screw, the channel suddenly gets deeper, which relieves the pressure and allows any trapped gases (moisture, air, solvents, or reactants) to be drawn out by vacuum.
* Second metering zone. This zone is similar to the first metering zone, but with greater channel depth. It serves to repressurize the melt to get it through the resistance of the screens and the die.

Often screw length is referenced to its diameter as L:D ratio. For instance, a {{convert|6|in|mm|adj=on}} diameter screw at 24:1 will be 144 inches (12 ft) long, and at 32:1 it is 192 inches (16 ft) long. An L:D ratio of 25:1 is common, but some machines go up to 40:1 for more mixing and more output at the same screw diameter. Two-stage (vented) screws are typically 36:1 to account for the two extra zones.

Each zone is equipped with one or more [[thermocouple]]s or [[Resistance temperature detector|RTDs]] in the barrel wall for temperature control. The "temperature profile" i.e., the temperature of each zone is very important to the quality and characteristics of the final extrudate.

==Typical extrusion materials==
Typical plastic materials that are used in extrusion include but are not limited to: [[polyethylene]] (PE), [[polypropylene]], [[acetal]], [[acrylic resin|acrylic]], [[nylon]] (polyamides), [[polystyrene]], [[polyvinyl chloride]] (PVC), [[acrylonitrile butadiene styrene]] (ABS) and [[polycarbonate]].<ref name="todd">{{harvnb|Todd|Allen|Alting|1994|pp=223–227}}.</ref>

==Die types==

{{Main|Die forming (plastics)}}

There are a variety of dies used in plastics extrusion. While there can be significant differences between die types and complexity, all dies allow for the continuous extrusion of polymer melt, as opposed to non-continuous processing such as [[injection molding]].

===Blown film extrusion===
[[File:Film extrusion.jpg|thumb|Blow extrusion of plastic film]]

The manufacture of [[plastic film]] for products such as [[shopping bag]]s and continuous sheeting is achieved using a [[blown film]] line.<ref>{{cite web|title=HOW TO SOLVE BLOWN FILM PROBLEMS|url=http://www.lyondellbasell.com/techlit/techlit/Handbooks%20and%20Manuals/BlownFilmProblems.pdf|publisher=Lyondell Chemical Company|accessdate=31 August 2012}}</ref>

This process is the same as a regular extrusion process up until the die. There are three main types of dies used in this process: annular (or crosshead), spider, and spiral. Annular dies are the simplest, and rely on the polymer melt channeling around the entire cross section of the die before exiting the die; this can result in uneven flow. Spider dies consist of a central mandrel attached to the outer die ring via a number of "legs"; while flow is more symmetrical than in annular dies, a number of weld lines are produced which weaken the film. Spiral dies remove the issue of weld lines and asymmetrical flow, but are by far the most complex.<ref>{{cite book|title=Small Scale Recycling of Plastics|author=John Vogler|pages=6–7|publisher=Intermediate Technology Publication|year=1984}}</ref>

The melt is cooled somewhat before leaving the die to yield a weak semi-solid tube. This tube's diameter is rapidly expanded via air pressure, and the tube is drawn upwards with rollers, stretching the plastic in both the transverse and draw directions. The drawing and blowing cause the film to be thinner than the extruded tube, and also preferentially aligns the polymer molecular chains in the direction that sees the most [[Elastic and plastic strain|plastic strain]]. If the film is drawn more than it is blown (the final tube diameter is close to the extruded diameter) the polymer molecules will be highly aligned with the draw direction, making a film that is strong in that direction, but weak in the transverse direction. A film that has significantly larger diameter than the extruded diameter will have more strength in the transverse direction, but less in the draw direction.

In the case of polyethylene and other semi-crystalline polymers, as the film cools it crystallizes at what is known as the frost line. As the film continues to cool, it is drawn through several sets of nip rollers to flatten it into lay-flat tubing, which can then be spooled or slit into two or more rolls of sheeting.

===Sheet/film extrusion===

Sheet/film extrusion is used to extrude plastic sheets or [[plastic film|films]] that are too thick to be blown. There are two types of dies used: T-shaped and coat hanger. The purpose of these dies is to reorient and guide the flow of polymer melt from a single round output from the extruder to a thin, flat planar flow. In both die types ensure constant, uniform flow across the entire cross sectional area of the die. Cooling is typically by pulling through a set of cooling rolls ([[calender]] or "chill" rolls). In sheet extrusion, these rolls not only deliver the necessary cooling but also determine sheet thickness and surface texture.<ref>{{Citation | title = Process, Methods and Features of plastic extrusion technology | url= http://www.sheetextruderline.com/article_10.htm }}</ref> Often co-extrusion is used to apply one or more layers on top of a base material to obtain specific properties such as UV-absorption, texture, oxygen permeation resistance, or energy reflection.

A common post-extrusion process for plastic sheet stock is [[thermoforming]], where the sheet is heated until soft (plastic), and formed via a mold into a new shape. When vacuum is used, this is often described as [[vacuum forming]]. Orientation (i.e. ability/ available density of the sheet to be drawn to the mold which can vary in depths from 1 to 36 inches typically) is highly important and greatly affects forming cycle times for most plastics.

===Tubing extrusion===
Extruded [[Tubing (material)|tubing]], such as PVC pipes, is manufactured using very similar dies as used in blown film extrusion. Positive pressure can be applied to the internal cavities through the pin, or negative pressure can be applied to the outside diameter using a vacuum sizer to ensure correct final dimensions. Additional lumens or holes may be introduced by adding the appropriate inner mandrels to the die.

[[File:A Boston Matthews Medical Extrusion Line.jpg|thumb|A Boston Matthews Medical Extrusion Line]]

Multi-layer tubing applications are also ever present within the automotive industry, plumbing & heating industry and packaging industry.

===Over jacketing extrusion===
Over jacketing extrusion allows for the application of an outer layer of plastic onto an existing wire or cable. This is the typical process for insulating wires.

There are two different types of die tooling used for coating over a wire, tubing (or jacketing) and pressure. In jacketing tooling, the polymer melt does not touch the inner wire until immediately before the die lips. In pressure tooling, the melt contacts the inner wire long before it reaches the die lips; this is done at a high pressure to ensure good adhesion of the melt. If intimate contact or adhesion is required between the new layer and existing wire, pressure tooling is used. If adhesion is not desired/necessary, jacketing tooling is used instead.

===Coextrusion===
Coextrusion is the extrusion of multiple layers of material simultaneously. This type of extrusion utilizes two or more extruders to melt and deliver a steady volumetric throughput of different viscous plastics to a single extrusion head (die) which will extrude the materials in the desired form. This technology is used on any of the processes described above (blown film, overjacketing, tubing, sheet). The layer thicknesses are controlled by the relative speeds and sizes of the individual extruders delivering the materials.

[[File:5 Layer Extrusion Technology.jpg|thumb|5 :5 Layer co-extrusion of cosmetic "squeeze" tube]]

In many real-world scenarios, a single polymer cannot meet all the demands of an application. Compound extrusion allows a blended material to be extruded, but coextrusion retains the separate materials as different layers in the extruded product, allowing appropriate placement of materials with differing properties such as oxygen permeability, strength, stiffness, and wear resistance.

===Extrusion coating===
[[Extrusion coating]] is using a blown or cast film process to coat an additional layer onto an existing rollstock of paper, foil or film. For example, this process can be used to improve the characteristics of paper by coating it with polyethylene to make it more resistant to water. The extruded layer can also be used as an adhesive to bring two other materials together. [[Tetrapak]] is a commercial example of this process.

==Compound extrusions==
Compounding extrusion is a process that mixes one or more polymers with additives to give plastic compounds. The feeds may be pellets, powder and/or liquids, but the product is usually in pellet form, to be used in other plastic-forming processes such as extrusion and injection molding. As with traditional extrusion, there is a wide range in machine sizes depending on application and desired throughput. While either single- or double-screw extruders may be used in traditional extrusion, the necessity of adequate mixing in compounding extrusion makes twin-screw extruders all but mandatory.<ref>{{Citation | last = Rosato | first = Marlene G. | title = Concise encyclopedia of plastics | page = 245 | publisher = Springer | year = 2000 | url = https://books.google.com/books?id=0g9QjxsbqmUC&pg=PA245 | isbn = 978-0-7923-8496-0}}.</ref><ref>{{Citation | last = Giles | first = Harold F. | last2 = Wagner | first2 = John R. | last3 = Mount | first3 = Eldridge M. | title = Extrusion: the definitive processing guide and handbook | page = 151 | publisher = William Andrew | year = 2005 | url = https://books.google.com/books?id=EUl2snQQ_OUC&pg=PT173 | isbn = 978-0-8155-1473-2}}.</ref>

==Types of extruder==

There are two sub-types of twin screw extruders: co-rotating and counter-rotating. This nomenclature refers to the relative direction each screw spins compared to the other. In co-rotation mode, both screws spin either clockwise or counter clockwise; in counter-rotation, one screw spins clockwise while the other spins counter clockwise. It has been shown that, for a given cross sectional area and degree of overlap (intermeshing), axial velocity and degree of mixing is higher in co-rotating twin extruders. However, pressure buildup is higher in counter-rotating extruders.<ref>Shah, A and Gupta, M (2004). "Comparison of the flow in co-rotating and counter-rotating twin-screw extruders". ANTEC, www.plasticflow.com.</ref> The screw design is commonly modular in that various conveying and mixing elements are arranged on the shafts to allow for rapid reconfiguration for a process change or replacement of individual components due to wear or corrosive damage. The machine sizes range from as small as 12 mm to as large as 380mm [12- Polymer Mixing by James White, pages 129-140]

==Advantages==

A great advantage of extrusion is that profiles such as pipes can be made to any length. If the material is sufficiently flexible, pipes can be made at long lengths even coiling on a reel. Another advantage is the extrusion of pipes with integrated coupler including rubber seal.<ref>{{Cite web|url = http://www.teppfa.eu/production-processes/|title = Production Processes|date = |accessdate = |website = |publisher = |last = TEPPFA, The European Plastic Pipes and Fittings Association|first = }}</ref>

==See also==
{{Div col}}
*[[3D printer extruder]]
*[[Extrusion coating]]
*[[Fused deposition modeling]]
*[[Industrial finishing]]
*[[Thermal cleaning]]
{{Div col end}}

==References==
{{reflist}}

===Bibliography===
*{{Citation | first1 = Robert H. | last1 = Todd | first2 = Dell K. | last2 = Allen | first3 = Leo | last3 = Alting | year = 1994 | title = Manufacturing Processes Reference Guide | publisher = Industrial Press Inc. | url = https://books.google.com/books?id=6x1smAf_PAcC | isbn = 0-8311-3049-0}}.

[[Category:Plastics industry]]
[[Category:Forming processes]]

Plastic extrusion

2018-08-13T18:37:03Z

173.165.237.1: /* Process */

{{More citations needed|date=October 2009}}
{{Use American English|date=April 2014}}
[[File:Extruder with sheet die.jpg|400px|thumb|right|Cross-section of a plastic extruder to show the screw]]

'''Plastics extrusion''' is a high-volume manufacturing process in which raw [[plastic]] is melted and formed into a continuous profile. Extrusion produces items such as pipe/tubing, [[weatherstripping]], fencing, [[deck railing]]s, [[window|window frames]], [[plastic film]]s and sheeting, [[thermoplastic]] coatings, and wire insulation.

This process starts by feeding plastic material (pellets, granules, flakes or powders) from a hopper into the barrel of the extruder. The material is gradually melted by the mechanical energy generated by turning screws and by heaters arranged along the barrel. The molten polymer is then forced into a die, which shapes the polymer into a shape that hardens during cooling.<ref>{{Cite web|url = http://www.teppfa.eu/production-processes/|title = Production Processes|date = |accessdate = |website = |publisher = |last = TEPPFA, The European Plastic Pipes and Fittings Association|first = }}</ref>

==History==
[[File:Production processes.png|thumb|Pipe extrusion]]
The first precursors to the modern extruder were developed in the early 19th century. In 1820, Thomas Hancock invented a rubber "masticator" designed to reclaim processed rubber scraps, and in 1836 Edwin Chaffee developed a two-roller machine to mix additives into [[rubber]].<ref>Tadmor and Gogos (2006). ‘’Principles of Polymer Processing’’. John Wiley and Sons. {{ISBN|978-0-471-38770-1}}</ref> The first thermoplastic extrusion was in 1935 by Paul Troester and his wife Ashley Gershoff in [[Hamburg]], Germany. Shortly after, Roberto Colombo of LMP developed the first twin screw extruders in Italy.<ref>{{Citation | last = Rauwendaal | first = Chris | title = Polymer Extrusion, 4th ed | page = | publisher = Hanser | year = 2001 | isbn = 3-446-21774-6}}.</ref>

==Process==
In the extrusion of plastics, the raw compound material is commonly in the form of nurdles (small beads, often called resin) that are gravity fed from a top mounted [[:wikt:hopper|hopper]] into the barrel of the extruder. Additives such as colorants and UV inhibitors (in either liquid or pellet form) are often used and can be mixed into the resin prior to arriving at the hopper. The process has much in common with [[injection molding|plastic injection molding]] from the point of the extruder technology, although it differs in that it is usually a continuous process. While [[pultrusion]] can offer many similar profiles in continuous lengths, usually with added reinforcing, this is achieved by pulling the finished product out of a die instead of extruding the polymer melt through a die.

The material enters through the feed throat (an opening near the rear of the barrel) and comes into contact with the screw. The rotating screw (normally turning at e.g. 120 rpm) forces the plastic beads forward into the heated barrel. The desired extrusion temperature is rarely equal to the set temperature of the barrel due to viscous heating and other effects. In most processes, a heating profile is set for the barrel in which three or more independent [[PID controller|PID]]-controlled heater zones gradually increase the temperature of the barrel from the rear (where the plastic enters) to the front. This allows the plastic beads to melt gradually as they are pushed through the barrel and lowers the risk of overheating which may cause degradation in the polymer.

Extra heat is contributed by the intense pressure and friction taking place inside the barrel. In fact, if an extrusion line is running certain materials fast enough, the heaters can be shut off and the melt temperature maintained by pressure and friction alone inside the barrel. In most extruders, cooling fans are present to keep the temperature below a set value if too much heat is generated. If forced air cooling proves insufficient then cast-in cooling jackets are employed.

[[File:Extruder section.jpg|450px|thumb|left|Plastic extruder cut in half to show the components]]

At the front of the barrel, the [[wikt:molten|molten]] plastic leaves the screw and travels through a screen pack to remove any contaminants in the melt. The screens are reinforced by a breaker plate (a thick metal puck with many holes drilled through it) since the pressure at this point can exceed 5,000 [[Pound-force per square inch|psi]] (34 [[MPa]]). The screen pack/breaker plate assembly also serves to create [[back pressure]] in the barrel. Back pressure is required for uniform melting and proper mixing of the polymer, and how much pressure is generated can be "tweaked" by varying screen pack composition (the number of screens, their wire weave size, and other parameters). This breaker plate and screen pack combination also eliminates the "rotational memory" of the molten plastic and creates instead, "longitudinal memory".

After passing through the breaker plate molten plastic enters the die. The die is what gives the final product its profile and must be designed so that the molten plastic evenly flows from a cylindrical profile, to the product's profile shape. Uneven flow at this stage can produce a product with unwanted residual stresses at certain points in the profile which can cause warping upon cooling. A wide variety of shapes can be created, restricted to continuous profiles.

The product must now be cooled and this is usually achieved by pulling the extrudate through a water bath. Plastics are very good thermal insulators and are therefore difficult to cool quickly. Compared to [[steel]], plastic conducts its heat away 2,000 times more slowly. In a tube or pipe extrusion line, a sealed water bath is acted upon by a carefully controlled vacuum to keep the newly formed and still molten tube or pipe from collapsing. For products such as plastic sheeting, the cooling is achieved by pulling through a set of cooling rolls. For films and very thin sheeting, air cooling can be effective as an initial cooling stage, as in blown film extrusion.

Plastic extruders are also extensively used to reprocess recycled [[plastic pollution|plastic waste]] or other raw materials after cleaning, sorting and/or blending. This material is commonly extruded into filaments suitable for chopping into the bead or pellet stock to use as a precursor for further processing.

==Screw design==
There are five possible zones in a thermoplastic screw. Since terminology is not standardized in the industry, different names may refer to these zones. Different types of polymer will have differing screw designs, some not incorporating all of the possible zones.

[[File:Plastic extruder screw.jpg|600px|thumb|centre|A simple plastic extrusion screw]]

[[File:Extruder Screws From Boston Matthews.jpg|thumb|Extruder screws From Boston Matthews]]

Most screws have these three zones:
* Feed zone (also called the solids conveying zone): this zone feeds the resin into the extruder, and the channel depth is usually the same throughout the zone.
* Melting zone (also called the transition or compression zone): most of the polymer is melted in this section, and the channel depth gets progressively smaller.
* Metering zone (also called the melt conveying zone): this zone melts the last particles and mixes to a uniform temperature and composition. Like the feed zone, the channel depth is constant throughout this zone.
In addition, a vented (two-stage) screw will have:
* Decompression zone. In this zone, about two-thirds down the screw, the channel suddenly gets deeper, which relieves the pressure and allows any trapped gases (moisture, air, solvents, or reactants) to be drawn out by vacuum.
* Second metering zone. This zone is similar to the first metering zone, but with greater channel depth. It serves to repressurize the melt to get it through the resistance of the screens and the die.

Often screw length is referenced to its diameter as L:D ratio. For instance, a {{convert|6|in|mm|adj=on}} diameter screw at 24:1 will be 144 inches (12 ft) long, and at 32:1 it is 192 inches (16 ft) long. An L:D ratio of 25:1 is common, but some machines go up to 40:1 for more mixing and more output at the same screw diameter. Two-stage (vented) screws are typically 36:1 to account for the two extra zones.

Each zone is equipped with one or more [[thermocouple]]s or [[Resistance temperature detector|RTDs]] in the barrel wall for temperature control. The "temperature profile" i.e., the temperature of each zone is very important to the quality and characteristics of the final extrudate.

==Typical extrusion materials==
Typical plastic materials that are used in extrusion include but are not limited to: [[polyethylene]] (PE), [[polypropylene]], [[acetal]], [[acrylic resin|acrylic]], [[nylon]] (polyamides), [[polystyrene]], [[polyvinyl chloride]] (PVC), [[acrylonitrile butadiene styrene]] (ABS) and [[polycarbonate]].<ref name="todd">{{harvnb|Todd|Allen|Alting|1994|pp=223–227}}.</ref>

==Die types==

{{Main|Die forming (plastics)}}

There are a variety of dies used in plastics extrusion. While there can be significant differences between die types and complexity, all dies allow for the continuous extrusion of polymer melt, as opposed to non-continuous processing such as [[injection molding]].

===Blown film extrusion===
[[File:Film extrusion.jpg|thumb|Blow extrusion of plastic film]]

The manufacture of [[plastic film]] for products such as [[shopping bag]]s and continuous sheeting is achieved using a [[blown film]] line.<ref>{{cite web|title=HOW TO SOLVE BLOWN FILM PROBLEMS|url=http://www.lyondellbasell.com/techlit/techlit/Handbooks%20and%20Manuals/BlownFilmProblems.pdf|publisher=Lyondell Chemical Company|accessdate=31 August 2012}}</ref>

This process is the same as a regular extrusion process up until the die. There are three main types of dies used in this process: annular (or crosshead), spider, and spiral. Annular dies are the simplest, and rely on the polymer melt channeling around the entire cross section of the die before exiting the die; this can result in uneven flow. Spider dies consist of a central mandrel attached to the outer die ring via a number of "legs"; while flow is more symmetrical than in annular dies, a number of weld lines are produced which weaken the film. Spiral dies remove the issue of weld lines and asymmetrical flow, but are by far the most complex.<ref>{{cite book|title=Small Scale Recycling of Plastics|author=John Vogler|pages=6–7|publisher=Intermediate Technology Publication|year=1984}}</ref>

The melt is cooled somewhat before leaving the die to yield a weak semi-solid tube. This tube's diameter is rapidly expanded via air pressure, and the tube is drawn upwards with rollers, stretching the plastic in both the transverse and draw directions. The drawing and blowing cause the film to be thinner than the extruded tube, and also preferentially aligns the polymer molecular chains in the direction that sees the most [[Elastic and plastic strain|plastic strain]]. If the film is drawn more than it is blown (the final tube diameter is close to the extruded diameter) the polymer molecules will be highly aligned with the draw direction, making a film that is strong in that direction, but weak in the transverse direction. A film that has significantly larger diameter than the extruded diameter will have more strength in the transverse direction, but less in the draw direction.

In the case of polyethylene and other semi-crystalline polymers, as the film cools it crystallizes at what is known as the frost line. As the film continues to cool, it is drawn through several sets of nip rollers to flatten it into lay-flat tubing, which can then be spooled or slit into two or more rolls of sheeting.

===Sheet/film extrusion===

Sheet/film extrusion is used to extrude plastic sheets or [[plastic film|films]] that are too thick to be blown. There are two types of dies used: T-shaped and coat hanger. The purpose of these dies is to reorient and guide the flow of polymer melt from a single round output from the extruder to a thin, flat planar flow. In both die types ensure constant, uniform flow across the entire cross sectional area of the die. Cooling is typically by pulling through a set of cooling rolls ([[calender]] or "chill" rolls). In sheet extrusion, these rolls not only deliver the necessary cooling but also determine sheet thickness and surface texture.<ref>{{Citation | title = Process, Methods and Features of plastic extrusion technology | url= http://www.sheetextruderline.com/article_10.htm }}</ref> Often co-extrusion is used to apply one or more layers on top of a base material to obtain specific properties such as UV-absorption, texture, oxygen permeation resistance, or energy reflection.

A common post-extrusion process for plastic sheet stock is [[thermoforming]], where the sheet is heated until soft (plastic), and formed via a mold into a new shape. When vacuum is used, this is often described as [[vacuum forming]]. Orientation (i.e. ability/ available density of the sheet to be drawn to the mold which can vary in depths from 1 to 36 inches typically) is highly important and greatly affects forming cycle times for most plastics.

===Tubing extrusion===
Extruded [[Tubing (material)|tubing]], such as PVC pipes, is manufactured using very similar dies as used in blown film extrusion. Positive pressure can be applied to the internal cavities through the pin, or negative pressure can be applied to the outside diameter using a vacuum sizer to ensure correct final dimensions. Additional lumens or holes may be introduced by adding the appropriate inner mandrels to the die.

[[File:A Boston Matthews Medical Extrusion Line.jpg|thumb|A Boston Matthews Medical Extrusion Line]]

Multi-layer tubing applications are also ever present within the automotive industry, plumbing & heating industry and packaging industry.

===Over jacketing extrusion===
Over jacketing extrusion allows for the application of an outer layer of plastic onto an existing wire or cable. This is the typical process for insulating wires.

There are two different types of die tooling used for coating over a wire, tubing (or jacketing) and pressure. In jacketing tooling, the polymer melt does not touch the inner wire until immediately before the die lips. In pressure tooling, the melt contacts the inner wire long before it reaches the die lips; this is done at a high pressure to ensure good adhesion of the melt. If intimate contact or adhesion is required between the new layer and existing wire, pressure tooling is used. If adhesion is not desired/necessary, jacketing tooling is used instead.

===Coextrusion===
Coextrusion is the extrusion of multiple layers of material simultaneously. This type of extrusion utilizes two or more extruders to melt and deliver a steady volumetric throughput of different viscous plastics to a single extrusion head (die) which will extrude the materials in the desired form. This technology is used on any of the processes described above (blown film, overjacketing, tubing, sheet). The layer thicknesses are controlled by the relative speeds and sizes of the individual extruders delivering the materials.

[[File:5 Layer Extrusion Technology.jpg|thumb|5 :5 Layer co-extrusion of cosmetic "squeeze" tube]]

In many real-world scenarios, a single polymer cannot meet all the demands of an application. Compound extrusion allows a blended material to be extruded, but coextrusion retains the separate materials as different layers in the extruded product, allowing appropriate placement of materials with differing properties such as oxygen permeability, strength, stiffness, and wear resistance.

===Extrusion coating===
[[Extrusion coating]] is using a blown or cast film process to coat an additional layer onto an existing rollstock of paper, foil or film. For example, this process can be used to improve the characteristics of paper by coating it with polyethylene to make it more resistant to water. The extruded layer can also be used as an adhesive to bring two other materials together. [[Tetrapak]] is a commercial example of this process.

==Compound extrusions==
Compounding extrusion is a process that mixes one or more polymers with additives to give plastic compounds. The feeds may be pellets, powder and/or liquids, but the product is usually in pellet form, to be used in other plastic-forming processes such as extrusion and injection molding. As with traditional extrusion, there is a wide range in machine sizes depending on application and desired throughput. While either single- or double-screw extruders may be used in traditional extrusion, the necessity of adequate mixing in compounding extrusion makes twin-screw extruders all but mandatory.<ref>{{Citation | last = Rosato | first = Marlene G. | title = Concise encyclopedia of plastics | page = 245 | publisher = Springer | year = 2000 | url = https://books.google.com/books?id=0g9QjxsbqmUC&pg=PA245 | isbn = 978-0-7923-8496-0}}.</ref><ref>{{Citation | last = Giles | first = Harold F. | last2 = Wagner | first2 = John R. | last3 = Mount | first3 = Eldridge M. | title = Extrusion: the definitive processing guide and handbook | page = 151 | publisher = William Andrew | year = 2005 | url = https://books.google.com/books?id=EUl2snQQ_OUC&pg=PT173 | isbn = 978-0-8155-1473-2}}.</ref>

==Types of extruder==

There are two sub-types of twin screw extruders: co-rotating and counter-rotating. This nomenclature refers to the relative direction each screw spins compared to the other. In co-rotation mode, both screws spin either clockwise or counter clockwise; in counter-rotation, one screw spins clockwise while the other spins counter clockwise. It has been shown that, for a given cross sectional area and degree of overlap (intermeshing), axial velocity and degree of mixing is higher in co-rotating twin extruders. However, pressure buildup is higher in counter-rotating extruders.<ref>Shah, A and Gupta, M (2004). "Comparison of the flow in co-rotating and counter-rotating twin-screw extruders". ANTEC, www.plasticflow.com.</ref> The screw design is commonly modular in that various conveying and mixing elements are arranged on the shafts to allow for rapid reconfiguration for a process change or replacement of individual components due to wear or corrosive damage. The machine sizes range from as small as 12 mm to as large as 380mm [12- Polymer Mixing by James White, pages 129-140]

==Advantages==

A great advantage of extrusion is that profiles such as pipes can be made to any length. If the material is sufficiently flexible, pipes can be made at long lengths even coiling on a reel. Another advantage is the extrusion of pipes with integrated coupler including rubber seal.<ref>{{Cite web|url = http://www.teppfa.eu/production-processes/|title = Production Processes|date = |accessdate = |website = |publisher = |last = TEPPFA, The European Plastic Pipes and Fittings Association|first = }}</ref>

==See also==
{{Div col}}
*[[3D printer extruder]]
*[[Extrusion coating]]
*[[Fused deposition modeling]]
*[[Industrial finishing]]
*[[Thermal cleaning]]
{{Div col end}}

==References==
{{reflist}}

===Bibliography===
*{{Citation | first1 = Robert H. | last1 = Todd | first2 = Dell K. | last2 = Allen | first3 = Leo | last3 = Alting | year = 1994 | title = Manufacturing Processes Reference Guide | publisher = Industrial Press Inc. | url = https://books.google.com/books?id=6x1smAf_PAcC | isbn = 0-8311-3049-0}}.

[[Category:Plastics industry]]
[[Category:Forming processes]]

Workweek and weekend

2018-08-13T15:26:35Z

173.165.237.1: /* Friday weekend (One day weekend) */

{{redirect|Weekend}}
{{See also|Working time}}
{{Use mdy dates|date=December 2014}}
{{refimprove|date=January 2014}}
[[File:Changfu Bridge on Weekend.jpg|thumb|right|200px|In some countries, [[market (place)|markets]] are held on weekends. Pictured is the Chanfu Bridge market in China.]]
{{Labour|expanded=rights|sp=uk}}
The '''workweek''' and '''weekend''' are those complementary parts of the [[week]] devoted to [[Labour (economics)|labor]] and [[Leisure|rest]], respectively. The legal '''working week''' ([[British English]]), or '''workweek''' ([[American English]]), is the part of the seven-day week devoted to labor. In most of the [[Western world]], it is [[Monday]] to [[Friday]]; the '''weekend''' is [[Saturday]] and [[Sunday]]. A '''weekday''' or '''workday''' is any day of the working week. Other institutions often follow the pattern, such as places of [[education]]. Sometimes the term “weekend” is expanded to include the time after work hours on the last workday of the week; e.g. Friday evening is often referred to as the start of the weekend.

In some Christian traditions, [[Sunday]] is the "[[Lord's Day|day of rest and worship]]". [[Judaism|Jewish]] ''[[Shabbat]]'' or [[Biblical Sabbath (Hebrew)|Biblical Sabbath]] lasts from sunset on [[Friday]] to the fall of full darkness on [[Saturday]]; as a result, the weekend in Israel is observed on Friday–Saturday. Some Muslim-majority countries historically had a Thursday–Friday or Friday–Saturday weekend; however, recently many such countries have shifted from Thursday–Friday to Friday–Saturday, or to Saturday–Sunday.

The [[Christian Sabbath]] was just one day each week, but the preceding day (the Jewish Sabbath) came to be taken as a holiday as well in the twentieth century. This shift has been accompanied by a reduction in the total number of hours worked per week, following changes in employer expectations. The present-day concept of the 'week-end' first arose in the industrial north of Britain in the early part of nineteenth century<ref name="etymonline.com">http://www.etymonline.com/index.php?term=weekend</ref> and was originally a voluntary arrangement between factory owners and workers allowing Saturday afternoon off from 2pm in agreement that staff would be available for work sober and refreshed on Monday morning.<ref name="ReferenceA">Waiting for the Weekend, Witold Rybzinski, 1991</ref> The Amalgamated Clothing Workers of America Union was the first to successfully demand a five-day work week in 1929.

Most countries have adopted a two-day weekend, however, the days of the weekend differ according to religious tradition, i.e. either Thursday–Friday, Friday–Saturday, or Saturday–Sunday, with the previous evening post-work often considered part of the weekend. Proposals have continued to be put forward for further reductions in the number of days or hours worked per week, on the basis of predicted social and economic benefits.
{{TOC limit|3}}

== History ==
{{Labour|expanded=rights|sp=uk}}
{{expand section|date=September 2013}}
A continuous seven-day cycle that runs throughout history paying no attention whatsoever to the phases of the moon, having a fixed day of rest, was probably first practiced in [[Judaism]], dated to the 6th century BC at the latest.<ref>{{Cite book |url=https://books.google.com/books?id=Cd5ZjRsNj4sC&pg=PA11#v=onepage&q&f=false |title=The Seven Day Circle: The History and Meaning of the Week |last=[[Eviatar Zerubavel]] |first= |date=1989-03-15 |publisher=University of Chicago Press |year= |isbn=978-0-226-98165-9 |location= |pages= |language=en}}</ref><ref>{{Cite book |url=https://books.google.com/books?id=g5c7C2rQzU0C&redir_esc=y |title=Christian Liturgy: Catholic and Evangelical |last=Senn |first=Frank C. |date=1997 |publisher=Fortress Press |isbn=978-0-8006-2726-3 |language=en}}</ref>

In [[Ancient Rome]], every eight days there was a [[nundinae]]. It was a market day, during which children were exempted from school<ref>The Teacher in Ancient Rome: The Magister and His World, Lisa Maurice, Lexington Books, 2013, pp. 26</ref> and [[plebs]] ceased from work in the field and came to the city to sell the produce of their labor<ref>Ancient Rome in So Many Words, Christopher Francese, Hippocrene Books, 2007, pp. 76</ref><ref>{{Cite web |url=http://penelope.uchicago.edu/Thayer/E/Roman/Texts/secondary/SMIGRA*/Nundinae.html |title=LacusCurtius • Roman Calendar — Nundinae (Smith's Dictionary, 1875) |website=penelope.uchicago.edu |language=en |access-date=2017-06-19}}</ref> or practice religious rites.{{Citation needed|reason=nundunae page says it's doubtful that this day had religious characteristics. || date=June 2017}}.

The [[French Revolutionary Calendar]] had ten-day weeks (called ''décades'') and allowed ''décadi'', one out of the ten days, as a leisure day.

In cultures with a [[four-day week]], the three [[Sabbath]]s derives from the culture's main religious tradition: Friday ([[Muslim Sabbath|Muslim]]), Saturday ([[Jewish Sabbath|Jewish]]), and Sunday ([[Christian Sabbath|Christian]]).

The present-day concept of the relatively longer 'week-end' first arose in the industrial north of Britain in the early part of nineteenth century<ref name="etymonline.com" /> and was originally a voluntary arrangement between factory owners and workers allowing Saturday afternoon off from 2pm in agreement that staff would be available for work sober and refreshed on Monday morning.<ref name="ReferenceA" /> The Oxford English Dictionary traces the first use of the term '''weekend''' to the British magazine ''[[Notes and Queries]]'' in 1879.<ref>{{cite news |last1=Stanton |first1=Kate |title=The origin of the weekend |url=http://www.smh.com.au/national/the-origin-of-the-weekend-20150807-giu3ay.html |accessdate=10 June 2017 |work=The Sydney Morning Herald |date=9 August 2015}}</ref>

In 1908, the first five-day workweek in [[United States|the United States]] was instituted by a [[New England]] [[cotton mill]] so that [[Jewish]] workers would not have to work on the Sabbath from sundown Friday to sundown Saturday.<ref name="theatlantic.com">{{cite web |author=Witold Rybczynski |url=https://www.theatlantic.com/past/docs/issues/91aug/rybczynski-p2.htm |title=Waiting for the Weekend |pages=35–52 |date=August 1991 |work=[[The Atlantic]]}}</ref> In 1926, [[Henry Ford]] began shutting down his [[car factory|automotive factories]] for all of Saturday and Sunday. In 1929, the [[Amalgamated Clothing Workers of America]] Union was the first union to demand a five-day workweek and receive it. After that, the rest of the [[United States]] slowly followed, but it was not until 1940, when a provision of the 1938 [[Fair Labor Standards Act of 1938|Fair Labor Standards Act]] mandating a maximum 40-hour workweek went into effect, that the two-day weekend was adopted nationwide.<ref name="theatlantic.com" />

Over the succeeding decades, particularly in the 1940s, 1950s, and 1960s, an increasing number of countries adopted either a Friday–Saturday or Saturday–Sunday weekend to harmonize with international markets. A series of workweek reforms in the mid-to-late 2000s and early 2010s brought much of the [[Arab World]] in synchronization with the majority of countries around the world, in terms of working hours, the length of the workweek, and the days of the weekend. The [[International Labour Organization]] (ILO) currently defines a workweek exceeding 48 hours as excessive. A 2007 study by the ILO found that at least 614.2 million people around the world were working excessive hours.<ref>{{cite web |last=Sahadi |first=Jeanne |url=http://money.cnn.com/2007/06/07/news/ilo_study/ |title=22% of workers work more than 48 hours a week, study finds – Jun. 7, 2007 |publisher=Money.cnn.com |date=2007-06-07 |accessdate=2016-09-10}}</ref>

== Length ==
[[File:Almost empty calendar.JPG|thumb|right|200px|This day planner chart (which can be used for any months) shows the workweek days as white boxes and the weekend days as light blue-coloured boxes.]]
Actual workweek lengths have been falling in the developed world. Every reduction of the length of the workweek has been accompanied by an increase in real per-capita income.<ref name=gapminder>Gapminder Foundation (2011) [http://www.gapminder.org/world/#$majorMode=chart$is;shi=t;ly=2003;lb=f;il=t;fs=11;al=30;stl=t;st=t;nsl=t;se=t$wst;tts=C$ts;sp=5.59290322580644;ti=2007$zpv;v=0$inc_x;mmid=XCOORDS;iid=phAwcNAVuyj1jiMAkmq1iMg;by=ind$inc_y;mmid=YCOORDS;iid=rdCufG2vozTpKw7TBGbyoWw;by=ind$inc_s;uniValue=8.21;iid=phAwcNAVuyj0XOoBL_n5tAQ;by=ind$inc_c;uniValue=255;gid=CATID0;by=grp$map_x;scale=log;dataMin=295;dataMax=79210$map_y;scale=lin;dataMin=26;dataMax=56$map_s;sma=49;smi=2.65$cd;bd=0$inds=i239_t001980,,,,;i156_t001987,,,,;i168_t001980,,,,;i110_t001980,,,,;i117_t001980,,,,;i143_t001990,,,,;i238_t001980,,,, "Gapminder World" graph of working hours per week plotted against purchasing power- and inflation-adjusted GDP per capita over time] {{webarchive |url=https://web.archive.org/web/20161127055214/http://www.gapminder.org/world/#$majorMode=chart$is;shi=t;ly=2003;lb=f;il=t;fs=11;al=30;stl=t;st=t;nsl=t;se=t$wst;tts=C$ts;sp=5.59290322580644;ti=2007$zpv;v=0$inc_x;mmid=XCOORDS;iid=phAwcNAVuyj1jiMAkmq1iMg;by=ind$inc_y;mmid=YCOORDS;iid=rdCufG2vozTpKw7TBGbyoWw;by=ind$inc_s;uniValue=8.21;iid=phAwcNAVuyj0XOoBL_n5tAQ;by=ind$inc_c;uniValue=255;gid=CATID0;by=grp$map_x;scale=log;dataMin=295;dataMax=79210$map_y;scale=lin;dataMin=26;dataMax=56$map_s;sma=49;smi=2.65$cd;bd=0$inds=i239_t001980,,,,;i156_t001987,,,,;i168_t001980,,,,;i110_t001980,,,,;i117_t001980,,,,;i143_t001990,,,,;i238_t001980,,,, |date=November 27, 2016 }} ''gapminder.org''</ref>{{verify source|date=September 2015}} In the [[United States]], the workweek length reduced slowly from before the Civil War to the turn of the 20th century. A rapid reduction took place from 1900 to 1920, especially between 1913 and 1919, when weekly hours fell by about eight percent.<ref name=hunnicutt>Hunnicutt, B.K. (1984) [http://www.uiowa.edu/~lsa/bkh/lla/eosh.htm "The End of Shorter Hours"] {{webarchive |url=https://web.archive.org/web/20150321034221/http://www.uiowa.edu/~lsa/bkh/lla/eosh.htm |date=March 21, 2015 }} ''Labor History'' '''25''':373–404</ref> In 1926, [[Henry Ford]] standardized on a five-day workweek, instead of the prevalent six days, without reducing employees' pay.<ref name=lombardo>Lombardo, C.N. (February 4, 2010) [http://www.hrhero.com/hl/articles/2010/02/04/shorter-workweek-in-a-tough-economy/ "Shorter Workweek in a Tough Economy"] {{webarchive |url=https://web.archive.org/web/20161128134109/http://www.hrhero.com/hl/articles/2010/02/04/shorter-workweek-in-a-tough-economy/ |date=November 28, 2016 }} ''Wisconsin Employment Law Letter'' (hrhero.com)</ref> Hours worked stabilized at about 49 per week during the 1920s, and during the [[Great Depression]] fell below 40.<ref name=hunnicutt /> During the Depression, President [[Herbert Hoover]] called for a reduction in work hours in lieu of layoffs. Later, President [[Franklin Roosevelt]] signed the [[Fair Labor Standards Act of 1938]], which established a five-day, 40-hour workweek for many workers.<ref name=lombardo /> The proportion of people working very long weeks has since risen, and the full-time employment of women has increased dramatically.<ref name=rones>Rones ''et al.'' (1997) [http://heinonline.org/HOL/LandingPage?collection=journals&handle=hein.journals/month120&div=32&id=&page= "Trends in Hours of Work since the Mid-1970s"] {{webarchive|url=https://web.archive.org/web/20160624123602/http://heinonline.org/HOL/LandingPage?collection=journals&handle=hein.journals%2Fmonth120&div=32&id=&page= |date=June 24, 2016 }} ''Monthly Labor Review'' '''120'''(3):3–12</ref>

The [[New Economics Foundation]] has recommended moving to a 21-hour standard workweek to address problems with unemployment, high carbon emissions, low well-being, entrenched inequalities, overworking, family care, and the general lack of free time.<ref name=lombardo /><ref name="nef21">{{cite web |last1=Coote |first1=Anna |last2=Franklin |first2=Jane |last3=Simms |first3=Andrew |title=21 hours: Why a shorter working week can help us all to flourish in the 21st century |url=http://neweconomics.org/page/-/files/21_Hours.pdf |publisher=New Economics Foundation |accessdate=18 October 2016 |ref=nef21 |archiveurl=https://web.archive.org/web/20160209144546/http://b.3cdn.net/nefoundation/f49406d81b9ed9c977_p1m6ibgje.pdf |archivedate=9 February 2016 |location=London |date=February 2010 |isbn=978-1-904882-70-1}}</ref><ref name=guardian>Stuart, H. (January 7, 2012) [https://www.theguardian.com/society/2012/jan/08/cut-working-week-urges-thinktank "Cut the working week to a maximum of 20 hours, urge top economists"] {{webarchive |url=https://web.archive.org/web/20121120065059/http://www.guardian.co.uk/society/2012/jan/08/cut-working-week-urges-thinktank |date=November 20, 2012 }} ''The Guardian''</ref><ref name=gam>Schachter, H. (February 10, 2012) [https://www.theglobeandmail.com/report-on-business/careers/management/morning-manager/save-the-world-with-a-3-day-work-week/article2332609/ "Save the world with a 3-day work week"] {{webarchive |url=https://web.archive.org/web/20160505185931/http://www.theglobeandmail.com/report-on-business/careers/management/morning-manager/save-the-world-with-a-3-day-work-week/article2332609/ |date=May 5, 2016 }} ''Globe and Mail''</ref><ref name=baker>Baker, D. (January 27, 2009) [http://www.nydailynews.com/opinion/pass-stimulus-shorten-work-week-article-1.425158 "Pass the stimulus – then help shorten the work week"] {{webarchive |url=https://web.archive.org/web/20160304101541/http://www.nydailynews.com/opinion/pass-stimulus-shorten-work-week-article-1.425158 |date=March 4, 2016 }} ''New York Daily News''</ref><ref name=abate>Abate, T. (July 11, 2010) [http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2010/07/10/BUAG1EC1MH.DTL "Get to Work: Want more jobs? Shorten the workweek"] {{webarchive|url=https://web.archive.org/web/20100712203928/http://www.sfgate.com/cgi-bin/article.cgi?f=%2Fc%2Fa%2F2010%2F07%2F10%2FBUAG1EC1MH.DTL |date=July 12, 2010 }} ''San Francisco Chronicle'' page D-3</ref> The [[Center for Economic and Policy Research]] states that reducing the length of the work week would slow [[climate change]] and have other environmental benefits.<ref>[http://www.cepr.net/documents/publications/climate-change-workshare-2013-02.pdf "Reduced Work Hours as a Means of Slowing Climate Change"] {{webarchive |url=https://web.archive.org/web/20160509143743/http://www.cepr.net/documents/publications/climate-change-workshare-2013-02.pdf |date=May 9, 2016 }} David Rosnick, February 2013</ref>

== Around the world ==
(Countries listed alphabetically. Some countries have Saturday a normal school day. Some countries appear under the subsections for [[#Muslim countries|Muslim countries]] and the [[#EU|European Union]].)


{| class="wikitable sortable"
|-
! Nation !! Typical Hours per Week !! Working week !! Typical hours worked (Maximum per day)
|-
| Afghanistan || 40 || Sunday–Thursday || 8
|-
| Albania || 40 || Monday–Friday || 8
|-
| Algeria || 40 || Sunday–Thursday || 8
|-
| Angola || 40 || Monday–Friday || 8
|-
| Argentina || 40 || Monday–Friday || 8
|-
| Armenia || 40 || Monday–Friday || 8
|-
| Azerbaijan || 40 || Monday–Friday || 8
|-
| Austria || 38.5 || Monday–Friday || 7.7
|-
| Australia || 38<ref>{{cite web |url=https://www.fairwork.gov.au/how-we-will-help/templates-and-guides/fact-sheets/minimum-workplace-entitlements/maximum-weekly-hours#maximum-weekly-work-hours |title=Welcome to the Fair Work Ombudsman website |last=Ombudsman |first=Fair Work |website=Fair Work Ombudsman |access-date=2016-07-20}}</ref> || Monday–Friday || 7.6
|-
| Bahrain || 40 || Sunday–Thursday || 8 (6 during [[Ramadan]] for Muslim employees)<ref>Art.51-b of 2012 Labor Law, http://lmra.bh/portal/files/cms/shared/file/labour%20law%202012.pdf</ref>
|-
| Bangladesh || 40 || Government offices and Banks: Sunday-Thursday
Else: Saturday-Thursday
| 8
|-
| Benin || 40 || Monday–Friday || 8
|-
| Belarus || 40 || Monday–Friday || 8
|-
| Belgium || 38 || Monday–Friday || 7.6
|-
| Brazil || 44 || Monday–Friday || 8.5
|-
| Brunei Darussalam || 40 || Monday–Thursday and Saturday || 8
|-
| Burundi || 50 || Monday–Friday || 10
|-
| Bulgaria || 40 || Monday–Friday || 8
|-
| Canada || 40 || Monday–Friday || 8
|- day.
| Cameroon || 50 || Monday–Friday || 10
|-
| Chile || 45 || Monday–Friday || 9
|-
| China || 42|| Monday–Friday || 8
|-
| Croatia || 40 || Monday–Friday || 8
|-
| Colombia || 48 || Monday–Friday /
Monday–Saturday
| 8
|-
| Costa Rica || 48 || Monday–Friday || 8
|-
| Czech Republic || 40 || Monday–Friday || 8
|-
| Denmark || 37 || Monday–Friday || 7.4
|-
| Djibouti || 40 || Saturday–Thursday || 6.7
|-
| Dominican Republic || 40 || Monday-Friday || 8
|-
| Egypt || 40 (30 during [[Ramadan]]) || Sunday–Thursday || 8 (6 during [[Ramadan]])
|-
| Ethiopia || 40 || Monday–Friday || 8
|-
| Estonia || 40 || Monday–Friday || 8
|-
| Equatorial Guinea || 48 || Monday–Saturday || 8
|-
| Finland || 38 || Monday–Friday || 8
|-
| France || 35 || Monday–Friday || 7
|-
| Gabon || 40 || Monday–Friday || 8
|-
| Gambia || 40 || Monday–Friday || 8
|-
| Germany || 40 || Monday–Friday || 8
|-
| Ghana || 40 || Monday–Friday || 8
|-
| Greece || 40 || Monday–Friday || 8
|-
| Hungary || 40 || Monday–Friday || 8
|-
| Hong Kong || 40-48 || Monday–Saturday || 8 (many people work on Saturday either a half-day or full-day)
|-
| India || 45-60 || Government offices and IT industry: Monday-Friday
Else: Monday–Saturday Sometimes: Monday
| 9 (including 1 hour lunch break) most of the Businesses are open on Saturdays. So often it is Monday-Saturday.
|-
| Indonesia || 40 || Monday–Friday || 8, many people work a 6-day week with 7-hour days.
|-
| Iran || 45 || Saturday-Thursday/Saturday-Wednesday ||8, (except 5-hours on thursday)
|-
| Iraq || 40 || Sunday–Thursday || 8
|-
| Ireland || 40 || Monday–Friday || 8
|-
| Israel || 42 || Sunday–Thursday || 8.4. Some people have a partial six-day workweek.
|-
| Italy || 40 || Monday–Friday || 8
|-
| Côte d'Ivoire || 40 || Monday–Friday || 8
|-
| Japan || 40 || Monday–Friday || 8
|-
| Jordan || 45 || Sunday–Thursday || 9
|-
| Kazakhstan || 40 || Monday–Friday || 8
|-
| Kuwait || 40 || Sunday–Thursday || 8
|-
| Kenya || 40 || Monday–Friday || 8
|-
| Lao People’s Democratic Republic || 40 || Monday–Friday || 8
|-
| Latvia || 40 || Monday–Friday || 8
|-
| Lebanon || 40 || Monday-Friday || 8, Most of the people have a six-day workweek, with Saturday as a partial workday.
|-
| Lesotho || 40 || Monday–Friday || 8
|-
| Libya || 40 || Sunday–Thursday || 8
|-
| Lithuania || 40 || Monday–Friday || 8
|-
| Madagascar || 40 || Monday–Friday || 8
|-
| Maldives || 40 || Sunday–Thursday || 8
|-
| Malawi || 40 || Monday–Friday || 8
|-
| Mali || 40 || Monday–Friday || 8
|-
| Malta || 40 || Monday–Friday || 8
|-
| Mauritania || 40 || Monday–Friday || 8
|-
| Malaysia || 40 || Sunday–Thursday ([[Johor]], [[Kedah]], [[Kelantan]], and [[Terengganu]]) Monday–Friday ([[Federal Territory of Malaysia]], [[Sabah]], [[Sarawak]], [[Pahang]], [[Malacca]], [[Negeri Sembilan]], [[Selangor]], [[Perak]], [[Penang]], [[Perlis]]) || 8
|-
| Mexico || 48 || Monday–Saturday || 8
|-
| Mongolia || 40 || Monday–Friday || 8
|-
| Morocco || 44 || Monday–Friday || 8
|-
| Mozambique || 40 || Monday–Friday || 8
|-
| Nepal || 48 || Sunday–Friday || 7 (5 on Friday and 6 in Winter)
|-
| The Netherlands || 40 || Monday–Friday || 8
|-
| New Zealand || 40 || Monday–Friday || 8<ref>{{cite web |url=http://www.legislation.govt.nz/act/public/1983/0115/latest/DLM74459.html |title=Minimum Wage Act 1983 |publisher=}}</ref>
|-
| Nigeria || 40 || Monday–Friday || 8
|-
| Norway || 37.5 || Monday–Friday || 7.5
|-
| Oman || 40 (30 during [[Ramadan]]) || Sunday–Thursday || 8 (6 during [[Ramadan]])
|-
| Pakistan || 45 & 54 || Monday–Friday || 9 (including 1 hour lunch break) most of the Businesses are open on Saturdays. So often it is Monday-Saturday.
|-
| Palestine || 45<ref>[http://carim-south.eu/carim/public/legaltexts/LE3PAL1204_1034.pdf The Labour Law No. (7) of 2000 AD, Article 68]</ref> || Saturday–Thursday <ref>[http://carim-south.eu/carim/public/legaltexts/LE3PAL1204_1034.pdf The Labour Law No. (7) of 2000 AD, Article 73]</ref>|| 8
|-
| Philippines || 48 || Monday–Saturday || 9 (including 1 hour lunch break)
|-
| Poland || 40 || Monday–Friday || 8
|-
| Portugal || 40 || Monday–Friday || 8
|-
| Qatar || 40 (25 During [[Ramadan]]) || Sunday–Thursday || 8 (5 during [[Ramadan]]) (Line staff work 48 hours of the week, Saturday-Thursday)
|-
| Romania || 40 || Monday–Friday || 8
|-
| Russia || 40 || Monday–Friday || 8
|-
| Rwanda || 40 || Monday–Friday || 8
|-
| Saudi Arabia || 40 (30 during [[Ramadan]]) || Sunday–Thursday || 8 (6 during [[Ramadan]] for Muslim employees)<ref>Art. 98 of Royal Decree No. M/51 dated 23 / 8 / 1426 H, https://www.boe.gov.sa/ViewSystemDetails.aspx?lang=en&SystemID=186&VersionID=201</ref>
|-
| Senegal || 40 || Monday–Friday || 8
|-
| Singapore || 44 || Monday–Friday || 9<ref>{{cite web |url=http://www.mom.gov.sg/employment-practices/hours-of-work-overtime-and-rest-days |title=Hours of work, overtime and rest days |publisher=}}</ref>
|-
| Slovakia (Slovak Republic) || 40 || Monday–Friday || 8
|-
| Spain || 40 || Monday–Friday || 8
|-
| Sri Lanka
| 40
| Monday–Friday
| 8
|-
| South Africa || 45 || Monday–Friday || 9<ref>{{cite web |url=http://www.labour.gov.za/DOL/legislation/acts/basic-guides/basic-guide-to-working-hours |title=Basic Guide to Working Hours |publisher=}}</ref>
|-
| South Korea || 40 || Monday–Friday || 8
|- Somalia || 45 || Saturday–Thursday || 8
|-
| Sudan || 40 || Sunday–Thursday || 8
|-
| Suriname || 39.5 || Monday–Friday || 8; Monday–Thursday 7:00 – 15:00 / Friday 7:00 – 14.30
|-
| Swaziland || 40 || Monday–Friday || 8
|-
| Sweden || 40 || Monday–Friday || 8
|-
| Switzerland || 42 || Monday–Friday || 8.4
|-
| Syria || 40 || Sunday–Thursday || 8
|-
| Seychelles || 40 || Monday–Friday || 8
|-
| Taiwan || 40 || Monday–Friday || 8; The Labor Standards Act stipulates that a worker shall have one mandatory day off and one flexible rest day in every seven days. See [[One fixed day off and one flexible rest day policy]].
|-
| Tanzania || 40 || Monday–Friday || 9
|-
| Togo || 40 || Monday–Friday || 8
|-
| Thailand || 40 || Monday–Friday || 8
|-
| Trinidad and Tobago || 40 || Monday–Friday || 8
|-
| Tunisia || 40 || Monday–Friday || 8
|-
| Turkey || 45 || Monday–Friday || 9
|-
| Ukraine || 40 || Monday–Friday || 8
|-
| United Arab Emirates || 40-45 (30 during [[Ramadan]]) || Sunday–Thursday (since September 2006<ref name=gulfnews>{{cite web |url=http://gulfnews.com/news/gulf/uae/general/friday-saturday-weekend-in-uae-from-september-1.237326 |title=Friday-Saturday weekend in UAE from September |publisher=}}</ref>) || 8 to 9 (regular hours minus 2 hours during [[Ramadan]] for all employees)<ref>Title 4, Art. 65 of the UAE Labor Law, http://www.mohre.gov.ae/en/labour-law/labour-law.aspx</ref>
|-
| United Kingdom || 40 || Monday–Friday || 8
|-
| United States || 40<ref>{{cite web |url=http://www.gallup.com/poll/175286/hour-workweek-actually-longer-seven-hours.aspx |title=The "40-Hour" Workweek Is Actually Longer -- by Seven Hours |author=Gallup, Inc. |work=Gallup.com}}</ref> || Monday–Friday || 8
|-
| Uganda || 48 || Monday–Saturday || 8
|-
| Vietnam || 40<ref>{{cite web |url=http://www.hocmon.hochiminhcity.gov.vn/Hnh%20nh%20bn%20tin/2011-11/TT%2033%20BLDTBXH_18%2011%202011_Lam%20viec%20thoi%20vu%20va%20Gia%20cong_Thay%20the%20TT%2016%202003.pdf |title=Ministry of Labour – Invalids and Social Affairs |author=Molisa |work=Molisa.gov.vn}}</ref> || Monday–Friday || 8
|-
| Yemen || 40 || Sunday–Thursday || 8
|-
| Congo, Democratic Republic of || 40 || Monday–Friday || 8
|-
| Zambia || 40 || Monday–Friday || 8
|-
| Zimbabwe
| 40
| Monday–Friday
| 8; Most people work half a day on Saturday
|}

=== Australia ===
In [[Australia]] the working week begins on Monday and terminates on Friday. An eight-hour working day is the norm. Working three weekdays a fortnight, for example, would therefore be approximately twenty-four hours (including or excluding traditional breaks tallying up to two hours). Some people work overtime with extra pay on offer for those that do, especially for weekend work. Shops open seven days a week in most states with opening hours from 9am to 5.30pm on weekdays, with some states having two "late night trading" nights on Thursday and Friday, when trading ceases at 9pm. Many supermarkets and low end department stores remain open until midnight and some trade 24/7. Restaurants and cinemas can open at all hours, save for some public holidays. Bars generally trade seven days a week but there are local municipal restrictions concerning trading hours. Banks trade on Monday to Friday, with some branches opening on Saturdays (and in some cases Sundays) in high demand areas. The Post Office (Australia Post) trades Monday to Friday as per retail shops but some retail post offices may trade on Saturdays and Sundays in some shopping centres. A notable exception to the above is South Australia whereby retail establishments are restricted to trading between the hours of 11am-5pm on Sundays.

=== Brazil ===
As a general rule, [[Brazil]] adopts a 44-hour working week, which typically begins on Monday and ends on Friday, with a Saturday-Sunday weekend. [[Brazilian Law]],<ref>Consolidação das Leis do Trabalho: http://www.planalto.gov.br/ccivil_03/decreto-lei/Del5452.htm</ref> however, also allows for shorter Monday-to-Friday working hours so employees can work on Saturdays or Sundays, as long as the weekly 44-hour limit is respected and the employee gets at least one weekend day. This is usually the case for malls, supermarkets and shops. The law also grants [[labor unions]] the right to negotiate different work weeks, within certain limits, which then become binding for that union's labor category. Overtime is allowed, limited to two extra hours a day, with an increase in pay.

=== Chile ===
The working week in [[Chile]] averages 45 hours, most often worked on a Monday-Friday schedule, but is not uncommon to work on Saturdays. Retail businesses mostly operate Monday through Saturday, with larger establishments being open seven days a week.

=== China (People's Republic) ===
In [[China]], there is a five-day Monday-Friday working week, prior to which work on Saturday was standard. China began the two-day Saturday–Sunday weekend on May 1, 1995. Most government employees work 5 days a week (including officials and industrial management). Most manufacturing facilities operate on Saturdays as well. However, most shops, museums, cinemas and commercial establishments open on Saturdays, Sundays and holidays. Banks are also open throughout the weekend and on most public holidays.

During the period of [[Public holidays in China|public holidays]], swapped holidays are common between the actual holiday and weekend, so a three-day or seven-day holiday periods are created. The nearby Saturday or Sunday may be changed to a normal working day. For example, on a three-day holiday period, if the actual holiday falls on a Tuesday, Monday will be swapped as a holiday, and citizens are required to work on the previous Saturday.

A number of provinces and municipalities across China, including Hebei, Jiangxi and Chongqing, have issued new policies, calling on companies to create 2.5-day weekends. Under the plan, government institutions, state-owned companies, joint-ventures and privately held companies are to be given incentives to allow their workers to take off at noon on Friday before coming back to the office on Monday.<ref>{{cite web |title=China to implement 2.5-day weekend this summer |url=http://www.chinadaily.com.cn/china/2016-02/03/content_23369098.htm |website=www.chinadaily.com.cn |access-date=2016-02-03 |last=江巍}}</ref>

==== Hong Kong SAR ====
In [[Hong Kong]], a typical working week for local enterprises begins on Monday and ends at 1pm on Saturday, although most employees have alternate Saturdays off. After the introduction of the five-day working week for the majority of government departments in 2006, most multinational enterprises and large local companies followed suit, extended the working day from 9am to 6pm so as to adopt a five-day work week. Despite the aforementioned official hours, many employees work overtime, and in the case of the financial industry in particular, working 12-hour days on a chronic basis is not uncommon.

Most commercial establishments in the retail sector such as restaurants, shops and cinemas, as well as public venues such as museums and libraries are open on Saturdays, Sundays and most public holidays. For schools, lessons are not normally held on Saturdays, but students may be required to go school on Saturdays for extra-curricular activities or make-up classes.

=== Colombia ===
In general, [[Colombia]] has a 48-hour working week. Depending on the business, people work five days for [http://www.mintrabajo.gov.co/preguntas-frecuentes/jornada-de-trabajo.html max 8 hours per day], typically Monday to Friday, or six days for eight hours a day, Monday to Saturday.<ref>{{Cite news |url=https://www.justlanded.com/english/Colombia/Colombia-Guide/Jobs/Legal-regulations-in-the-Colombian-job-market |title=Legal regulations in the Colombian job market |work=Just Landed |access-date=2017-06-19 |language=en}}</ref>

=== European Union members ===
{{Expand section|date=March 2009}}
In [[Europe]], the standard full-time working week begins on Monday and ends on Saturday. Most retail shops are open for business on Saturday. In Ireland, Italy, Finland, Sweden, the Netherlands and the former socialist states of Europe, large [[shopping center|shopping centres]] open on Sunday. 
In European countries such as Germany, there are laws regulating shop hours. With exceptions, shops must be closed on Sundays and from midnight until the early morning hours of every day.

==== Austria ====
The working week is Monday to Friday 8 hours per day. Shops are open on Saturday. By law, almost no shop is open on Sunday. However, exceptions have been made, for example for bakeries, petrol stations and shops at railway stations, especially in the largest cities (Vienna, Graz, Salzburg, Linz).

==== Belgium ====
The working week is Monday to Friday.
Working time must not exceed 8 hours per day and 38 hours per week (on average, annualised). Very few shops are open on Sunday.

==== Bulgaria ====
The working week is Monday to Friday, eight hours per day, forty hours per week. Most pharmacies, shops, bars, cafés, and restaurants will operate on Saturdays and Sundays.

==== Croatia ====
The working week is Monday to Friday, seven and a half hours per day (+ 30 minutes lunch break), 37.5 hours per week (or 40 hours per week if lunch breaks are included as working hours).
Most pharmacies, shops, bars, cafés, and restaurants are open on Saturday and Sunday.

==== Czech Republic ====
In the [[Czech Republic]], full-time employment is usually Monday to Friday, eight hours per day and forty hours per week.
Many shops and restaurants are open on Saturday and Sunday, but employees still usually work forty hours per week.

==== Denmark ====
[[Denmark]] has an official 37-hour working week, with primary work hours between 6:00 and 18:00, Monday to Friday. In public institutions, a 30-minute lunch break every day is included as per collective agreements, so that the actual required working time is 34.5 hours. In private companies, the 30-minute lunch break is normally not included. The workday is usually 7.5 hours Monday to Thursday and 7 hours on Friday. Some small shops are closed Monday.<ref name="Workindenmark">{{cite web |url=https://www.workindenmark.dk/en/Find_information/Information_for_job_seekers/Working_in_Denmark/Working_hours |title=Working hours |publisher=Workindenmark.dk (Danish Agency for Labour Retention and International Recruitment) |accessdate=April 30, 2012}}</ref>

==== Estonia ====
In [[Estonia]], the working week begins on Monday and ends on Friday. Usually a working week is forty hours.

==== Finland ====
In [[Finland]], the working week begins on Monday and ends on Friday. A full-time job is defined by law as being at least 32 and at most forty hours per week. In retail and restaurant occupations, among others, the weekly hours may be calculated as an average over three to ten weeks, depending on the employment contract. Banks and bureaus are closed on weekends. Most shops are open on Saturdays, while some are closed on Sundays.

==== France ====
The standard working week is Monday to Friday. Shops are also open on Saturday. Small shops may close on a weekday (generally Monday) to compensate workers for having worked on Saturday. By law, préfets may authorise a small number of specific shops to open on Sunday such as bars, cafés, restaurants, and bakeries, which are traditionally open every day but only during the morning on Sunday. Workers are not obliged to work on Sunday. School children have traditionally taken Wednesday off, or had only a half day, making up the time either with longer days for the rest of the week or sometimes a half day on Saturday. This practice was made much less common under new legislation rolled out over 2013–14.<ref>{{cite news |title=France: Weird about Wednesday |url=https://www.economist.com/news/europe/21586572-state-primary-schools-are-abandoning-their-four-day-week-weird-about-wednesday |work=[[The Economist]] |date=21 September 2013 |accessdate=18 January 2015}}</ref>

==== Greece ====
The standard working week is Monday to Friday. State jobs are from 07:00 until 15:00. Shops are open generally Mondays-Wednesdays from 09:30–15:00 and then from 17:30–21:00 and Tuesday-Thursday-Fridays 09:30-21:00. Saturdays generally 09:00-15:00. It is very rare for a shop to open on Sunday.

==== Hungary ====
In [[Hungary]] the working week begins on Monday and ends on Friday. Full-time employment is usually considered forty hours per week. For office workers, the work day usually begins between 8 and 9 o'clock and ends between 16:00 and 18:00, depending on the contract and lunch time agreements.

The forty-hour workweek of public servants includes lunch time. Their work schedule typically consists of 8.5 hours between Monday and Thursday (from 8:00 to 16:30) and 6 hours on Fridays (8:00–14:00).

==== Ireland ====
[[Republic of Ireland|Ireland]] has a working week from Monday to Friday, with core working hours from 09:00 to 17:30. Retail stores are usually open until 21:00 every Thursday. Many grocery stores, especially in urban areas, are open until 21:00 or later, and some supermarkets and convenience stores may open around the clock. Shops are generally open all day Saturday and a shorter day Sunday (usually 10:00–12:00 to 17:00–19:00).

==== Italy ====
In [[Italy]] the 40-hour rule applies: Monday to Friday, 09:00 to 18:00, with a one-hour break for lunch. Sunday is always a holiday; Saturday is seldom a work day at most companies and universities, but it is generally a regular day for elementary, middle, and high schools.

In the past, shops had a break from 13:00 to 16:00 and they were generally open until 19:00/20:00. Working times for shops have been changed recently and now are at the owner's discretion; malls are generally open Tuesday to Sunday 09:00 to 20:00, 15:00 to 20:00 on Monday, with no lunchtime closing.<ref>{{cite web |url=http://www.ricerca24.ilsole24ore.com/fc?cmd=static&chId=30&path=%2Fsearch%2Fsearch_engine.jsp&keyWords=liberalizzazione+orari+negozi&field=Titolo%7cTesto&id=&maxDocs=&orderByString=score+desc&criteria=0&pageNumber=1&simili=false&action=&chiaviSelezionate=&description=&flagPartialResult=&senv=r24&layout=r24 |title=liberalizzazione orari negozi – Cerca nel sito www.ilsole24ore.com |work=ilsole24ore.com}}</ref>

==== Latvia ====
[[Latvia]] has a Monday to Friday working week capped at forty hours.<ref>[http://www.vdi.gov.lv/index.php?zinas_id=6&lang_id=1&menu_id=13&start=0 Latvian State Labour Inspectorate]</ref> Shops are mostly open on weekends, many large retail chains having full working hours even on Sunday. Private enterprises usually hold hours from 9:00 to 18:00, however government institutions and others may have a shorter working day, ending at 17:00.

==== Luxembourg ====
The standard working week in [[Luxembourg]] is 40 hours per week with 8 hours per day.<ref>http://www.guichet.public.lu/entreprises/en/ressources-humaines/temps-travail/gestion/organisation/index.html</ref> Monday through Friday is the standard working week, though many shops and businesses open on Saturdays (though for somewhat restricted hours). Trading on Sundays is extremely restricted and generally limited to grocery stores opening on Sunday mornings.<ref>http://www.guichet.public.lu/entreprises/en/commerce/prix-horaires/horaires-d-ouverture/magasins-detail/index.html</ref> However, shops are allowed to open in Luxembourg City during the first Sunday of the month<ref>{{Cite web |url=http://www.visitluxembourg.com/en/place/marketsandrummagesales/sunday-shopping |title=Sunday shopping in Luxembourg City |website=www.visitluxembourg.com |language=en |access-date=2017-10-09}}</ref>, as well as in Luxembourg City and other larger towns on weekends towards the end of the year (Christmas shopping season)<ref>{{Cite web |url=http://www.luxembourg.public.lu/en/visiter/que-faire/shopping/index.html |title=Shopping – Luxembourg |last= |first= |date= |website= |archive-url= |archive-date= |dead-url= |access-date=}}</ref>. A few shopping malls located in the north of the country and in border towns (e.g. KNAUF<ref>{{Cite web |url=http://www.knaufshopping.lu |title=Knauf Center Pommerloch et Schmiede |website=www.knaufshopping.lu |access-date=2017-10-09}}</ref>, MASSEN<ref>{{Cite web |url=https://www.massen.lu |title=Shopping-Center Massen – Wemperhardt – Luxemburg – Enjoy shopping |website=Massen |language=de-DE |access-date=2017-10-09}}</ref> and Pall Center Pommerloch<ref>{{Cite web |url=http://www.pallcenter.lu/en/our-stores/ |title=Pall Center |last= |first= |date= |website= |archive-url= |archive-date= |dead-url= |access-date=}}</ref>) are also allowed to open almost every day of the year.

==== Netherlands ====
In the Netherlands, the standard working week is Monday to Friday (40 hours).<ref>{{cite web |title=More two-income couples with one full-time job and one large part-time job |url=https://www.cbs.nl/en-gb/news/2015/05/more-two-income-couples-with-one-full-time-job-and-one-large-part-time-job |website=CBS – Statistics Netherlands |publisher=CBS – Statistics Netherlands |accessdate=21 July 2016}}</ref> Shops are almost always open on Saturdays and often on Sundays.

==== Poland ====
The working week is Monday to Friday; 8 hours per day, 40 hours in total per week. Large malls are open on Saturday and Sunday; many small shops are closed on Sunday. SINCE 11 March 2018 all Malls and shops are close on Sunday trading is banned.

Under the new rules, trading will be banned on two Sundays a month.

The ban will be stepped up to three Sundays a month in 2019, while in 2020 trading will be prohibited on all Sundays except seven, including those in the run-up to Christmas and Easter.

March 11 will be the first Sunday on which trading is banned.

Bakeries, confectioners, petrol stations, florists, post offices, train stations and airports will be exempt from the ban.

Owners will be able to open their shops as long as they serve customers themselves.

Anyone infringing the new rules faces a fine of up to PLN 100,000 (EUR 23,900; USD 29,250). Repeat offenders may face a prison sentence

==== Portugal ====
The working week is Monday to Friday; 8 hours per day, 40 hours in total per week. Street shops are almost always open on Saturday mornings but shopping centres are typically open every day (including Saturdays and Sundays).

==== Romania ====
The working week is Monday to Friday; 8 hours per day, 40 hours in total per week. Shops are open on Saturday and Sunday. The weekend begins on Friday, and ends on Monday.

==== Slovakia ====
The working week is Monday to Friday; 8 hours per day, 40 hours in total per week. Large malls are open on Saturday and Sunday; many small shops are closed on Sunday. All shops are closed on public holidays.

==== Spain ====
The working week is Monday to Friday; 8 hours per day, 40 hours in total per week. The traditional opening hours are 9:00 to 13:00–14:00 and then 15:00–16:00 to 18:00 for most offices and workplaces. Most shops are open on Saturday mornings and many of the larger shopping malls are open all day Saturday and in some cities like Madrid, they are open most Sundays. Some restaurants, bars, and shops are closed Mondays, as Mondays are commonly a slow business day.<ref>Weekend spanish traditions – ''[http://escapadasdefindesemana.net/ escapadas de fin de semana]''</ref>

==== Sweden ====
In [[Sweden]], the standard working week is Monday to Friday, both for offices and industry workers. The standard workday is eight hours, although it may vary greatly between different fields and businesses. Most office workers have flexible working hours and can largely decide themselves on how to divide these over the week. The working week is regulated by ''Arbetstidslagen'' (''Work time law'') to a maximum of 40 hours per week.<ref>{{cite web |title=Arbetstidslagen |url=http://www.av.se/lagochratt/atl/kapitel02.aspx |publisher=Arbetsmiljöverket |accessdate=August 5, 2011 |deadurl=yes |archiveurl=https://web.archive.org/web/20130318050210/http://www.av.se/lagochratt/atl/kapitel02.aspx |archivedate=March 18, 2013 |df=mdy-all}}</ref> The 40-hour-week is however easily bypassed by overtime. The law allows a maximum of 200 hours overtime per year.<ref>{{cite web |title=Arbetstidslagen – Övertid |url=http://www.av.se/lagochratt/atl/Kapitel03.aspx |publisher=Arbetsmiljöverket |accessdate=August 5, 2011}}</ref> There is however no overseeing government agency; the law is often cited as toothless.{{citation needed|date=December 2012}}

Shops are almost always open on Saturdays and often on Sundays, supermarkets and shopping centres, so that employees there have to work. Traditionally, restaurants were closed on Mondays if they were opened during the weekend, but this has in recent years largely fallen out of practice. Many museums do however still remain closed on Mondays.

==== United Kingdom ====
The traditional business working week is from Monday to Friday (35 to 40 hours depending on contract). In retail, and other fields such as healthcare, days off might be taken on any day of the week. Employers can make their employees work every day of a week, although the employer is required to allow each employee breaks of either a continuous period of 24 hours every week or a continuous period of 48 hours every two weeks.

Laws for shop opening hours differ between Scotland and the rest of the UK. In England, Wales, and Northern Ireland, many shops and services are open on Saturdays and increasingly so on Sundays as well. In England and Wales, stores' maximum Sunday opening hours vary according to the total floor space of the store.<ref>{{cite web |url=http://www.bizhelp24.com/law/business-trading-hours-law.html |title=Working Hours – Business Trading Hours |publisher=}}</ref> In Scotland, however, there is no restriction in law on shop opening hours on a Sunday.

Under the EU [[Working Time Directive]], workers cannot be forced to work for more than 48 hours per week on average. However, the UK allows individuals to opt out if they so choose. Individuals can choose to opt in again after opting out, even if opting out was part of their employment contract. It is illegal to dismiss them or treat them unfairly for so doing – but they may be required to give up to 3 months notice to give the employer time to prepare, depending on what their employment contract says.<ref name="govuk-workingtime">{{cite web |url=https://www.gov.uk/maximum-weekly-working-hours/weekly-maximum-working-hours-and-opting-out |title=Maximum weekly working hours |publisher=HMG |accessdate=October 25, 2014 |date=June 27, 2014}}</ref>

The minimum holiday entitlement is now 28 days per year, but that can include public holidays, depending on the employee's contract.<ref>{{cite web |url=http://www.direct.gov.uk/en/Employment/Employees/Timeoffandholidays/DG_10029788 |title=Holiday entitlement |publisher=}}</ref> England & Wales have eight, Scotland has nine, and Northern Ireland has ten permanent public holidays each year.<ref>{{cite web |url=http://www.direct.gov.uk/en/Governmentcitizensandrights/LivingintheUK/DG_073741 |title=UK bank holidays |publisher=}}</ref><ref>[http://www.direct.gov.uk/en/Employment/Employees/WorkingHoursAndTimeOff/DG_10029426 Directgov: Working time limits (the 48-hour week)], business trading hours law.</ref> The 28 days holiday entitlement means that if the government creates a one-off public holiday in a given year, it is not necessarily a day off and it does not add 1 day to employees' holiday entitlement – unless the employer says otherwise, which some do.

=== Belarus ===
The working week is Monday to Friday.
Working time must not exceed 8 hours per day and 40 hours per week (on average, annualised).

=== India ===
The standard working week in [[India]] for most office jobs begins on Monday and ends on Saturday. The work schedule is 60 hours per week, Sunday being a rest day. However, most government offices and the software industry follow a five-day workweek.<ref>{{Cite book |url=https://books.google.com/books?id=RWcTBwAAQBAJ&lpg=PT38&ots=IT3sxY-MiS&dq=india%20%22work%20week%22%20(friday%20OR%20saturday)&hl=iw&pg=PT38#v=onepage&q=india%20%22work%20week%22%20(friday%20OR%20saturday)&f=false |title=bWise: Doing Business in India |last=Dunung |first=Sanjyot P. |date=2015-01-15 |publisher=Atma Global |isbn=978-0-9905459-2-7 |language=en}}</ref> All major industries along with services like transport, hospitality, healthcare etc. work in shifts.

Central government offices follow a five-day week. State governments follow half-day working on the first, third, and fifth Saturdays of each month and rest on the second and fourth Saturdays, except West Bengal's government which follows a Monday–Friday workweek. There is usually no half working day in the private sector and people work in two or three shifts of 8hours each.

Generally establishments other than those having pure desk jobs are open until late evening in most cities, offering more flexibility of time to visitors. Most stores are open for six or seven days a week. Retail shops in malls are open on all days. Doctors are mostly available in morning and evening in their clinics and at hospitals during the day. Doctors usually work twelve hour days, six-days a week. Senior doctors and surgeons work more. Most visiting doctors attached to hospitals visit on all days.

Many services are open till 8:00 pm or 9:00 pm. Most restaurants are open on all days. Small eateries open early and bigger ones open around 11:00 am. Most eateries close between 9:00 pm and 11:00 pm. Many highway restaurants called ''[[dhaba]]s'' are open for 24 hours a day. Dhabas are available in large numbers on all major state and national highways; outside city or village limits. Some highway fuel stations are open for 24 hours. Overall India works longer hours in most areas than most of the world and offers more flexibility of time for visitors.

=== Muslim countries ===

==== Thursday–Friday weekend ====
Friday is the Muslim holiday when [[Jumu'ah]] prayers take place. Most of the Middle Eastern countries and some other predominantly Muslim countries used to consider Thursday and Friday as their weekend. However, this weekend arrangement is no longer observed by a significant number of Muslim countries ([[Workweek and weekend#Friday–Saturday weekend|
see below]]).

==== Friday weekend (One day weekend) ====
Three countries in the Muslim world have Friday as the only weekend day and have a six-day working week.
* In [[Iran]], Thursday is half a day of work for most public offices and all schools are closed, but for most jobs, Thursday is a working day. Foreign companies normally have Friday and Saturday as their weekend.
* In [[Djibouti]], many offices also tend to open early – around 7:00 or 8:00, then closing at 13:00 or 14:00, especially during the summer due to the afternoon heat.

==== Friday–Saturday weekend ====
Following reforms in a number of [[Gulf Cooperation Council|Arab states in the Persian Gulf]] in the 2000s and 2010s, the Thursday–Friday weekend was replaced by the Friday–Saturday weekend. This change provided for the Muslim offering of Friday prayers and afforded more work days to coincide with the working calendars of international financial markets.
* [[Algeria]] (2009)<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/africa/8198365.stm |publisher=BBC News |title=Algeria switches weekend, again |date=August 14, 2009}}</ref>
* [[Afghanistan]] (2015)
* [[Bahrain]] (2006)
* [[Bangladesh]]
* [[Egypt]]<ref name="TSG">{{cite web |url=https://travel.state.gov/travel/cis_pa_tw/cis/cis_1144.html |title=Country Information |publisher=}}</ref>
* [[Iraq]] (2005–2006)<ref name="TSG" />
* [[Jordan]] (Week of January 8, 2000)<ref name="api_jordan">{{cite news |publisher=Associated Press International |title=Jordan shifts weekend to Friday-Saturday |date=December 25, 2000}}</ref><ref name="wfn">{{cite web |url=http://archive.wfn.org/2000/01/msg00078.html |title=Jordan Announces new Friday/Saturday Weekend |publisher=wfn.org |date=January 5, 2000 |accessdate=August 23, 2016}}</ref>
* [[Kuwait]] (2007)
* [[Libya]] (2005–2006)
* [[Malaysia]] (only in the states of [[Johor]], [[Kelantan]], [[Terengganu]], and [[Kedah]])
* [[Maldives]] (2013)
* [[Oman]] (2013)
* [[State of Palestine|Palestine]]
* [[Qatar]]
* [[Saudi Arabia]] (2013)<ref>{{cite web |url=http://www.voyage.gc.ca/dest/report-en.asp?country=258000 |title=Erreur 404 |publisher=Voyage.gc.ca |date=2016-04-27 |accessdate=2016-09-10}}</ref><ref>{{cite web |url=http://english.ahram.org.eg/NewsContent/2/8/74730/World/Region/Saudi-Arabia-changes-working-week-to-SunThurs-Offi.aspx |title=Saudi Arabia changes working week to Sun-Thurs: Official statement |work=ahram.org.eg}}</ref><ref>[http://www.spa.gov.sa/English/viewphotonews.php?id=1122964&pic=]{{dead link|date=September 2016}}</ref>
* [[Sudan]] (2008)
* [[Syria]] (2005–2006)<ref>{{cite web |url=http://www.syritour.com/content/en/travelfacts.asp |title=Travel Facts |last= |first= |date= |website=Syritour |publisher=Syritour.com |archive-url=https://web.archive.org/web/20080507172827/http://www.syritour.com/content/en/travelfacts.asp |archive-date=2005-05-07 |dead-url=yes |accessdate=2016-09-10}}</ref>
* [[United Arab Emirates]] (2006)<ref name="gulfnews" />
* [[Yemen]] (2013)<ref>{{cite web |url=http://www.yemenpost.net/Detail123456789.aspx?ID=3&SubID=7132&MainCat=3 |title=Yemen introduces its new weekend- Yemen Post English Newspaper Online |work=yemenpost.net}}</ref>

==== Saturday–Sunday weekend ====
Other countries with Muslim-majority populations or significant Muslim populations follow the Saturday–Sunday weekend, such as [[Indonesia]], [[Lebanon]], [[Turkey]], [[Tunisia]] and [[Morocco]]. While Friday is a working day, a long midday break is given to allow time for worship.
* [[Indonesia]] On Friday, due to prayer time for Muslims, the lunch break is extended up to 2 hours or more. Shopping malls are always open and very crowded on Saturday and Sunday. Thus, some banks offer weekend banking services, especially for branches located in or near shopping malls.
* [[Lebanon]] The working week is Monday to Friday; 8 hours per day, 40 hours in total per week. Some institutions, however, also work 4 hours on Saturdays . Large malls are open on Saturday and Sunday; many small shops close on Sunday.
* [[Malaysia]] (Federal Territories of [[Kuala Lumpur]], [[Labuan]] and [[Putrajaya]], [[Selangor]], [[Perak]], [[Penang]], [[Perlis]], [[Sarawak]], [[Sabah]], [[Pahang]], [[Malacca]], [[Negeri Sembilan]] except the states of [[Johor]], [[Kelantan]], [[Terengganu]] and [[Kedah]], which have a Friday–Saturday weekend)
* [[Mauritania]] (2014)<ref name="Mauritania weekend">{{cite web|url=https://www.bbc.com/news/blogs-news-from-elsewhere-29174054|title=weekend}}</ref>
* [[Morocco]] The working week is Monday to Friday, 8 hours per day, 40 hours in total per week.
* [[Pakistan]] follows the standard international 40-hour working week, from Monday to Friday, with Saturday and Sunday being the weekend.<ref name="Pakistan weekend">{{cite web |title=Pakistani Weekend Public Holidays Update |url=http://www.qppstudio.net/public-holidays-news/2010/pakistan_004010.htm |publisher=Reuters |accessdate=December 14, 2011 |date=April 24, 2010}}</ref> However, in many schools and enterprises, Friday is usually considered a half-day.
* [[Senegal]] The working week is Monday to Friday, with a large break on Friday afternoon.
* [[Tunisia]] The working week is Monday to Friday; 8 hours per day, 40 hours in total per week.
* [[Turkey]] Working above 45 hours is considered overtime, and the employer is required to pay 1.5x the hourly wage per hour.

==== Non-contiguous working week ====
[[Brunei Darussalam]] has a non-contiguous working week, consisting of Monday to Thursday plus Saturday. The days of rest are Friday (for [[Jumu'ah]] prayers) and Sunday.

Some non-government companies in Brunei adopted the working week of Monday to Friday, while the weekend starts on Saturday until Sunday. Depending on the company rules, employees may be required to work half-day on Saturday.

=== Israel ===
In [[Israel]], the standard workweek is 42 hours as prescribed by law. The typical workweek is five days, Sunday to Thursday, with 8.4 hours a day as the standard, with anything beyond that considered overtime. A minority of jobs operate on a partial six-day Sunday-Friday workweek.
<ref> http://www.davar1.co.il/118603</ref> Many Israelis work overtime hours, with a maximum of 12 overtime hours a week permitted by law. Most offices and businesses run on a five-day week, though many stores, post offices, banks, and schools are open and public transportation runs six days a week. Almost all businesses are closed during Saturday, and most public services except for emergency services, including almost all public transport, are unavailable on Saturdays. However, some shops, restaurants, cafes, places of entertainment, and factories are open on Saturdays, and a few bus and [[share taxi]] lines are active.<ref>http://www.timesofisrael.com/open-on-shabbat-israels-fray-of-rest/</ref><ref>http://www.haaretz.com/israel-news/.premium-1.725835</ref><ref>http://transport-in-israel.wikidot.com/shabbat-and-holidays</ref> Employees who work Saturdays, particularly service industry workers, public sector workers, and pilots, are compensated with alternative days off.<ref>https://www.justlanded.com/english/Israel/Israel-Guide/Jobs/Working-Conditions</ref> In 2014, the average workweek was 45.8 hours for men and 37.1 hours for women.<ref>{{cite web |author=By Lee Yaron |url=http://www.haaretz.com/israel-news/business/.premium-1.624900 |title=Israeli Workers’ Average Salary Rose 1.4% in 2013 to $2,376 – Business |publisher=Haaretz |date=2014-11-06 |accessdate=2016-09-10}}</ref>

=== Japan ===
The standard business office working week in [[Japan]] begins on Monday and ends on Friday, 40 hours per week. This system became common between 1980 and 2000. Before then, most workers in Japan worked full-time from Monday to Friday and a half day on Saturday, 45–48 hours per week. Public schools and facilities (excluding city offices) are generally open on Saturdays for half a day.<ref name="Jappleng University">{{cite web |title=Jappleng University (Days of the Week) |url=http://www.jappleng.com/education/jplearn/japanese_lessons/398/days-of-the-week-japanese}}</ref>

=== Mexico ===
[[Mexico]] has a 48-hour work week (8 hours × 6 days),<ref>{{cite web |title=Ley federal del trabajo. |url=http://www.diputados.gob.mx/LeyesBiblio/pdf/125.pdf |accessdate=May 23, 2014 |deadurl=yes |archiveurl=https://web.archive.org/web/20140604154515/http://www.diputados.gob.mx/LeyesBiblio/pdf/125.pdf |archivedate=June 4, 2014 |df=mdy-all}}</ref> it is a custom in most industries and trades to work half day on Saturday. Most public employees work Monday to Friday as well in some office companies. Shops and retailers open on Saturday and Sunday in most large cities.

=== Mongolia ===
[[Mongolia]] has a Monday to Friday working week, with a normal maximum time of 40 hours. Most shops are also open on weekends, many large retail chains having full opening hours even on Sunday. Private enterprises conduct business from 9:00 to 18:00, and government institutions may have full working hours.

=== Nepal ===
Nepal follows the ancient [[Hindu calendar|Vedic calendar]], which has the resting day on Saturday and the first day of the working week on Sunday.<ref name="Vedic Books">[http://vedicbooks.net/blog/?p=34 Vedic Books], The Vedic Week.</ref> Schools in Nepal are off on Saturdays, so it is common for pupils to go to school from Sunday to Friday.

In November 2012, the home ministry proposed a two-day holiday per week plan for all government offices except at those providing essential services like electricity, water, and telecommunications.<ref>{{cite web |url=http://www.myrepublica.com/portal/index.php?action=news_details&news_id=44273 |title=MYREPUBLICA.com – News in English from Nepal: Fast, Full & Factual News |publisher=}}</ref> This proposal followed a previous proposal by the Nepali government, i.e. ''Load-shedding Reduction Work Plan 2069 BS'', for a five working day plan for government offices as part of efforts to address the problem of [[load shedding|load-shedding]]. The proposal has been discussed in the Administration Committee; it is not yet clear whether the plan includes private offices and educational institutions.

=== New Zealand ===
In [[New Zealand]] the working week is typically Monday to Friday 8:30 to 17:00, but it is not uncommon for many industries (especially construction) to work a half day on Saturday, normally from 8:00 or 9:00 to about 13:00. Supermarkets, malls, independent retailers, and increasingly, banks, remain open seven days a week.

=== Russia ===
In [[Russia]] the common working week begins on Monday and ends on Friday with 8 hours per day.

Federal law defines a working week duration of 5 or 6 days with no more than 40 hours worked. In all cases Sunday is a holiday. With a 5-day working week the employer chooses which day of the week will be the second day off. Usually this is a Saturday, but in some organizations (mostly government), it is Monday. Government offices can thereby offer Saturday service to people with a normal working schedule.

There are non-working public holidays in Russia; all of them fall on a fixed date. By law, if such a holiday coincides with an ordinary day off, the next work day becomes a day off. An official public holiday cannot replace a regular day off. Each year the government can modify working weeks near public holidays in order to optimize the labor schedule. For example, if a five-day week has a public holiday on Tuesday or Thursday, the calendar is rearranged to provide a reasonable working week.

Exceptions include occupations such as transit workers, shop assistants, and security guards. In many cases independent schemes are used. For example, the service industry often uses the X-through-Y scheme (Russian: ''X через Y'') when every worker uses X days for work and the next Y days for rest.

==== Soviet Union ====
In the [[Soviet Union]] the standard working week was 41 hours: 8 hours, 12 min. Monday to Friday. Before the mid-1960s there was a 42-hour 6-day standard working week: 7 hours Monday to Friday and 6 hours on Saturday.

=== Singapore ===
In [[Singapore]] the common working week is 5-day work week, which runs from Monday to Friday beginning 8:30 a.m. and end at 5 p.m. – 6 p.m. Some companies work a half day on Saturdays. Shops, supermarkets and malls are open seven days a week and on most public holidays.

=== South Africa ===
In [[South Africa]] the working week traditionally was Monday to Friday with a half-day on Saturday and Sunday a public holiday. However, since 2013 there have been changes to the working week concept based on more than one variation. The week can be 5 days of work, or more. The maximum number of hours someone can work in a week remains 45.<ref>{{cite web |url=http://www.labour.gov.za/DOL/legislation/acts/basic-guides/basic-guide-to-working-hours |title=Basic Guide to Working Hours — Department of Labour |publisher=Labour.gov.za |date= |accessdate=2016-09-10}}</ref>

=== Thailand ===
In [[Thailand]] the working week is Monday to Saturday for a maximum of 44 to 48 hours per week (Saturday can be a half or full day).{{citation needed|date=December 2014}}

However, government offices and some private companies have modernised through enacting the American and European standard of working Monday through Friday.{{citation needed|date=December 2014}}

Currently, 50% of the luxury beach resorts in [[Phuket Province|Phuket]] have a five-day working week. Of the remaining 50%, 23% have taken steps to reform their 6-day workweek through such measures as reducing the working week from 6 days to 5.5 days.{{citation needed|date=December 2014}}

=== United States ===
The standard working week in the [[United States]] begins on Monday and ends on Friday, 40 hours per week, with Saturday and Sunday being weekend days. However, in practice, only 42% of employees work 40-hour weeks. The average workweek for full-time employees is 47 hours.<ref>{{cite web |url=http://www.latimes.com/business/la-fi-average-workweek-gallup-labor-day-20140829-story.html |title=Average full-time workweek is 47 hours, Gallup says |publisher=LA Times |date=2014-08-29 |accessdate=2016-09-10}}</ref> Most stores are open for business on Saturday and often on Sunday as well, except in a few places where prohibited by law (see [[Blue law]]). Increasingly, employers are offering compressed work schedules to employees. Some government and corporate employees now work a 9/80 work schedule (80 hours over 9 days during a two-week period)—commonly 9 hour days Monday to Thursday, 8 hours on one Friday, and off the following Friday. There are also some government or corporate employees that work a 10/40 schedule–40 hours per week over 4 days, usually with Fridays off. Jobs in healthcare, law enforcement, transportation, retail, and other service positions commonly require employees to work on the weekend or to do shift work.<ref>{{cite web |url=http://blog.tnsemployeeinsights.com/non-traditional-work-hours-and-retention/ |title=Non-Traditional Work Hours and Retention |publisher=tnsemployeeinsights.com|date=April 10, 2012|accessdate=June 27, 2018}}</ref>

=== Vietnam ===
[[Vietnam]] has a standard 48-hour six-day workweek. Monday to Friday are full workdays and Saturday is a partial day. Work typically begins at 8:00 AM and lasts until 5:00 PM from Monday to Friday and until 12:00 PM on Saturdays. This includes a one-hour lunch break. Government offices and banks follow a five-day workweek from Monday to Friday..<ref>''Vietnam Labor Laws and Regulations Handbook: Strategic Information and Basic Laws''</ref><ref>http://www.vietnamcheaptours.com/Tourist-Information/Time-and-working-hours/Time-and-working-hours.html</ref>

== See also ==
{{Portal|Organized labour}}
* [[Feria]]
* [[Labour and employment law]]
* [[Long weekend]]
* [[Business day]]
* [[Calendar day]]
* [[Days of the week]]
* [[Shopping hours]]
* [[Saint Monday]] (precursor of modern weekend)
* [[Thank God It's Friday (disambiguation)|TGIF]]
* [[Waiting for the Weekend]]
* [[Working time]] – how much time people spend working in a day, week, or year
* [[Work–life balance]]

== References ==
{{Reflist|30em}}

{{Employment}}

{{Authority control}}

[[Category:Working time|Week]]
[[Category:Weeks]]
[[Category:Labor rights]]
[[Category:Labour relations]]
[[Category:Labor history]]

Workweek and weekend

2018-08-13T15:26:03Z

173.165.237.1: /* Friday weekend (One day weekend) */

{{redirect|Weekend}}
{{See also|Working time}}
{{Use mdy dates|date=December 2014}}
{{refimprove|date=January 2014}}
[[File:Changfu Bridge on Weekend.jpg|thumb|right|200px|In some countries, [[market (place)|markets]] are held on weekends. Pictured is the Chanfu Bridge market in China.]]
{{Labour|expanded=rights|sp=uk}}
The '''workweek''' and '''weekend''' are those complementary parts of the [[week]] devoted to [[Labour (economics)|labor]] and [[Leisure|rest]], respectively. The legal '''working week''' ([[British English]]), or '''workweek''' ([[American English]]), is the part of the seven-day week devoted to labor. In most of the [[Western world]], it is [[Monday]] to [[Friday]]; the '''weekend''' is [[Saturday]] and [[Sunday]]. A '''weekday''' or '''workday''' is any day of the working week. Other institutions often follow the pattern, such as places of [[education]]. Sometimes the term “weekend” is expanded to include the time after work hours on the last workday of the week; e.g. Friday evening is often referred to as the start of the weekend.

In some Christian traditions, [[Sunday]] is the "[[Lord's Day|day of rest and worship]]". [[Judaism|Jewish]] ''[[Shabbat]]'' or [[Biblical Sabbath (Hebrew)|Biblical Sabbath]] lasts from sunset on [[Friday]] to the fall of full darkness on [[Saturday]]; as a result, the weekend in Israel is observed on Friday–Saturday. Some Muslim-majority countries historically had a Thursday–Friday or Friday–Saturday weekend; however, recently many such countries have shifted from Thursday–Friday to Friday–Saturday, or to Saturday–Sunday.

The [[Christian Sabbath]] was just one day each week, but the preceding day (the Jewish Sabbath) came to be taken as a holiday as well in the twentieth century. This shift has been accompanied by a reduction in the total number of hours worked per week, following changes in employer expectations. The present-day concept of the 'week-end' first arose in the industrial north of Britain in the early part of nineteenth century<ref name="etymonline.com">http://www.etymonline.com/index.php?term=weekend</ref> and was originally a voluntary arrangement between factory owners and workers allowing Saturday afternoon off from 2pm in agreement that staff would be available for work sober and refreshed on Monday morning.<ref name="ReferenceA">Waiting for the Weekend, Witold Rybzinski, 1991</ref> The Amalgamated Clothing Workers of America Union was the first to successfully demand a five-day work week in 1929.

Most countries have adopted a two-day weekend, however, the days of the weekend differ according to religious tradition, i.e. either Thursday–Friday, Friday–Saturday, or Saturday–Sunday, with the previous evening post-work often considered part of the weekend. Proposals have continued to be put forward for further reductions in the number of days or hours worked per week, on the basis of predicted social and economic benefits.
{{TOC limit|3}}

== History ==
{{Labour|expanded=rights|sp=uk}}
{{expand section|date=September 2013}}
A continuous seven-day cycle that runs throughout history paying no attention whatsoever to the phases of the moon, having a fixed day of rest, was probably first practiced in [[Judaism]], dated to the 6th century BC at the latest.<ref>{{Cite book |url=https://books.google.com/books?id=Cd5ZjRsNj4sC&pg=PA11#v=onepage&q&f=false |title=The Seven Day Circle: The History and Meaning of the Week |last=[[Eviatar Zerubavel]] |first= |date=1989-03-15 |publisher=University of Chicago Press |year= |isbn=978-0-226-98165-9 |location= |pages= |language=en}}</ref><ref>{{Cite book |url=https://books.google.com/books?id=g5c7C2rQzU0C&redir_esc=y |title=Christian Liturgy: Catholic and Evangelical |last=Senn |first=Frank C. |date=1997 |publisher=Fortress Press |isbn=978-0-8006-2726-3 |language=en}}</ref>

In [[Ancient Rome]], every eight days there was a [[nundinae]]. It was a market day, during which children were exempted from school<ref>The Teacher in Ancient Rome: The Magister and His World, Lisa Maurice, Lexington Books, 2013, pp. 26</ref> and [[plebs]] ceased from work in the field and came to the city to sell the produce of their labor<ref>Ancient Rome in So Many Words, Christopher Francese, Hippocrene Books, 2007, pp. 76</ref><ref>{{Cite web |url=http://penelope.uchicago.edu/Thayer/E/Roman/Texts/secondary/SMIGRA*/Nundinae.html |title=LacusCurtius • Roman Calendar — Nundinae (Smith's Dictionary, 1875) |website=penelope.uchicago.edu |language=en |access-date=2017-06-19}}</ref> or practice religious rites.{{Citation needed|reason=nundunae page says it's doubtful that this day had religious characteristics. || date=June 2017}}.

The [[French Revolutionary Calendar]] had ten-day weeks (called ''décades'') and allowed ''décadi'', one out of the ten days, as a leisure day.

In cultures with a [[four-day week]], the three [[Sabbath]]s derives from the culture's main religious tradition: Friday ([[Muslim Sabbath|Muslim]]), Saturday ([[Jewish Sabbath|Jewish]]), and Sunday ([[Christian Sabbath|Christian]]).

The present-day concept of the relatively longer 'week-end' first arose in the industrial north of Britain in the early part of nineteenth century<ref name="etymonline.com" /> and was originally a voluntary arrangement between factory owners and workers allowing Saturday afternoon off from 2pm in agreement that staff would be available for work sober and refreshed on Monday morning.<ref name="ReferenceA" /> The Oxford English Dictionary traces the first use of the term '''weekend''' to the British magazine ''[[Notes and Queries]]'' in 1879.<ref>{{cite news |last1=Stanton |first1=Kate |title=The origin of the weekend |url=http://www.smh.com.au/national/the-origin-of-the-weekend-20150807-giu3ay.html |accessdate=10 June 2017 |work=The Sydney Morning Herald |date=9 August 2015}}</ref>

In 1908, the first five-day workweek in [[United States|the United States]] was instituted by a [[New England]] [[cotton mill]] so that [[Jewish]] workers would not have to work on the Sabbath from sundown Friday to sundown Saturday.<ref name="theatlantic.com">{{cite web |author=Witold Rybczynski |url=https://www.theatlantic.com/past/docs/issues/91aug/rybczynski-p2.htm |title=Waiting for the Weekend |pages=35–52 |date=August 1991 |work=[[The Atlantic]]}}</ref> In 1926, [[Henry Ford]] began shutting down his [[car factory|automotive factories]] for all of Saturday and Sunday. In 1929, the [[Amalgamated Clothing Workers of America]] Union was the first union to demand a five-day workweek and receive it. After that, the rest of the [[United States]] slowly followed, but it was not until 1940, when a provision of the 1938 [[Fair Labor Standards Act of 1938|Fair Labor Standards Act]] mandating a maximum 40-hour workweek went into effect, that the two-day weekend was adopted nationwide.<ref name="theatlantic.com" />

Over the succeeding decades, particularly in the 1940s, 1950s, and 1960s, an increasing number of countries adopted either a Friday–Saturday or Saturday–Sunday weekend to harmonize with international markets. A series of workweek reforms in the mid-to-late 2000s and early 2010s brought much of the [[Arab World]] in synchronization with the majority of countries around the world, in terms of working hours, the length of the workweek, and the days of the weekend. The [[International Labour Organization]] (ILO) currently defines a workweek exceeding 48 hours as excessive. A 2007 study by the ILO found that at least 614.2 million people around the world were working excessive hours.<ref>{{cite web |last=Sahadi |first=Jeanne |url=http://money.cnn.com/2007/06/07/news/ilo_study/ |title=22% of workers work more than 48 hours a week, study finds – Jun. 7, 2007 |publisher=Money.cnn.com |date=2007-06-07 |accessdate=2016-09-10}}</ref>

== Length ==
[[File:Almost empty calendar.JPG|thumb|right|200px|This day planner chart (which can be used for any months) shows the workweek days as white boxes and the weekend days as light blue-coloured boxes.]]
Actual workweek lengths have been falling in the developed world. Every reduction of the length of the workweek has been accompanied by an increase in real per-capita income.<ref name=gapminder>Gapminder Foundation (2011) [http://www.gapminder.org/world/#$majorMode=chart$is;shi=t;ly=2003;lb=f;il=t;fs=11;al=30;stl=t;st=t;nsl=t;se=t$wst;tts=C$ts;sp=5.59290322580644;ti=2007$zpv;v=0$inc_x;mmid=XCOORDS;iid=phAwcNAVuyj1jiMAkmq1iMg;by=ind$inc_y;mmid=YCOORDS;iid=rdCufG2vozTpKw7TBGbyoWw;by=ind$inc_s;uniValue=8.21;iid=phAwcNAVuyj0XOoBL_n5tAQ;by=ind$inc_c;uniValue=255;gid=CATID0;by=grp$map_x;scale=log;dataMin=295;dataMax=79210$map_y;scale=lin;dataMin=26;dataMax=56$map_s;sma=49;smi=2.65$cd;bd=0$inds=i239_t001980,,,,;i156_t001987,,,,;i168_t001980,,,,;i110_t001980,,,,;i117_t001980,,,,;i143_t001990,,,,;i238_t001980,,,, "Gapminder World" graph of working hours per week plotted against purchasing power- and inflation-adjusted GDP per capita over time] {{webarchive |url=https://web.archive.org/web/20161127055214/http://www.gapminder.org/world/#$majorMode=chart$is;shi=t;ly=2003;lb=f;il=t;fs=11;al=30;stl=t;st=t;nsl=t;se=t$wst;tts=C$ts;sp=5.59290322580644;ti=2007$zpv;v=0$inc_x;mmid=XCOORDS;iid=phAwcNAVuyj1jiMAkmq1iMg;by=ind$inc_y;mmid=YCOORDS;iid=rdCufG2vozTpKw7TBGbyoWw;by=ind$inc_s;uniValue=8.21;iid=phAwcNAVuyj0XOoBL_n5tAQ;by=ind$inc_c;uniValue=255;gid=CATID0;by=grp$map_x;scale=log;dataMin=295;dataMax=79210$map_y;scale=lin;dataMin=26;dataMax=56$map_s;sma=49;smi=2.65$cd;bd=0$inds=i239_t001980,,,,;i156_t001987,,,,;i168_t001980,,,,;i110_t001980,,,,;i117_t001980,,,,;i143_t001990,,,,;i238_t001980,,,, |date=November 27, 2016 }} ''gapminder.org''</ref>{{verify source|date=September 2015}} In the [[United States]], the workweek length reduced slowly from before the Civil War to the turn of the 20th century. A rapid reduction took place from 1900 to 1920, especially between 1913 and 1919, when weekly hours fell by about eight percent.<ref name=hunnicutt>Hunnicutt, B.K. (1984) [http://www.uiowa.edu/~lsa/bkh/lla/eosh.htm "The End of Shorter Hours"] {{webarchive |url=https://web.archive.org/web/20150321034221/http://www.uiowa.edu/~lsa/bkh/lla/eosh.htm |date=March 21, 2015 }} ''Labor History'' '''25''':373–404</ref> In 1926, [[Henry Ford]] standardized on a five-day workweek, instead of the prevalent six days, without reducing employees' pay.<ref name=lombardo>Lombardo, C.N. (February 4, 2010) [http://www.hrhero.com/hl/articles/2010/02/04/shorter-workweek-in-a-tough-economy/ "Shorter Workweek in a Tough Economy"] {{webarchive |url=https://web.archive.org/web/20161128134109/http://www.hrhero.com/hl/articles/2010/02/04/shorter-workweek-in-a-tough-economy/ |date=November 28, 2016 }} ''Wisconsin Employment Law Letter'' (hrhero.com)</ref> Hours worked stabilized at about 49 per week during the 1920s, and during the [[Great Depression]] fell below 40.<ref name=hunnicutt /> During the Depression, President [[Herbert Hoover]] called for a reduction in work hours in lieu of layoffs. Later, President [[Franklin Roosevelt]] signed the [[Fair Labor Standards Act of 1938]], which established a five-day, 40-hour workweek for many workers.<ref name=lombardo /> The proportion of people working very long weeks has since risen, and the full-time employment of women has increased dramatically.<ref name=rones>Rones ''et al.'' (1997) [http://heinonline.org/HOL/LandingPage?collection=journals&handle=hein.journals/month120&div=32&id=&page= "Trends in Hours of Work since the Mid-1970s"] {{webarchive|url=https://web.archive.org/web/20160624123602/http://heinonline.org/HOL/LandingPage?collection=journals&handle=hein.journals%2Fmonth120&div=32&id=&page= |date=June 24, 2016 }} ''Monthly Labor Review'' '''120'''(3):3–12</ref>

The [[New Economics Foundation]] has recommended moving to a 21-hour standard workweek to address problems with unemployment, high carbon emissions, low well-being, entrenched inequalities, overworking, family care, and the general lack of free time.<ref name=lombardo /><ref name="nef21">{{cite web |last1=Coote |first1=Anna |last2=Franklin |first2=Jane |last3=Simms |first3=Andrew |title=21 hours: Why a shorter working week can help us all to flourish in the 21st century |url=http://neweconomics.org/page/-/files/21_Hours.pdf |publisher=New Economics Foundation |accessdate=18 October 2016 |ref=nef21 |archiveurl=https://web.archive.org/web/20160209144546/http://b.3cdn.net/nefoundation/f49406d81b9ed9c977_p1m6ibgje.pdf |archivedate=9 February 2016 |location=London |date=February 2010 |isbn=978-1-904882-70-1}}</ref><ref name=guardian>Stuart, H. (January 7, 2012) [https://www.theguardian.com/society/2012/jan/08/cut-working-week-urges-thinktank "Cut the working week to a maximum of 20 hours, urge top economists"] {{webarchive |url=https://web.archive.org/web/20121120065059/http://www.guardian.co.uk/society/2012/jan/08/cut-working-week-urges-thinktank |date=November 20, 2012 }} ''The Guardian''</ref><ref name=gam>Schachter, H. (February 10, 2012) [https://www.theglobeandmail.com/report-on-business/careers/management/morning-manager/save-the-world-with-a-3-day-work-week/article2332609/ "Save the world with a 3-day work week"] {{webarchive |url=https://web.archive.org/web/20160505185931/http://www.theglobeandmail.com/report-on-business/careers/management/morning-manager/save-the-world-with-a-3-day-work-week/article2332609/ |date=May 5, 2016 }} ''Globe and Mail''</ref><ref name=baker>Baker, D. (January 27, 2009) [http://www.nydailynews.com/opinion/pass-stimulus-shorten-work-week-article-1.425158 "Pass the stimulus – then help shorten the work week"] {{webarchive |url=https://web.archive.org/web/20160304101541/http://www.nydailynews.com/opinion/pass-stimulus-shorten-work-week-article-1.425158 |date=March 4, 2016 }} ''New York Daily News''</ref><ref name=abate>Abate, T. (July 11, 2010) [http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2010/07/10/BUAG1EC1MH.DTL "Get to Work: Want more jobs? Shorten the workweek"] {{webarchive|url=https://web.archive.org/web/20100712203928/http://www.sfgate.com/cgi-bin/article.cgi?f=%2Fc%2Fa%2F2010%2F07%2F10%2FBUAG1EC1MH.DTL |date=July 12, 2010 }} ''San Francisco Chronicle'' page D-3</ref> The [[Center for Economic and Policy Research]] states that reducing the length of the work week would slow [[climate change]] and have other environmental benefits.<ref>[http://www.cepr.net/documents/publications/climate-change-workshare-2013-02.pdf "Reduced Work Hours as a Means of Slowing Climate Change"] {{webarchive |url=https://web.archive.org/web/20160509143743/http://www.cepr.net/documents/publications/climate-change-workshare-2013-02.pdf |date=May 9, 2016 }} David Rosnick, February 2013</ref>

== Around the world ==
(Countries listed alphabetically. Some countries have Saturday a normal school day. Some countries appear under the subsections for [[#Muslim countries|Muslim countries]] and the [[#EU|European Union]].)


{| class="wikitable sortable"
|-
! Nation !! Typical Hours per Week !! Working week !! Typical hours worked (Maximum per day)
|-
| Afghanistan || 40 || Sunday–Thursday || 8
|-
| Albania || 40 || Monday–Friday || 8
|-
| Algeria || 40 || Sunday–Thursday || 8
|-
| Angola || 40 || Monday–Friday || 8
|-
| Argentina || 40 || Monday–Friday || 8
|-
| Armenia || 40 || Monday–Friday || 8
|-
| Azerbaijan || 40 || Monday–Friday || 8
|-
| Austria || 38.5 || Monday–Friday || 7.7
|-
| Australia || 38<ref>{{cite web |url=https://www.fairwork.gov.au/how-we-will-help/templates-and-guides/fact-sheets/minimum-workplace-entitlements/maximum-weekly-hours#maximum-weekly-work-hours |title=Welcome to the Fair Work Ombudsman website |last=Ombudsman |first=Fair Work |website=Fair Work Ombudsman |access-date=2016-07-20}}</ref> || Monday–Friday || 7.6
|-
| Bahrain || 40 || Sunday–Thursday || 8 (6 during [[Ramadan]] for Muslim employees)<ref>Art.51-b of 2012 Labor Law, http://lmra.bh/portal/files/cms/shared/file/labour%20law%202012.pdf</ref>
|-
| Bangladesh || 40 || Government offices and Banks: Sunday-Thursday
Else: Saturday-Thursday
| 8
|-
| Benin || 40 || Monday–Friday || 8
|-
| Belarus || 40 || Monday–Friday || 8
|-
| Belgium || 38 || Monday–Friday || 7.6
|-
| Brazil || 44 || Monday–Friday || 8.5
|-
| Brunei Darussalam || 40 || Monday–Thursday and Saturday || 8
|-
| Burundi || 50 || Monday–Friday || 10
|-
| Bulgaria || 40 || Monday–Friday || 8
|-
| Canada || 40 || Monday–Friday || 8
|- day.
| Cameroon || 50 || Monday–Friday || 10
|-
| Chile || 45 || Monday–Friday || 9
|-
| China || 42|| Monday–Friday || 8
|-
| Croatia || 40 || Monday–Friday || 8
|-
| Colombia || 48 || Monday–Friday /
Monday–Saturday
| 8
|-
| Costa Rica || 48 || Monday–Friday || 8
|-
| Czech Republic || 40 || Monday–Friday || 8
|-
| Denmark || 37 || Monday–Friday || 7.4
|-
| Djibouti || 40 || Saturday–Thursday || 6.7
|-
| Dominican Republic || 40 || Monday-Friday || 8
|-
| Egypt || 40 (30 during [[Ramadan]]) || Sunday–Thursday || 8 (6 during [[Ramadan]])
|-
| Ethiopia || 40 || Monday–Friday || 8
|-
| Estonia || 40 || Monday–Friday || 8
|-
| Equatorial Guinea || 48 || Monday–Saturday || 8
|-
| Finland || 38 || Monday–Friday || 8
|-
| France || 35 || Monday–Friday || 7
|-
| Gabon || 40 || Monday–Friday || 8
|-
| Gambia || 40 || Monday–Friday || 8
|-
| Germany || 40 || Monday–Friday || 8
|-
| Ghana || 40 || Monday–Friday || 8
|-
| Greece || 40 || Monday–Friday || 8
|-
| Hungary || 40 || Monday–Friday || 8
|-
| Hong Kong || 40-48 || Monday–Saturday || 8 (many people work on Saturday either a half-day or full-day)
|-
| India || 45-60 || Government offices and IT industry: Monday-Friday
Else: Monday–Saturday Sometimes: Monday
| 9 (including 1 hour lunch break) most of the Businesses are open on Saturdays. So often it is Monday-Saturday.
|-
| Indonesia || 40 || Monday–Friday || 8, many people work a 6-day week with 7-hour days.
|-
| Iran || 45 || Saturday-Thursday/Saturday-Wednesday ||8, (except 5-hours on thursday)
|-
| Iraq || 40 || Sunday–Thursday || 8
|-
| Ireland || 40 || Monday–Friday || 8
|-
| Israel || 42 || Sunday–Thursday || 8.4. Some people have a partial six-day workweek.
|-
| Italy || 40 || Monday–Friday || 8
|-
| Côte d'Ivoire || 40 || Monday–Friday || 8
|-
| Japan || 40 || Monday–Friday || 8
|-
| Jordan || 45 || Sunday–Thursday || 9
|-
| Kazakhstan || 40 || Monday–Friday || 8
|-
| Kuwait || 40 || Sunday–Thursday || 8
|-
| Kenya || 40 || Monday–Friday || 8
|-
| Lao People’s Democratic Republic || 40 || Monday–Friday || 8
|-
| Latvia || 40 || Monday–Friday || 8
|-
| Lebanon || 40 || Monday-Friday || 8, Most of the people have a six-day workweek, with Saturday as a partial workday.
|-
| Lesotho || 40 || Monday–Friday || 8
|-
| Libya || 40 || Sunday–Thursday || 8
|-
| Lithuania || 40 || Monday–Friday || 8
|-
| Madagascar || 40 || Monday–Friday || 8
|-
| Maldives || 40 || Sunday–Thursday || 8
|-
| Malawi || 40 || Monday–Friday || 8
|-
| Mali || 40 || Monday–Friday || 8
|-
| Malta || 40 || Monday–Friday || 8
|-
| Mauritania || 40 || Monday–Friday || 8
|-
| Malaysia || 40 || Sunday–Thursday ([[Johor]], [[Kedah]], [[Kelantan]], and [[Terengganu]]) Monday–Friday ([[Federal Territory of Malaysia]], [[Sabah]], [[Sarawak]], [[Pahang]], [[Malacca]], [[Negeri Sembilan]], [[Selangor]], [[Perak]], [[Penang]], [[Perlis]]) || 8
|-
| Mexico || 48 || Monday–Saturday || 8
|-
| Mongolia || 40 || Monday–Friday || 8
|-
| Morocco || 44 || Monday–Friday || 8
|-
| Mozambique || 40 || Monday–Friday || 8
|-
| Nepal || 48 || Sunday–Friday || 7 (5 on Friday and 6 in Winter)
|-
| The Netherlands || 40 || Monday–Friday || 8
|-
| New Zealand || 40 || Monday–Friday || 8<ref>{{cite web |url=http://www.legislation.govt.nz/act/public/1983/0115/latest/DLM74459.html |title=Minimum Wage Act 1983 |publisher=}}</ref>
|-
| Nigeria || 40 || Monday–Friday || 8
|-
| Norway || 37.5 || Monday–Friday || 7.5
|-
| Oman || 40 (30 during [[Ramadan]]) || Sunday–Thursday || 8 (6 during [[Ramadan]])
|-
| Pakistan || 45 & 54 || Monday–Friday || 9 (including 1 hour lunch break) most of the Businesses are open on Saturdays. So often it is Monday-Saturday.
|-
| Palestine || 45<ref>[http://carim-south.eu/carim/public/legaltexts/LE3PAL1204_1034.pdf The Labour Law No. (7) of 2000 AD, Article 68]</ref> || Saturday–Thursday <ref>[http://carim-south.eu/carim/public/legaltexts/LE3PAL1204_1034.pdf The Labour Law No. (7) of 2000 AD, Article 73]</ref>|| 8
|-
| Philippines || 48 || Monday–Saturday || 9 (including 1 hour lunch break)
|-
| Poland || 40 || Monday–Friday || 8
|-
| Portugal || 40 || Monday–Friday || 8
|-
| Qatar || 40 (25 During [[Ramadan]]) || Sunday–Thursday || 8 (5 during [[Ramadan]]) (Line staff work 48 hours of the week, Saturday-Thursday)
|-
| Romania || 40 || Monday–Friday || 8
|-
| Russia || 40 || Monday–Friday || 8
|-
| Rwanda || 40 || Monday–Friday || 8
|-
| Saudi Arabia || 40 (30 during [[Ramadan]]) || Sunday–Thursday || 8 (6 during [[Ramadan]] for Muslim employees)<ref>Art. 98 of Royal Decree No. M/51 dated 23 / 8 / 1426 H, https://www.boe.gov.sa/ViewSystemDetails.aspx?lang=en&SystemID=186&VersionID=201</ref>
|-
| Senegal || 40 || Monday–Friday || 8
|-
| Singapore || 44 || Monday–Friday || 9<ref>{{cite web |url=http://www.mom.gov.sg/employment-practices/hours-of-work-overtime-and-rest-days |title=Hours of work, overtime and rest days |publisher=}}</ref>
|-
| Slovakia (Slovak Republic) || 40 || Monday–Friday || 8
|-
| Spain || 40 || Monday–Friday || 8
|-
| Sri Lanka
| 40
| Monday–Friday
| 8
|-
| South Africa || 45 || Monday–Friday || 9<ref>{{cite web |url=http://www.labour.gov.za/DOL/legislation/acts/basic-guides/basic-guide-to-working-hours |title=Basic Guide to Working Hours |publisher=}}</ref>
|-
| South Korea || 40 || Monday–Friday || 8
|- Somalia || 45 || Saturday–Thursday || 8
|-
| Sudan || 40 || Sunday–Thursday || 8
|-
| Suriname || 39.5 || Monday–Friday || 8; Monday–Thursday 7:00 – 15:00 / Friday 7:00 – 14.30
|-
| Swaziland || 40 || Monday–Friday || 8
|-
| Sweden || 40 || Monday–Friday || 8
|-
| Switzerland || 42 || Monday–Friday || 8.4
|-
| Syria || 40 || Sunday–Thursday || 8
|-
| Seychelles || 40 || Monday–Friday || 8
|-
| Taiwan || 40 || Monday–Friday || 8; The Labor Standards Act stipulates that a worker shall have one mandatory day off and one flexible rest day in every seven days. See [[One fixed day off and one flexible rest day policy]].
|-
| Tanzania || 40 || Monday–Friday || 9
|-
| Togo || 40 || Monday–Friday || 8
|-
| Thailand || 40 || Monday–Friday || 8
|-
| Trinidad and Tobago || 40 || Monday–Friday || 8
|-
| Tunisia || 40 || Monday–Friday || 8
|-
| Turkey || 45 || Monday–Friday || 9
|-
| Ukraine || 40 || Monday–Friday || 8
|-
| United Arab Emirates || 40-45 (30 during [[Ramadan]]) || Sunday–Thursday (since September 2006<ref name=gulfnews>{{cite web |url=http://gulfnews.com/news/gulf/uae/general/friday-saturday-weekend-in-uae-from-september-1.237326 |title=Friday-Saturday weekend in UAE from September |publisher=}}</ref>) || 8 to 9 (regular hours minus 2 hours during [[Ramadan]] for all employees)<ref>Title 4, Art. 65 of the UAE Labor Law, http://www.mohre.gov.ae/en/labour-law/labour-law.aspx</ref>
|-
| United Kingdom || 40 || Monday–Friday || 8
|-
| United States || 40<ref>{{cite web |url=http://www.gallup.com/poll/175286/hour-workweek-actually-longer-seven-hours.aspx |title=The "40-Hour" Workweek Is Actually Longer -- by Seven Hours |author=Gallup, Inc. |work=Gallup.com}}</ref> || Monday–Friday || 8
|-
| Uganda || 48 || Monday–Saturday || 8
|-
| Vietnam || 40<ref>{{cite web |url=http://www.hocmon.hochiminhcity.gov.vn/Hnh%20nh%20bn%20tin/2011-11/TT%2033%20BLDTBXH_18%2011%202011_Lam%20viec%20thoi%20vu%20va%20Gia%20cong_Thay%20the%20TT%2016%202003.pdf |title=Ministry of Labour – Invalids and Social Affairs |author=Molisa |work=Molisa.gov.vn}}</ref> || Monday–Friday || 8
|-
| Yemen || 40 || Sunday–Thursday || 8
|-
| Congo, Democratic Republic of || 40 || Monday–Friday || 8
|-
| Zambia || 40 || Monday–Friday || 8
|-
| Zimbabwe
| 40
| Monday–Friday
| 8; Most people work half a day on Saturday
|}

=== Australia ===
In [[Australia]] the working week begins on Monday and terminates on Friday. An eight-hour working day is the norm. Working three weekdays a fortnight, for example, would therefore be approximately twenty-four hours (including or excluding traditional breaks tallying up to two hours). Some people work overtime with extra pay on offer for those that do, especially for weekend work. Shops open seven days a week in most states with opening hours from 9am to 5.30pm on weekdays, with some states having two "late night trading" nights on Thursday and Friday, when trading ceases at 9pm. Many supermarkets and low end department stores remain open until midnight and some trade 24/7. Restaurants and cinemas can open at all hours, save for some public holidays. Bars generally trade seven days a week but there are local municipal restrictions concerning trading hours. Banks trade on Monday to Friday, with some branches opening on Saturdays (and in some cases Sundays) in high demand areas. The Post Office (Australia Post) trades Monday to Friday as per retail shops but some retail post offices may trade on Saturdays and Sundays in some shopping centres. A notable exception to the above is South Australia whereby retail establishments are restricted to trading between the hours of 11am-5pm on Sundays.

=== Brazil ===
As a general rule, [[Brazil]] adopts a 44-hour working week, which typically begins on Monday and ends on Friday, with a Saturday-Sunday weekend. [[Brazilian Law]],<ref>Consolidação das Leis do Trabalho: http://www.planalto.gov.br/ccivil_03/decreto-lei/Del5452.htm</ref> however, also allows for shorter Monday-to-Friday working hours so employees can work on Saturdays or Sundays, as long as the weekly 44-hour limit is respected and the employee gets at least one weekend day. This is usually the case for malls, supermarkets and shops. The law also grants [[labor unions]] the right to negotiate different work weeks, within certain limits, which then become binding for that union's labor category. Overtime is allowed, limited to two extra hours a day, with an increase in pay.

=== Chile ===
The working week in [[Chile]] averages 45 hours, most often worked on a Monday-Friday schedule, but is not uncommon to work on Saturdays. Retail businesses mostly operate Monday through Saturday, with larger establishments being open seven days a week.

=== China (People's Republic) ===
In [[China]], there is a five-day Monday-Friday working week, prior to which work on Saturday was standard. China began the two-day Saturday–Sunday weekend on May 1, 1995. Most government employees work 5 days a week (including officials and industrial management). Most manufacturing facilities operate on Saturdays as well. However, most shops, museums, cinemas and commercial establishments open on Saturdays, Sundays and holidays. Banks are also open throughout the weekend and on most public holidays.

During the period of [[Public holidays in China|public holidays]], swapped holidays are common between the actual holiday and weekend, so a three-day or seven-day holiday periods are created. The nearby Saturday or Sunday may be changed to a normal working day. For example, on a three-day holiday period, if the actual holiday falls on a Tuesday, Monday will be swapped as a holiday, and citizens are required to work on the previous Saturday.

A number of provinces and municipalities across China, including Hebei, Jiangxi and Chongqing, have issued new policies, calling on companies to create 2.5-day weekends. Under the plan, government institutions, state-owned companies, joint-ventures and privately held companies are to be given incentives to allow their workers to take off at noon on Friday before coming back to the office on Monday.<ref>{{cite web |title=China to implement 2.5-day weekend this summer |url=http://www.chinadaily.com.cn/china/2016-02/03/content_23369098.htm |website=www.chinadaily.com.cn |access-date=2016-02-03 |last=江巍}}</ref>

==== Hong Kong SAR ====
In [[Hong Kong]], a typical working week for local enterprises begins on Monday and ends at 1pm on Saturday, although most employees have alternate Saturdays off. After the introduction of the five-day working week for the majority of government departments in 2006, most multinational enterprises and large local companies followed suit, extended the working day from 9am to 6pm so as to adopt a five-day work week. Despite the aforementioned official hours, many employees work overtime, and in the case of the financial industry in particular, working 12-hour days on a chronic basis is not uncommon.

Most commercial establishments in the retail sector such as restaurants, shops and cinemas, as well as public venues such as museums and libraries are open on Saturdays, Sundays and most public holidays. For schools, lessons are not normally held on Saturdays, but students may be required to go school on Saturdays for extra-curricular activities or make-up classes.

=== Colombia ===
In general, [[Colombia]] has a 48-hour working week. Depending on the business, people work five days for [http://www.mintrabajo.gov.co/preguntas-frecuentes/jornada-de-trabajo.html max 8 hours per day], typically Monday to Friday, or six days for eight hours a day, Monday to Saturday.<ref>{{Cite news |url=https://www.justlanded.com/english/Colombia/Colombia-Guide/Jobs/Legal-regulations-in-the-Colombian-job-market |title=Legal regulations in the Colombian job market |work=Just Landed |access-date=2017-06-19 |language=en}}</ref>

=== European Union members ===
{{Expand section|date=March 2009}}
In [[Europe]], the standard full-time working week begins on Monday and ends on Saturday. Most retail shops are open for business on Saturday. In Ireland, Italy, Finland, Sweden, the Netherlands and the former socialist states of Europe, large [[shopping center|shopping centres]] open on Sunday. 
In European countries such as Germany, there are laws regulating shop hours. With exceptions, shops must be closed on Sundays and from midnight until the early morning hours of every day.

==== Austria ====
The working week is Monday to Friday 8 hours per day. Shops are open on Saturday. By law, almost no shop is open on Sunday. However, exceptions have been made, for example for bakeries, petrol stations and shops at railway stations, especially in the largest cities (Vienna, Graz, Salzburg, Linz).

==== Belgium ====
The working week is Monday to Friday.
Working time must not exceed 8 hours per day and 38 hours per week (on average, annualised). Very few shops are open on Sunday.

==== Bulgaria ====
The working week is Monday to Friday, eight hours per day, forty hours per week. Most pharmacies, shops, bars, cafés, and restaurants will operate on Saturdays and Sundays.

==== Croatia ====
The working week is Monday to Friday, seven and a half hours per day (+ 30 minutes lunch break), 37.5 hours per week (or 40 hours per week if lunch breaks are included as working hours).
Most pharmacies, shops, bars, cafés, and restaurants are open on Saturday and Sunday.

==== Czech Republic ====
In the [[Czech Republic]], full-time employment is usually Monday to Friday, eight hours per day and forty hours per week.
Many shops and restaurants are open on Saturday and Sunday, but employees still usually work forty hours per week.

==== Denmark ====
[[Denmark]] has an official 37-hour working week, with primary work hours between 6:00 and 18:00, Monday to Friday. In public institutions, a 30-minute lunch break every day is included as per collective agreements, so that the actual required working time is 34.5 hours. In private companies, the 30-minute lunch break is normally not included. The workday is usually 7.5 hours Monday to Thursday and 7 hours on Friday. Some small shops are closed Monday.<ref name="Workindenmark">{{cite web |url=https://www.workindenmark.dk/en/Find_information/Information_for_job_seekers/Working_in_Denmark/Working_hours |title=Working hours |publisher=Workindenmark.dk (Danish Agency for Labour Retention and International Recruitment) |accessdate=April 30, 2012}}</ref>

==== Estonia ====
In [[Estonia]], the working week begins on Monday and ends on Friday. Usually a working week is forty hours.

==== Finland ====
In [[Finland]], the working week begins on Monday and ends on Friday. A full-time job is defined by law as being at least 32 and at most forty hours per week. In retail and restaurant occupations, among others, the weekly hours may be calculated as an average over three to ten weeks, depending on the employment contract. Banks and bureaus are closed on weekends. Most shops are open on Saturdays, while some are closed on Sundays.

==== France ====
The standard working week is Monday to Friday. Shops are also open on Saturday. Small shops may close on a weekday (generally Monday) to compensate workers for having worked on Saturday. By law, préfets may authorise a small number of specific shops to open on Sunday such as bars, cafés, restaurants, and bakeries, which are traditionally open every day but only during the morning on Sunday. Workers are not obliged to work on Sunday. School children have traditionally taken Wednesday off, or had only a half day, making up the time either with longer days for the rest of the week or sometimes a half day on Saturday. This practice was made much less common under new legislation rolled out over 2013–14.<ref>{{cite news |title=France: Weird about Wednesday |url=https://www.economist.com/news/europe/21586572-state-primary-schools-are-abandoning-their-four-day-week-weird-about-wednesday |work=[[The Economist]] |date=21 September 2013 |accessdate=18 January 2015}}</ref>

==== Greece ====
The standard working week is Monday to Friday. State jobs are from 07:00 until 15:00. Shops are open generally Mondays-Wednesdays from 09:30–15:00 and then from 17:30–21:00 and Tuesday-Thursday-Fridays 09:30-21:00. Saturdays generally 09:00-15:00. It is very rare for a shop to open on Sunday.

==== Hungary ====
In [[Hungary]] the working week begins on Monday and ends on Friday. Full-time employment is usually considered forty hours per week. For office workers, the work day usually begins between 8 and 9 o'clock and ends between 16:00 and 18:00, depending on the contract and lunch time agreements.

The forty-hour workweek of public servants includes lunch time. Their work schedule typically consists of 8.5 hours between Monday and Thursday (from 8:00 to 16:30) and 6 hours on Fridays (8:00–14:00).

==== Ireland ====
[[Republic of Ireland|Ireland]] has a working week from Monday to Friday, with core working hours from 09:00 to 17:30. Retail stores are usually open until 21:00 every Thursday. Many grocery stores, especially in urban areas, are open until 21:00 or later, and some supermarkets and convenience stores may open around the clock. Shops are generally open all day Saturday and a shorter day Sunday (usually 10:00–12:00 to 17:00–19:00).

==== Italy ====
In [[Italy]] the 40-hour rule applies: Monday to Friday, 09:00 to 18:00, with a one-hour break for lunch. Sunday is always a holiday; Saturday is seldom a work day at most companies and universities, but it is generally a regular day for elementary, middle, and high schools.

In the past, shops had a break from 13:00 to 16:00 and they were generally open until 19:00/20:00. Working times for shops have been changed recently and now are at the owner's discretion; malls are generally open Tuesday to Sunday 09:00 to 20:00, 15:00 to 20:00 on Monday, with no lunchtime closing.<ref>{{cite web |url=http://www.ricerca24.ilsole24ore.com/fc?cmd=static&chId=30&path=%2Fsearch%2Fsearch_engine.jsp&keyWords=liberalizzazione+orari+negozi&field=Titolo%7cTesto&id=&maxDocs=&orderByString=score+desc&criteria=0&pageNumber=1&simili=false&action=&chiaviSelezionate=&description=&flagPartialResult=&senv=r24&layout=r24 |title=liberalizzazione orari negozi – Cerca nel sito www.ilsole24ore.com |work=ilsole24ore.com}}</ref>

==== Latvia ====
[[Latvia]] has a Monday to Friday working week capped at forty hours.<ref>[http://www.vdi.gov.lv/index.php?zinas_id=6&lang_id=1&menu_id=13&start=0 Latvian State Labour Inspectorate]</ref> Shops are mostly open on weekends, many large retail chains having full working hours even on Sunday. Private enterprises usually hold hours from 9:00 to 18:00, however government institutions and others may have a shorter working day, ending at 17:00.

==== Luxembourg ====
The standard working week in [[Luxembourg]] is 40 hours per week with 8 hours per day.<ref>http://www.guichet.public.lu/entreprises/en/ressources-humaines/temps-travail/gestion/organisation/index.html</ref> Monday through Friday is the standard working week, though many shops and businesses open on Saturdays (though for somewhat restricted hours). Trading on Sundays is extremely restricted and generally limited to grocery stores opening on Sunday mornings.<ref>http://www.guichet.public.lu/entreprises/en/commerce/prix-horaires/horaires-d-ouverture/magasins-detail/index.html</ref> However, shops are allowed to open in Luxembourg City during the first Sunday of the month<ref>{{Cite web |url=http://www.visitluxembourg.com/en/place/marketsandrummagesales/sunday-shopping |title=Sunday shopping in Luxembourg City |website=www.visitluxembourg.com |language=en |access-date=2017-10-09}}</ref>, as well as in Luxembourg City and other larger towns on weekends towards the end of the year (Christmas shopping season)<ref>{{Cite web |url=http://www.luxembourg.public.lu/en/visiter/que-faire/shopping/index.html |title=Shopping – Luxembourg |last= |first= |date= |website= |archive-url= |archive-date= |dead-url= |access-date=}}</ref>. A few shopping malls located in the north of the country and in border towns (e.g. KNAUF<ref>{{Cite web |url=http://www.knaufshopping.lu |title=Knauf Center Pommerloch et Schmiede |website=www.knaufshopping.lu |access-date=2017-10-09}}</ref>, MASSEN<ref>{{Cite web |url=https://www.massen.lu |title=Shopping-Center Massen – Wemperhardt – Luxemburg – Enjoy shopping |website=Massen |language=de-DE |access-date=2017-10-09}}</ref> and Pall Center Pommerloch<ref>{{Cite web |url=http://www.pallcenter.lu/en/our-stores/ |title=Pall Center |last= |first= |date= |website= |archive-url= |archive-date= |dead-url= |access-date=}}</ref>) are also allowed to open almost every day of the year.

==== Netherlands ====
In the Netherlands, the standard working week is Monday to Friday (40 hours).<ref>{{cite web |title=More two-income couples with one full-time job and one large part-time job |url=https://www.cbs.nl/en-gb/news/2015/05/more-two-income-couples-with-one-full-time-job-and-one-large-part-time-job |website=CBS – Statistics Netherlands |publisher=CBS – Statistics Netherlands |accessdate=21 July 2016}}</ref> Shops are almost always open on Saturdays and often on Sundays.

==== Poland ====
The working week is Monday to Friday; 8 hours per day, 40 hours in total per week. Large malls are open on Saturday and Sunday; many small shops are closed on Sunday. SINCE 11 March 2018 all Malls and shops are close on Sunday trading is banned.

Under the new rules, trading will be banned on two Sundays a month.

The ban will be stepped up to three Sundays a month in 2019, while in 2020 trading will be prohibited on all Sundays except seven, including those in the run-up to Christmas and Easter.

March 11 will be the first Sunday on which trading is banned.

Bakeries, confectioners, petrol stations, florists, post offices, train stations and airports will be exempt from the ban.

Owners will be able to open their shops as long as they serve customers themselves.

Anyone infringing the new rules faces a fine of up to PLN 100,000 (EUR 23,900; USD 29,250). Repeat offenders may face a prison sentence

==== Portugal ====
The working week is Monday to Friday; 8 hours per day, 40 hours in total per week. Street shops are almost always open on Saturday mornings but shopping centres are typically open every day (including Saturdays and Sundays).

==== Romania ====
The working week is Monday to Friday; 8 hours per day, 40 hours in total per week. Shops are open on Saturday and Sunday. The weekend begins on Friday, and ends on Monday.

==== Slovakia ====
The working week is Monday to Friday; 8 hours per day, 40 hours in total per week. Large malls are open on Saturday and Sunday; many small shops are closed on Sunday. All shops are closed on public holidays.

==== Spain ====
The working week is Monday to Friday; 8 hours per day, 40 hours in total per week. The traditional opening hours are 9:00 to 13:00–14:00 and then 15:00–16:00 to 18:00 for most offices and workplaces. Most shops are open on Saturday mornings and many of the larger shopping malls are open all day Saturday and in some cities like Madrid, they are open most Sundays. Some restaurants, bars, and shops are closed Mondays, as Mondays are commonly a slow business day.<ref>Weekend spanish traditions – ''[http://escapadasdefindesemana.net/ escapadas de fin de semana]''</ref>

==== Sweden ====
In [[Sweden]], the standard working week is Monday to Friday, both for offices and industry workers. The standard workday is eight hours, although it may vary greatly between different fields and businesses. Most office workers have flexible working hours and can largely decide themselves on how to divide these over the week. The working week is regulated by ''Arbetstidslagen'' (''Work time law'') to a maximum of 40 hours per week.<ref>{{cite web |title=Arbetstidslagen |url=http://www.av.se/lagochratt/atl/kapitel02.aspx |publisher=Arbetsmiljöverket |accessdate=August 5, 2011 |deadurl=yes |archiveurl=https://web.archive.org/web/20130318050210/http://www.av.se/lagochratt/atl/kapitel02.aspx |archivedate=March 18, 2013 |df=mdy-all}}</ref> The 40-hour-week is however easily bypassed by overtime. The law allows a maximum of 200 hours overtime per year.<ref>{{cite web |title=Arbetstidslagen – Övertid |url=http://www.av.se/lagochratt/atl/Kapitel03.aspx |publisher=Arbetsmiljöverket |accessdate=August 5, 2011}}</ref> There is however no overseeing government agency; the law is often cited as toothless.{{citation needed|date=December 2012}}

Shops are almost always open on Saturdays and often on Sundays, supermarkets and shopping centres, so that employees there have to work. Traditionally, restaurants were closed on Mondays if they were opened during the weekend, but this has in recent years largely fallen out of practice. Many museums do however still remain closed on Mondays.

==== United Kingdom ====
The traditional business working week is from Monday to Friday (35 to 40 hours depending on contract). In retail, and other fields such as healthcare, days off might be taken on any day of the week. Employers can make their employees work every day of a week, although the employer is required to allow each employee breaks of either a continuous period of 24 hours every week or a continuous period of 48 hours every two weeks.

Laws for shop opening hours differ between Scotland and the rest of the UK. In England, Wales, and Northern Ireland, many shops and services are open on Saturdays and increasingly so on Sundays as well. In England and Wales, stores' maximum Sunday opening hours vary according to the total floor space of the store.<ref>{{cite web |url=http://www.bizhelp24.com/law/business-trading-hours-law.html |title=Working Hours – Business Trading Hours |publisher=}}</ref> In Scotland, however, there is no restriction in law on shop opening hours on a Sunday.

Under the EU [[Working Time Directive]], workers cannot be forced to work for more than 48 hours per week on average. However, the UK allows individuals to opt out if they so choose. Individuals can choose to opt in again after opting out, even if opting out was part of their employment contract. It is illegal to dismiss them or treat them unfairly for so doing – but they may be required to give up to 3 months notice to give the employer time to prepare, depending on what their employment contract says.<ref name="govuk-workingtime">{{cite web |url=https://www.gov.uk/maximum-weekly-working-hours/weekly-maximum-working-hours-and-opting-out |title=Maximum weekly working hours |publisher=HMG |accessdate=October 25, 2014 |date=June 27, 2014}}</ref>

The minimum holiday entitlement is now 28 days per year, but that can include public holidays, depending on the employee's contract.<ref>{{cite web |url=http://www.direct.gov.uk/en/Employment/Employees/Timeoffandholidays/DG_10029788 |title=Holiday entitlement |publisher=}}</ref> England & Wales have eight, Scotland has nine, and Northern Ireland has ten permanent public holidays each year.<ref>{{cite web |url=http://www.direct.gov.uk/en/Governmentcitizensandrights/LivingintheUK/DG_073741 |title=UK bank holidays |publisher=}}</ref><ref>[http://www.direct.gov.uk/en/Employment/Employees/WorkingHoursAndTimeOff/DG_10029426 Directgov: Working time limits (the 48-hour week)], business trading hours law.</ref> The 28 days holiday entitlement means that if the government creates a one-off public holiday in a given year, it is not necessarily a day off and it does not add 1 day to employees' holiday entitlement – unless the employer says otherwise, which some do.

=== Belarus ===
The working week is Monday to Friday.
Working time must not exceed 8 hours per day and 40 hours per week (on average, annualised).

=== India ===
The standard working week in [[India]] for most office jobs begins on Monday and ends on Saturday. The work schedule is 60 hours per week, Sunday being a rest day. However, most government offices and the software industry follow a five-day workweek.<ref>{{Cite book |url=https://books.google.com/books?id=RWcTBwAAQBAJ&lpg=PT38&ots=IT3sxY-MiS&dq=india%20%22work%20week%22%20(friday%20OR%20saturday)&hl=iw&pg=PT38#v=onepage&q=india%20%22work%20week%22%20(friday%20OR%20saturday)&f=false |title=bWise: Doing Business in India |last=Dunung |first=Sanjyot P. |date=2015-01-15 |publisher=Atma Global |isbn=978-0-9905459-2-7 |language=en}}</ref> All major industries along with services like transport, hospitality, healthcare etc. work in shifts.

Central government offices follow a five-day week. State governments follow half-day working on the first, third, and fifth Saturdays of each month and rest on the second and fourth Saturdays, except West Bengal's government which follows a Monday–Friday workweek. There is usually no half working day in the private sector and people work in two or three shifts of 8hours each.

Generally establishments other than those having pure desk jobs are open until late evening in most cities, offering more flexibility of time to visitors. Most stores are open for six or seven days a week. Retail shops in malls are open on all days. Doctors are mostly available in morning and evening in their clinics and at hospitals during the day. Doctors usually work twelve hour days, six-days a week. Senior doctors and surgeons work more. Most visiting doctors attached to hospitals visit on all days.

Many services are open till 8:00 pm or 9:00 pm. Most restaurants are open on all days. Small eateries open early and bigger ones open around 11:00 am. Most eateries close between 9:00 pm and 11:00 pm. Many highway restaurants called ''[[dhaba]]s'' are open for 24 hours a day. Dhabas are available in large numbers on all major state and national highways; outside city or village limits. Some highway fuel stations are open for 24 hours. Overall India works longer hours in most areas than most of the world and offers more flexibility of time for visitors.

=== Muslim countries ===

==== Thursday–Friday weekend ====
Friday is the Muslim holiday when [[Jumu'ah]] prayers take place. Most of the Middle Eastern countries and some other predominantly Muslim countries used to consider Thursday and Friday as their weekend. However, this weekend arrangement is no longer observed by a significant number of Muslim countries ([[Workweek and weekend#Friday–Saturday weekend|
see below]]).

==== Friday weekend (One day weekend) ====
Three countries in the Muslim world have Friday as the only weekend day and have a six-day working week.
* In [[Iran]], Thursday is half a day of work for most public offices and all schools are closed, but for most jobs, Thursday is a working day. Foreign companies normally have the Friday and Saturdays as their weekends.
* In [[Djibouti]], many offices also tend to open early – around 7:00 or 8:00, then closing at 13:00 or 14:00, especially during the summer due to the afternoon heat.

==== Friday–Saturday weekend ====
Following reforms in a number of [[Gulf Cooperation Council|Arab states in the Persian Gulf]] in the 2000s and 2010s, the Thursday–Friday weekend was replaced by the Friday–Saturday weekend. This change provided for the Muslim offering of Friday prayers and afforded more work days to coincide with the working calendars of international financial markets.
* [[Algeria]] (2009)<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/africa/8198365.stm |publisher=BBC News |title=Algeria switches weekend, again |date=August 14, 2009}}</ref>
* [[Afghanistan]] (2015)
* [[Bahrain]] (2006)
* [[Bangladesh]]
* [[Egypt]]<ref name="TSG">{{cite web |url=https://travel.state.gov/travel/cis_pa_tw/cis/cis_1144.html |title=Country Information |publisher=}}</ref>
* [[Iraq]] (2005–2006)<ref name="TSG" />
* [[Jordan]] (Week of January 8, 2000)<ref name="api_jordan">{{cite news |publisher=Associated Press International |title=Jordan shifts weekend to Friday-Saturday |date=December 25, 2000}}</ref><ref name="wfn">{{cite web |url=http://archive.wfn.org/2000/01/msg00078.html |title=Jordan Announces new Friday/Saturday Weekend |publisher=wfn.org |date=January 5, 2000 |accessdate=August 23, 2016}}</ref>
* [[Kuwait]] (2007)
* [[Libya]] (2005–2006)
* [[Malaysia]] (only in the states of [[Johor]], [[Kelantan]], [[Terengganu]], and [[Kedah]])
* [[Maldives]] (2013)
* [[Oman]] (2013)
* [[State of Palestine|Palestine]]
* [[Qatar]]
* [[Saudi Arabia]] (2013)<ref>{{cite web |url=http://www.voyage.gc.ca/dest/report-en.asp?country=258000 |title=Erreur 404 |publisher=Voyage.gc.ca |date=2016-04-27 |accessdate=2016-09-10}}</ref><ref>{{cite web |url=http://english.ahram.org.eg/NewsContent/2/8/74730/World/Region/Saudi-Arabia-changes-working-week-to-SunThurs-Offi.aspx |title=Saudi Arabia changes working week to Sun-Thurs: Official statement |work=ahram.org.eg}}</ref><ref>[http://www.spa.gov.sa/English/viewphotonews.php?id=1122964&pic=]{{dead link|date=September 2016}}</ref>
* [[Sudan]] (2008)
* [[Syria]] (2005–2006)<ref>{{cite web |url=http://www.syritour.com/content/en/travelfacts.asp |title=Travel Facts |last= |first= |date= |website=Syritour |publisher=Syritour.com |archive-url=https://web.archive.org/web/20080507172827/http://www.syritour.com/content/en/travelfacts.asp |archive-date=2005-05-07 |dead-url=yes |accessdate=2016-09-10}}</ref>
* [[United Arab Emirates]] (2006)<ref name="gulfnews" />
* [[Yemen]] (2013)<ref>{{cite web |url=http://www.yemenpost.net/Detail123456789.aspx?ID=3&SubID=7132&MainCat=3 |title=Yemen introduces its new weekend- Yemen Post English Newspaper Online |work=yemenpost.net}}</ref>

==== Saturday–Sunday weekend ====
Other countries with Muslim-majority populations or significant Muslim populations follow the Saturday–Sunday weekend, such as [[Indonesia]], [[Lebanon]], [[Turkey]], [[Tunisia]] and [[Morocco]]. While Friday is a working day, a long midday break is given to allow time for worship.
* [[Indonesia]] On Friday, due to prayer time for Muslims, the lunch break is extended up to 2 hours or more. Shopping malls are always open and very crowded on Saturday and Sunday. Thus, some banks offer weekend banking services, especially for branches located in or near shopping malls.
* [[Lebanon]] The working week is Monday to Friday; 8 hours per day, 40 hours in total per week. Some institutions, however, also work 4 hours on Saturdays . Large malls are open on Saturday and Sunday; many small shops close on Sunday.
* [[Malaysia]] (Federal Territories of [[Kuala Lumpur]], [[Labuan]] and [[Putrajaya]], [[Selangor]], [[Perak]], [[Penang]], [[Perlis]], [[Sarawak]], [[Sabah]], [[Pahang]], [[Malacca]], [[Negeri Sembilan]] except the states of [[Johor]], [[Kelantan]], [[Terengganu]] and [[Kedah]], which have a Friday–Saturday weekend)
* [[Mauritania]] (2014)<ref name="Mauritania weekend">{{cite web|url=https://www.bbc.com/news/blogs-news-from-elsewhere-29174054|title=weekend}}</ref>
* [[Morocco]] The working week is Monday to Friday, 8 hours per day, 40 hours in total per week.
* [[Pakistan]] follows the standard international 40-hour working week, from Monday to Friday, with Saturday and Sunday being the weekend.<ref name="Pakistan weekend">{{cite web |title=Pakistani Weekend Public Holidays Update |url=http://www.qppstudio.net/public-holidays-news/2010/pakistan_004010.htm |publisher=Reuters |accessdate=December 14, 2011 |date=April 24, 2010}}</ref> However, in many schools and enterprises, Friday is usually considered a half-day.
* [[Senegal]] The working week is Monday to Friday, with a large break on Friday afternoon.
* [[Tunisia]] The working week is Monday to Friday; 8 hours per day, 40 hours in total per week.
* [[Turkey]] Working above 45 hours is considered overtime, and the employer is required to pay 1.5x the hourly wage per hour.

==== Non-contiguous working week ====
[[Brunei Darussalam]] has a non-contiguous working week, consisting of Monday to Thursday plus Saturday. The days of rest are Friday (for [[Jumu'ah]] prayers) and Sunday.

Some non-government companies in Brunei adopted the working week of Monday to Friday, while the weekend starts on Saturday until Sunday. Depending on the company rules, employees may be required to work half-day on Saturday.

=== Israel ===
In [[Israel]], the standard workweek is 42 hours as prescribed by law. The typical workweek is five days, Sunday to Thursday, with 8.4 hours a day as the standard, with anything beyond that considered overtime. A minority of jobs operate on a partial six-day Sunday-Friday workweek.
<ref> http://www.davar1.co.il/118603</ref> Many Israelis work overtime hours, with a maximum of 12 overtime hours a week permitted by law. Most offices and businesses run on a five-day week, though many stores, post offices, banks, and schools are open and public transportation runs six days a week. Almost all businesses are closed during Saturday, and most public services except for emergency services, including almost all public transport, are unavailable on Saturdays. However, some shops, restaurants, cafes, places of entertainment, and factories are open on Saturdays, and a few bus and [[share taxi]] lines are active.<ref>http://www.timesofisrael.com/open-on-shabbat-israels-fray-of-rest/</ref><ref>http://www.haaretz.com/israel-news/.premium-1.725835</ref><ref>http://transport-in-israel.wikidot.com/shabbat-and-holidays</ref> Employees who work Saturdays, particularly service industry workers, public sector workers, and pilots, are compensated with alternative days off.<ref>https://www.justlanded.com/english/Israel/Israel-Guide/Jobs/Working-Conditions</ref> In 2014, the average workweek was 45.8 hours for men and 37.1 hours for women.<ref>{{cite web |author=By Lee Yaron |url=http://www.haaretz.com/israel-news/business/.premium-1.624900 |title=Israeli Workers’ Average Salary Rose 1.4% in 2013 to $2,376 – Business |publisher=Haaretz |date=2014-11-06 |accessdate=2016-09-10}}</ref>

=== Japan ===
The standard business office working week in [[Japan]] begins on Monday and ends on Friday, 40 hours per week. This system became common between 1980 and 2000. Before then, most workers in Japan worked full-time from Monday to Friday and a half day on Saturday, 45–48 hours per week. Public schools and facilities (excluding city offices) are generally open on Saturdays for half a day.<ref name="Jappleng University">{{cite web |title=Jappleng University (Days of the Week) |url=http://www.jappleng.com/education/jplearn/japanese_lessons/398/days-of-the-week-japanese}}</ref>

=== Mexico ===
[[Mexico]] has a 48-hour work week (8 hours × 6 days),<ref>{{cite web |title=Ley federal del trabajo. |url=http://www.diputados.gob.mx/LeyesBiblio/pdf/125.pdf |accessdate=May 23, 2014 |deadurl=yes |archiveurl=https://web.archive.org/web/20140604154515/http://www.diputados.gob.mx/LeyesBiblio/pdf/125.pdf |archivedate=June 4, 2014 |df=mdy-all}}</ref> it is a custom in most industries and trades to work half day on Saturday. Most public employees work Monday to Friday as well in some office companies. Shops and retailers open on Saturday and Sunday in most large cities.

=== Mongolia ===
[[Mongolia]] has a Monday to Friday working week, with a normal maximum time of 40 hours. Most shops are also open on weekends, many large retail chains having full opening hours even on Sunday. Private enterprises conduct business from 9:00 to 18:00, and government institutions may have full working hours.

=== Nepal ===
Nepal follows the ancient [[Hindu calendar|Vedic calendar]], which has the resting day on Saturday and the first day of the working week on Sunday.<ref name="Vedic Books">[http://vedicbooks.net/blog/?p=34 Vedic Books], The Vedic Week.</ref> Schools in Nepal are off on Saturdays, so it is common for pupils to go to school from Sunday to Friday.

In November 2012, the home ministry proposed a two-day holiday per week plan for all government offices except at those providing essential services like electricity, water, and telecommunications.<ref>{{cite web |url=http://www.myrepublica.com/portal/index.php?action=news_details&news_id=44273 |title=MYREPUBLICA.com – News in English from Nepal: Fast, Full & Factual News |publisher=}}</ref> This proposal followed a previous proposal by the Nepali government, i.e. ''Load-shedding Reduction Work Plan 2069 BS'', for a five working day plan for government offices as part of efforts to address the problem of [[load shedding|load-shedding]]. The proposal has been discussed in the Administration Committee; it is not yet clear whether the plan includes private offices and educational institutions.

=== New Zealand ===
In [[New Zealand]] the working week is typically Monday to Friday 8:30 to 17:00, but it is not uncommon for many industries (especially construction) to work a half day on Saturday, normally from 8:00 or 9:00 to about 13:00. Supermarkets, malls, independent retailers, and increasingly, banks, remain open seven days a week.

=== Russia ===
In [[Russia]] the common working week begins on Monday and ends on Friday with 8 hours per day.

Federal law defines a working week duration of 5 or 6 days with no more than 40 hours worked. In all cases Sunday is a holiday. With a 5-day working week the employer chooses which day of the week will be the second day off. Usually this is a Saturday, but in some organizations (mostly government), it is Monday. Government offices can thereby offer Saturday service to people with a normal working schedule.

There are non-working public holidays in Russia; all of them fall on a fixed date. By law, if such a holiday coincides with an ordinary day off, the next work day becomes a day off. An official public holiday cannot replace a regular day off. Each year the government can modify working weeks near public holidays in order to optimize the labor schedule. For example, if a five-day week has a public holiday on Tuesday or Thursday, the calendar is rearranged to provide a reasonable working week.

Exceptions include occupations such as transit workers, shop assistants, and security guards. In many cases independent schemes are used. For example, the service industry often uses the X-through-Y scheme (Russian: ''X через Y'') when every worker uses X days for work and the next Y days for rest.

==== Soviet Union ====
In the [[Soviet Union]] the standard working week was 41 hours: 8 hours, 12 min. Monday to Friday. Before the mid-1960s there was a 42-hour 6-day standard working week: 7 hours Monday to Friday and 6 hours on Saturday.

=== Singapore ===
In [[Singapore]] the common working week is 5-day work week, which runs from Monday to Friday beginning 8:30 a.m. and end at 5 p.m. – 6 p.m. Some companies work a half day on Saturdays. Shops, supermarkets and malls are open seven days a week and on most public holidays.

=== South Africa ===
In [[South Africa]] the working week traditionally was Monday to Friday with a half-day on Saturday and Sunday a public holiday. However, since 2013 there have been changes to the working week concept based on more than one variation. The week can be 5 days of work, or more. The maximum number of hours someone can work in a week remains 45.<ref>{{cite web |url=http://www.labour.gov.za/DOL/legislation/acts/basic-guides/basic-guide-to-working-hours |title=Basic Guide to Working Hours — Department of Labour |publisher=Labour.gov.za |date= |accessdate=2016-09-10}}</ref>

=== Thailand ===
In [[Thailand]] the working week is Monday to Saturday for a maximum of 44 to 48 hours per week (Saturday can be a half or full day).{{citation needed|date=December 2014}}

However, government offices and some private companies have modernised through enacting the American and European standard of working Monday through Friday.{{citation needed|date=December 2014}}

Currently, 50% of the luxury beach resorts in [[Phuket Province|Phuket]] have a five-day working week. Of the remaining 50%, 23% have taken steps to reform their 6-day workweek through such measures as reducing the working week from 6 days to 5.5 days.{{citation needed|date=December 2014}}

=== United States ===
The standard working week in the [[United States]] begins on Monday and ends on Friday, 40 hours per week, with Saturday and Sunday being weekend days. However, in practice, only 42% of employees work 40-hour weeks. The average workweek for full-time employees is 47 hours.<ref>{{cite web |url=http://www.latimes.com/business/la-fi-average-workweek-gallup-labor-day-20140829-story.html |title=Average full-time workweek is 47 hours, Gallup says |publisher=LA Times |date=2014-08-29 |accessdate=2016-09-10}}</ref> Most stores are open for business on Saturday and often on Sunday as well, except in a few places where prohibited by law (see [[Blue law]]). Increasingly, employers are offering compressed work schedules to employees. Some government and corporate employees now work a 9/80 work schedule (80 hours over 9 days during a two-week period)—commonly 9 hour days Monday to Thursday, 8 hours on one Friday, and off the following Friday. There are also some government or corporate employees that work a 10/40 schedule–40 hours per week over 4 days, usually with Fridays off. Jobs in healthcare, law enforcement, transportation, retail, and other service positions commonly require employees to work on the weekend or to do shift work.<ref>{{cite web |url=http://blog.tnsemployeeinsights.com/non-traditional-work-hours-and-retention/ |title=Non-Traditional Work Hours and Retention |publisher=tnsemployeeinsights.com|date=April 10, 2012|accessdate=June 27, 2018}}</ref>

=== Vietnam ===
[[Vietnam]] has a standard 48-hour six-day workweek. Monday to Friday are full workdays and Saturday is a partial day. Work typically begins at 8:00 AM and lasts until 5:00 PM from Monday to Friday and until 12:00 PM on Saturdays. This includes a one-hour lunch break. Government offices and banks follow a five-day workweek from Monday to Friday..<ref>''Vietnam Labor Laws and Regulations Handbook: Strategic Information and Basic Laws''</ref><ref>http://www.vietnamcheaptours.com/Tourist-Information/Time-and-working-hours/Time-and-working-hours.html</ref>

== See also ==
{{Portal|Organized labour}}
* [[Feria]]
* [[Labour and employment law]]
* [[Long weekend]]
* [[Business day]]
* [[Calendar day]]
* [[Days of the week]]
* [[Shopping hours]]
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Turbofan

2018-08-07T16:31:55Z

173.165.237.1: /* Low-bypass turbofan */

{{distinguish|propfan}}
[[File:Turbofan3 Unlabelled.gif|thumb|right|An animated turbofan engine]]
{{Seriesbox aircraft propulsion}}
[[File:Turbofan operation.svg|thumb|300px|Schematic diagram of a high-bypass turbofan engine]]
[[File:787 - Flickr - Beige Alert (8).jpg|thumb|[[Rolls-Royce Trent 1000]] turbofan powering a [[Boeing 787 Dreamliner]] testflight]]
[[File:Airbus Lagardère - GP7200 engine MSN108 (1).JPG|thumb|[[Engine Alliance GP7000]] turbofan (view from the rear) awaiting installation on an [[Airbus A380]] under construction]]

The '''turbofan''' or '''fanjet''' is a type of [[airbreathing jet engine]] that is widely used in [[aircraft engine|aircraft propulsion]]. The word "turbofan" is a [[portmanteau]] of "turbine" and "fan": the ''turbo'' portion refers to a [[gas turbine engine]] which achieves [[mechanical energy]] from combustion,<ref name=stuffworks>{{cite web|url= http://science.howstuffworks.com/turbine.htm |title= How Gas Turbine Engines Work |publisher= howstuffworks.com |author= Marshall Brain |accessdate=2010-11-24}}</ref> and the ''fan'', a [[ducted fan]] that uses the mechanical energy from the gas turbine to accelerate air rearwards. Thus, whereas all the air taken in by a [[turbojet]] passes through the turbine (through the [[combustion chamber]]), in a turbofan some of that air bypasses the turbine. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of those contributing to the [[thrust]].

The ratio of the mass-flow of air bypassing the engine core divided by the mass-flow of air passing through the core is referred to as the [[bypass ratio]]. The engine produces thrust through a combination of these two portions working together; engines that use more [[Propelling nozzle|jet thrust]] relative to fan thrust are known as ''low-bypass turbofans'', conversely those that have considerably more fan thrust than jet thrust are known as ''high-bypass''. Most commercial aviation jet engines in use today are of the high-bypass type,<ref>{{cite web|url=https://www.grc.nasa.gov/www/k-12/airplane/aturbf.html|title=Turbofan Engine|last1=Hall|first1=Nancy|date=May 5, 2015|website=Glenn Research Center|publisher=NASA|accessdate=October 25, 2015|quote=Most modern airliners use turbofan engines because of their high thrust and good fuel efficiency.}}</ref><ref name="HackerBurghardt2009">{{cite book|author1=Michael Hacker|author2=David Burghardt|author3=Linnea Fletcher |author4=Anthony Gordon |author5=William Peruzzi |title=Engineering and Technology|url=https://books.google.com/books?id=0-xuCgAAQBAJ&pg=PT336|accessdate=October 25, 2015|date=March 18, 2009|publisher=Cengage Learning|isbn=978-1-285-95643-5|page=319|quote=All modern jet-powered commercial aircraft use high bypass turbofan engines [...]}}</ref> and most modern military fighter engines are low-bypass.<ref name="Verma2013">{{cite book|author=Bharat Verma|title=Indian Defence Review: Apr–Jun 2012|url=https://books.google.com/books?id=IvAzNhvLK6AC&pg=PA18|accessdate=October 25, 2015|date=January 1, 2013|publisher=Lancer Publishers|isbn=978-81-7062-259-8|page=18|quote=Military power plants may be divided into some major categories – low bypass turbofans that generally power fighter jets [...]}}</ref><ref>{{cite book|editor=Frank Northen Magill|title=Magill's Survey of Science: Applied science series, Volume 3|date=1993|publisher=Salem Press|isbn=9780893567088|page=1431|quote=Most tactical military aircraft are powered by low-bypass turbofan engines.}}</ref> [[Afterburner]]s are not used on high-bypass turbofan engines but may be used on either low-bypass turbofan or [[turbojet]] engines.

Modern turbofans have either a large single-stage fan or a smaller fan with several stages. An early configuration combined a low-pressure turbine and fan in a single rear-mounted unit.

==Principles==
Turbofans were invented to circumvent an awkward feature of turbojets, which was that they were inefficient for subsonic flight. To raise the efficiency of a turbojet, the obvious approach would be to increase the burner temperature, to give better [[Carnot efficiency]] and fit larger compressors and nozzles. However, while that does increase thrust somewhat, the exhaust jet leaves the engine with even higher velocity, which at subsonic flight speeds, takes most of the extra energy with it, wasting fuel.

Instead, a turbofan can be thought of as a turbojet being used to drive a [[ducted fan]], with both of those contributing to the [[thrust]]. Whereas all the air taken in by a [[turbojet]] passes through the turbine (through the [[combustion chamber]]), in a turbofan some of that air bypasses the turbine.

Because the turbine has to additionally drive the fan, the turbine is larger and has larger pressure and temperature drops, and so the nozzles are smaller. This means that the exhaust velocity of the core is reduced. The fan also has lower exhaust velocity, giving much more thrust per unit energy (lower [[specific thrust]]). The overall effective exhaust velocity of the two exhaust jets can be made closer to a normal subsonic aircraft's flight speed. In effect, a turbofan emits a large amount of air more slowly, whereas a turbojet emits a smaller amount of air quickly, which is a far less efficient way to generate the same thrust.

The ratio of the mass-flow of air bypassing the engine core compared to the mass-flow of air passing through the core is referred to as the [[bypass ratio]]. The engine produces thrust through a combination of these two portions working together; engines that use more [[Propelling nozzle|jet thrust]] relative to fan thrust are known as ''low-bypass turbofans'', conversely those that have considerably more fan thrust than jet thrust are known as ''high-bypass''. Most commercial aviation jet engines in use today are of the high-bypass type,<ref>{{cite web|url=https://www.grc.nasa.gov/www/k-12/airplane/aturbf.html|title=Turbofan Engine|last1=Hall|first1=Nancy|date=May 5, 2015|website=Glenn Research Center|publisher=NASA|accessdate=October 25, 2015|quote=Most modern airliners use turbofan engines because of their high thrust and good fuel efficiency.}}</ref><ref name="HackerBurghardt2009">{{cite book|author1=Michael Hacker|author2=David Burghardt|author3=Linnea Fletcher |author4=Anthony Gordon |author5=William Peruzzi |title=Engineering and Technology|url=https://books.google.com/books?id=0-xuCgAAQBAJ&pg=PT336|accessdate=October 25, 2015|date=March 18, 2009|publisher=Cengage Learning|isbn=978-1-285-95643-5|page=319|quote=All modern jet-powered commercial aircraft use high bypass turbofan engines [...]}}</ref> and most modern military fighter engines are low-bypass.<ref name="Verma2013">{{cite book|author=Bharat Verma|title=Indian Defence Review: Apr–Jun 2012|url=https://books.google.com/books?id=IvAzNhvLK6AC&pg=PA18|accessdate=October 25, 2015|date=January 1, 2013|publisher=Lancer Publishers|isbn=978-81-7062-259-8|page=18|quote=Military power plants may be divided into some major categories – low bypass turbofans that generally power fighter jets [...]}}</ref><ref>{{cite book|editor=Frank Northen Magill|title=Magill's Survey of Science: Applied science series, Volume 3|date=1993|publisher=Salem Press|isbn=9780893567088|page=1431|quote=Most tactical military aircraft are powered by low-bypass turbofan engines.}}</ref> [[Afterburner]]s are not used on high-bypass turbofan engines but may be used on either low-bypass turbofan or [[turbojet]] engines.

=== Bypass ratio ===
{{main|Bypass ratio}}
The ''bypass ratio (BPR)'' of a turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core.<ref>https://www.britannica.com/technology/bypass-ratio</ref> A 10:1 bypass ratio, for example, means that 10 kg of air passes through the bypass duct for every 1 kg of air passing through the core.

Turbofan engines are usually described in terms of bpr, which together with overall pressure ratio, turbine inlet temperature and fan pressure ratio are important design parameters. In addition bpr is quoted for turboprop and unducted fan installations because their high propulsive efficiency gives them the overall efficiency characteristics of very high bypass turbofans. This allows them to be shown together with turbofans on plots which show trends of reducing sfc with increasing bpr. Bpr is also quoted for lift fan installations where the fan airflow is remote from the engine and doesn't physically touch the engine core.

Bypass provides a lower fuel consumption for the same thrust, measured as [[thrust specific fuel consumption]] (grams/second fuel per unit of thrust in kN using [[SI units]]). Lower fuel consumption that comes with high bypass ratios applies to [[turboprop]]s, using a [[Propeller (aeronautics)|propeller]] rather than a ducted fan.<ref name=kroo>Ilan Kroo and Juan Alonso. "[http://adg.stanford.edu/aa241/propulsion/propulsionintro.html Aircraft Design: Synthesis and Analysis, Propulsion Systems: Basic Concepts] [https://web.archive.org/web/20150418150746/http://adg.stanford.edu/aa241/propulsion/propulsionintro.html Archive]" ''[[Stanford University School of Engineering#Current departments at the school|Stanford University School of Engineering, Department of Aeronautics and Astronautics]]''. Quote: "When the bypass ratio is increased to 10-20 for very efficient low speed performance, the weight and wetted area of the fan shroud (inlet) become large, and at some point it makes sense to eliminate it altogether. The fan then becomes a propeller and the engine is called a turboprop. Turboprop engines provide efficient power from low speeds up to as high as M=0.8 with bypass ratios of 50-100."</ref><ref name=Spak>[http://web.mit.edu/aeroastro/people/spakovszky.html Prof. Z. S. Spakovszky]. "[http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node84.html 11.5 Trends in thermal and propulsive efficiency] [https://web.archive.org/web/20130528034153/http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node84.html Archive]" ''[[School of Engineering, Massachusetts Institute of Technology#Aeronautics and Astronautics|MIT turbines]]'', 2002. [http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/notes.html Thermodynamics and Propulsion]</ref><ref name=nag>Nag, P.K. "[https://books.google.com/books?id=Rq7uBQAAQBAJ Basic And Applied Thermodynamics]" p550. Published by Tata McGraw-Hill Education. Quote: "If the cowl is removed from the fan the result is a turboprop engine. Turbofan and turboprop engines differ mainly in their bypass ratio 5 or 6 for turbofans and as high as 100 for turboprop."</ref><ref>[http://www.animatedengines.com/jets.html Animated Engines]</ref> High bypass designs are the dominant type for commercial passenger aircraft and both civilian and military jet transports.

Business jets use medium bpr engines.<ref>http://www.abcm.org.br/anais/cobem/2013/PDF/1874.pdf</ref>

Combat aircraft use engines with ''low bypass'' ratios to compromise between fuel economy and the requirements of combat: high [[power-to-weight ratio]]s, supersonic performance, and the ability to use [[afterburners]].

If all the gas power from a gas turbine is converted to kinetic energy in a propelling nozzle, the aircraft is best suited to high supersonic speeds. If it is all transferred to a separate big mass of air with low kinetic energy, the aircraft is best suited to zero speed (hovering). For speeds in between, the gas power is shared between a separate airstream and the gas turbine's own nozzle flow in a proportion which gives the aircraft performance required. The first jet aircraft were subsonic and the poor suitability of the propelling nozzle for these speeds due to high fuel consumption was understood, and bypass proposed, as early as 1936 (U.K. Patent 471,368).
The underlying principle behind bypass is trading exhaust velocity for extra mass flow which still gives the required thrust but uses less fuel. [[Frank Whittle]] called it "gearing down the flow".<ref>Gas Turbine Aerodynamics, Sir Frank Whittle, Pergamon Press 1981, p.217</ref> Power is transferred from the gas generator to an extra mass of air, i.e. a bigger diameter propelling jet, moving more slowly. The bypass spreads the available mechanical power across more air to reduce the velocity of the jet.<ref>Aircraft Engine Design Second Edition, Mattingley, Heiser, Pratt, AIAA Education Series, {{ISBN|1-56347-538-3}}, p.539</ref> The trade off between mass flow and velocity is also seen with propellers and helicopter rotors by comparing disc loading and power loading.<ref>https://www.flightglobal.com/pdfarchive/view/1964/1964%20-%202596.html</ref> For example, the same helicopter weight can be supported by a high power engine and small diameter rotor or, for less fuel, a lower power engine and bigger rotor with lower velocity through the rotor.

Bypass usually refers to transferring gas power from a gas turbine to a bypass stream of air to reduce fuel consumption and jet noise. Alternatively, there may be a requirement for an afterburning engine where the sole requirement for bypass is to provide cooling air. This sets the lower limit for bpr and these engines have been called "leaky" or continuous bleed turbojets<ref>Jane's All The World's Aircraft 1975-1976, edited by John W.R. Taylor, Jane's Yearbooks, Paulton House, 8 Sheperdess Walk, London N1 7LW, p.748</ref> (General Electric YJ-101 bpr 0.25) and low bpr turbojets<ref>http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2275853</ref> (Pratt & Whitney PW1120). Low bpr (0.2) has also been used to provide surge margin as well as afterburner cooling for the [[Pratt & Whitney J58]].<ref>http://roadrunnersinternationale.com/pw_tales.htm</ref>

===Efficiency===
Since the [[propulsive efficiency|efficiency of propulsion]] is a function of the relative airspeed of the exhaust to the surrounding air, propellers are most efficient for low speed, pure jets for high speeds, and ducted fans in the middle. Turbofans are thus the most efficient engines in the range of speeds from about {{convert|500|to|1000|km/h|abbr=on}}, the speed at which most commercial aircraft operate.<ref name=grc_nasa>{{cite web|url= http://www.grc.nasa.gov/WWW/K-12/airplane/aturbf.html |title= Turbofan Engine |publisher= www.grc.nasa.gov |accessdate=2010-11-24}}</ref><ref name="Neumann_2004_1984_pp228-230">{{Citation | last = Neumann | first = Gerhard | authorlink = Gerhard Neumann | year = 2004 | origyear = 1984 | title = Herman the German: Just Lucky I Guess |publisher = Authorhouse | location = Bloomington, IN, USA | isbn = 1-4184-7925-X | postscript = . ''First published by Morrow in 1984 as ''Herman the German: Enemy Alien U.S. Army Master Sergeant''. Republished with a new title in 2004 by Authorhouse, with minor or no changes.''}}, pp. 228–230.</ref> Turbofans retain an efficiency edge over pure jets at low [[supersonic speed]]s up to roughly {{convert|1.6|Mach}}.

In a zero-bypass (turbojet) engine the high temperature and high pressure exhaust gas is accelerated by expansion through a [[propelling nozzle]] and produces all the thrust. The compressor absorbs all the mechanical power produced by the turbine. In a bypass design extra turbines drive a [[ducted fan]] that accelerates air rearward from the front of the engine. In a high-bypass design, the ducted fan and nozzle produce most of the thrust. Turbofans are closely related to [[turboprop]]s in principle because both transfer some of the gas turbine's gas power, using extra machinery, to a bypass stream leaving less for the hot nozzle to convert to kinetic energy. Turbofans represent an intermediate stage between [[turbojet]]s, which derive all their thrust from exhaust gases, and turbo-props which derive minimal thrust from exhaust gases (typically 10% or less).<ref name=srm>"[http://www.srmuniv.ac.in/downloads/turbofan-2012.pdf The turbofan engine] {{Webarchive|url=https://web.archive.org/web/20150418181832/http://www.srmuniv.ac.in/downloads/turbofan-2012.pdf |date=2015-04-18 }}", page 7. ''[[SRM University]], Department of aerospace engineering''</ref> Extracting shaft power and transferring it to a bypass stream introduces extra losses which are more than made up by the improved propulsive efficiency. The turboprop at its best flight speed gave significant fuel savings over a turbojet even though an extra turbine, a gearbox and a propeller were added to the turbojet's low-loss propelling nozzle.<ref>Gas Turbine Theory Second Edition, Cohen, Rogers and Saravanamuttoo, Longmans Group Limited 1972, {{ISBN|0 582 44927 8}}, p.85</ref> The turbofan has additional losses from its extra turbines, fan, bypass duct and extra propelling nozzle compared to the turbojet's single nozzle.

===Thrust===
While a turbojet engine uses all of the engine's output to produce thrust in the form of a hot high-velocity exhaust gas jet, a turbofan's cool low-velocity bypass air yields between 30% and 70% of the total thrust produced by a turbofan system.<ref>{{cite book|author=Federal Aviation Administration (FAA)|url=http://www.faa.gov/library/manuals/aircraft/airplane_handbook/media/FAA-H-8083-3B.pdf|title=FAA-H-8083-3B Airplane Flying Handbook Handbook|publisher=Federal Aviation Administration|edition=|year=2004|isbn=|deadurl=yes|archiveurl=https://web.archive.org/web/20120921094453/http://www.faa.gov/library/manuals/aircraft/airplane_handbook/media/FAA-H-8083-3B.pdf|archivedate=2012-09-21|df=}}</ref>

The thrust ('''''FN''''') generated by a turbofan depends on the [[effective exhaust velocity]] of the total exhaust, as with any jet engine, but because two exhaust jets are present the thrust equation can be expanded as:<ref>{{cite web|url=http://www.grc.nasa.gov/WWW/K-12/airplane/turbfan.html|title=Turbofan Thrust|publisher=}}</ref>

:<math>F_N = \dot{m}_e v_{he} - \dot{m}_o v_o + BPR\, (\dot{m}_c v_f)</math>

where:

{| border="0" cellpadding="2"
|-
|align="right"|'''''ṁ e'''''
|align="left"|= the mass rate of hot combustion exhaust flow from the core engine
|-
|align=right|'''''ṁo'''''
|align=left|= the mass rate of total air flow entering the turbofan = '''''ṁc''''' + '''''ṁf'''''
|-
|align=right|'''''ṁc'''''
|align=left|= the mass rate of intake air that flows to the core engine
|-
|align=right|'''''ṁf'''''
|align=left|= the mass rate of intake air that bypasses the core engine
|-
|align=right|'''''vf'''''
|align=left|= the velocity of the air flow bypassed around the core engine
|-
|align=right|'''''vhe'''''
|align=left|= the velocity of the hot exhaust gas from the core engine
|-
|align=right|'''''vo'''''
|align=left|= the velocity of the total air intake = the true airspeed of the aircraft
|-
|align=left|'''''BPR'''''
|align-right|= Bypass Ratio
|}

===Nozzles===
The cold duct and core duct's nozzle systems are relatively complex due to there being two exhaust flows.

In high bypass engines the fan is generally situated in a short duct near the front of the engine and typically has a convergent cold nozzle, with the tail of the duct forming a low pressure ratio nozzle that under normal conditions will choke creating supersonic flow patterns around the core.

The core nozzle is more conventional, but generates less of the thrust, and depending on design choices, such as noise considerations, may conceivably not choke.<ref>https://dspace.lib.cranfield.ac.uk/bitstream/handle/1826/12476/Civil_turbofan_engine_exhaust_aerodynamics-2017.pdf</ref>

In low bypass engines the two flows may combine within the ducts, and share a common nozzle, which can be fitted with afterburner.

===Noise===
Most of the air flow through a high-bypass turbofan is lower velocity bypass flow: even when combined with the much higher velocity engine exhaust, the average exhaust velocity is considerably lower than in a pure turbojet. Turbojet engine noise is predominately jet noise from the high exhaust velocity, therefore turbofan engines are significantly quieter than a pure-jet of the same thrust with jet noise no longer the predominant source. Other noise sources are the fan, compressor and turbine.<ref>"Softtly, softly towards the quiet jet" Michael J.T.Smith, New Scientist, 19 February 1970, Figure 5</ref>

Modern commercial aircraft employ high-bypass-ratio (HBPR) engines with separate flow, non-mixing, short-duct exhaust systems. These propulsion systems are known to generate significantly high noise levels due to the high-speed, high-temperature, and high-pressure nature of the exhaust jet, especially during high thrust conditions such as those required for takeoff. The primary source of jet noise is the turbulent mixing of shear layers in the engine’s exhaust. These shear layers contain instabilities that lead to highly turbulent vortices that generate the pressure fluctuations responsible for sound. In order to reduce the noise associated with jet flow, the aerospace industry has focused on developing various technologies to disrupt shear layer turbulence and reduce the overall noise produced.

Turbofan engine noise propagates both upstream the inlet and downstream the primary nozzle and the by-pass duct. The main noise sources are the turbine and the compressor, the jet and the fan. The contribution of each noise source significantly evolved in the last decades:<ref name="Kempton2011">[http://www.win.tue.nl/ceas-asc/Workshop15/CEAS-ASC_XNoise-EV_K1_Kempton.pdf Kempton, A, "Acoustic liners for modern aero-engines", 15th CEAS-ASC Workshop and 1st Scientific Workshop of X-Noise EV, 2011.]</ref> in typical 1960s design the jet was the main source whereas in modern turbofans the fan is the main noise source.

The fan noise is a tonal noise and its signature depends on the fan rotational speed:
* at low speed, the fan noise is due to the interaction of the blades with the distorted flow injected in the engine; this happens for example during the approach;
* at high engine ratings, the fan tip is supersonic and this allows intense rotor-locked duct modes to propagate upstream; this noise is known as "buzz saw" and is typical at take-off.<ref name=buzz_saw>[http://www.southampton.ac.uk/engineering/research/projects/buzz_saw_noise_and_non_linear_acoustics.page A. McAlpine "Research project: Buzz-saw noise and nonlinear acoustics"]</ref>

All modern turbofan engines are equipped with [[acoustic liner]]s to damp the noise generated. These are installed in the [[nacelle]], and they extend as much as possible to cover the largest area. The acoustic performance of the engine can be experimentally evaluated by means of ground tests<ref name="Schuster2010">Schuster, B., Lieber, L., & Vavalle, A., Optimization of a seamless inlet liner using an empirically validated prediction method. In 16th AIAA/CEAS Aeroacoustics Conference, Stockholm, Sweden.</ref> or in dedicated experimental test rigs.<ref name="Ferrante2011">Ferrante, P. G., Copiello, D., & Beutke, M.. Design and experimental verification of “true zero-splice” acoustic liners in the universal fan facility adaptation (UFFA) modular rig,”. In 17h AIAA/CEAS Aeroacoustics Conference, AIAA-2011-2728, Portland, OR.</ref>

[[File:GEnx-1B on Air India B787 (2).jpg|thumb|Chevrons on an [[Air India]] [[Boeing 787]] [[General Electric GEnx|GE GEnx]] engine.]]

In the [[aerospace]] industry, ''chevrons'' are the saw tooth patterns on the trailing edges of some [[jet engine]] nozzles<ref name=NASA>{{cite web |url=http://www.nasa.gov/topics/aeronautics/features/bridges_chevron_events.html |title=NASA Helps Create a More Silent Night |last1=Banke |first1=Jim |date=2012-12-13 |publisher=[[NASA]] |accessdate=January 12, 2013}}</ref> that are used for [[noise control|noise reduction]]. Their principle of operation is that, as hot air from the engine core mixes with cooler air blowing through the engine fan, the shaped edges serve to smooth the mixing, which reduces noise-creating turbulence.<ref name=NASA/> Chevrons were developed by Boeing with the help of [[NASA]].<ref name=NASA/><ref name="chevron technology">{{cite journal |url=https://www.researchgate.net/profile/K_Zaman/publication/273550214_Evolution_from_%27Tabs%27_to_%27Chevron_Technology%27__a_Review/links/5457d9110cf2bccc491117fa.pdf | work=Proceedings of the 13th Asian Congress of Fluid Mechanics 17–21 December 2010, Dhaka, Bangladesh | title=Evolution from 'Tabs' to 'Chevron Technology’–a Review | format=PDF-1.34 Mb | author1=Zaman, K.B.M.Q.|author2=Bridges, J. E.|author3=Huff, D. L. | date=17–21 December 2010 | publisher=[[NASA Glenn Research Center]]. Cleveland, Ohio | accessdate=January 29, 2013}}</ref> Some notable examples of such designs are [[Boeing 787]] and [[Boeing 747-8]] - on the [[Rolls-Royce Trent 1000]] and [[General Electric GEnx]] engines.
<ref>https://web.archive.org/web/20140325205124/http://www.afmc.org.cn/13thacfm/invited/201.pdf</ref>

==Common types==
===Low-bypass turbofan===

[[File:Turbofan operation lbp.svg|thumb|Schematic diagram illustrating a 2-spool, low-bypass turbofan engine with a mixed exhaust, showing the low-pressure (green) and high-pressure (purple) spools. The fan (and booster stages) are driven by the low-pressure turbine, whereas the high-pressure compressor is powered by the high-pressure turbine.]]

A high-specific-thrust/low-bypass-ratio turbofan normally has a multi-stage fan, developing a relatively high pressure ratio and, thus, yielding a high (mixed or cold) exhaust velocity. The core airflow needs to be large enough to give sufficient [[core power]] to drive the fan. A smaller core flow/higher bypass ratio cycle can be achieved by raising the high-pressure (HP) turbine rotor inlet temperature.

To illustrate one aspect of how a turbofan differs from a turbojet, they may be compared, as in a re-engining assessment, at the same airflow (to keep a common intake for example) and the same net thrust (i.e. same specific thrust). A bypass flow can be added only if the turbine inlet temperature is not too high to compensate for the smaller core flow. Future improvements in turbine cooling/material technology can allow higher turbine inlet temperature, which is necessary because of increased cooling air temperature, resulting from an [[overall pressure ratio]] increase.

The resulting turbofan, with reasonable efficiencies and duct loss for the added components, would probably operate at a higher nozzle pressure ratio than the turbojet, but with a lower exhaust temperature to retain net thrust. Since the temperature rise across the whole engine (intake to nozzle) would be lower, the (dry power) fuel flow would also be reduced, resulting in a better [[Thrust specific fuel consumption|specific fuel consumption]] (SFC).

Some low-bypass ratio military turbofans (e.g. F404) have variable inlet guide vanes to direct air onto the first fan rotor stage. This improves the fan [[compressor stall|surge]] margin (see [[compressor map]]).

=== Afterburning turbofan ===
{{further|Afterburner}}
[[File:Pratt & Whitney F119.JPEG|thumb|[[Pratt & Whitney F119]] afterburning turbofan on test]]

Since the 1970s, most [[jet fighter]] engines have been low/medium bypass turbofans with a mixed exhaust, [[afterburner]] and variable area final nozzle. An afterburner is a combustor located downstream of the turbine blades and directly upstream of the nozzle, which burns fuel from afterburner-specific fuel injectors. When lit, prodigious amounts of fuel are burnt in the afterburner, raising the temperature of exhaust gases by a significant degree, resulting in a higher exhaust velocity/engine specific thrust. The variable geometry nozzle must open to a larger throat area to accommodate the extra volume flow when the afterburner is lit. Afterburning is often designed to give a significant thrust boost for take off, transonic acceleration and combat maneuvers, but is very fuel intensive. Consequently, afterburning can be used only for short portions of a mission.

Unlike the main combustor, where the downstream turbine blades must not be damaged by high temperatures, an afterburner can operate at the ideal maximum ([[stoichiometric]]) temperature (i.e., about 2100K/3780Ra/3320F/1826C). At a fixed total applied fuel:air ratio, the total fuel flow for a given fan airflow will be the same, regardless of the dry specific thrust of the engine. However, a high specific thrust turbofan will, by definition, have a higher nozzle pressure ratio, resulting in a higher afterburning net thrust and, therefore, a lower afterburning specific fuel consumption (SFC). However, high specific thrust engines have a high dry SFC. The situation is reversed for a medium specific thrust afterburning turbofan: i.e., poor afterburning SFC/good dry SFC. The former engine is suitable for a combat aircraft which must remain in afterburning combat for a fairly long period, but has to fight only fairly close to the airfield (e.g. cross border skirmishes) The latter engine is better for an aircraft that has to fly some distance, or loiter for a long time, before going into combat. However, the pilot can afford to stay in afterburning only for a short period, before aircraft fuel reserves become dangerously low.

The first production afterburning turbofan engine was the [[Pratt & Whitney TF30]], which initially powered the [[General Dynamics F-111 Aardvark|F-111 Aardvark]] and [[Grumman F-14 Tomcat|F-14 Tomcat]]. Current low-bypass military turbofans include the [[Pratt & Whitney F119]], the [[Eurojet EJ200]], the [[General Electric F110]], the [[Klimov RD-33]], and the [[Saturn AL-31]], all of which feature a mixed exhaust, afterburner and variable area propelling nozzle.

=== High-bypass turbofan ===
{{further|Bypass ratio}}
[[File:Turbofan3 Labelled.gif|thumb|300px|alt=Animation of turbofan, which shows flow of air and the spinning of blades.|Animation of a 2-spool, high-bypass turbofan. {{ordered list
|list_style_type=upper-alpha
|1=Low-pressure spool
|2=High-pressure spool
|3=Stationary components
}}{{ordered list
|1=Nacelle
|2=Fan
|3=Low-pressure compressor
|4=High-pressure compressor
|5=Combustion chamber
|6=High-pressure turbine
|7=Low-pressure turbine
|8=Core nozzle
|9=Fan nozzle
}}]]


[[File:Turbofan operation.svg|thumb|Schematic diagram illustrating a 2-spool, high-bypass turbofan engine with an unmixed exhaust. The low-pressure spool is coloured green and the high-pressure one purple. Again, the fan (and booster stages) are driven by the low-pressure turbine, but more stages are required. A mixed exhaust is often employed nowadays.]]

To boost fuel economy and reduce noise, almost all of today's jet airliners and most military transport aircraft (e.g., the [[C-17 Globemaster III|C-17]]) are powered by low-specific-thrust/high-bypass-ratio turbofans. These engines evolved from the high-specific-thrust/low-bypass-ratio turbofans used in such aircraft in the 1960s. (Modern combat aircraft tend to use low-bypass ratio turbofans, and some military transport aircraft use [[turboprops]].)

Low specific thrust is achieved by replacing the multi-stage fan with a single-stage unit. Unlike some military engines, modern civil turbofans lack stationary inlet guide vanes in front of the fan rotor. The fan is scaled to achieve the desired net thrust.

The core (or gas generator) of the engine must generate enough power to drive the fan at its design flow and pressure ratio. Improvements in turbine cooling/material technology allow a higher (HP) turbine rotor inlet temperature, which allows a smaller (and lighter) core and (potentially) improving the core thermal efficiency. Reducing the core mass flow tends to increase the load on the LP turbine, so this unit may require additional stages to reduce the average stage loading and to maintain LP turbine efficiency. Reducing core flow also increases bypass ratio. Bypass ratios greater than 5:1 are increasingly common; the [[Pratt & Whitney PW1000G]], which entered commercial service in 2016, attains 12.5:1.

Further improvements in core thermal efficiency can be achieved by raising the overall pressure ratio of the core. Improved blade aerodynamics reduces the number of extra compressor stages required. With multiple compressors (i.e., LPC, IPC, and HPC) dramatic increases in overall pressure ratio have become possible. Variable geometry (i.e., [[Axial compressor#Bleed air, variable stators|stators]]) enable high-pressure-ratio compressors to work surge-free at all throttle settings.

[[File:CF6-6 engine cutaway.jpg|thumb|Cutaway diagram of the [[General Electric CF6]]-6 engine]]

The first (experimental) high-bypass turbofan engine was built and run on February 13, 1964 by [[Lycoming Engines|AVCO-Lycoming]].<ref>Decher, S., Rauch, D., “Potential of the High Bypass Turbofan,” American Society of Mechanical Engineers paper 64-GTP-15, presented at the Gas Turbine Conference and Products Show, Houston, Texas, March 1–5, 1964.</ref><ref>US Patent 3,390,527, High Bypass Ratio Turbofan, July 2, 1968.</ref> Shortly after, the [[General Electric TF39]] became the first production model, designed to power the [[Lockheed Corporation|Lockheed]] [[C-5 Galaxy]] military transport aircraft.<ref name="Neumann_2004_1984_pp228-230"/> The civil [[General Electric CF6]] engine used a derived design. Other high-bypass turbofans are the [[Pratt & Whitney JT9D]], the three-shaft [[Rolls-Royce RB211]] and the [[CFM International CFM56]]; also the smaller [[TF34]]. More recent large high-bypass turbofans include the [[Pratt & Whitney PW4000]], the three-shaft [[Rolls-Royce Trent]], the [[General Electric GE90]]/[[GEnx]] and the [[GP7000]], produced jointly by GE and P&W.

The lower the specific thrust of a turbofan, the lower the mean jet outlet velocity, which in turn translates into a high [[Thrust lapse|thrust lapse rate]] ( i.e. decreasing thrust with increasing flight speed). See technical discussion below, item 2. Consequently, an engine sized to propel an aircraft at high subsonic flight speed (e.g., Mach 0.83) generates a relatively high thrust at low flight speed, thus enhancing runway performance. Low specific thrust engines tend to have a high bypass ratio, but this is also a function of the temperature of the turbine system.

The turbofans on twin engined airliners are further more powerful to cope with losing one engine during take-off, which reduces the aircraft's net thrust by half. Modern twin engined airliners normally climb very steeply immediately after take-off. If one engine is lost, the climb-out is much shallower, but sufficient to clear obstacles in the flightpath.

The Soviet Union's engine technology was less advanced than the West's and its first wide-body aircraft, the [[Ilyushin Il-86]], was powered by low-bypass engines. The [[Yakovlev Yak-42]], a medium-range, rear-engined aircraft seating up to 120 passengers introduced in 1980 was the first Soviet aircraft to use high-bypass engines.

==Turbofan configurations==
Turbofan engines come in a variety of engine configurations. For a given engine cycle (i.e., same airflow, bypass ratio, fan pressure ratio, overall pressure ratio and HP turbine rotor inlet temperature), the choice of turbofan configuration has little impact upon the design point performance (e.g., net thrust, SFC), as long as overall component performance is maintained. Off-design performance and stability is, however, affected by engine configuration.

As the design overall pressure ratio of an engine cycle increases, it becomes more difficult to operate at low rpm, without encountering an instability known as compressor surge. This occurs when some of the compressor aerofoils stall (like the wings of an aircraft) causing a violent change in the direction of the airflow. However, compressor stall can be avoided, at low rpm, by progressively:

# opening interstage/intercompressor blow-off valves (inefficient), and/or
# closing variable stators within the compressor

Most modern western civil turbofans employ a relatively high-pressure-ratio high-pressure (HP) compressor, with many rows of variable stators to control surge margin at low rpm. In the three-spool [[Rolls-Royce RB211|RB211]]/[[Rolls-Royce Trent|Trent]] the core compression system is split into two, with the IP compressor, which supercharges the HP compressor, being on a different coaxial shaft and driven by a separate (IP) turbine. As the HP compressor has a modest pressure ratio its speed can be reduced surge-free, without employing variable geometry. However, because a shallow IP compressor working line is inevitable, the IPC has one stage of variable geometry on all variants except the -535, which has none.<ref>[https://web.archive.org/web/20110103084411/http://www.rolls-royce.com/Images/RB211-535E4%20_tcm92-11348.pdf RB211-535E4]</ref>

===Single-shaft turbofan===
Although far from common, the single-shaft turbofan is probably the simplest configuration, comprising a fan and high-pressure compressor driven by a single turbine unit, all on the same shaft. The [[SNECMA M53]], which powers [[Dassault Mirage 2000]] fighter aircraft, is an example of a single-shaft turbofan. Despite the simplicity of the turbomachinery configuration, the M53 requires a variable area mixer to facilitate part-throttle operation.

===Aft-fan turbofan===
One of the earliest turbofans was a derivative of the [[General Electric J79]] turbojet, known as the [[General Electric CJ805|CJ805-23]], which featured an integrated aft fan/low-pressure (LP) turbine unit located in the turbojet exhaust jetpipe. Hot gas from the turbojet turbine exhaust expanded through the LP turbine, the fan blades being a radial extension of the turbine blades. This aft-fan configuration was later exploited in the [[General Electric GE-36]] UDF (propfan) demonstrator of the early 80s. One of the problems with the aft fan configuration is hot gas leakage from the LP turbine to the fan.{{citation needed|date=November 2010}}

===Basic two-spool===
Many turbofans have the basic two-spool configuration where both the fan and LP turbine (i.e., LP spool) are mounted on a second (LP) shaft, running concentrically with the HP spool (i.e., HP compressor driven by HP turbine). The [[Rolls-Royce BR700|BR710]] is typical of this configuration. At the smaller thrust sizes, instead of all-axial blading, the HP compressor configuration may be axial-centrifugal (e.g., [[General Electric CFE738]]), double-centrifugal or even diagonal/centrifugal (e.g., [[Pratt & Whitney Canada PW600]]).

===Boosted two-spool===
Higher overall pressure ratios can be achieved by either raising the HP compressor pressure ratio or adding an intermediate-pressure (IP) compressor between the fan and HP compressor, to supercharge or boost the latter unit helping to raise the [[overall pressure ratio]] of the engine cycle to the very high levels employed today (i.e., greater than 40:1, typically). All of the large American turbofans (e.g., [[General Electric CF6]], [[GE90]] and [[GEnx]] plus [[Pratt & Whitney JT9D]] and [[Pratt & Whitney PW4000|PW4000]]) feature an IP compressor mounted on the LP shaft and driven, like the fan, by the LP turbine, the mechanical speed of which is dictated by the tip speed and diameter of the fan. The Rolls-Royce BR715 is a non-American example of this. The high bypass ratios (i.e., fan duct flow/core flow) used in modern civil turbofans tends to reduce the relative diameter of the attached IP compressor, causing its mean tip speed to decrease. Consequently, more IPC stages are required to develop the necessary IPC pressure rise.

===Three-spool===
Rolls-Royce chose a three-spool configuration for their large civil turbofans (i.e., the [[Rolls-Royce RB211|RB211]] and [[Rolls-Royce Trent|Trent]] families), where the intermediate pressure (IP) compressor is mounted on a separate (IP) shaft, running concentrically with the LP and HP shafts, and is driven by a separate IP turbine. The first three-spool engine was the earlier [[Rolls-Royce RB.203 Trent]] of 1967.

[[Ivchenko-Progress|Ivchenko Design Bureau]] chose the same configuration for their [[Lotarev D-36]] engine, followed by [[Progress D-18|Lotarev/Progress D-18T]] and [[Progress D-436]].

The [[Turbo-Union RB199]] military turbofan also has a three-spool configuration, as do the military [[Kuznetsov NK-25]] and [[Kuznetsov NK-321|NK-321]].

===Geared fan===
{{main article|Geared turbofan}}
[[File:Geared Turbofan NT.PNG|thumb|Geared turbofan]]

As bypass ratio increases, the mean radius ratio of the fan and low-pressure turbine (LPT) increases. Consequently, if the fan is to rotate at its optimum blade speed the LPT blading will spin slowly, so additional LPT stages will be required, to extract sufficient energy to drive the fan. Introducing a [[epicyclic gearing|(planetary) reduction gearbox]], with a suitable gear ratio, between the LP shaft and the fan enables both the fan and LP turbine to operate at their optimum speeds. Typical of this configuration are the long-established [[Honeywell TFE731]], the [[Honeywell ALF 502]]/507, and the recent [[Pratt & Whitney PW1000G]].

===Military turbofans===
[[File:Alpha Jet E47 2.JPG|thumb|Ducting on a [[Dassault/Dornier Alpha Jet]] – At subsonic speeds, the increasing diameter of the inlet duct [[Continuity equation|slows incoming air]], causing its static pressure to increase.]]
Most of the configurations discussed above are used in civilian turbofans, while modern military turbofans (e.g., [[SNECMA M88]]) are usually basic two-spool.

===High-pressure turbine===
Most civil turbofans use a high-efficiency, 2-stage HP turbine to drive the HP compressor. The [[CFM56]] uses an alternative approach: a single-stage, high-work unit. While this approach is probably less efficient, there are savings on cooling air, weight and cost.

In the [[Rolls-Royce RB211|RB211]] and [[Rolls-Royce Trent|Trent]] 3-spool engine series, the HP compressor pressure ratio is modest so only a single HP stage is required. Rather than adding stage/s to the LP turbine to drive the higher pressure ratio IP (intermediate pressure) compressor, Rolls-Royce mounts it on a separate shaft and drives it with an IP turbine.

Because the HP compressor pressure ratio is modest, modern military turbofans tend to use a single-stage HP turbine.

===Low-pressure turbine===
Modern civil turbofans have multi-stage LP turbines (e.g., 3, 4, 5, 6, 7). The number of stages required depends on the engine cycle bypass ratio and how much supercharging (i.e., IP compression) is on the LP shaft, behind the fan. A geared fan may reduce the number of required LPT stages in some applications.<ref>{{cite web |url= http://www.mtu.de/en/technologies/engineering_news/others/Riegler_Geared_turbofan_technology.pdf |title= "The geared turbofan technology – Opportunities, challenges and readiness status" |deadurl= bot: unknown |archiveurl= https://web.archive.org/web/20130520065423/http://www.mtu.de/en/technologies/engineering_news/others/Riegler_Geared_turbofan_technology.pdf |archivedate= 2013-05-20 |df= }} C. Riegler, C. Bichlmaier:, 1st CEAS European Air and Space Conference, 10–13 September 2007, Berlin, Germany</ref> Because of the much lower bypass ratios employed, military turbofans require only one or two LP turbine stages.

==Overall performance==

===Cycle improvements===

Consider a mixed turbofan with a fixed bypass ratio and airflow. Increasing the overall pressure ratio of the compression system raises the combustor entry temperature. Therefore, at a fixed fuel flow there is an increase in (HP) turbine rotor inlet temperature. Although the higher temperature rise across the compression system implies a larger temperature drop over the turbine system, the mixed nozzle temperature is unaffected, because the same amount of heat is being added to the system. There is, however, a rise in nozzle pressure, because overall pressure ratio increases faster than the turbine expansion ratio, causing an increase in the hot mixer entry pressure. Consequently, net thrust increases, whilst specific fuel consumption (fuel flow/net thrust) decreases. A similar trend occurs with unmixed turbofans.

So turbofans can be made more fuel efficient by raising overall pressure ratio and turbine rotor inlet temperature in unison. However, better turbine materials and/or improved vane/blade cooling are required to cope with increases in both turbine rotor inlet temperature and compressor delivery temperature. Increasing the latter may require better compressor materials.

Overall pressure ratio can be increased by improving fan (or) LP compressor pressure ratio and/or HP compressor pressure ratio. If the latter is held constant, the increase in (HP) compressor delivery temperature (from raising overall pressure ratio) implies an increase in HP mechanical speed. However, stressing considerations might limit this parameter, implying, despite an increase in overall pressure ratio, a reduction in HP compressor pressure ratio.

According to simple theory, if the ratio of turbine rotor inlet temperature/(HP) compressor delivery temperature is maintained, the HP turbine throat area can be retained. However, this assumes that cycle improvements are obtained, while retaining the datum (HP) compressor exit flow function (non-dimensional flow). In practice, changes to the non-dimensional speed of the (HP) compressor and cooling bleed extraction would probably make this assumption invalid, making some adjustment to HP turbine throat area unavoidable. This means the HP turbine nozzle guide vanes would have to be different from the original. In all probability, the downstream LP turbine nozzle guide vanes would have to be changed anyway.

===Thrust growth===

Thrust growth is obtained by increasing [[core power]]. There are two basic routes available:
# hot route: increase HP turbine rotor inlet temperature
# cold route: increase core mass flow

Both routes require an increase in the combustor fuel flow and, therefore, the heat energy added to the core stream.

The hot route may require changes in turbine blade/vane materials and/or better blade/vane cooling. The cold route can be obtained by one of the following:

# adding [[T-stage]]s to the LP/IP compression
# adding a [[zero-stage]] to the HP compression
# improving the compression process, without adding stages (e.g. higher fan hub pressure ratio)

all of which increase both overall pressure ratio and core airflow.

Alternatively, the [[core size]] can be increased, to raise core airflow, without changing overall pressure ratio. This route is expensive, since a new (upflowed) turbine system (and possibly a larger IP compressor) is also required.

Changes must also be made to the fan to absorb the extra core power. On a civil engine, jet noise considerations mean that any significant increase in take-off thrust must be accompanied by a corresponding increase in fan mass flow (to maintain a T/O specific thrust of about 30 lbf/lb/s).

===Technical discussion===
# Specific thrust (net thrust/intake airflow) is an important parameter for turbofans and jet engines in general. Imagine a fan (driven by an appropriately sized electric motor) operating within a pipe, which is connected to a propelling nozzle. It is fairly obvious, the higher the fan pressure ratio (fan discharge pressure/fan inlet pressure), the higher the jet velocity and the corresponding specific thrust. Now imagine we replace this set-up with an equivalent turbofan – same airflow and same fan pressure ratio. Obviously, the core of the turbofan must produce sufficient power to drive the fan via the low-pressure (LP) turbine. If we choose a low (HP) turbine inlet temperature for the gas generator, the core airflow needs to be relatively high to compensate. The corresponding bypass ratio is therefore relatively low. If we raise the turbine inlet temperature, the core airflow can be smaller, thus increasing bypass ratio. Raising turbine inlet temperature tends to increase thermal efficiency and, therefore, improve fuel efficiency.
# Naturally, as altitude increases, there is a decrease in air density and, therefore, the net thrust of an engine. There is also a flight speed effect, termed thrust lapse rate. Consider the approximate equation for net thrust again:<blockquote><math>F_n = m \cdot (V_{jfe} - V_a)</math></blockquote> With a high specific thrust (e.g., fighter) engine, the jet velocity is relatively high, so intuitively one can see that increases in flight velocity have less of an impact upon net thrust than a medium specific thrust (e.g., trainer) engine, where the jet velocity is lower. The impact of thrust lapse rate upon a low specific thrust (e.g., civil) engine is even more severe. At high flight speeds, high-specific-thrust engines can pick up net thrust through the ram rise in the intake, but this effect tends to diminish at supersonic speeds because of shock wave losses.
# Thrust growth on civil turbofans is usually obtained by increasing fan airflow, thus preventing the jet noise becoming too high. However, the larger fan airflow requires more power from the core. This can be achieved by raising the overall pressure ratio (combustor inlet pressure/intake delivery pressure) to induce more airflow into the core and by increasing turbine inlet temperature. Together, these parameters tend to increase core thermal efficiency and improve fuel efficiency.
# Some high-bypass-ratio civil turbofans use an extremely low area ratio (less than 1.01), convergent-divergent, nozzle on the bypass (or mixed exhaust) stream, to control the fan working line. The nozzle acts as if it has variable geometry. At low flight speeds the nozzle is unchoked (less than a Mach number of unity), so the exhaust gas speeds up as it approaches the throat and then slows down slightly as it reaches the divergent section. Consequently, the nozzle exit area controls the fan match and, being larger than the throat, pulls the fan working line slightly away from surge. At higher flight speeds, the ram rise in the intake increases nozzle pressure ratio to the point where the throat becomes choked (M=1.0). Under these circumstances, the throat area dictates the fan match and, being smaller than the exit, pushes the fan working line slightly towards surge. This is not a problem, since fan surge margin is much better at high flight speeds.
# The off-design behaviour of turbofans is illustrated under [[compressor map]] and [[turbine map]].
# Because modern civil turbofans operate at low specific thrust, they require only a single fan stage to develop the required fan pressure ratio. The desired overall pressure ratio for the engine cycle is usually achieved by multiple axial stages on the core compression. Rolls-Royce tend to split the core compression into two with an intermediate pressure (IP) supercharging the HP compressor, both units being driven by turbines with a single stage, mounted on separate shafts. Consequently, the HP compressor need develop only a modest pressure ratio (e.g., ~4.5:1). US civil engines use much higher HP compressor pressure ratios (e.g., ~23:1 on the [[General Electric GE90]]) and tend to be driven by a two-stage HP turbine. Even so, there are usually a few IP axial stages mounted on the LP shaft, behind the fan, to further supercharge the core compression system. Civil engines have multi-stage LP turbines, the number of stages being determined by the bypass ratio, the amount of IP compression on the LP shaft and the LP turbine blade speed.
# Because military engines usually have to be able to fly very fast at sea level, the limit on HP compressor delivery temperature is reached at a fairly modest design overall pressure ratio, compared with that of a civil engine. Also the fan pressure ratio is relatively high, to achieve a medium to high specific thrust. Consequently, modern military turbofans usually have only 5 or 6 HP compressor stages and require only a single-stage HP turbine. Low-bypass-ratio military turbofans usually have one LP turbine stage, but higher bypass ratio engines need two stages. In theory, by adding IP compressor stages, a modern military turbofan HP compressor could be used in a civil turbofan derivative, but the core would tend to be too small for high thrust applications.

==Early turbofans==
[[File:Rolls Royce Conway Mk508 (1959) used in Boeing 707-420 at Flugausstellung Hermeskeil, pic1.JPG|thumb|[[Rolls-Royce Conway]] low bypass turbofan from a [[Boeing 707]]. The bypass air exits from the fins whilst the exhaust from the core exits from the central nozzle. This fluted jetpipe design is a noise-reducing method devised by Frederick Greatorex at Rolls-Royce]]
[[File:Outer nozzle of GEnx-2B turbofan engine.jpg|thumb|[[General Electric GEnx|General Electric GEnx-2B]] turbofan engine from a [[Boeing 747|Boeing 747-8]]. View into the outer (propelling or "cold") nozzle.]]
Early turbojet engines were not very fuel-efficient as their overall pressure ratio and turbine inlet temperature were severely limited by the technology available at the time. The first turbofan to run was the German [[Daimler-Benz DB 007|Daimler-Benz DB 670]] (designated as the 109-007 by the [[Ministry of Aviation (Germany)|RLM]]) with a first run date of 27 May 1943. Turbomachinery testing, using an electric motor, had started on 1 April 1943.<ref>"Turbojet History And Development 1930–1960 Volume 1", The Crowood Press Ltd. 2007, {{ISBN|978 1 86126 912 6}}, p.241</ref> The engine was abandoned later while the war went on and problems could not be solved. The British wartime [[Metropolitan-Vickers F.2|Metrovick F.2]] axial flow jet was given a fan, as the Metrovick F.3 in 1943, to create the first British turbofan.<ref>{{cite web|url=http://www.flightglobal.com/airspace/media/aeroenginesjetcutaways/metrovick-f3-cutaway-5614.aspx |title=Metrovick F3 Cutaway – Pictures & Photos on FlightGlobal Airspace |publisher=Flightglobal.com |date=2007-11-07 |accessdate=2013-04-29}}</ref>

Improved materials, and the introduction of twin compressors such as in the [[Rolls-Royce Olympus|Bristol Olympus]]<ref>{{cite web|url=http://www.flightglobal.com/pdfarchive/view/1954/1954%20-%200985.html |title=1954 | 0985 | Flight Archive |publisher=Flightglobal.com |date=1954-04-09 |accessdate=2013-04-29}}</ref> and [[Pratt & Whitney JT3C]] engines, increased the overall pressure ratio and thus the [[thermodynamics|thermodynamic]] efficiency of engines, but they also led to a poor propulsive efficiency, as pure turbojets have a high specific thrust/high velocity exhaust better suited to supersonic flight.

The original '''low-bypass turbofan''' engines were designed to improve propulsive efficiency by reducing the exhaust velocity to a value closer to that of the aircraft. The [[Rolls-Royce Conway]], the world's first production turbofan, had a bypass ratio of 0.3, similar to the modern [[General Electric F404]] fighter engine. Civilian turbofan engines of the 1960s, such as the [[Pratt & Whitney JT8D]] and the [[Rolls-Royce Spey]] had bypass ratios closer to 1, and were similar to their military equivalents.

The first General Electric turbofan was the aft-fan [[General Electric CJ805|CJ805-23]] based on the CJ805-3 turbojet. It was followed by the aft-fan [[General Electric CF700]] engine with a 2.0 bypass ratio. This was derived from the [[General Electric J85|General Electric J85/CJ610]] turbojet (2,850 lbf or 12,650 N) to power the larger Rockwell Sabreliner 75/80 model aircraft, as well as the Dassault Falcon 20 with about a 50% increase in thrust (4,200 lbf or 18,700 N). The CF700 was the first small turbofan in the world to be certified by the [[Federal Aviation Administration]] (FAA). There were at one time over 400 CF700 aircraft in operation around the world, with an experience base of over 10 million service hours. The CF700 turbofan engine was also used to train Moon-bound astronauts in [[Project Apollo]] as the powerplant for the [[LLRV|Lunar Landing Research Vehicle]].

== Recent developments ==

=== Aerodynamic modelling ===

[[Aerodynamics]] is a mix of [[Speed of sound|subsonic]], [[transonic]] and [[supersonic]] airflow on a single fan/[[gas compressor]] blade in a modern turbofan. The airflow past the blades has to be maintained within close angular limits to keep the air flowing against an increasing pressure. Otherwise the air will come back out of the intake.<ref name=LN161021>{{cite web |url= https://leehamnews.com/2016/10/21/bjorns-corner-engine-challenge/ |title= Bjorn’s Corner: The Engine challenge |author= Bjorn Fehrm |date= October 21, 2016 |work= Leeham News}}</ref>

The [[FADEC|Full Authority Digital Engine Control]] (FADEC) needs accurate data for controlling the engine. The critical [[turbine]] inlet temperature (TIT) is too harsh an environment, at 1,700 °C and 17 bars, for reliable [[temperature sensor|sensor]]s. During development of a new engine type a relation is established between a more easily measured temperature like [[Exhaust gas]] temperature and the TIT. The EGT is then used to make sure the engine doesn't run too hot.<ref name=LN161021/>

=== Blade technology ===

A 100 g [[turbine]] blade is subjected to 1,700 °C/3100 °F, at 17 bars/250 Psi and a [[centrifugal force]] of 40 kN/ 9,000 lbf, well above the point of [[plastic deformation]] and even above the [[melting point]].
Exotic [[alloy]]s, sophisticated [[air cooling]] schemes and special mechanical design are needed to keep the [[physical stress]]es within the strength of the material.
[[Rotating seal]]s must withstand harsh conditions for 10 years, 20,000 missions and rotating at 10–20,000 rpm.<ref name=LN161021/>

The high-temperature performance of fan blades has increased through developments in the casting manufacturing process, the cooling design, [[thermal barrier coating]]s, and [[alloy]]s.
Cycle-wise, the HP turbine inlet temperature is less important than its rotor inlet temperature (RIT), after the temperature drop across its stator.
Although modern engines have peak RITs of the order of {{cvt|1560|°C}}, such temperatures are experienced only for a short time during take-off on civil engines.


Originally standard [[polycrystalline]] metals were used to make fan blades, but developments in [[material science]] have allowed blades to be constructed from aligned metallic crystals and more recently [[single crystal]]s to operate at higher temperatures with less distortion.
These alloys and [[Nickel]]-based [[superalloys]] are utilized in HP turbine blades in most modern jet engines.


HP turbine inlet is cooled below its melting point with air bled from the compressor, bypassing the combustor and entering the hollow blade or vane.<ref name=spt>{{cite article |author= Peter Spittle, [[Rolls-Royce plc]] |url= http://users.encs.concordia.ca/~kadem/Rolls%20Royce.pdf |title= Gas turbine technology |date= November 2003 |journal= [[Physics Education]]}}</ref>
After picking up heat, the cooling air is dumped into the main gas stream and downstream stages are uncooled if the local temperatures are low enough.

=== Fan blades ===

Fan blades have been growing as jet engines have been getting bigger: each fan blade carries the equivalent of nine [[double-decker bus]]es and swallows the volume of a [[squash court]] every second.
Advances in [[computational fluid dynamics]] (CFD) modelling have permitted complex, 3D curved shapes with very wide [[Chord (aeronautics)|chord]], keeping the fan capabilities while minimizing the blade count to lower costs.
Coincidentally, the [[bypass ratio]] grew to achieve higher [[propulsive efficiency]] and the fan diameter increased.<ref name=MRO28sep2017/>

Rolls-Royce pioneered the hollow, [[titanium]] wide-chord fan blade in the 1980s for aerodynamic efficiency and [[foreign object damage]] resistance in the [[RB211]] then for the [[Rolls-Royce Trent|Trent]].
[[GE Aviation]] introduced [[carbon fiber composite]] fan blades on the [[GE90]] in 1995, manufactured today with a [[carbon-fiber tape|carbon-fiber tape-layer]] process.
GE partner [[Safran]] developed a [[3D weaving|3D woven]] technology with [[Albany Engineered Composites|Albany Composites]] for the [[CFM56]] and [[CFM LEAP]] engines.<ref name=MRO28sep2017>{{cite news |url= http://www.mro-network.com/engines-engine-systems/understanding-complexities-bigger-fan-blades |title= Understanding Complexities Of Bigger Fan Blades |author= Ben Hargreaves |date= Sep 28, 2017 |work= Aviation Week Network}}</ref>

=== Future progress ===

Engine cores are shrinking as they are operating at higher [[Overall pressure ratio|pressure ratio]]s and becoming more efficient, and become smaller compared to the fan as bypass ratios increase.
Blade [[tip clearance]]s are harder to maintain at the exit of the high-pressure compressor where blades are {{cvt|0.5|in|mm}} high or less, [[Structural system|backbone]] bending further affects clearance control as the core is proportionately longer and thinner and the fan to low-pressure turbine driveshaft is in constrained space within the core.<ref name=AvWeek26Mar2015>{{cite news |url= http://aviationweek.com/technology/reversed-tilted-future-pratt-s-geared-turbofan |title= A Reversed, Tilted Future For Pratt’s Geared Turbofan? |date= Mar 26, 2015 |author= Guy Norris and Graham Warwick |work= Aviation Week & Space Technology}}</ref>

For [[Pratt & Whitney]] VP technology and environment [[Alan H. Epstein|Alan Epstein]] "Over the history of commercial aviation, we have gone from 20% to 40% [cruise efficiency], and there is a consensus among the engine community that we can probably get to 60%".<ref name=AvWeek8Aug2017>{{cite news |url= http://aviationweek.com/technology/turbofans-are-not-finished-yet |title= Turbofans Are Not Finished Yet |date= Aug 8, 2017 |author= Guy Norris |work= Aviation Week & Space Technology}}</ref>


[[Geared turbofan]]s and further fan [[Overall pressure ratio|pressure ratio]] reductions will continue to improve [[propulsive efficiency]].
The second phase of the FAA’s [[Continuous Lower Energy, Emissions and Noise]] (CLEEN) program is targeting for the late 2020s reductions of 33% fuel burn, 60% emissions and 32 dB EPNdb noise compared with the 2000s state-of-the-art.
In summer 2017 at [[NASA Glenn Research Center]] in [[Cleveland, Ohio]], Pratt has finished testing a very-low-pressure-ratio fan on a [[PW1000G]], resembling an [[open rotor]] with less blades than the PW1000G's 20.<ref name=AvWeek8Aug2017/>

The weight and size of the [[nacelle]] would be reduced by a short duct inlet, imposing higher aerodynamic turning loads on the blades and leaving less space for soundproofing, but a lower-pressure-ratio fan is slower.
[[UTC Aerospace Systems]] Aerostructures will have a full-scale ground test in 2019 of its low-drag Integrated Propulsion System with a [[thrust reverser]], improving fuel burn by 1% and with 2.5-3 EPNdB lower noise.<ref name=AvWeek8Aug2017/>


[[Safran]] can probably deliver another 10–15% in fuel efficiency through the mid-2020s before reaching an [[asymptote]], and next will have to introduce a breakthrough : to increase the [[bypass ratio]] to 35:1 instead of 11:1 for the [[CFM LEAP]], it is demonstrating a counterrotating [[open rotor]] unducted fan (propfan) in [[Istres, France]], under the European [[Clean Sky]] technology program.
[[Computational fluid dynamics|Modeling]] advances and high [[specific strength]] materials may help it succeed where previous attempts failed.
When noise levels will be within current standards and similar to the Leap engine, 15% lower fuel burn will be available and for that Safran is testing its controls, vibration and operation, while [[airframe]] integration is still challenging.<ref name=AvWeek8Aug2017/>


For [[GE Aviation]], the [[energy density]] of jet fuel still maximises the [[Breguet range equation]] and higher pressure ratio cores, lower pressure ratio fans, low-loss inlets and lighter structures can further improve thermal, transfer and propulsive efficiency.
Under the [[U.S. Air Force]]’s [[Adaptive Engine Transition Program]], adaptive [[thermodynamic cycle]]s will be used for the [[sixth-generation jet fighter]], based on a modified [[Brayton cycle]] and [[Constant volume]] combustion.
[[Additive manufacturing]] in the [[General Electric Advanced Turboprop|advanced turboprop]] will reduce weight by 5% and fuel burn by 20%.<ref name=AvWeek8Aug2017/>

Rotating and static [[ceramic matrix composite]] (CMC) parts operates {{cvt|500|°F}} hotter than metal and are one-third its weight.
With $21.9 million from the [[Air Force Research Laboratory]], GE is investing $200 million in a CMC facility in [[Huntsville, Alabama]], in addition to its [[Asheville, North Carolina]] site, mass-producing [[silicon carbide]] matrix with silicon-carbide fibers in 2018.
CMCs will be used ten times more by the mid-2020s : the CFM LEAP requires 18 CMC turbine shrouds per engine and the [[GE9X]] will use it in the combustor and for 42 HP turbine nozzles.<ref name=AvWeek8Aug2017/>


[[Rolls-Royce Plc]] aim for a 60:1 pressure ratio core for the 2020s [[Ultrafan]] and began ground tests of its {{cvt|100,000|hp}} gear for {{cvt|100,000|lbf|kN}} and 15:1 bypass ratios.
Nearly [[stoichiometric]] turbine entry temperatures approaches the theoretical limit and its impact on emissions has to be balanced with environmental performance goals.
Open rotors, lower pressure ratio fans and potentially [[distributed propulsion]] offers more room for better propulsive efficiency.
Exotic cycles, [[heat exchanger]]s and pressure gain/constant volume combustion can improve [[thermodynamic efficiency]].
Additive manufacturing could be an enabler for [[intercooler]] and [[recuperator]]s.
Closer airframe integration and [[Hybrid electric vehicle#Aircraft|hybrid]] or [[electric aircraft]] can be combined with gas turbines.<ref name=AvWeek8Aug2017/>

Current Rolls-Royce engines have a 72–82% propulsive efficiency and 42–49% thermal efficiency for a {{cvt|0.63|-|0.49|lb/lbf/h|g/kN/h}} [[Thrust specific fuel consumption|TSFC]] at Mach 0.8, and aim for theoretical limits of 95% for open rotor propulsive efficiency and 60% for thermal efficiency with stoichiometric [[turbine]] entry temperature and 80:1 [[overall pressure ratio]] for a {{cvt|0.35|lb/lbf/h|g/kN/h}} TSFC<ref>{{citation |url= http://www.fzt.haw-hamburg.de/pers/Scholz/dglr/hh/text_2014_03_20_EnginesTechnology.pdf |title= Rolls-Royce technology for future aircraft engines |date= March 20, 2014 |author= Ulrich Wenger |publisher= Rolls-Royce Deutschland}}</ref>

As teething troubles may not show up until several thousand hours, the latest turbofans technical problems disrupt [[airline]]s operations and [[aerospace manufacturer|manufacturer]]s deliveries while production rates are rising sharply.
[[Trent 1000]] cracked blades [[aircraft on ground|grounded]] almost 50 [[Boeing 787]]s and reduced [[ETOPS]] to 2.3 hours down from 5.5, costing [[Rolls-Royce plc]] almost $950 million.
[[PW1000G]] knife-edge seal fractures have caused [[Pratt & Whitney]] to fall way behind in deliveries, leaving about 100 engineless [[A320neo]]s waiting for their powerplants.
The [[CFM LEAP]] introduction was smoother but a [[ceramic composite]] {{abbr|HP|High-Pressure}} Turbine coating is prematurely lost, necessitating a new design, causing 60 A320neo engine removal for modification, as deliveries are up to six weeks late.<ref name=SeattleTimes15jun2018>{{cite news |url= https://www.seattletimes.com/business/boeing-aerospace/troublesome-advanced-engines-for-boeing-and-airbus-jets-disrupt-airlines-and-production-lines/ |title= Troublesome advanced engines for Boeing, Airbus jets have disrupted airlines and shaken travelers |date= June 15, 2018 |author= Dominic Gates |newspaper= The Seattle Times}}</ref>

==Manufacturers==
{{main|List of turbofan manufacturers}}
The turbofan engine market is dominated by [[GE Aircraft Engines|General Electric]], [[Rolls-Royce plc]] and [[Pratt & Whitney]], in order of market share. General Electric and [[SNECMA]] of France have a joint venture, [[CFM International]]. Pratt & Whitney also have a joint venture, [[International Aero Engines]] with [[Japanese Aero Engine Corporation]] and [[MTU Aero Engines]] of Germany, specializing in engines for the [[Airbus A320 family|Airbus A320]] family. Pratt & Whitney and General Electric have a joint venture, [[Engine Alliance]] selling a range of engines for aircraft such as the [[Airbus A380]].

For [[airliner]]s and [[cargo aircraft]], the in-service fleet in 2016 is 60,000 engines and should grow to 103,000 in 2035 with 86,500 deliveries according to [[Flight Global]]. A majority will be medium-thrust engines for [[narrow-body aircraft]] with 54,000 deliveries, for a fleet growing from 28,500 to 61,000. High-thrust engines for [[wide-body aircraft]], worth 40–45% of the market by value, will grow from 12,700 engines to over 21,000 with 18,500 deliveries. The [[regional jet]] engines below 20,000 lb (89 kN) fleet will grow from 7,500 to 9,000 and the fleet of [[turboprop]]s for airliners will increase from 9,400 to 10,200. The manufacturers [[market share]] should be led by CFM with 44% followed by Pratt & Whitney with 29% and then Rolls-Royce and General Electric with 10% each.<ref>{{cite news |url= https://www.flightglobal.com/news/articles/insight-from-flightglobal-flight-fleet-forecasts-e-430071/ |title= Flight Fleet Forecast's engine outlook |work= Flight Global |date= 2 November 2016 }}</ref>

=== Gallery ===
<gallery mode="packed" heights="129" perrow="5">
File:Solowjow D-30 III.jpg|[[Soloviev D-30]] which powers the [[Mikoyan MiG-31]], [[Ilyushin Il-76]], [[Ilyushin Il-62]]M, [[Xian H-6]]K, [[Xian Y-20]]
File:AL-31FN.jpg|[[Saturn AL-31]] which powers the [[Sukhoi Su-30]], [[Sukhoi Su-27]], [[Chengdu J-10]], [[Shenyang J-11]]
File:SaM146 back.jpg|[[PowerJet SaM146]] which powers [[Sukhoi Superjet 100]]
File:Ge cf6 turbofan.jpg|[[General Electric CF6]] which powers the [[Airbus A300]], [[Boeing 747]], [[Douglas DC-10]] and other aircraft
File:Rolls-Royce Trent 900 AEDC-d0404084 USAF.jpg|[[Rolls-Royce Trent 900]] undergoing climatic testing
File:N7771@GVA;09.09.1995-engine (6083468531).jpg|[[Pratt & Whitney PW4000]] which powered the first [[Boeing 777]]
File:CFM56 P1220759.jpg|The [[CFM International CFM56|CFM56]] which powers the [[Boeing 737]], the [[Airbus A320]] and other aircraft
File:EA GP7200.jpg|[[Engine Alliance GP7000]] turbofan for the [[Airbus A380]]
File:PS-90A.jpg|[[Aviadvigatel PS-90]] which powers the [[Ilyushin Il-96]], [[Tupolev Tu-204]], [[Ilyushin Il-76]]
File:Williams Research F107.jpg|[[Williams F107]] which powers the [[Raytheon]] [[Tomahawk (missile)|BGM-109 Tomahawk]] cruise missile
File:ALF502.JPG|[[Honeywell Aerospace]] [[Lycoming ALF 502]] which powers the [[British Aerospace 146]]
File:MAKS Airshow 2013 (Ramenskoye Airport, Russia) (524-34).jpg|[[Aviadvigatel PD-14]] which will be used on the [[Irkut MC-21]]
File:D-436-148 MAKS-2009.jpg|[[Ivchenko-Progress]] [[Progress D-436|D-436]] sharing the three shaft principle with Rolls-Royce Trent
File:AL-55 at the MAKS-2011 (01).jpg|[[NPO Saturn AL-55]] which powers certain [[HAL HJT-36 Sitara]]
File:RD-33MK ok.JPG|[[Klimov RD-33]] which powers the [[Mikoyan MiG-29]] and [[Mikoyan MiG-35]] fighters
File:Eurojet EJ200 for Eurofighter Typhoon PAS 2013 01 free.jpg|[[Eurojet EJ200]] which powers the [[Eurofighter Typhoon]]
File:XF3 KASM001.jpg|[[Ishikawajima-Harima F3]] which powers the [[Kawasaki T-4]]
File:GTX-35VS_Kaveri.jpg|[[GTRE GTX-35VS Kaveri]] developed by [[Gas Turbine Research Establishment|GTRE]] for [[HAL Tejas]]
</gallery>

=== Commercial turbofans in production ===
{| class="wikitable sortable"
|+ Commercial turbofans in production<ref>{{cite book |title= Jane's All the World's Aircraft |issn= 0075-3017 |date=2005 |pages= 850–853}}</ref>
! Model
! Start !! Bypass !! Length !! Fan !! Weight !! Thrust
! Major applications
|-
| [[General Electric GE90|GE GE90]]
| 1992 || 8.7–9.9 || 5.18m–5.40m || 3.12–3.25 m || 7.56–8.62t || 330–510 kN
| [[Boeing 777|B777]]
|-
| [[Pratt & Whitney PW4000|P&W PW4000]]
| 1984 || 4.8–6.4 || 3.37–4.95m || 2.84 m || 4.18–7.48t || 222–436 kN
| [[Airbus A300|A300]]/[[A310]], [[A330]], [[B747]], [[Boeing 767|B767]], [[Boeing 777|B777]], [[MD-11]]
|-
| [[Rolls-Royce Trent XWB|R-R Trent XWB]]
| 2010 || 9.3 || 5.22 m || 3.00 m || 7.28 t || 330–430 kN
| [[A350XWB]]
|-
| [[Rolls-Royce Trent 800|R-R Trent 800]]
| 1993 || 5.7–5.79 || 4.37m || 2.79m || 5.96–5.98t || 411–425 kN
| [[Boeing 777|B777]]
|-
| [[Engine Alliance GP7000|EA GP7000]]
| 2004 || 8.7 || 4.75 m || 2.95 m || 6.09–6.71 t || 311–363 kN
| [[A380]]
|-
| [[Rolls-Royce Trent 900|R-R Trent 900]]
| 2004 || 8.7 || 4.55 m || 2.95 m || 6.18–6.25 t || 340–357 kN
| [[A380]]
|-
| [[Rolls-Royce Trent 1000|R-R Trent 1000]]
| 2006 || 10.8–11 || 4.74 m || 2.85 m || 5.77 t || 265.3–360.4 kN
| [[B787]]
|-
| [[General Electric GEnx|GE GEnx]]<ref>{{cite web |url= http://www.geaviation.com/commercial/engines/genx/ |title= GEnx |publisher= GE}}</ref>
| 2006
| 8.0–9.3
| {{#expr:169.7*.0254round2}}-{{#expr:184.7*.0254round2}} m
| {{#expr:104.7*.0254round2}}-{{#expr:111.1*.0254round2}} m
| {{#expr:12400*0.00045359237round2}}-{{#expr:12822*0.00045359237round2}} t
| {{#expr:66500*0.00444822162round0}}-{{#expr:76100*0.00444822162round0}} kN
| [[B747-8]], [[B787]]
|-
| [[Rolls-Royce Trent 700|R-R Trent 700]]
| 1990 || 4.9 || 3.91 m || 2.47 m || 4.79 t || 320 kN
| [[A330]]
|-
| [[General Electric CF6|GE CF6]]
| 1971 || 4.3–5.3 || 4.00–4.41 m || 2.20–2.79 m || 3.82–5.08 t || 222–298 kN
| [[Airbus A300|A300]]/[[A310]], [[A330]], [[B747]], [[Boeing 767|B767]], [[MD-11]], [[McDonnell Douglas DC-10|DC-10]]
|-
| [[Rolls-Royce Trent 500|R-R Trent 500]]
| 1999 || 8.5 || 3.91 m || 2.47 m || 4.72 t || 252 kN
| [[A340]]-500/600
|-
| [[Pratt & Whitney PW1000G|P&W PW1000G]]<ref>{{cite web |url= http://www.mtu.de/engines/commercial-aircraft-engines/narrowbody-and-regional-jets/pw1000g/ |title= PW1000G |publisher= [[MTU Aero Engines|MTU]]}}</ref>
| 2008 || 9.0–12.5 || 3.40 m || 1.42–2.06 m || 2.86 t || 67–160 kN
| [[Airbus A320neo|A320neo]], [[Airbus A220|A220]], [[E-Jets E2]]
|-
| [[CFM International LEAP|CFM LEAP]]<ref>{{cite web|url=http://www.cfmaeroengines.com/engines/leap |title=The Leap Engine |publisher= CFM International }}</ref>
| 2013 || 9.0–11.0 || 3.15–3.33m || 1.76–1.98m || 2.78–3.15t || 100–146 kN
| [[A320neo]], [[B737Max]]
|-
| [[CFM International CFM56|CFM56]]
| 1974 || 5.0–6.6 || 2.36–2.52m || 1.52–1.84m || 1.95–2.64t || 97.9-151 kN
| [[A320]], [[A340]]-200/300, [[B737]], [[KC-135]], [[Douglas DC-8|DC-8]]
|-
| [[IAE V2500]]
| 1987 || 4.4–4.9 || 3.20m || 1.60m || 2.36–2.54t || 97.9-147 kN
| [[A320]], [[MD-90]]
|-
| [[Pratt & Whitney PW6000|P&W PW6000]]
| 2000 || 4.90 || 2.73m || 1.44m || 2.36t || 100.2 kN
| [[Airbus A318]]
|-
| [[Rolls-Royce BR700|R-R BR700]]
| 1994 || 4.2–4.5 || 3.41–3.60m || 1.32–1.58m || 1.63–2.11t || 68.9–102.3 kN
| [[Boeing 717|B717]], [[Global Express]], [[Gulfstream V]]
|-
| [[General Electric Passport|GE Passport]]
| 2013 || 5.6 || 3.37m || 1.30m || 2.07t || 78.9–84.2 kN
| [[Global 7000]]/8000
|-
| [[General Electric CF34|GE CF34]]
| 1982 || 5.3–6.3 || 2.62–3.26m || 1.25–1.32m || 0.74–1.12t || 41–82.3 kN
| [[Challenger 600]], [[Bombardier CRJ|CRJ]], [[E-jets]]
|-
| [[Pratt & Whitney Canada PW800|P&WC PW800]]
| 2012 || 5.5 || || 1.30m || || 67.4–69.7 kN
| [[Gulfstream G500/G600]]
|-
| [[Rolls-Royce RB.183 Tay|R-R Tay]]
| 1984 || 3.1–3.2 || 2.41m || 1.12–1.14m || 1.42–1.53t || 61.6–68.5 kN
| [[Gulfstream IV]], [[Fokker 70]]/[[Fokker 100|100]]
|-
| [[Snecma Silvercrest|Silvercrest]]
| 2012 || 5.9 || 1.90m || 1.08m || 1.09t || 50.9 kN
| [[Cessna Citation Hemisphere|Cit. Hemisphere]], [[Dassault Falcon 5X|Falcon 5X]]
|-
| [[Rolls-Royce AE 3007|R-R AE 3007]]
| 1991 || 5.0 || 2.71m || 1.11m || 0.72t || 33,7 kN
| [[ERJ]], [[Citation X]]
|-
| [[Pratt & Whitney Canada PW300|P&WC PW300]]
| 1988 || 3.8–4.5 || 1.92–2.07 || 0.97m || 0.45–0.47t || 23.4–35.6 kN
| [[Citation Sovereign|Cit. Sovereign]], [[Gulfstream G200|G200]], [[Falcon 7X|F. 7X]], [[Falcon 2000|F. 2000]]
|-
| [[Honeywell HTF7000|HW HTF7000]]
| 1999 || 4.4 || 2.29m || 0.87m || 0.62t || 28.9 kN
| [[Challenger 300]], [[Gulfstream G280|G280]], [[Embraer Legacy 500|Legacy 500]]
|-
| [[Garrett TFE731|HW TFE731]]
| 1970 || 2.66–3.9 || 1.52–2.08m || .072-0.78m || 0.34–0.45t || 15.6–22.2 kN
| [[Learjet 70/75]], [[G150]], [[Falcon 900]]
|-
| [[Williams FJ44]]
| 1985 || 3.3–4.1 || 1.36–2.09m || .53-0.57m || 0.21–0.24t || 6.7–15.6 kN
| [[Cessna CitationJet|CitationJet]], [[Cessna Citation M2|Cit. M2]]
|-
| [[Pratt & Whitney Canada PW500|P&WC PW500]]
| 1993 || 3.90 || 1.52m || 0.70m || 0.28t || 13.3 kN
| [[Citation Excel]], [[Phenom 300]]
|-
| [[GE-Honda HF120|GE-H HF120]]
| 2009 || 4.43 || 1.12m || 0.54 m || 0.18t || 7.4 kN
| [[HondaJet]]
|-
| [[Williams FJ33]]
| 1998 || || 0.98m || 0.53 m || 0.14 t || 6.7 kN
| [[Cirrus SF50]]
|-
| [[Pratt & Whitney Canada PW600|P&WC PW600]]
| 2001 || 1.8–2.8 || 0.67m || 0.36m || 0.15t || 6.0 kN
| [[Citation Mustang|Cit. Mustang]], [[Eclipse 500]], [[Phenom 100]]
|-
| [[Aviadvigatel PS-90|PS-90]]
| 1992 || 4.4 || 4.96m || 1.9m || 2.95t || 157–171 kN
| [[Ilyushin Il-76]], [[Ilyushin Il-96]], [[Tupolev Tu-204]]
|-
| [[PowerJet SaM146]]
| 2008 || 4-4.1 || 3.59m || 1.22m || 2.260t || 71.6–79.2 kN
| [[Sukhoi Superjet 100]]
|}

==Extreme bypass jet engines==

In the 1970s, Rolls-Royce/SNECMA tested a [[M45SD-02]] turbofan fitted with variable pitch fan blades to improve handling at ultra low fan pressure ratios and to provide thrust reverse down to zero aircraft speed. The engine was aimed at ultra quiet [[STOL]] aircraft operating from city centre airports.

In a bid for increased efficiency with speed, a development of the ''turbofan'' and ''turboprop'' known as a [[propfan]] engine was created that had an unducted fan. The fan blades are situated outside of the duct, so that it appears like a turboprop with wide scimitar-like blades. Both General Electric and Pratt & Whitney/Allison demonstrated propfan engines in the 1980s. Excessive cabin noise and relatively cheap jet fuel prevented the engines being put into service. The [[Progress D-27]] propfan, developed in the U.S.S.R., was the only propfan engine equipped on a production aircraft.

==Terminology==
; [[Afterburner]]: extra combustor immediately upstream of final nozzle (also called reheat)
; Augmentor: afterburner on low-bypass turbofan engines.
; Average stage loading: constant × (delta temperature)/[(blade speed) × (blade speed) × (number of stages)]
; Bypass: airstream that completely bypasses the core compression system, combustor and turbine system
; [[Bypass ratio]]: bypass airflow /core compression inlet airflow
; Core: turbomachinery handling the airstream that passes through the combustor.
; [[Core power]]: residual shaft power from ideal turbine expansion to ambient pressure after deducting core compression power
; Core thermal efficiency: core power/power equivalent of fuel flow
; Dry: afterburner (if fitted) not lit
; EGT: exhaust gas temperature
; EPR: engine pressure ratio
; Fan: turbofan LP compressor
; Fan pressure ratio: fan outlet total pressure/intake delivery total pressure
; [[Flex temp]]: use of artificially high apparent air temperature to reduce engine wear
; Gas generator: engine core
; HP compressor: high-pressure compressor (also HPC)
; HP turbine: high-pressure turbine
; Intake ram drag: penalty associated with jet engines picking up air from the atmosphere (conventional rocket motors do not have this drag term, because the oxidiser travels with the vehicle)
; [[IEPR]]: integrated engine pressure ratio
; IP compressor: intermediate pressure compressor (also IPC)
; IP turbine: intermediate pressure turbine (also IPT)
; LP compressor: low-pressure compressor (also LPC)
; LP turbine: low-pressure turbine (also LPT)
; Net thrust: nozzle total gross thrust – intake ram drag (excluding nacelle drag, etc., this is the basic thrust acting on the airframe)
; Overall pressure ratio: combustor inlet total pressure/intake delivery total pressure
; Overall efficiency: thermal efficiency * propulsive efficiency
; [[Propulsive efficiency]]: propulsive power/rate of production of propulsive kinetic energy (maximum propulsive efficiency occurs when jet velocity equals flight velocity, which implies zero net thrust!)
; [[Thrust specific fuel consumption|Specific fuel consumption]] (SFC): total fuel flow/net thrust (proportional to flight velocity/overall thermal efficiency)
; Spooling up: accelerating, marked by a delay
; Static pressure: pressure of the fluid which is associated not with its motion but with its state<ref>Clancy, L.J., ''Aerodynamics'', page 21</ref>
; [[Specific thrust]]: net thrust/intake airflow
; [[Thermal efficiency]]: rate of production of propulsive kinetic energy/fuel power
; Total fuel flow: combustor (plus any afterburner) fuel flow rate (e.g., lb/s or g/s)
; Total pressure: static pressure '''plus''' kinetic energy term
; Turbine rotor inlet temperature: gas absolute mean temperature at principal (e.g., HP) turbine rotor entry

==See also==
* [[Jet engine]]
* [[Turbojet]]
* [[Turboprop]]
* [[Turboshaft]]
* [[Propfan]]
* [[Axial fan design]]
* [[Variable cycle engine]]
* [[Jet engine performance]]
* [[Gas turbine]]
* [[Turbine engine failure]]

==References==
{{Reflist|35em}}

==External links==
{{Commons category|Turbofan engines}}
*[[Wikibooks:Jet Propulsion|Wikibooks: Jet propulsion]]
* {{cite web |url= https://www.hq.nasa.gov/office/aero/ebooks/downloads/nasa_innovation_in_aeronautics.pdf |author= Malcolm Gibson |work= NASA Innovation in Aeronautics NASA/TM-2011-216987 |date= Aug 2011 |title= The Chevron Nozzle: A Novel Approach to Reducing Jet Noise}}
* {{cite news |url= https://scribd.com/doc/105381018/Engine-Yearbook |title= The Engine Yearbook |date= 2012 |publisher= UBM Aviation}}
* {{cite news |url= https://www.flightglobal.com/asset/17069 |title= Commercial engines 2017 |work= Flight Global}}
* {{cite news |url= https://leehamnews.com/2017/04/14/bjorns-corner-aircraft-engines-sum/ |title= Bjorn’s Corner: Aircraft engines, sum up |date= April 14, 2017 |work= Leeham Co |author= Bjorn Fehrm}} and previous series

{{Aircraft gas turbine engine components}}
{{Heat engines|state=uncollapsed}}

[[Category:Gas turbines]]
[[Category:Jet engines]]

Turbofan

2018-08-07T16:29:36Z

173.165.237.1: /* Blade technology */

{{distinguish|propfan}}
[[File:Turbofan3 Unlabelled.gif|thumb|right|An animated turbofan engine]]
{{Seriesbox aircraft propulsion}}
[[File:Turbofan operation.svg|thumb|300px|Schematic diagram of a high-bypass turbofan engine]]
[[File:787 - Flickr - Beige Alert (8).jpg|thumb|[[Rolls-Royce Trent 1000]] turbofan powering a [[Boeing 787 Dreamliner]] testflight]]
[[File:Airbus Lagardère - GP7200 engine MSN108 (1).JPG|thumb|[[Engine Alliance GP7000]] turbofan (view from the rear) awaiting installation on an [[Airbus A380]] under construction]]

The '''turbofan''' or '''fanjet''' is a type of [[airbreathing jet engine]] that is widely used in [[aircraft engine|aircraft propulsion]]. The word "turbofan" is a [[portmanteau]] of "turbine" and "fan": the ''turbo'' portion refers to a [[gas turbine engine]] which achieves [[mechanical energy]] from combustion,<ref name=stuffworks>{{cite web|url= http://science.howstuffworks.com/turbine.htm |title= How Gas Turbine Engines Work |publisher= howstuffworks.com |author= Marshall Brain |accessdate=2010-11-24}}</ref> and the ''fan'', a [[ducted fan]] that uses the mechanical energy from the gas turbine to accelerate air rearwards. Thus, whereas all the air taken in by a [[turbojet]] passes through the turbine (through the [[combustion chamber]]), in a turbofan some of that air bypasses the turbine. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of those contributing to the [[thrust]].

The ratio of the mass-flow of air bypassing the engine core divided by the mass-flow of air passing through the core is referred to as the [[bypass ratio]]. The engine produces thrust through a combination of these two portions working together; engines that use more [[Propelling nozzle|jet thrust]] relative to fan thrust are known as ''low-bypass turbofans'', conversely those that have considerably more fan thrust than jet thrust are known as ''high-bypass''. Most commercial aviation jet engines in use today are of the high-bypass type,<ref>{{cite web|url=https://www.grc.nasa.gov/www/k-12/airplane/aturbf.html|title=Turbofan Engine|last1=Hall|first1=Nancy|date=May 5, 2015|website=Glenn Research Center|publisher=NASA|accessdate=October 25, 2015|quote=Most modern airliners use turbofan engines because of their high thrust and good fuel efficiency.}}</ref><ref name="HackerBurghardt2009">{{cite book|author1=Michael Hacker|author2=David Burghardt|author3=Linnea Fletcher |author4=Anthony Gordon |author5=William Peruzzi |title=Engineering and Technology|url=https://books.google.com/books?id=0-xuCgAAQBAJ&pg=PT336|accessdate=October 25, 2015|date=March 18, 2009|publisher=Cengage Learning|isbn=978-1-285-95643-5|page=319|quote=All modern jet-powered commercial aircraft use high bypass turbofan engines [...]}}</ref> and most modern military fighter engines are low-bypass.<ref name="Verma2013">{{cite book|author=Bharat Verma|title=Indian Defence Review: Apr–Jun 2012|url=https://books.google.com/books?id=IvAzNhvLK6AC&pg=PA18|accessdate=October 25, 2015|date=January 1, 2013|publisher=Lancer Publishers|isbn=978-81-7062-259-8|page=18|quote=Military power plants may be divided into some major categories – low bypass turbofans that generally power fighter jets [...]}}</ref><ref>{{cite book|editor=Frank Northen Magill|title=Magill's Survey of Science: Applied science series, Volume 3|date=1993|publisher=Salem Press|isbn=9780893567088|page=1431|quote=Most tactical military aircraft are powered by low-bypass turbofan engines.}}</ref> [[Afterburner]]s are not used on high-bypass turbofan engines but may be used on either low-bypass turbofan or [[turbojet]] engines.

Modern turbofans have either a large single-stage fan or a smaller fan with several stages. An early configuration combined a low-pressure turbine and fan in a single rear-mounted unit.

==Principles==
Turbofans were invented to circumvent an awkward feature of turbojets, which was that they were inefficient for subsonic flight. To raise the efficiency of a turbojet, the obvious approach would be to increase the burner temperature, to give better [[Carnot efficiency]] and fit larger compressors and nozzles. However, while that does increase thrust somewhat, the exhaust jet leaves the engine with even higher velocity, which at subsonic flight speeds, takes most of the extra energy with it, wasting fuel.

Instead, a turbofan can be thought of as a turbojet being used to drive a [[ducted fan]], with both of those contributing to the [[thrust]]. Whereas all the air taken in by a [[turbojet]] passes through the turbine (through the [[combustion chamber]]), in a turbofan some of that air bypasses the turbine.

Because the turbine has to additionally drive the fan, the turbine is larger and has larger pressure and temperature drops, and so the nozzles are smaller. This means that the exhaust velocity of the core is reduced. The fan also has lower exhaust velocity, giving much more thrust per unit energy (lower [[specific thrust]]). The overall effective exhaust velocity of the two exhaust jets can be made closer to a normal subsonic aircraft's flight speed. In effect, a turbofan emits a large amount of air more slowly, whereas a turbojet emits a smaller amount of air quickly, which is a far less efficient way to generate the same thrust.

The ratio of the mass-flow of air bypassing the engine core compared to the mass-flow of air passing through the core is referred to as the [[bypass ratio]]. The engine produces thrust through a combination of these two portions working together; engines that use more [[Propelling nozzle|jet thrust]] relative to fan thrust are known as ''low-bypass turbofans'', conversely those that have considerably more fan thrust than jet thrust are known as ''high-bypass''. Most commercial aviation jet engines in use today are of the high-bypass type,<ref>{{cite web|url=https://www.grc.nasa.gov/www/k-12/airplane/aturbf.html|title=Turbofan Engine|last1=Hall|first1=Nancy|date=May 5, 2015|website=Glenn Research Center|publisher=NASA|accessdate=October 25, 2015|quote=Most modern airliners use turbofan engines because of their high thrust and good fuel efficiency.}}</ref><ref name="HackerBurghardt2009">{{cite book|author1=Michael Hacker|author2=David Burghardt|author3=Linnea Fletcher |author4=Anthony Gordon |author5=William Peruzzi |title=Engineering and Technology|url=https://books.google.com/books?id=0-xuCgAAQBAJ&pg=PT336|accessdate=October 25, 2015|date=March 18, 2009|publisher=Cengage Learning|isbn=978-1-285-95643-5|page=319|quote=All modern jet-powered commercial aircraft use high bypass turbofan engines [...]}}</ref> and most modern military fighter engines are low-bypass.<ref name="Verma2013">{{cite book|author=Bharat Verma|title=Indian Defence Review: Apr–Jun 2012|url=https://books.google.com/books?id=IvAzNhvLK6AC&pg=PA18|accessdate=October 25, 2015|date=January 1, 2013|publisher=Lancer Publishers|isbn=978-81-7062-259-8|page=18|quote=Military power plants may be divided into some major categories – low bypass turbofans that generally power fighter jets [...]}}</ref><ref>{{cite book|editor=Frank Northen Magill|title=Magill's Survey of Science: Applied science series, Volume 3|date=1993|publisher=Salem Press|isbn=9780893567088|page=1431|quote=Most tactical military aircraft are powered by low-bypass turbofan engines.}}</ref> [[Afterburner]]s are not used on high-bypass turbofan engines but may be used on either low-bypass turbofan or [[turbojet]] engines.

=== Bypass ratio ===
{{main|Bypass ratio}}
The ''bypass ratio (BPR)'' of a turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core.<ref>https://www.britannica.com/technology/bypass-ratio</ref> A 10:1 bypass ratio, for example, means that 10 kg of air passes through the bypass duct for every 1 kg of air passing through the core.

Turbofan engines are usually described in terms of bpr, which together with overall pressure ratio, turbine inlet temperature and fan pressure ratio are important design parameters. In addition bpr is quoted for turboprop and unducted fan installations because their high propulsive efficiency gives them the overall efficiency characteristics of very high bypass turbofans. This allows them to be shown together with turbofans on plots which show trends of reducing sfc with increasing bpr. Bpr is also quoted for lift fan installations where the fan airflow is remote from the engine and doesn't physically touch the engine core.

Bypass provides a lower fuel consumption for the same thrust, measured as [[thrust specific fuel consumption]] (grams/second fuel per unit of thrust in kN using [[SI units]]). Lower fuel consumption that comes with high bypass ratios applies to [[turboprop]]s, using a [[Propeller (aeronautics)|propeller]] rather than a ducted fan.<ref name=kroo>Ilan Kroo and Juan Alonso. "[http://adg.stanford.edu/aa241/propulsion/propulsionintro.html Aircraft Design: Synthesis and Analysis, Propulsion Systems: Basic Concepts] [https://web.archive.org/web/20150418150746/http://adg.stanford.edu/aa241/propulsion/propulsionintro.html Archive]" ''[[Stanford University School of Engineering#Current departments at the school|Stanford University School of Engineering, Department of Aeronautics and Astronautics]]''. Quote: "When the bypass ratio is increased to 10-20 for very efficient low speed performance, the weight and wetted area of the fan shroud (inlet) become large, and at some point it makes sense to eliminate it altogether. The fan then becomes a propeller and the engine is called a turboprop. Turboprop engines provide efficient power from low speeds up to as high as M=0.8 with bypass ratios of 50-100."</ref><ref name=Spak>[http://web.mit.edu/aeroastro/people/spakovszky.html Prof. Z. S. Spakovszky]. "[http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node84.html 11.5 Trends in thermal and propulsive efficiency] [https://web.archive.org/web/20130528034153/http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node84.html Archive]" ''[[School of Engineering, Massachusetts Institute of Technology#Aeronautics and Astronautics|MIT turbines]]'', 2002. [http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/notes.html Thermodynamics and Propulsion]</ref><ref name=nag>Nag, P.K. "[https://books.google.com/books?id=Rq7uBQAAQBAJ Basic And Applied Thermodynamics]" p550. Published by Tata McGraw-Hill Education. Quote: "If the cowl is removed from the fan the result is a turboprop engine. Turbofan and turboprop engines differ mainly in their bypass ratio 5 or 6 for turbofans and as high as 100 for turboprop."</ref><ref>[http://www.animatedengines.com/jets.html Animated Engines]</ref> High bypass designs are the dominant type for commercial passenger aircraft and both civilian and military jet transports.

Business jets use medium bpr engines.<ref>http://www.abcm.org.br/anais/cobem/2013/PDF/1874.pdf</ref>

Combat aircraft use engines with ''low bypass'' ratios to compromise between fuel economy and the requirements of combat: high [[power-to-weight ratio]]s, supersonic performance, and the ability to use [[afterburners]].

If all the gas power from a gas turbine is converted to kinetic energy in a propelling nozzle, the aircraft is best suited to high supersonic speeds. If it is all transferred to a separate big mass of air with low kinetic energy, the aircraft is best suited to zero speed (hovering). For speeds in between, the gas power is shared between a separate airstream and the gas turbine's own nozzle flow in a proportion which gives the aircraft performance required. The first jet aircraft were subsonic and the poor suitability of the propelling nozzle for these speeds due to high fuel consumption was understood, and bypass proposed, as early as 1936 (U.K. Patent 471,368).
The underlying principle behind bypass is trading exhaust velocity for extra mass flow which still gives the required thrust but uses less fuel. [[Frank Whittle]] called it "gearing down the flow".<ref>Gas Turbine Aerodynamics, Sir Frank Whittle, Pergamon Press 1981, p.217</ref> Power is transferred from the gas generator to an extra mass of air, i.e. a bigger diameter propelling jet, moving more slowly. The bypass spreads the available mechanical power across more air to reduce the velocity of the jet.<ref>Aircraft Engine Design Second Edition, Mattingley, Heiser, Pratt, AIAA Education Series, {{ISBN|1-56347-538-3}}, p.539</ref> The trade off between mass flow and velocity is also seen with propellers and helicopter rotors by comparing disc loading and power loading.<ref>https://www.flightglobal.com/pdfarchive/view/1964/1964%20-%202596.html</ref> For example, the same helicopter weight can be supported by a high power engine and small diameter rotor or, for less fuel, a lower power engine and bigger rotor with lower velocity through the rotor.

Bypass usually refers to transferring gas power from a gas turbine to a bypass stream of air to reduce fuel consumption and jet noise. Alternatively, there may be a requirement for an afterburning engine where the sole requirement for bypass is to provide cooling air. This sets the lower limit for bpr and these engines have been called "leaky" or continuous bleed turbojets<ref>Jane's All The World's Aircraft 1975-1976, edited by John W.R. Taylor, Jane's Yearbooks, Paulton House, 8 Sheperdess Walk, London N1 7LW, p.748</ref> (General Electric YJ-101 bpr 0.25) and low bpr turbojets<ref>http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2275853</ref> (Pratt & Whitney PW1120). Low bpr (0.2) has also been used to provide surge margin as well as afterburner cooling for the [[Pratt & Whitney J58]].<ref>http://roadrunnersinternationale.com/pw_tales.htm</ref>

===Efficiency===
Since the [[propulsive efficiency|efficiency of propulsion]] is a function of the relative airspeed of the exhaust to the surrounding air, propellers are most efficient for low speed, pure jets for high speeds, and ducted fans in the middle. Turbofans are thus the most efficient engines in the range of speeds from about {{convert|500|to|1000|km/h|abbr=on}}, the speed at which most commercial aircraft operate.<ref name=grc_nasa>{{cite web|url= http://www.grc.nasa.gov/WWW/K-12/airplane/aturbf.html |title= Turbofan Engine |publisher= www.grc.nasa.gov |accessdate=2010-11-24}}</ref><ref name="Neumann_2004_1984_pp228-230">{{Citation | last = Neumann | first = Gerhard | authorlink = Gerhard Neumann | year = 2004 | origyear = 1984 | title = Herman the German: Just Lucky I Guess |publisher = Authorhouse | location = Bloomington, IN, USA | isbn = 1-4184-7925-X | postscript = . ''First published by Morrow in 1984 as ''Herman the German: Enemy Alien U.S. Army Master Sergeant''. Republished with a new title in 2004 by Authorhouse, with minor or no changes.''}}, pp. 228–230.</ref> Turbofans retain an efficiency edge over pure jets at low [[supersonic speed]]s up to roughly {{convert|1.6|Mach}}.

In a zero-bypass (turbojet) engine the high temperature and high pressure exhaust gas is accelerated by expansion through a [[propelling nozzle]] and produces all the thrust. The compressor absorbs all the mechanical power produced by the turbine. In a bypass design extra turbines drive a [[ducted fan]] that accelerates air rearward from the front of the engine. In a high-bypass design, the ducted fan and nozzle produce most of the thrust. Turbofans are closely related to [[turboprop]]s in principle because both transfer some of the gas turbine's gas power, using extra machinery, to a bypass stream leaving less for the hot nozzle to convert to kinetic energy. Turbofans represent an intermediate stage between [[turbojet]]s, which derive all their thrust from exhaust gases, and turbo-props which derive minimal thrust from exhaust gases (typically 10% or less).<ref name=srm>"[http://www.srmuniv.ac.in/downloads/turbofan-2012.pdf The turbofan engine] {{Webarchive|url=https://web.archive.org/web/20150418181832/http://www.srmuniv.ac.in/downloads/turbofan-2012.pdf |date=2015-04-18 }}", page 7. ''[[SRM University]], Department of aerospace engineering''</ref> Extracting shaft power and transferring it to a bypass stream introduces extra losses which are more than made up by the improved propulsive efficiency. The turboprop at its best flight speed gave significant fuel savings over a turbojet even though an extra turbine, a gearbox and a propeller were added to the turbojet's low-loss propelling nozzle.<ref>Gas Turbine Theory Second Edition, Cohen, Rogers and Saravanamuttoo, Longmans Group Limited 1972, {{ISBN|0 582 44927 8}}, p.85</ref> The turbofan has additional losses from its extra turbines, fan, bypass duct and extra propelling nozzle compared to the turbojet's single nozzle.

===Thrust===
While a turbojet engine uses all of the engine's output to produce thrust in the form of a hot high-velocity exhaust gas jet, a turbofan's cool low-velocity bypass air yields between 30% and 70% of the total thrust produced by a turbofan system.<ref>{{cite book|author=Federal Aviation Administration (FAA)|url=http://www.faa.gov/library/manuals/aircraft/airplane_handbook/media/FAA-H-8083-3B.pdf|title=FAA-H-8083-3B Airplane Flying Handbook Handbook|publisher=Federal Aviation Administration|edition=|year=2004|isbn=|deadurl=yes|archiveurl=https://web.archive.org/web/20120921094453/http://www.faa.gov/library/manuals/aircraft/airplane_handbook/media/FAA-H-8083-3B.pdf|archivedate=2012-09-21|df=}}</ref>

The thrust ('''''FN''''') generated by a turbofan depends on the [[effective exhaust velocity]] of the total exhaust, as with any jet engine, but because two exhaust jets are present the thrust equation can be expanded as:<ref>{{cite web|url=http://www.grc.nasa.gov/WWW/K-12/airplane/turbfan.html|title=Turbofan Thrust|publisher=}}</ref>

:<math>F_N = \dot{m}_e v_{he} - \dot{m}_o v_o + BPR\, (\dot{m}_c v_f)</math>

where:

{| border="0" cellpadding="2"
|-
|align="right"|'''''ṁ e'''''
|align="left"|= the mass rate of hot combustion exhaust flow from the core engine
|-
|align=right|'''''ṁo'''''
|align=left|= the mass rate of total air flow entering the turbofan = '''''ṁc''''' + '''''ṁf'''''
|-
|align=right|'''''ṁc'''''
|align=left|= the mass rate of intake air that flows to the core engine
|-
|align=right|'''''ṁf'''''
|align=left|= the mass rate of intake air that bypasses the core engine
|-
|align=right|'''''vf'''''
|align=left|= the velocity of the air flow bypassed around the core engine
|-
|align=right|'''''vhe'''''
|align=left|= the velocity of the hot exhaust gas from the core engine
|-
|align=right|'''''vo'''''
|align=left|= the velocity of the total air intake = the true airspeed of the aircraft
|-
|align=left|'''''BPR'''''
|align-right|= Bypass Ratio
|}

===Nozzles===
The cold duct and core duct's nozzle systems are relatively complex due to there being two exhaust flows.

In high bypass engines the fan is generally situated in a short duct near the front of the engine and typically has a convergent cold nozzle, with the tail of the duct forming a low pressure ratio nozzle that under normal conditions will choke creating supersonic flow patterns around the core.

The core nozzle is more conventional, but generates less of the thrust, and depending on design choices, such as noise considerations, may conceivably not choke.<ref>https://dspace.lib.cranfield.ac.uk/bitstream/handle/1826/12476/Civil_turbofan_engine_exhaust_aerodynamics-2017.pdf</ref>

In low bypass engines the two flows may combine within the ducts, and share a common nozzle, which can be fitted with afterburner.

===Noise===
Most of the air flow through a high-bypass turbofan is lower velocity bypass flow: even when combined with the much higher velocity engine exhaust, the average exhaust velocity is considerably lower than in a pure turbojet. Turbojet engine noise is predominately jet noise from the high exhaust velocity, therefore turbofan engines are significantly quieter than a pure-jet of the same thrust with jet noise no longer the predominant source. Other noise sources are the fan, compressor and turbine.<ref>"Softtly, softly towards the quiet jet" Michael J.T.Smith, New Scientist, 19 February 1970, Figure 5</ref>

Modern commercial aircraft employ high-bypass-ratio (HBPR) engines with separate flow, non-mixing, short-duct exhaust systems. These propulsion systems are known to generate significantly high noise levels due to the high-speed, high-temperature, and high-pressure nature of the exhaust jet, especially during high thrust conditions such as those required for takeoff. The primary source of jet noise is the turbulent mixing of shear layers in the engine’s exhaust. These shear layers contain instabilities that lead to highly turbulent vortices that generate the pressure fluctuations responsible for sound. In order to reduce the noise associated with jet flow, the aerospace industry has focused on developing various technologies to disrupt shear layer turbulence and reduce the overall noise produced.

Turbofan engine noise propagates both upstream the inlet and downstream the primary nozzle and the by-pass duct. The main noise sources are the turbine and the compressor, the jet and the fan. The contribution of each noise source significantly evolved in the last decades:<ref name="Kempton2011">[http://www.win.tue.nl/ceas-asc/Workshop15/CEAS-ASC_XNoise-EV_K1_Kempton.pdf Kempton, A, "Acoustic liners for modern aero-engines", 15th CEAS-ASC Workshop and 1st Scientific Workshop of X-Noise EV, 2011.]</ref> in typical 1960s design the jet was the main source whereas in modern turbofans the fan is the main noise source.

The fan noise is a tonal noise and its signature depends on the fan rotational speed:
* at low speed, the fan noise is due to the interaction of the blades with the distorted flow injected in the engine; this happens for example during the approach;
* at high engine ratings, the fan tip is supersonic and this allows intense rotor-locked duct modes to propagate upstream; this noise is known as "buzz saw" and is typical at take-off.<ref name=buzz_saw>[http://www.southampton.ac.uk/engineering/research/projects/buzz_saw_noise_and_non_linear_acoustics.page A. McAlpine "Research project: Buzz-saw noise and nonlinear acoustics"]</ref>

All modern turbofan engines are equipped with [[acoustic liner]]s to damp the noise generated. These are installed in the [[nacelle]], and they extend as much as possible to cover the largest area. The acoustic performance of the engine can be experimentally evaluated by means of ground tests<ref name="Schuster2010">Schuster, B., Lieber, L., & Vavalle, A., Optimization of a seamless inlet liner using an empirically validated prediction method. In 16th AIAA/CEAS Aeroacoustics Conference, Stockholm, Sweden.</ref> or in dedicated experimental test rigs.<ref name="Ferrante2011">Ferrante, P. G., Copiello, D., & Beutke, M.. Design and experimental verification of “true zero-splice” acoustic liners in the universal fan facility adaptation (UFFA) modular rig,”. In 17h AIAA/CEAS Aeroacoustics Conference, AIAA-2011-2728, Portland, OR.</ref>

[[File:GEnx-1B on Air India B787 (2).jpg|thumb|Chevrons on an [[Air India]] [[Boeing 787]] [[General Electric GEnx|GE GEnx]] engine.]]

In the [[aerospace]] industry, ''chevrons'' are the saw tooth patterns on the trailing edges of some [[jet engine]] nozzles<ref name=NASA>{{cite web |url=http://www.nasa.gov/topics/aeronautics/features/bridges_chevron_events.html |title=NASA Helps Create a More Silent Night |last1=Banke |first1=Jim |date=2012-12-13 |publisher=[[NASA]] |accessdate=January 12, 2013}}</ref> that are used for [[noise control|noise reduction]]. Their principle of operation is that, as hot air from the engine core mixes with cooler air blowing through the engine fan, the shaped edges serve to smooth the mixing, which reduces noise-creating turbulence.<ref name=NASA/> Chevrons were developed by Boeing with the help of [[NASA]].<ref name=NASA/><ref name="chevron technology">{{cite journal |url=https://www.researchgate.net/profile/K_Zaman/publication/273550214_Evolution_from_%27Tabs%27_to_%27Chevron_Technology%27__a_Review/links/5457d9110cf2bccc491117fa.pdf | work=Proceedings of the 13th Asian Congress of Fluid Mechanics 17–21 December 2010, Dhaka, Bangladesh | title=Evolution from 'Tabs' to 'Chevron Technology’–a Review | format=PDF-1.34 Mb | author1=Zaman, K.B.M.Q.|author2=Bridges, J. E.|author3=Huff, D. L. | date=17–21 December 2010 | publisher=[[NASA Glenn Research Center]]. Cleveland, Ohio | accessdate=January 29, 2013}}</ref> Some notable examples of such designs are [[Boeing 787]] and [[Boeing 747-8]] - on the [[Rolls-Royce Trent 1000]] and [[General Electric GEnx]] engines.
<ref>https://web.archive.org/web/20140325205124/http://www.afmc.org.cn/13thacfm/invited/201.pdf</ref>

==Common types==
===Low-bypass turbofan===

[[File:Turbofan operation lbp.svg|thumb|Schematic diagram illustrating a 2-spool, low-bypass turbofan engine with a mixed exhaust, showing the low-pressure (green) and high-pressure (purple) spools. The fan (and booster stages) are driven by the low-pressure turbine, whereas the high-pressure compressor is powered by the high-pressure turbine.]]

A high-specific-thrust/low-bypass-ratio turbofan normally has a multi-stage fan, developing a relatively high pressure ratio and, thus, yielding a high (mixed or cold) exhaust velocity. The core airflow needs to be large enough to give sufficient [[core power]] to drive the fan. A smaller core flow/higher bypass ratio cycle can be achieved by raising the (HP) turbine rotor inlet temperature.

To illustrate one aspect of how a turbofan differs from a turbojet, they may be compared, as in a re-engining assessment, at the same airflow (to keep a common intake for example) and the same net thrust (i.e. same specific thrust). A bypass flow can be added only if the turbine inlet temperature is not too high to compensate for the smaller core flow. Future improvements in turbine cooling/material technology can allow higher turbine inlet temperature, which is necessary because of increased cooling air temperature, resulting from an [[overall pressure ratio]] increase.

The resulting turbofan, with reasonable efficiencies and duct loss for the added components, would probably operate at a higher nozzle pressure ratio than the turbojet, but with a lower exhaust temperature to retain net thrust. Since the temperature rise across the whole engine (intake to nozzle) would be lower, the (dry power) fuel flow would also be reduced, resulting in a better [[Thrust specific fuel consumption|specific fuel consumption]] (SFC).

Some low-bypass ratio military turbofans (e.g. F404) have variable inlet guide vanes to direct air onto the first fan rotor stage. This improves the fan [[compressor stall|surge]] margin (see [[compressor map]]).

=== Afterburning turbofan ===
{{further|Afterburner}}
[[File:Pratt & Whitney F119.JPEG|thumb|[[Pratt & Whitney F119]] afterburning turbofan on test]]

Since the 1970s, most [[jet fighter]] engines have been low/medium bypass turbofans with a mixed exhaust, [[afterburner]] and variable area final nozzle. An afterburner is a combustor located downstream of the turbine blades and directly upstream of the nozzle, which burns fuel from afterburner-specific fuel injectors. When lit, prodigious amounts of fuel are burnt in the afterburner, raising the temperature of exhaust gases by a significant degree, resulting in a higher exhaust velocity/engine specific thrust. The variable geometry nozzle must open to a larger throat area to accommodate the extra volume flow when the afterburner is lit. Afterburning is often designed to give a significant thrust boost for take off, transonic acceleration and combat maneuvers, but is very fuel intensive. Consequently, afterburning can be used only for short portions of a mission.

Unlike the main combustor, where the downstream turbine blades must not be damaged by high temperatures, an afterburner can operate at the ideal maximum ([[stoichiometric]]) temperature (i.e., about 2100K/3780Ra/3320F/1826C). At a fixed total applied fuel:air ratio, the total fuel flow for a given fan airflow will be the same, regardless of the dry specific thrust of the engine. However, a high specific thrust turbofan will, by definition, have a higher nozzle pressure ratio, resulting in a higher afterburning net thrust and, therefore, a lower afterburning specific fuel consumption (SFC). However, high specific thrust engines have a high dry SFC. The situation is reversed for a medium specific thrust afterburning turbofan: i.e., poor afterburning SFC/good dry SFC. The former engine is suitable for a combat aircraft which must remain in afterburning combat for a fairly long period, but has to fight only fairly close to the airfield (e.g. cross border skirmishes) The latter engine is better for an aircraft that has to fly some distance, or loiter for a long time, before going into combat. However, the pilot can afford to stay in afterburning only for a short period, before aircraft fuel reserves become dangerously low.

The first production afterburning turbofan engine was the [[Pratt & Whitney TF30]], which initially powered the [[General Dynamics F-111 Aardvark|F-111 Aardvark]] and [[Grumman F-14 Tomcat|F-14 Tomcat]]. Current low-bypass military turbofans include the [[Pratt & Whitney F119]], the [[Eurojet EJ200]], the [[General Electric F110]], the [[Klimov RD-33]], and the [[Saturn AL-31]], all of which feature a mixed exhaust, afterburner and variable area propelling nozzle.

=== High-bypass turbofan ===
{{further|Bypass ratio}}
[[File:Turbofan3 Labelled.gif|thumb|300px|alt=Animation of turbofan, which shows flow of air and the spinning of blades.|Animation of a 2-spool, high-bypass turbofan. {{ordered list
|list_style_type=upper-alpha
|1=Low-pressure spool
|2=High-pressure spool
|3=Stationary components
}}{{ordered list
|1=Nacelle
|2=Fan
|3=Low-pressure compressor
|4=High-pressure compressor
|5=Combustion chamber
|6=High-pressure turbine
|7=Low-pressure turbine
|8=Core nozzle
|9=Fan nozzle
}}]]


[[File:Turbofan operation.svg|thumb|Schematic diagram illustrating a 2-spool, high-bypass turbofan engine with an unmixed exhaust. The low-pressure spool is coloured green and the high-pressure one purple. Again, the fan (and booster stages) are driven by the low-pressure turbine, but more stages are required. A mixed exhaust is often employed nowadays.]]

To boost fuel economy and reduce noise, almost all of today's jet airliners and most military transport aircraft (e.g., the [[C-17 Globemaster III|C-17]]) are powered by low-specific-thrust/high-bypass-ratio turbofans. These engines evolved from the high-specific-thrust/low-bypass-ratio turbofans used in such aircraft in the 1960s. (Modern combat aircraft tend to use low-bypass ratio turbofans, and some military transport aircraft use [[turboprops]].)

Low specific thrust is achieved by replacing the multi-stage fan with a single-stage unit. Unlike some military engines, modern civil turbofans lack stationary inlet guide vanes in front of the fan rotor. The fan is scaled to achieve the desired net thrust.

The core (or gas generator) of the engine must generate enough power to drive the fan at its design flow and pressure ratio. Improvements in turbine cooling/material technology allow a higher (HP) turbine rotor inlet temperature, which allows a smaller (and lighter) core and (potentially) improving the core thermal efficiency. Reducing the core mass flow tends to increase the load on the LP turbine, so this unit may require additional stages to reduce the average stage loading and to maintain LP turbine efficiency. Reducing core flow also increases bypass ratio. Bypass ratios greater than 5:1 are increasingly common; the [[Pratt & Whitney PW1000G]], which entered commercial service in 2016, attains 12.5:1.

Further improvements in core thermal efficiency can be achieved by raising the overall pressure ratio of the core. Improved blade aerodynamics reduces the number of extra compressor stages required. With multiple compressors (i.e., LPC, IPC, and HPC) dramatic increases in overall pressure ratio have become possible. Variable geometry (i.e., [[Axial compressor#Bleed air, variable stators|stators]]) enable high-pressure-ratio compressors to work surge-free at all throttle settings.

[[File:CF6-6 engine cutaway.jpg|thumb|Cutaway diagram of the [[General Electric CF6]]-6 engine]]

The first (experimental) high-bypass turbofan engine was built and run on February 13, 1964 by [[Lycoming Engines|AVCO-Lycoming]].<ref>Decher, S., Rauch, D., “Potential of the High Bypass Turbofan,” American Society of Mechanical Engineers paper 64-GTP-15, presented at the Gas Turbine Conference and Products Show, Houston, Texas, March 1–5, 1964.</ref><ref>US Patent 3,390,527, High Bypass Ratio Turbofan, July 2, 1968.</ref> Shortly after, the [[General Electric TF39]] became the first production model, designed to power the [[Lockheed Corporation|Lockheed]] [[C-5 Galaxy]] military transport aircraft.<ref name="Neumann_2004_1984_pp228-230"/> The civil [[General Electric CF6]] engine used a derived design. Other high-bypass turbofans are the [[Pratt & Whitney JT9D]], the three-shaft [[Rolls-Royce RB211]] and the [[CFM International CFM56]]; also the smaller [[TF34]]. More recent large high-bypass turbofans include the [[Pratt & Whitney PW4000]], the three-shaft [[Rolls-Royce Trent]], the [[General Electric GE90]]/[[GEnx]] and the [[GP7000]], produced jointly by GE and P&W.

The lower the specific thrust of a turbofan, the lower the mean jet outlet velocity, which in turn translates into a high [[Thrust lapse|thrust lapse rate]] ( i.e. decreasing thrust with increasing flight speed). See technical discussion below, item 2. Consequently, an engine sized to propel an aircraft at high subsonic flight speed (e.g., Mach 0.83) generates a relatively high thrust at low flight speed, thus enhancing runway performance. Low specific thrust engines tend to have a high bypass ratio, but this is also a function of the temperature of the turbine system.

The turbofans on twin engined airliners are further more powerful to cope with losing one engine during take-off, which reduces the aircraft's net thrust by half. Modern twin engined airliners normally climb very steeply immediately after take-off. If one engine is lost, the climb-out is much shallower, but sufficient to clear obstacles in the flightpath.

The Soviet Union's engine technology was less advanced than the West's and its first wide-body aircraft, the [[Ilyushin Il-86]], was powered by low-bypass engines. The [[Yakovlev Yak-42]], a medium-range, rear-engined aircraft seating up to 120 passengers introduced in 1980 was the first Soviet aircraft to use high-bypass engines.

==Turbofan configurations==
Turbofan engines come in a variety of engine configurations. For a given engine cycle (i.e., same airflow, bypass ratio, fan pressure ratio, overall pressure ratio and HP turbine rotor inlet temperature), the choice of turbofan configuration has little impact upon the design point performance (e.g., net thrust, SFC), as long as overall component performance is maintained. Off-design performance and stability is, however, affected by engine configuration.

As the design overall pressure ratio of an engine cycle increases, it becomes more difficult to operate at low rpm, without encountering an instability known as compressor surge. This occurs when some of the compressor aerofoils stall (like the wings of an aircraft) causing a violent change in the direction of the airflow. However, compressor stall can be avoided, at low rpm, by progressively:

# opening interstage/intercompressor blow-off valves (inefficient), and/or
# closing variable stators within the compressor

Most modern western civil turbofans employ a relatively high-pressure-ratio high-pressure (HP) compressor, with many rows of variable stators to control surge margin at low rpm. In the three-spool [[Rolls-Royce RB211|RB211]]/[[Rolls-Royce Trent|Trent]] the core compression system is split into two, with the IP compressor, which supercharges the HP compressor, being on a different coaxial shaft and driven by a separate (IP) turbine. As the HP compressor has a modest pressure ratio its speed can be reduced surge-free, without employing variable geometry. However, because a shallow IP compressor working line is inevitable, the IPC has one stage of variable geometry on all variants except the -535, which has none.<ref>[https://web.archive.org/web/20110103084411/http://www.rolls-royce.com/Images/RB211-535E4%20_tcm92-11348.pdf RB211-535E4]</ref>

===Single-shaft turbofan===
Although far from common, the single-shaft turbofan is probably the simplest configuration, comprising a fan and high-pressure compressor driven by a single turbine unit, all on the same shaft. The [[SNECMA M53]], which powers [[Dassault Mirage 2000]] fighter aircraft, is an example of a single-shaft turbofan. Despite the simplicity of the turbomachinery configuration, the M53 requires a variable area mixer to facilitate part-throttle operation.

===Aft-fan turbofan===
One of the earliest turbofans was a derivative of the [[General Electric J79]] turbojet, known as the [[General Electric CJ805|CJ805-23]], which featured an integrated aft fan/low-pressure (LP) turbine unit located in the turbojet exhaust jetpipe. Hot gas from the turbojet turbine exhaust expanded through the LP turbine, the fan blades being a radial extension of the turbine blades. This aft-fan configuration was later exploited in the [[General Electric GE-36]] UDF (propfan) demonstrator of the early 80s. One of the problems with the aft fan configuration is hot gas leakage from the LP turbine to the fan.{{citation needed|date=November 2010}}

===Basic two-spool===
Many turbofans have the basic two-spool configuration where both the fan and LP turbine (i.e., LP spool) are mounted on a second (LP) shaft, running concentrically with the HP spool (i.e., HP compressor driven by HP turbine). The [[Rolls-Royce BR700|BR710]] is typical of this configuration. At the smaller thrust sizes, instead of all-axial blading, the HP compressor configuration may be axial-centrifugal (e.g., [[General Electric CFE738]]), double-centrifugal or even diagonal/centrifugal (e.g., [[Pratt & Whitney Canada PW600]]).

===Boosted two-spool===
Higher overall pressure ratios can be achieved by either raising the HP compressor pressure ratio or adding an intermediate-pressure (IP) compressor between the fan and HP compressor, to supercharge or boost the latter unit helping to raise the [[overall pressure ratio]] of the engine cycle to the very high levels employed today (i.e., greater than 40:1, typically). All of the large American turbofans (e.g., [[General Electric CF6]], [[GE90]] and [[GEnx]] plus [[Pratt & Whitney JT9D]] and [[Pratt & Whitney PW4000|PW4000]]) feature an IP compressor mounted on the LP shaft and driven, like the fan, by the LP turbine, the mechanical speed of which is dictated by the tip speed and diameter of the fan. The Rolls-Royce BR715 is a non-American example of this. The high bypass ratios (i.e., fan duct flow/core flow) used in modern civil turbofans tends to reduce the relative diameter of the attached IP compressor, causing its mean tip speed to decrease. Consequently, more IPC stages are required to develop the necessary IPC pressure rise.

===Three-spool===
Rolls-Royce chose a three-spool configuration for their large civil turbofans (i.e., the [[Rolls-Royce RB211|RB211]] and [[Rolls-Royce Trent|Trent]] families), where the intermediate pressure (IP) compressor is mounted on a separate (IP) shaft, running concentrically with the LP and HP shafts, and is driven by a separate IP turbine. The first three-spool engine was the earlier [[Rolls-Royce RB.203 Trent]] of 1967.

[[Ivchenko-Progress|Ivchenko Design Bureau]] chose the same configuration for their [[Lotarev D-36]] engine, followed by [[Progress D-18|Lotarev/Progress D-18T]] and [[Progress D-436]].

The [[Turbo-Union RB199]] military turbofan also has a three-spool configuration, as do the military [[Kuznetsov NK-25]] and [[Kuznetsov NK-321|NK-321]].

===Geared fan===
{{main article|Geared turbofan}}
[[File:Geared Turbofan NT.PNG|thumb|Geared turbofan]]

As bypass ratio increases, the mean radius ratio of the fan and low-pressure turbine (LPT) increases. Consequently, if the fan is to rotate at its optimum blade speed the LPT blading will spin slowly, so additional LPT stages will be required, to extract sufficient energy to drive the fan. Introducing a [[epicyclic gearing|(planetary) reduction gearbox]], with a suitable gear ratio, between the LP shaft and the fan enables both the fan and LP turbine to operate at their optimum speeds. Typical of this configuration are the long-established [[Honeywell TFE731]], the [[Honeywell ALF 502]]/507, and the recent [[Pratt & Whitney PW1000G]].

===Military turbofans===
[[File:Alpha Jet E47 2.JPG|thumb|Ducting on a [[Dassault/Dornier Alpha Jet]] – At subsonic speeds, the increasing diameter of the inlet duct [[Continuity equation|slows incoming air]], causing its static pressure to increase.]]
Most of the configurations discussed above are used in civilian turbofans, while modern military turbofans (e.g., [[SNECMA M88]]) are usually basic two-spool.

===High-pressure turbine===
Most civil turbofans use a high-efficiency, 2-stage HP turbine to drive the HP compressor. The [[CFM56]] uses an alternative approach: a single-stage, high-work unit. While this approach is probably less efficient, there are savings on cooling air, weight and cost.

In the [[Rolls-Royce RB211|RB211]] and [[Rolls-Royce Trent|Trent]] 3-spool engine series, the HP compressor pressure ratio is modest so only a single HP stage is required. Rather than adding stage/s to the LP turbine to drive the higher pressure ratio IP (intermediate pressure) compressor, Rolls-Royce mounts it on a separate shaft and drives it with an IP turbine.

Because the HP compressor pressure ratio is modest, modern military turbofans tend to use a single-stage HP turbine.

===Low-pressure turbine===
Modern civil turbofans have multi-stage LP turbines (e.g., 3, 4, 5, 6, 7). The number of stages required depends on the engine cycle bypass ratio and how much supercharging (i.e., IP compression) is on the LP shaft, behind the fan. A geared fan may reduce the number of required LPT stages in some applications.<ref>{{cite web |url= http://www.mtu.de/en/technologies/engineering_news/others/Riegler_Geared_turbofan_technology.pdf |title= "The geared turbofan technology – Opportunities, challenges and readiness status" |deadurl= bot: unknown |archiveurl= https://web.archive.org/web/20130520065423/http://www.mtu.de/en/technologies/engineering_news/others/Riegler_Geared_turbofan_technology.pdf |archivedate= 2013-05-20 |df= }} C. Riegler, C. Bichlmaier:, 1st CEAS European Air and Space Conference, 10–13 September 2007, Berlin, Germany</ref> Because of the much lower bypass ratios employed, military turbofans require only one or two LP turbine stages.

==Overall performance==

===Cycle improvements===

Consider a mixed turbofan with a fixed bypass ratio and airflow. Increasing the overall pressure ratio of the compression system raises the combustor entry temperature. Therefore, at a fixed fuel flow there is an increase in (HP) turbine rotor inlet temperature. Although the higher temperature rise across the compression system implies a larger temperature drop over the turbine system, the mixed nozzle temperature is unaffected, because the same amount of heat is being added to the system. There is, however, a rise in nozzle pressure, because overall pressure ratio increases faster than the turbine expansion ratio, causing an increase in the hot mixer entry pressure. Consequently, net thrust increases, whilst specific fuel consumption (fuel flow/net thrust) decreases. A similar trend occurs with unmixed turbofans.

So turbofans can be made more fuel efficient by raising overall pressure ratio and turbine rotor inlet temperature in unison. However, better turbine materials and/or improved vane/blade cooling are required to cope with increases in both turbine rotor inlet temperature and compressor delivery temperature. Increasing the latter may require better compressor materials.

Overall pressure ratio can be increased by improving fan (or) LP compressor pressure ratio and/or HP compressor pressure ratio. If the latter is held constant, the increase in (HP) compressor delivery temperature (from raising overall pressure ratio) implies an increase in HP mechanical speed. However, stressing considerations might limit this parameter, implying, despite an increase in overall pressure ratio, a reduction in HP compressor pressure ratio.

According to simple theory, if the ratio of turbine rotor inlet temperature/(HP) compressor delivery temperature is maintained, the HP turbine throat area can be retained. However, this assumes that cycle improvements are obtained, while retaining the datum (HP) compressor exit flow function (non-dimensional flow). In practice, changes to the non-dimensional speed of the (HP) compressor and cooling bleed extraction would probably make this assumption invalid, making some adjustment to HP turbine throat area unavoidable. This means the HP turbine nozzle guide vanes would have to be different from the original. In all probability, the downstream LP turbine nozzle guide vanes would have to be changed anyway.

===Thrust growth===

Thrust growth is obtained by increasing [[core power]]. There are two basic routes available:
# hot route: increase HP turbine rotor inlet temperature
# cold route: increase core mass flow

Both routes require an increase in the combustor fuel flow and, therefore, the heat energy added to the core stream.

The hot route may require changes in turbine blade/vane materials and/or better blade/vane cooling. The cold route can be obtained by one of the following:

# adding [[T-stage]]s to the LP/IP compression
# adding a [[zero-stage]] to the HP compression
# improving the compression process, without adding stages (e.g. higher fan hub pressure ratio)

all of which increase both overall pressure ratio and core airflow.

Alternatively, the [[core size]] can be increased, to raise core airflow, without changing overall pressure ratio. This route is expensive, since a new (upflowed) turbine system (and possibly a larger IP compressor) is also required.

Changes must also be made to the fan to absorb the extra core power. On a civil engine, jet noise considerations mean that any significant increase in take-off thrust must be accompanied by a corresponding increase in fan mass flow (to maintain a T/O specific thrust of about 30 lbf/lb/s).

===Technical discussion===
# Specific thrust (net thrust/intake airflow) is an important parameter for turbofans and jet engines in general. Imagine a fan (driven by an appropriately sized electric motor) operating within a pipe, which is connected to a propelling nozzle. It is fairly obvious, the higher the fan pressure ratio (fan discharge pressure/fan inlet pressure), the higher the jet velocity and the corresponding specific thrust. Now imagine we replace this set-up with an equivalent turbofan – same airflow and same fan pressure ratio. Obviously, the core of the turbofan must produce sufficient power to drive the fan via the low-pressure (LP) turbine. If we choose a low (HP) turbine inlet temperature for the gas generator, the core airflow needs to be relatively high to compensate. The corresponding bypass ratio is therefore relatively low. If we raise the turbine inlet temperature, the core airflow can be smaller, thus increasing bypass ratio. Raising turbine inlet temperature tends to increase thermal efficiency and, therefore, improve fuel efficiency.
# Naturally, as altitude increases, there is a decrease in air density and, therefore, the net thrust of an engine. There is also a flight speed effect, termed thrust lapse rate. Consider the approximate equation for net thrust again:<blockquote><math>F_n = m \cdot (V_{jfe} - V_a)</math></blockquote> With a high specific thrust (e.g., fighter) engine, the jet velocity is relatively high, so intuitively one can see that increases in flight velocity have less of an impact upon net thrust than a medium specific thrust (e.g., trainer) engine, where the jet velocity is lower. The impact of thrust lapse rate upon a low specific thrust (e.g., civil) engine is even more severe. At high flight speeds, high-specific-thrust engines can pick up net thrust through the ram rise in the intake, but this effect tends to diminish at supersonic speeds because of shock wave losses.
# Thrust growth on civil turbofans is usually obtained by increasing fan airflow, thus preventing the jet noise becoming too high. However, the larger fan airflow requires more power from the core. This can be achieved by raising the overall pressure ratio (combustor inlet pressure/intake delivery pressure) to induce more airflow into the core and by increasing turbine inlet temperature. Together, these parameters tend to increase core thermal efficiency and improve fuel efficiency.
# Some high-bypass-ratio civil turbofans use an extremely low area ratio (less than 1.01), convergent-divergent, nozzle on the bypass (or mixed exhaust) stream, to control the fan working line. The nozzle acts as if it has variable geometry. At low flight speeds the nozzle is unchoked (less than a Mach number of unity), so the exhaust gas speeds up as it approaches the throat and then slows down slightly as it reaches the divergent section. Consequently, the nozzle exit area controls the fan match and, being larger than the throat, pulls the fan working line slightly away from surge. At higher flight speeds, the ram rise in the intake increases nozzle pressure ratio to the point where the throat becomes choked (M=1.0). Under these circumstances, the throat area dictates the fan match and, being smaller than the exit, pushes the fan working line slightly towards surge. This is not a problem, since fan surge margin is much better at high flight speeds.
# The off-design behaviour of turbofans is illustrated under [[compressor map]] and [[turbine map]].
# Because modern civil turbofans operate at low specific thrust, they require only a single fan stage to develop the required fan pressure ratio. The desired overall pressure ratio for the engine cycle is usually achieved by multiple axial stages on the core compression. Rolls-Royce tend to split the core compression into two with an intermediate pressure (IP) supercharging the HP compressor, both units being driven by turbines with a single stage, mounted on separate shafts. Consequently, the HP compressor need develop only a modest pressure ratio (e.g., ~4.5:1). US civil engines use much higher HP compressor pressure ratios (e.g., ~23:1 on the [[General Electric GE90]]) and tend to be driven by a two-stage HP turbine. Even so, there are usually a few IP axial stages mounted on the LP shaft, behind the fan, to further supercharge the core compression system. Civil engines have multi-stage LP turbines, the number of stages being determined by the bypass ratio, the amount of IP compression on the LP shaft and the LP turbine blade speed.
# Because military engines usually have to be able to fly very fast at sea level, the limit on HP compressor delivery temperature is reached at a fairly modest design overall pressure ratio, compared with that of a civil engine. Also the fan pressure ratio is relatively high, to achieve a medium to high specific thrust. Consequently, modern military turbofans usually have only 5 or 6 HP compressor stages and require only a single-stage HP turbine. Low-bypass-ratio military turbofans usually have one LP turbine stage, but higher bypass ratio engines need two stages. In theory, by adding IP compressor stages, a modern military turbofan HP compressor could be used in a civil turbofan derivative, but the core would tend to be too small for high thrust applications.

==Early turbofans==
[[File:Rolls Royce Conway Mk508 (1959) used in Boeing 707-420 at Flugausstellung Hermeskeil, pic1.JPG|thumb|[[Rolls-Royce Conway]] low bypass turbofan from a [[Boeing 707]]. The bypass air exits from the fins whilst the exhaust from the core exits from the central nozzle. This fluted jetpipe design is a noise-reducing method devised by Frederick Greatorex at Rolls-Royce]]
[[File:Outer nozzle of GEnx-2B turbofan engine.jpg|thumb|[[General Electric GEnx|General Electric GEnx-2B]] turbofan engine from a [[Boeing 747|Boeing 747-8]]. View into the outer (propelling or "cold") nozzle.]]
Early turbojet engines were not very fuel-efficient as their overall pressure ratio and turbine inlet temperature were severely limited by the technology available at the time. The first turbofan to run was the German [[Daimler-Benz DB 007|Daimler-Benz DB 670]] (designated as the 109-007 by the [[Ministry of Aviation (Germany)|RLM]]) with a first run date of 27 May 1943. Turbomachinery testing, using an electric motor, had started on 1 April 1943.<ref>"Turbojet History And Development 1930–1960 Volume 1", The Crowood Press Ltd. 2007, {{ISBN|978 1 86126 912 6}}, p.241</ref> The engine was abandoned later while the war went on and problems could not be solved. The British wartime [[Metropolitan-Vickers F.2|Metrovick F.2]] axial flow jet was given a fan, as the Metrovick F.3 in 1943, to create the first British turbofan.<ref>{{cite web|url=http://www.flightglobal.com/airspace/media/aeroenginesjetcutaways/metrovick-f3-cutaway-5614.aspx |title=Metrovick F3 Cutaway – Pictures & Photos on FlightGlobal Airspace |publisher=Flightglobal.com |date=2007-11-07 |accessdate=2013-04-29}}</ref>

Improved materials, and the introduction of twin compressors such as in the [[Rolls-Royce Olympus|Bristol Olympus]]<ref>{{cite web|url=http://www.flightglobal.com/pdfarchive/view/1954/1954%20-%200985.html |title=1954 | 0985 | Flight Archive |publisher=Flightglobal.com |date=1954-04-09 |accessdate=2013-04-29}}</ref> and [[Pratt & Whitney JT3C]] engines, increased the overall pressure ratio and thus the [[thermodynamics|thermodynamic]] efficiency of engines, but they also led to a poor propulsive efficiency, as pure turbojets have a high specific thrust/high velocity exhaust better suited to supersonic flight.

The original '''low-bypass turbofan''' engines were designed to improve propulsive efficiency by reducing the exhaust velocity to a value closer to that of the aircraft. The [[Rolls-Royce Conway]], the world's first production turbofan, had a bypass ratio of 0.3, similar to the modern [[General Electric F404]] fighter engine. Civilian turbofan engines of the 1960s, such as the [[Pratt & Whitney JT8D]] and the [[Rolls-Royce Spey]] had bypass ratios closer to 1, and were similar to their military equivalents.

The first General Electric turbofan was the aft-fan [[General Electric CJ805|CJ805-23]] based on the CJ805-3 turbojet. It was followed by the aft-fan [[General Electric CF700]] engine with a 2.0 bypass ratio. This was derived from the [[General Electric J85|General Electric J85/CJ610]] turbojet (2,850 lbf or 12,650 N) to power the larger Rockwell Sabreliner 75/80 model aircraft, as well as the Dassault Falcon 20 with about a 50% increase in thrust (4,200 lbf or 18,700 N). The CF700 was the first small turbofan in the world to be certified by the [[Federal Aviation Administration]] (FAA). There were at one time over 400 CF700 aircraft in operation around the world, with an experience base of over 10 million service hours. The CF700 turbofan engine was also used to train Moon-bound astronauts in [[Project Apollo]] as the powerplant for the [[LLRV|Lunar Landing Research Vehicle]].

== Recent developments ==

=== Aerodynamic modelling ===

[[Aerodynamics]] is a mix of [[Speed of sound|subsonic]], [[transonic]] and [[supersonic]] airflow on a single fan/[[gas compressor]] blade in a modern turbofan. The airflow past the blades has to be maintained within close angular limits to keep the air flowing against an increasing pressure. Otherwise the air will come back out of the intake.<ref name=LN161021>{{cite web |url= https://leehamnews.com/2016/10/21/bjorns-corner-engine-challenge/ |title= Bjorn’s Corner: The Engine challenge |author= Bjorn Fehrm |date= October 21, 2016 |work= Leeham News}}</ref>

The [[FADEC|Full Authority Digital Engine Control]] (FADEC) needs accurate data for controlling the engine. The critical [[turbine]] inlet temperature (TIT) is too harsh an environment, at 1,700 °C and 17 bars, for reliable [[temperature sensor|sensor]]s. During development of a new engine type a relation is established between a more easily measured temperature like [[Exhaust gas]] temperature and the TIT. The EGT is then used to make sure the engine doesn't run too hot.<ref name=LN161021/>

=== Blade technology ===

A 100 g [[turbine]] blade is subjected to 1,700 °C/3100 °F, at 17 bars/250 Psi and a [[centrifugal force]] of 40 kN/ 9,000 lbf, well above the point of [[plastic deformation]] and even above the [[melting point]].
Exotic [[alloy]]s, sophisticated [[air cooling]] schemes and special mechanical design are needed to keep the [[physical stress]]es within the strength of the material.
[[Rotating seal]]s must withstand harsh conditions for 10 years, 20,000 missions and rotating at 10–20,000 rpm.<ref name=LN161021/>

The high-temperature performance of fan blades has increased through developments in the casting manufacturing process, the cooling design, [[thermal barrier coating]]s, and [[alloy]]s.
Cycle-wise, the HP turbine inlet temperature is less important than its rotor inlet temperature (RIT), after the temperature drop across its stator.
Although modern engines have peak RITs of the order of {{cvt|1560|°C}}, such temperatures are experienced only for a short time during take-off on civil engines.


Originally standard [[polycrystalline]] metals were used to make fan blades, but developments in [[material science]] have allowed blades to be constructed from aligned metallic crystals and more recently [[single crystal]]s to operate at higher temperatures with less distortion.
These alloys and [[Nickel]]-based [[superalloys]] are utilized in HP turbine blades in most modern jet engines.


HP turbine inlet is cooled below its melting point with air bled from the compressor, bypassing the combustor and entering the hollow blade or vane.<ref name=spt>{{cite article |author= Peter Spittle, [[Rolls-Royce plc]] |url= http://users.encs.concordia.ca/~kadem/Rolls%20Royce.pdf |title= Gas turbine technology |date= November 2003 |journal= [[Physics Education]]}}</ref>
After picking up heat, the cooling air is dumped into the main gas stream and downstream stages are uncooled if the local temperatures are low enough.

=== Fan blades ===

Fan blades have been growing as jet engines have been getting bigger: each fan blade carries the equivalent of nine [[double-decker bus]]es and swallows the volume of a [[squash court]] every second.
Advances in [[computational fluid dynamics]] (CFD) modelling have permitted complex, 3D curved shapes with very wide [[Chord (aeronautics)|chord]], keeping the fan capabilities while minimizing the blade count to lower costs.
Coincidentally, the [[bypass ratio]] grew to achieve higher [[propulsive efficiency]] and the fan diameter increased.<ref name=MRO28sep2017/>

Rolls-Royce pioneered the hollow, [[titanium]] wide-chord fan blade in the 1980s for aerodynamic efficiency and [[foreign object damage]] resistance in the [[RB211]] then for the [[Rolls-Royce Trent|Trent]].
[[GE Aviation]] introduced [[carbon fiber composite]] fan blades on the [[GE90]] in 1995, manufactured today with a [[carbon-fiber tape|carbon-fiber tape-layer]] process.
GE partner [[Safran]] developed a [[3D weaving|3D woven]] technology with [[Albany Engineered Composites|Albany Composites]] for the [[CFM56]] and [[CFM LEAP]] engines.<ref name=MRO28sep2017>{{cite news |url= http://www.mro-network.com/engines-engine-systems/understanding-complexities-bigger-fan-blades |title= Understanding Complexities Of Bigger Fan Blades |author= Ben Hargreaves |date= Sep 28, 2017 |work= Aviation Week Network}}</ref>

=== Future progress ===

Engine cores are shrinking as they are operating at higher [[Overall pressure ratio|pressure ratio]]s and becoming more efficient, and become smaller compared to the fan as bypass ratios increase.
Blade [[tip clearance]]s are harder to maintain at the exit of the high-pressure compressor where blades are {{cvt|0.5|in|mm}} high or less, [[Structural system|backbone]] bending further affects clearance control as the core is proportionately longer and thinner and the fan to low-pressure turbine driveshaft is in constrained space within the core.<ref name=AvWeek26Mar2015>{{cite news |url= http://aviationweek.com/technology/reversed-tilted-future-pratt-s-geared-turbofan |title= A Reversed, Tilted Future For Pratt’s Geared Turbofan? |date= Mar 26, 2015 |author= Guy Norris and Graham Warwick |work= Aviation Week & Space Technology}}</ref>

For [[Pratt & Whitney]] VP technology and environment [[Alan H. Epstein|Alan Epstein]] "Over the history of commercial aviation, we have gone from 20% to 40% [cruise efficiency], and there is a consensus among the engine community that we can probably get to 60%".<ref name=AvWeek8Aug2017>{{cite news |url= http://aviationweek.com/technology/turbofans-are-not-finished-yet |title= Turbofans Are Not Finished Yet |date= Aug 8, 2017 |author= Guy Norris |work= Aviation Week & Space Technology}}</ref>


[[Geared turbofan]]s and further fan [[Overall pressure ratio|pressure ratio]] reductions will continue to improve [[propulsive efficiency]].
The second phase of the FAA’s [[Continuous Lower Energy, Emissions and Noise]] (CLEEN) program is targeting for the late 2020s reductions of 33% fuel burn, 60% emissions and 32 dB EPNdb noise compared with the 2000s state-of-the-art.
In summer 2017 at [[NASA Glenn Research Center]] in [[Cleveland, Ohio]], Pratt has finished testing a very-low-pressure-ratio fan on a [[PW1000G]], resembling an [[open rotor]] with less blades than the PW1000G's 20.<ref name=AvWeek8Aug2017/>

The weight and size of the [[nacelle]] would be reduced by a short duct inlet, imposing higher aerodynamic turning loads on the blades and leaving less space for soundproofing, but a lower-pressure-ratio fan is slower.
[[UTC Aerospace Systems]] Aerostructures will have a full-scale ground test in 2019 of its low-drag Integrated Propulsion System with a [[thrust reverser]], improving fuel burn by 1% and with 2.5-3 EPNdB lower noise.<ref name=AvWeek8Aug2017/>


[[Safran]] can probably deliver another 10–15% in fuel efficiency through the mid-2020s before reaching an [[asymptote]], and next will have to introduce a breakthrough : to increase the [[bypass ratio]] to 35:1 instead of 11:1 for the [[CFM LEAP]], it is demonstrating a counterrotating [[open rotor]] unducted fan (propfan) in [[Istres, France]], under the European [[Clean Sky]] technology program.
[[Computational fluid dynamics|Modeling]] advances and high [[specific strength]] materials may help it succeed where previous attempts failed.
When noise levels will be within current standards and similar to the Leap engine, 15% lower fuel burn will be available and for that Safran is testing its controls, vibration and operation, while [[airframe]] integration is still challenging.<ref name=AvWeek8Aug2017/>


For [[GE Aviation]], the [[energy density]] of jet fuel still maximises the [[Breguet range equation]] and higher pressure ratio cores, lower pressure ratio fans, low-loss inlets and lighter structures can further improve thermal, transfer and propulsive efficiency.
Under the [[U.S. Air Force]]’s [[Adaptive Engine Transition Program]], adaptive [[thermodynamic cycle]]s will be used for the [[sixth-generation jet fighter]], based on a modified [[Brayton cycle]] and [[Constant volume]] combustion.
[[Additive manufacturing]] in the [[General Electric Advanced Turboprop|advanced turboprop]] will reduce weight by 5% and fuel burn by 20%.<ref name=AvWeek8Aug2017/>

Rotating and static [[ceramic matrix composite]] (CMC) parts operates {{cvt|500|°F}} hotter than metal and are one-third its weight.
With $21.9 million from the [[Air Force Research Laboratory]], GE is investing $200 million in a CMC facility in [[Huntsville, Alabama]], in addition to its [[Asheville, North Carolina]] site, mass-producing [[silicon carbide]] matrix with silicon-carbide fibers in 2018.
CMCs will be used ten times more by the mid-2020s : the CFM LEAP requires 18 CMC turbine shrouds per engine and the [[GE9X]] will use it in the combustor and for 42 HP turbine nozzles.<ref name=AvWeek8Aug2017/>


[[Rolls-Royce Plc]] aim for a 60:1 pressure ratio core for the 2020s [[Ultrafan]] and began ground tests of its {{cvt|100,000|hp}} gear for {{cvt|100,000|lbf|kN}} and 15:1 bypass ratios.
Nearly [[stoichiometric]] turbine entry temperatures approaches the theoretical limit and its impact on emissions has to be balanced with environmental performance goals.
Open rotors, lower pressure ratio fans and potentially [[distributed propulsion]] offers more room for better propulsive efficiency.
Exotic cycles, [[heat exchanger]]s and pressure gain/constant volume combustion can improve [[thermodynamic efficiency]].
Additive manufacturing could be an enabler for [[intercooler]] and [[recuperator]]s.
Closer airframe integration and [[Hybrid electric vehicle#Aircraft|hybrid]] or [[electric aircraft]] can be combined with gas turbines.<ref name=AvWeek8Aug2017/>

Current Rolls-Royce engines have a 72–82% propulsive efficiency and 42–49% thermal efficiency for a {{cvt|0.63|-|0.49|lb/lbf/h|g/kN/h}} [[Thrust specific fuel consumption|TSFC]] at Mach 0.8, and aim for theoretical limits of 95% for open rotor propulsive efficiency and 60% for thermal efficiency with stoichiometric [[turbine]] entry temperature and 80:1 [[overall pressure ratio]] for a {{cvt|0.35|lb/lbf/h|g/kN/h}} TSFC<ref>{{citation |url= http://www.fzt.haw-hamburg.de/pers/Scholz/dglr/hh/text_2014_03_20_EnginesTechnology.pdf |title= Rolls-Royce technology for future aircraft engines |date= March 20, 2014 |author= Ulrich Wenger |publisher= Rolls-Royce Deutschland}}</ref>

As teething troubles may not show up until several thousand hours, the latest turbofans technical problems disrupt [[airline]]s operations and [[aerospace manufacturer|manufacturer]]s deliveries while production rates are rising sharply.
[[Trent 1000]] cracked blades [[aircraft on ground|grounded]] almost 50 [[Boeing 787]]s and reduced [[ETOPS]] to 2.3 hours down from 5.5, costing [[Rolls-Royce plc]] almost $950 million.
[[PW1000G]] knife-edge seal fractures have caused [[Pratt & Whitney]] to fall way behind in deliveries, leaving about 100 engineless [[A320neo]]s waiting for their powerplants.
The [[CFM LEAP]] introduction was smoother but a [[ceramic composite]] {{abbr|HP|High-Pressure}} Turbine coating is prematurely lost, necessitating a new design, causing 60 A320neo engine removal for modification, as deliveries are up to six weeks late.<ref name=SeattleTimes15jun2018>{{cite news |url= https://www.seattletimes.com/business/boeing-aerospace/troublesome-advanced-engines-for-boeing-and-airbus-jets-disrupt-airlines-and-production-lines/ |title= Troublesome advanced engines for Boeing, Airbus jets have disrupted airlines and shaken travelers |date= June 15, 2018 |author= Dominic Gates |newspaper= The Seattle Times}}</ref>

==Manufacturers==
{{main|List of turbofan manufacturers}}
The turbofan engine market is dominated by [[GE Aircraft Engines|General Electric]], [[Rolls-Royce plc]] and [[Pratt & Whitney]], in order of market share. General Electric and [[SNECMA]] of France have a joint venture, [[CFM International]]. Pratt & Whitney also have a joint venture, [[International Aero Engines]] with [[Japanese Aero Engine Corporation]] and [[MTU Aero Engines]] of Germany, specializing in engines for the [[Airbus A320 family|Airbus A320]] family. Pratt & Whitney and General Electric have a joint venture, [[Engine Alliance]] selling a range of engines for aircraft such as the [[Airbus A380]].

For [[airliner]]s and [[cargo aircraft]], the in-service fleet in 2016 is 60,000 engines and should grow to 103,000 in 2035 with 86,500 deliveries according to [[Flight Global]]. A majority will be medium-thrust engines for [[narrow-body aircraft]] with 54,000 deliveries, for a fleet growing from 28,500 to 61,000. High-thrust engines for [[wide-body aircraft]], worth 40–45% of the market by value, will grow from 12,700 engines to over 21,000 with 18,500 deliveries. The [[regional jet]] engines below 20,000 lb (89 kN) fleet will grow from 7,500 to 9,000 and the fleet of [[turboprop]]s for airliners will increase from 9,400 to 10,200. The manufacturers [[market share]] should be led by CFM with 44% followed by Pratt & Whitney with 29% and then Rolls-Royce and General Electric with 10% each.<ref>{{cite news |url= https://www.flightglobal.com/news/articles/insight-from-flightglobal-flight-fleet-forecasts-e-430071/ |title= Flight Fleet Forecast's engine outlook |work= Flight Global |date= 2 November 2016 }}</ref>

=== Gallery ===
<gallery mode="packed" heights="129" perrow="5">
File:Solowjow D-30 III.jpg|[[Soloviev D-30]] which powers the [[Mikoyan MiG-31]], [[Ilyushin Il-76]], [[Ilyushin Il-62]]M, [[Xian H-6]]K, [[Xian Y-20]]
File:AL-31FN.jpg|[[Saturn AL-31]] which powers the [[Sukhoi Su-30]], [[Sukhoi Su-27]], [[Chengdu J-10]], [[Shenyang J-11]]
File:SaM146 back.jpg|[[PowerJet SaM146]] which powers [[Sukhoi Superjet 100]]
File:Ge cf6 turbofan.jpg|[[General Electric CF6]] which powers the [[Airbus A300]], [[Boeing 747]], [[Douglas DC-10]] and other aircraft
File:Rolls-Royce Trent 900 AEDC-d0404084 USAF.jpg|[[Rolls-Royce Trent 900]] undergoing climatic testing
File:N7771@GVA;09.09.1995-engine (6083468531).jpg|[[Pratt & Whitney PW4000]] which powered the first [[Boeing 777]]
File:CFM56 P1220759.jpg|The [[CFM International CFM56|CFM56]] which powers the [[Boeing 737]], the [[Airbus A320]] and other aircraft
File:EA GP7200.jpg|[[Engine Alliance GP7000]] turbofan for the [[Airbus A380]]
File:PS-90A.jpg|[[Aviadvigatel PS-90]] which powers the [[Ilyushin Il-96]], [[Tupolev Tu-204]], [[Ilyushin Il-76]]
File:Williams Research F107.jpg|[[Williams F107]] which powers the [[Raytheon]] [[Tomahawk (missile)|BGM-109 Tomahawk]] cruise missile
File:ALF502.JPG|[[Honeywell Aerospace]] [[Lycoming ALF 502]] which powers the [[British Aerospace 146]]
File:MAKS Airshow 2013 (Ramenskoye Airport, Russia) (524-34).jpg|[[Aviadvigatel PD-14]] which will be used on the [[Irkut MC-21]]
File:D-436-148 MAKS-2009.jpg|[[Ivchenko-Progress]] [[Progress D-436|D-436]] sharing the three shaft principle with Rolls-Royce Trent
File:AL-55 at the MAKS-2011 (01).jpg|[[NPO Saturn AL-55]] which powers certain [[HAL HJT-36 Sitara]]
File:RD-33MK ok.JPG|[[Klimov RD-33]] which powers the [[Mikoyan MiG-29]] and [[Mikoyan MiG-35]] fighters
File:Eurojet EJ200 for Eurofighter Typhoon PAS 2013 01 free.jpg|[[Eurojet EJ200]] which powers the [[Eurofighter Typhoon]]
File:XF3 KASM001.jpg|[[Ishikawajima-Harima F3]] which powers the [[Kawasaki T-4]]
File:GTX-35VS_Kaveri.jpg|[[GTRE GTX-35VS Kaveri]] developed by [[Gas Turbine Research Establishment|GTRE]] for [[HAL Tejas]]
</gallery>

=== Commercial turbofans in production ===
{| class="wikitable sortable"
|+ Commercial turbofans in production<ref>{{cite book |title= Jane's All the World's Aircraft |issn= 0075-3017 |date=2005 |pages= 850–853}}</ref>
! Model
! Start !! Bypass !! Length !! Fan !! Weight !! Thrust
! Major applications
|-
| [[General Electric GE90|GE GE90]]
| 1992 || 8.7–9.9 || 5.18m–5.40m || 3.12–3.25 m || 7.56–8.62t || 330–510 kN
| [[Boeing 777|B777]]
|-
| [[Pratt & Whitney PW4000|P&W PW4000]]
| 1984 || 4.8–6.4 || 3.37–4.95m || 2.84 m || 4.18–7.48t || 222–436 kN
| [[Airbus A300|A300]]/[[A310]], [[A330]], [[B747]], [[Boeing 767|B767]], [[Boeing 777|B777]], [[MD-11]]
|-
| [[Rolls-Royce Trent XWB|R-R Trent XWB]]
| 2010 || 9.3 || 5.22 m || 3.00 m || 7.28 t || 330–430 kN
| [[A350XWB]]
|-
| [[Rolls-Royce Trent 800|R-R Trent 800]]
| 1993 || 5.7–5.79 || 4.37m || 2.79m || 5.96–5.98t || 411–425 kN
| [[Boeing 777|B777]]
|-
| [[Engine Alliance GP7000|EA GP7000]]
| 2004 || 8.7 || 4.75 m || 2.95 m || 6.09–6.71 t || 311–363 kN
| [[A380]]
|-
| [[Rolls-Royce Trent 900|R-R Trent 900]]
| 2004 || 8.7 || 4.55 m || 2.95 m || 6.18–6.25 t || 340–357 kN
| [[A380]]
|-
| [[Rolls-Royce Trent 1000|R-R Trent 1000]]
| 2006 || 10.8–11 || 4.74 m || 2.85 m || 5.77 t || 265.3–360.4 kN
| [[B787]]
|-
| [[General Electric GEnx|GE GEnx]]<ref>{{cite web |url= http://www.geaviation.com/commercial/engines/genx/ |title= GEnx |publisher= GE}}</ref>
| 2006
| 8.0–9.3
| {{#expr:169.7*.0254round2}}-{{#expr:184.7*.0254round2}} m
| {{#expr:104.7*.0254round2}}-{{#expr:111.1*.0254round2}} m
| {{#expr:12400*0.00045359237round2}}-{{#expr:12822*0.00045359237round2}} t
| {{#expr:66500*0.00444822162round0}}-{{#expr:76100*0.00444822162round0}} kN
| [[B747-8]], [[B787]]
|-
| [[Rolls-Royce Trent 700|R-R Trent 700]]
| 1990 || 4.9 || 3.91 m || 2.47 m || 4.79 t || 320 kN
| [[A330]]
|-
| [[General Electric CF6|GE CF6]]
| 1971 || 4.3–5.3 || 4.00–4.41 m || 2.20–2.79 m || 3.82–5.08 t || 222–298 kN
| [[Airbus A300|A300]]/[[A310]], [[A330]], [[B747]], [[Boeing 767|B767]], [[MD-11]], [[McDonnell Douglas DC-10|DC-10]]
|-
| [[Rolls-Royce Trent 500|R-R Trent 500]]
| 1999 || 8.5 || 3.91 m || 2.47 m || 4.72 t || 252 kN
| [[A340]]-500/600
|-
| [[Pratt & Whitney PW1000G|P&W PW1000G]]<ref>{{cite web |url= http://www.mtu.de/engines/commercial-aircraft-engines/narrowbody-and-regional-jets/pw1000g/ |title= PW1000G |publisher= [[MTU Aero Engines|MTU]]}}</ref>
| 2008 || 9.0–12.5 || 3.40 m || 1.42–2.06 m || 2.86 t || 67–160 kN
| [[Airbus A320neo|A320neo]], [[Airbus A220|A220]], [[E-Jets E2]]
|-
| [[CFM International LEAP|CFM LEAP]]<ref>{{cite web|url=http://www.cfmaeroengines.com/engines/leap |title=The Leap Engine |publisher= CFM International }}</ref>
| 2013 || 9.0–11.0 || 3.15–3.33m || 1.76–1.98m || 2.78–3.15t || 100–146 kN
| [[A320neo]], [[B737Max]]
|-
| [[CFM International CFM56|CFM56]]
| 1974 || 5.0–6.6 || 2.36–2.52m || 1.52–1.84m || 1.95–2.64t || 97.9-151 kN
| [[A320]], [[A340]]-200/300, [[B737]], [[KC-135]], [[Douglas DC-8|DC-8]]
|-
| [[IAE V2500]]
| 1987 || 4.4–4.9 || 3.20m || 1.60m || 2.36–2.54t || 97.9-147 kN
| [[A320]], [[MD-90]]
|-
| [[Pratt & Whitney PW6000|P&W PW6000]]
| 2000 || 4.90 || 2.73m || 1.44m || 2.36t || 100.2 kN
| [[Airbus A318]]
|-
| [[Rolls-Royce BR700|R-R BR700]]
| 1994 || 4.2–4.5 || 3.41–3.60m || 1.32–1.58m || 1.63–2.11t || 68.9–102.3 kN
| [[Boeing 717|B717]], [[Global Express]], [[Gulfstream V]]
|-
| [[General Electric Passport|GE Passport]]
| 2013 || 5.6 || 3.37m || 1.30m || 2.07t || 78.9–84.2 kN
| [[Global 7000]]/8000
|-
| [[General Electric CF34|GE CF34]]
| 1982 || 5.3–6.3 || 2.62–3.26m || 1.25–1.32m || 0.74–1.12t || 41–82.3 kN
| [[Challenger 600]], [[Bombardier CRJ|CRJ]], [[E-jets]]
|-
| [[Pratt & Whitney Canada PW800|P&WC PW800]]
| 2012 || 5.5 || || 1.30m || || 67.4–69.7 kN
| [[Gulfstream G500/G600]]
|-
| [[Rolls-Royce RB.183 Tay|R-R Tay]]
| 1984 || 3.1–3.2 || 2.41m || 1.12–1.14m || 1.42–1.53t || 61.6–68.5 kN
| [[Gulfstream IV]], [[Fokker 70]]/[[Fokker 100|100]]
|-
| [[Snecma Silvercrest|Silvercrest]]
| 2012 || 5.9 || 1.90m || 1.08m || 1.09t || 50.9 kN
| [[Cessna Citation Hemisphere|Cit. Hemisphere]], [[Dassault Falcon 5X|Falcon 5X]]
|-
| [[Rolls-Royce AE 3007|R-R AE 3007]]
| 1991 || 5.0 || 2.71m || 1.11m || 0.72t || 33,7 kN
| [[ERJ]], [[Citation X]]
|-
| [[Pratt & Whitney Canada PW300|P&WC PW300]]
| 1988 || 3.8–4.5 || 1.92–2.07 || 0.97m || 0.45–0.47t || 23.4–35.6 kN
| [[Citation Sovereign|Cit. Sovereign]], [[Gulfstream G200|G200]], [[Falcon 7X|F. 7X]], [[Falcon 2000|F. 2000]]
|-
| [[Honeywell HTF7000|HW HTF7000]]
| 1999 || 4.4 || 2.29m || 0.87m || 0.62t || 28.9 kN
| [[Challenger 300]], [[Gulfstream G280|G280]], [[Embraer Legacy 500|Legacy 500]]
|-
| [[Garrett TFE731|HW TFE731]]
| 1970 || 2.66–3.9 || 1.52–2.08m || .072-0.78m || 0.34–0.45t || 15.6–22.2 kN
| [[Learjet 70/75]], [[G150]], [[Falcon 900]]
|-
| [[Williams FJ44]]
| 1985 || 3.3–4.1 || 1.36–2.09m || .53-0.57m || 0.21–0.24t || 6.7–15.6 kN
| [[Cessna CitationJet|CitationJet]], [[Cessna Citation M2|Cit. M2]]
|-
| [[Pratt & Whitney Canada PW500|P&WC PW500]]
| 1993 || 3.90 || 1.52m || 0.70m || 0.28t || 13.3 kN
| [[Citation Excel]], [[Phenom 300]]
|-
| [[GE-Honda HF120|GE-H HF120]]
| 2009 || 4.43 || 1.12m || 0.54 m || 0.18t || 7.4 kN
| [[HondaJet]]
|-
| [[Williams FJ33]]
| 1998 || || 0.98m || 0.53 m || 0.14 t || 6.7 kN
| [[Cirrus SF50]]
|-
| [[Pratt & Whitney Canada PW600|P&WC PW600]]
| 2001 || 1.8–2.8 || 0.67m || 0.36m || 0.15t || 6.0 kN
| [[Citation Mustang|Cit. Mustang]], [[Eclipse 500]], [[Phenom 100]]
|-
| [[Aviadvigatel PS-90|PS-90]]
| 1992 || 4.4 || 4.96m || 1.9m || 2.95t || 157–171 kN
| [[Ilyushin Il-76]], [[Ilyushin Il-96]], [[Tupolev Tu-204]]
|-
| [[PowerJet SaM146]]
| 2008 || 4-4.1 || 3.59m || 1.22m || 2.260t || 71.6–79.2 kN
| [[Sukhoi Superjet 100]]
|}

==Extreme bypass jet engines==

In the 1970s, Rolls-Royce/SNECMA tested a [[M45SD-02]] turbofan fitted with variable pitch fan blades to improve handling at ultra low fan pressure ratios and to provide thrust reverse down to zero aircraft speed. The engine was aimed at ultra quiet [[STOL]] aircraft operating from city centre airports.

In a bid for increased efficiency with speed, a development of the ''turbofan'' and ''turboprop'' known as a [[propfan]] engine was created that had an unducted fan. The fan blades are situated outside of the duct, so that it appears like a turboprop with wide scimitar-like blades. Both General Electric and Pratt & Whitney/Allison demonstrated propfan engines in the 1980s. Excessive cabin noise and relatively cheap jet fuel prevented the engines being put into service. The [[Progress D-27]] propfan, developed in the U.S.S.R., was the only propfan engine equipped on a production aircraft.

==Terminology==
; [[Afterburner]]: extra combustor immediately upstream of final nozzle (also called reheat)
; Augmentor: afterburner on low-bypass turbofan engines.
; Average stage loading: constant × (delta temperature)/[(blade speed) × (blade speed) × (number of stages)]
; Bypass: airstream that completely bypasses the core compression system, combustor and turbine system
; [[Bypass ratio]]: bypass airflow /core compression inlet airflow
; Core: turbomachinery handling the airstream that passes through the combustor.
; [[Core power]]: residual shaft power from ideal turbine expansion to ambient pressure after deducting core compression power
; Core thermal efficiency: core power/power equivalent of fuel flow
; Dry: afterburner (if fitted) not lit
; EGT: exhaust gas temperature
; EPR: engine pressure ratio
; Fan: turbofan LP compressor
; Fan pressure ratio: fan outlet total pressure/intake delivery total pressure
; [[Flex temp]]: use of artificially high apparent air temperature to reduce engine wear
; Gas generator: engine core
; HP compressor: high-pressure compressor (also HPC)
; HP turbine: high-pressure turbine
; Intake ram drag: penalty associated with jet engines picking up air from the atmosphere (conventional rocket motors do not have this drag term, because the oxidiser travels with the vehicle)
; [[IEPR]]: integrated engine pressure ratio
; IP compressor: intermediate pressure compressor (also IPC)
; IP turbine: intermediate pressure turbine (also IPT)
; LP compressor: low-pressure compressor (also LPC)
; LP turbine: low-pressure turbine (also LPT)
; Net thrust: nozzle total gross thrust – intake ram drag (excluding nacelle drag, etc., this is the basic thrust acting on the airframe)
; Overall pressure ratio: combustor inlet total pressure/intake delivery total pressure
; Overall efficiency: thermal efficiency * propulsive efficiency
; [[Propulsive efficiency]]: propulsive power/rate of production of propulsive kinetic energy (maximum propulsive efficiency occurs when jet velocity equals flight velocity, which implies zero net thrust!)
; [[Thrust specific fuel consumption|Specific fuel consumption]] (SFC): total fuel flow/net thrust (proportional to flight velocity/overall thermal efficiency)
; Spooling up: accelerating, marked by a delay
; Static pressure: pressure of the fluid which is associated not with its motion but with its state<ref>Clancy, L.J., ''Aerodynamics'', page 21</ref>
; [[Specific thrust]]: net thrust/intake airflow
; [[Thermal efficiency]]: rate of production of propulsive kinetic energy/fuel power
; Total fuel flow: combustor (plus any afterburner) fuel flow rate (e.g., lb/s or g/s)
; Total pressure: static pressure '''plus''' kinetic energy term
; Turbine rotor inlet temperature: gas absolute mean temperature at principal (e.g., HP) turbine rotor entry

==See also==
* [[Jet engine]]
* [[Turbojet]]
* [[Turboprop]]
* [[Turboshaft]]
* [[Propfan]]
* [[Axial fan design]]
* [[Variable cycle engine]]
* [[Jet engine performance]]
* [[Gas turbine]]
* [[Turbine engine failure]]

==References==
{{Reflist|35em}}

==External links==
{{Commons category|Turbofan engines}}
*[[Wikibooks:Jet Propulsion|Wikibooks: Jet propulsion]]
* {{cite web |url= https://www.hq.nasa.gov/office/aero/ebooks/downloads/nasa_innovation_in_aeronautics.pdf |author= Malcolm Gibson |work= NASA Innovation in Aeronautics NASA/TM-2011-216987 |date= Aug 2011 |title= The Chevron Nozzle: A Novel Approach to Reducing Jet Noise}}
* {{cite news |url= https://scribd.com/doc/105381018/Engine-Yearbook |title= The Engine Yearbook |date= 2012 |publisher= UBM Aviation}}
* {{cite news |url= https://www.flightglobal.com/asset/17069 |title= Commercial engines 2017 |work= Flight Global}}
* {{cite news |url= https://leehamnews.com/2017/04/14/bjorns-corner-aircraft-engines-sum/ |title= Bjorn’s Corner: Aircraft engines, sum up |date= April 14, 2017 |work= Leeham Co |author= Bjorn Fehrm}} and previous series

{{Aircraft gas turbine engine components}}
{{Heat engines|state=uncollapsed}}

[[Category:Gas turbines]]
[[Category:Jet engines]]

Volkswagen Type 2

2018-08-06T15:06:16Z

173.165.237.1: /* {{Anchor|T6}}Sixth generation (T6; 2015–present) */

{{Use dmy dates|date=June 2011}}
{{Refimprove|date=January 2016}}
{{Infobox automobile
| name = Volkswagen Type 2
| image = 0385 Porsche Diesel Bus blau.jpg
| manufacturer = [[Volkswagen]]
| aka = Volkswagen Bus Volkswagen Kombi
| production = Nov 1949<ref name="Walters, p.46" />–present
| assembly =
| predecessor =
| successor = [[Volkswagen Type 2 (T3)]]
| class = [[Light commercial vehicle]] ([[M-segment|M]])
| body_style = 4/5-door [[panel van]] 4/5-door [[minibus]] 2-door [[pickup truck|pickup]] (regular cab) 4-door [[pickup truck|pickup]] (crew cab)
| layout = [[RR layout]]
| platform = [[Volkswagen Group T platform]]
| sp = uk
}}

The '''Volkswagen Type 2''', known officially (depending on body type) as the '''[[Volkswagen Transporter|Transporter]]''', '''[[Volkswagen Transporter|Kombi]]''' or Microbus, or, informally, as the '''Bus''' (US) or '''Camper''' (UK), is a [[forward control]] [[panel van]] introduced in 1950 by the German [[automotive industry|automaker]] [[Volkswagen]] as its second [[car model]]. Following – and initially deriving from Volkswagen's first model, the [[Volkswagen Beetle|Type 1 (Beetle)]] – it was given the factory designation Type 2.<ref>{{cite web|url=http://www.brinse.com/history-of-the-volkswagen-bus.html |title=History of the Volkswagen bus |publisher=Brinse.com |date= |accessdate=19 August 2011}}</ref>

As one of the forerunners of the modern cargo and passenger vans, the Type 2 gave rise to [[forward control]] competitors in the United States in the 1960s, including the [[Ford E-Series|Ford Econoline]], the [[Dodge A100]], and the [[Chevrolet Greenbrier|Chevrolet Corvair 95 Corvan]], the latter adapting the [[Rear-engine, rear-wheel-drive layout|rear-engine configuration]] of the Corvair car in the same manner in which the VW Type 2 adapted the Type 1 layout.

European competition included the 1947–1981 [[Citroën H Van]], the 1959–1980 [[Renault Estafette]] (both [[FF layout]]), and the 1953–1965 [[FR layout]] [[Ford Transit]].

Japanese manufacturers also introduced similar vehicles, such as the [[Nissan Caravan]], [[Toyota LiteAce]] and [[Subaru Sambar]].

Like the Beetle, the van has received numerous nicknames worldwide, including the "microbus", "minibus",<ref>{{cite news| url= http://www.projo.com/lifebeat/content/Mark28_07-28-09_T9F6IMQ_v12.27857d7.html |last= Patinkin| first= Mark| title= 1969 was the most tumultuous and normal year| newspaper= [[Providence Journal]]| date= 28 July 2009}}</ref> and, because of its popularity during the [[counterculture of the 1960s|counterculture movement of the 1960s]], "'''Hippie van/bus"''' has become its most popular.

Brazil contained the last factory in the world that produced the T2 series of Type 2, which ceased production on December 31, 2013, due to the introduction of more stringent safety regulations in the country.<ref name=TerminationAutocar>{{cite web| url= http://www.autocar.co.uk/car-news/sao-paulo-motor-show-2012/end-road-volkswagen-camper |last= Tisshaw| first= Mark |title= End of the road for Volkswagen camper| website= [[Autocar (magazine)|Autocar]]| date= 24 October 2012}}</ref> This (after the 2002 termination of its T3 successor in South Africa) marked the end of the era of rear-engine Volkswagens manufactured, which originated in 1935 with their Type 1 prototypes.

== History ==
[[File:Volkswagen Type 2 at The Henry Ford - July 2017.jpg|thumb|1959 Volkswagen Westfalia Camper at [[The Henry Ford]]]]

The concept for the Type 2 is credited to Dutch Volkswagen importer [[Ben Pon (senior)|Ben Pon]]. (It has similarities in concept to the 1920s [[Rumpler Tropfenwagen]] and 1930s [[Dymaxion car]] by [[Buckminster Fuller]], neither of which reached production.) Pon visited [[Wolfsburg]] in 1946, intending to purchase Type 1s for import to the Netherlands, where he saw an improvised parts-mover and realized something better was possible using the stock Type 1 pan.<ref>Walters, Jeff. "Type 2 Roots", in ''Hot VWs'', 7/84, p.45.</ref> He first sketched the van in a doodle dated April 23, 1947,<ref name="Walters, p.45">Walters, p.45.</ref> proposing a payload of {{convert|690|kg|lb|abbr=on}} and placing the driver at the very front.<ref name="Walters, p.46">Walters, p.46.</ref> Production would have to wait, however, as the factory was at capacity producing the Type 1.<ref name="Walters, p.46" />

When capacity freed up, a prototype known internally as the '''Type 29''' was produced in a short three months.<ref name="Walters, p.45" /> The stock Type 1 pan proved to be too weak so the prototype used a ladder chassis with [[unit body]] construction.<ref name="Walters, p.46">Walters, p.46.</ref> Coincidentally the wheelbase was the same as the Type 1's.<ref name="Walters, p.46" /> Engineers reused the reduction gear from the [[Volkswagen Kübelwagen|Type 81]], enabling the 1.5 ton van to use a {{convert|25|hp|kW|abbr=on}} flat four engine.<ref name="Walters, p.46" />

Although the [[aerodynamics]] of the first prototypes were poor (with an initial {{Cd|long=yes|link=car|0.75}}),<ref name="Walters, p.46" /> engineers used the [[wind tunnel]] at the Technical University of [[Braunschweig]] to optimize the design. Simple changes such as splitting the windshield and roofline into a "vee" helped the production Type 2 achieve {{Cd|0.44}}, exceeding the Type 1's {{Cd|0.48}}.<ref name="Walters, p.47">Walters, p.47.</ref> Volkswagen's new chief executive officer [[Heinz Nordhoff]] (appointed 1 January 1948)<ref>Walter, p.46.</ref> approved the van for production on 19 May 1949<ref name="Walters, p.46" /> and the first production model, now designated '''Type 2''',<ref name="Walters, p.47" /> rolled off the [[assembly line]] to debut 12 November.<ref name="Walters, p.46" /> Only two models were offered: the Kombi (with two side windows and middle and rear seats that were easily removable by one person),<ref name="Walters, p.47" /> and the Commercial.<ref name="Walters, p.46" /> The Microbus was added in May 1950,<ref name="Walters, p.46" /> joined by the Deluxe Microbus in June 1951.<ref name="Walters, p.46" /> In all 9,541 Type 2s were produced in their first year of production.<ref name="Walters, p.47" />

An ambulance model was added in December 1951 which repositioned the fuel tank in front of the transaxle, put the spare tire behind the front seat,<ref name="Walters, p.47" /> and added a "[[Trunk (automobile)#Door|tailgate]]"-style rear door.<ref name="Walters, p.47" /> These features became standard on the Type 2 from 1955 to 1967.<ref name="Walters, p.47" /> 11,805 Type 2s were built in the 1951 model year.<ref name="Walters, p.94">Walters, p.94.</ref>
These were joined by a single-cab pickup in August 1952, and it changed the least of the Type 2s until all were heavily modified in 1968.<ref name="Walters, p.94" />

Unlike other [[rear-engine design|rear engine]] Volkswagens, which evolved constantly over time but never saw the introduction of all-new models, the Transporter not only evolved, but was completely revised periodically with variations retrospectively referred to as versions "T1" to "T5" (a nomenclature only invented after the introduction of the front-drive T4 which replaced the T25). However, only generations T1 to T3 (or T25 as it is still called in Ireland and Great Britain) can be seen as directly related to the Beetle (see below for details){{Citation needed|date=May 2011}}.

The Type 2, along with the 1947 [[Citroën H Van]], are among the first 'forward control' vans in which the driver was placed above the front roadwheels. They started a trend in Europe, where the 1952 GM [[Bedford CA]], 1958 [[RAF-977]], 1959 [[Renault Estafette]], 1960 BMC [[Morris J4]], and 1960 [[Commer]] FC also used the concept. In the United States, the [[Chevrolet Corvair|Corvair]]-based Chevrolet Corvan cargo van and Greenbrier passenger van adopted the use of the rear-engine layout of the Corvair car in the same manner that the Type 2 had used the rear-engine layout of the Type 1, using the Corvair's horizontally opposed, 6 cylinder air-cooled engine for power. Except for the Greenbrier and various 1950s–70s [[Fiat]] minivans, the Type 2 remained unique in being rear-engined. This was a disadvantage for the early "barndoor" Panel Vans, which could not easily be loaded from the rear because the engine cover intruded on interior space, but generally advantageous in traction and interior noise. The Corvair pickup used a folding side panel that functioned as a ramp into the bed when opened, and was called the "Rampside". The VW "pickup" in both single and double cab versions had a bed/floor that was flat from front to back at the height of the engine compartment cover, which had the advantage of a flat load floor but at a greater height, while the Corvair "pickup" bed/floor stepped down in front of the engine compartment to a much lower load floor which worked well with the unique "Rampside" configuration for loading.

== Variants ==
[[File:VW T1-BD 20-5031.JPG|thumb|right|Rail-going [[draisine]]]]

The Type 2 was available as a:
*[[Panel van]], a delivery van without side windows or rear seats.
*Double-door Panel Van, a delivery van without side windows or rear seats and cargo doors on both sides.
*High Roof Panel Van ({{lang-de|Hochdach}}), a delivery van with raised roof.
*Kombi, from {{lang-de|Kombinationskraftwagen}} (combination motor vehicle), with side windows and removable rear seats, both a passenger and a cargo vehicle combined.
*Bus, also called a ''[[Volkswagen Caravelle (disambiguation)|Volkswagen Caravelle]]'', a van with more comfortable interior reminiscent of passenger cars since the third generation.
*Lotação (share-taxi), a version exclusive to Brazil, with 6 front-hinged doors for the passenger area and 4 bench-seats, catering to the supplemental public transport segment.{{citation needed|date=July 2016}} Available from 1960 to 1989, in both the split-window and "clipper" (fitted with the bay-window front panel) bodystyles.
*[[Samba (bus)|Samba-Bus]], a van with skylight windows and cloth sunroof, first generation only, also known as a ''Deluxe Microbus''. They were marketed for touring the [[Alps]].<ref>{{cite news|url=http://news.bbc.co.uk/1/hi/uk/8704175.stm|title=Volkswagen camper van marks 60 years of production|publisher=BBC |date=4 June 2010}}</ref>
*Flatbed [[pickup truck]], or Single Cab, also available with wider load bed.
*[[Crew cab]] pick-up, a [[flatbed truck]] with extended cab and two rows of seats, also called a '''Doka''', from {{lang-de|Doppelkabine}}.
*[[Volkswagen Westfalia Campers|Westfalia camping van]], "Westy", with [[Westfalia]] roof and interior. Included optional "pop up" top.
*Adventurewagen camping van, with high roof and camping units from [[Adventurewagen]].
*Semi-camping van that can also still be used as a passenger car and transporter, sacrificing some camping comforts. "Multivan" or "Weekender", available from the third generation on.

Apart from these factory variants, there were a multitude of third-party conversions available, some of which were offered through Volkswagen dealers. They included, but were not limited to, refrigerated vans, [[hearse]]s, [[ambulance]]s, police vans, [[fire apparatus|fire engines]] and ladder trucks, and camping van conversions by companies other than Westfalia. There were even 30 [[Klv 20]] rail-going [[draisine]]s built for [[Deutsche Bundesbahn]] in 1955.<ref>{{cite web |url=http://www.eisenbahndienstfahrzeuge.de/klv/klv20/klv20.htm |title=Klv 20 Draisine, VW Bus |publisher=Eisenbahndienstfahrzeuge.de |date= |accessdate=19 August 2011 |archive-url=https://web.archive.org/web/20110718233546/http://www.eisenbahndienstfahrzeuge.de/klv/klv20/klv20.htm |archive-date=18 July 2011 |dead-url=yes |df=dmy-all }}</ref>

In South Africa, it is known as a well-loved variation of the [[ice cream van]] (first, second and third generations).

{{-}}

== {{Anchor|T1}}First generation (T1; 1950–1967) ==
{{Infobox automobile
| name = Volkswagen Type 2 (T1)
| image = 1966 Volkswagen T1 2.0 Front.jpg
| caption = 1966 Volkswagen Type 2
| aka =
| manufacturer = [[Volkswagen]]
| production = 1950–1967 (Europe and US) 1950–1975 (Brazil)
| assembly = [[Wolfsburg]], Germany [[Hanover]], Germany [[São Bernardo do Campo]], Brazil [[Melbourne]], [[Australia]]<ref name=clubvw>[http://www.clubvw.org.au/austvw001 Australian Volkswagens] Retrieved from www.clubvw.org.au on 7 August 2012</ref>
| class = [[Light commercial vehicle]]/[[Full-size van]] ([[M-segment|M]])
| body_style = 4-/5-door [[panel van]] 4-/5-door [[minibus]] 2-door [[pickup truck|pickup]] (regular cab) 3-door [[pickup truck|pickup]] (crew cab)
| layout = [[RR layout]]
| platform = [[Volkswagen Group T platform#T1|Volkswagen Group T1 platform]]
| engine = 1.1 [[litre|L]] [[flat-four engine|B4]] ([[petrol engine|petrol]]) 1.2 L B4 (petrol) 1.5 L B4 (petrol) 1.6 L B4 (petrol) (Brazil, after 1967)
| transmission =
| wheelbase = {{convert|2400|mm|1|abbr=on}}
| length = {{convert|4280|mm|1|abbr=on}}
| width = {{convert|1720|mm|1|abbr=on}}
| height = {{convert|1940|mm|1|abbr=on}}
| weight =
| related =
| designer =
| sp = uk
}}
[[File:1964 Volkswagen T1 Transporter Kombi bus (6106456722).jpg|thumb|left|Volkswagen T1 13 window "Kombi" microbus]]
[[File:1962 Volkswagen Type 2 2-door utility (26928884264).jpg|thumb|left|Volkswagen T1 Single-cab utility pickup]]

The first generation of the Volkswagen Type 2 with the split [[windshield]], informally called the '''Microbus''', '''Splitscreen''', or '''Splittie''' among modern fans, was produced from 8 March 1950 through the end of the 1967 model year. From 1950 to 1956, the T1 (not called that at the time) was built in [[Wolfsburg]]; from 1956, it was built at the completely new Transporter [[list of Volkswagen Group factories|factory]] in [[Hanover]]. Like the Beetle, the first Transporters used the 1100 [[Volkswagen air-cooled engine]], an {{convert|1131|cc|1|lk=on|abbr=on}}, [[Deutsches Institut für Normung|DIN]]-rated {{convert|18|kW|PS bhp|0|lk=on|abbr=on}}, [[air-cooled engine|air-cooled]] [[flat-four engine|flat-four-cylinder]] [[flat engine|'boxer' engine]] mounted in the rear. This was upgraded to the 1200 – an {{convert|1192|cc|1|abbr=on}} {{convert|22|kW|PS bhp|0|abbr=on}} in 1953. A higher compression ratio became standard in 1955; while an unusual early version of the {{convert|30|kW|PS bhp|0|abbr=on}} engine debuted exclusively on the Type 2 in 1959. Any 1959 models that retain that early engine today are true survivors. Since the engine was totally discontinued at the outset, no parts were ever made available.

The early versions of the T1 until 1955 were often called the "Barndoor"<ref>{{cite web|title=VW Type 2 T1 Split Bus |work=TheGoldenBug.com |first= |last= |date= |url=http://www.thegoldenbug.com/en/air-cooled_vw_history/d37/t1_split_bus |accessdate=5 June 2012 }}</ref><ref>{{cite web|title=History of the VW T1 Split Bus (Bulli) |work=VW Heritage |first= |last= |date= |url=https://www.vwheritage.com/split-history }}</ref> (retrospectively called '''T1a''' since the 1990s), owing to the enormous rear engine cover, while the later versions with a slightly modified body (the roofline above the windshield is extended), smaller engine bay, and 15" roadwheels instead of the original 16" ones are nowadays called the '''T1b''' (again, only called this since the 1990s, based on VW's retrospective T1,2,3,4 etc. naming system.). From the 1964 model year, when the rear door was made wider (same as on the bay-window or T2), the vehicle could be referred to as the '''T1c'''. 1964 also saw the introduction of an optional sliding door for the passenger/cargo area instead of the outwardly hinged doors typical of cargo vans.

In 1962, a heavy-duty Transporter was introduced as a factory option. It featured a cargo capacity of {{convert|1000|kg|lb|0|abbr=on}} instead of the previous {{convert|750|kg|lb|0|abbr=on}}, smaller but wider 14" roadwheels, and a 1.5 Le, {{convert|31|kW|PS bhp|0|abbr=on}} DIN engine. This was so successful that only a year later, the 750 kg, 1.2 L Transporter was discontinued. The 1963 model year introduced the 1500 engine – {{convert|1493|cc|1|abbr=on}} as standard equipment to the US market at {{convert|38|kW|PS bhp|0|abbr=on}} DIN with an {{convert|83|mm|in|2|abbr=on}} bore, {{convert|69|mm|2|abbr=on}} stroke, and 7.8:1 compression ratio. When the Beetle received the 1.5 L engine for the 1967 model year, its power was increased to {{convert|40|kW|PS bhp|0|abbr=on}} DIN.

German production stopped after the 1967 model year; however, the T1 still was made in [[Brazil]] until 1975, when it was modified with a 1968–79 T2-style front end, and big 1972-vintage taillights into the so-called "T1.5" and produced until 1996. The Brazilian T1s were not identical to the last German models (the T1.5 was locally produced in Brazil using the 1950s and 1960s-era stamping dies to cut down on retooling, alongside the [[Volkswagen Beetle|Beetle]]/Fusca, where the pre-1965 body style was retained), though they sported some characteristic features of the T1a, such as the cargo doors and five-stud {{convert|205|mm|1|abbr=on}} [[Wheel_sizing#Bolt_circle|Pitch Circle Diameter]] rims. Wheel tracks varied between German and Brazilian production and with 14-inch, 15-inch and 16-inch wheel variants but commonly front track varied from 1290 mm to 1310 mm and rear track from 1370 mm to 1390 mm.

Among American enthusiasts, it is common to refer to the different models by the number of their windows. The basic Kombi or Bus is the '''11-window''' (a.k.a. three-window bus because of three side windows) with a split windshield, two front cabin door windows, six rear side windows, and one rear window. The DeLuxe model featured eight rear side windows and two rear corner windows, making it the '''15-window''' (not available in Europe). Meanwhile, the sunroof DeLuxe with its additional eight small skylight windows is, accordingly, the '''23-window'''. From the 1964 model year, with its wider rear door, the rear corner windows were discontinued, making the latter two the '''13-window''' and '''21-window''' respectively. The 23- and later 21-window variants each carry the nickname [[Samba (bus)|"Samba" or in Australia, officially "Alpine"]].

=== Samba ===
[[File:Samba(1).jpg|thumb|left|A red Volkswagen Samba bus 23 windows]]
[[File:Samba 21 windows.jpg|left|thumb|A Volkswagen Transporter (T1) Samba model 21 window]]

The Volkswagen Samba, in the United States also known as Sunroof Deluxe, was the most luxurious version of the T1. Volkswagen started producing Sambas in 1951.

In the USA Volkswagen vans were informally classified according to the number of windows they had. This particular model had 23 and later 21 windows including eight panoramic windows in the roof (the 23 window version had additional curved windows in the rear corners). To distinguish it from the normal Volkswagen van the name ''Samba'' was coined.

Instead of a sliding door at the side the Samba had two pivot doors. In addition the Samba had a fabric [[sunroof]]. At that time Volkswagen advertised with the idea of using the Samba to make tourist trips through the [[Alps]].

Sambas were painted standard in two colors. Usually, the upper part was colored white. The two colored sections were separated by a decorative strip. Further the bus had a so-called "hat": at the front of the van the roof was just a little longer than the car itself to block the sun for the driver. The windows had chrome tables and the van had a more comprehensive dashboard than the normal T1.

When Volkswagen started producing the successor of the T1 (the T2) the company also stopped producing the Samba so there are no Sambas in later versions of the Transporter.

=== US Chicken Tax ===
{{Main|Chicken tax}}
[[File:Kombi Pick Up Aço.jpg|thumb|U.S. sales of Volkswagen vans in pickup and commercial configurations were curtailed by the [[Chicken tax]]]]

Certain models of the Volkswagen Type 2 played a role in a historic episode during the early 1960s, known as the '''Chicken War'''. France and West Germany had placed tariffs on imports of U.S. chicken.<ref>{{cite web|title=To outfox the Chicken Tax, Ford strips its own vans|work=The Wall Street Journal|first=Matthew|last=Dolan|date=22 September 2009|url=https://www.wsj.com/articles/SB125357990638429655}}</ref> Diplomacy failed, and in January 1964, two months after taking office, [[Lyndon B. Johnson|President Johnson]] imposed a 25% tax (almost ten times the average U.S. tariff) on potato starch, dextrin, brandy, and [[light truck]]s. Officially, the tax targeted items imported from Europe as approximating the value of lost American chicken sales to Europe.<ref name="nyt1">{{cite news|title=Light Trucks increase profits, but foul air more than cars|work=The New York Times|first=Keith|last=Bradsher|date=30 November 1997|url=https://www.nytimes.com/1997/11/30/business/license-pollute-special-report-light-trucks-increase-profits-but-foul-air-more.html?sec=&spon=&pagewanted=all | accessdate=27 May 2010}}</ref>

In retrospect, audio tapes from the Johnson White House, revealed a [[quid pro quo]] unrelated to chicken. In January 1964, President Johnson attempted to convince [[United Auto Workers]]' president [[Walter Reuther]] not to initiate a strike just before the 1964 election, and to support the president's civil rights platform. Reuther, in turn, wanted Johnson to respond to [[Volkswagen]]'s increased shipments to the United States.<ref name="nyt1" />

The Chicken Tax directly curtailed importation of German-built Type 2s in configurations that qualified them as [[light truck]]s – that is, commercial vans (panel vans) and [[pickup truck|pickups]].<ref name="nyt1" /> In 1964, U.S. imports of automobile trucks from West Germany declined to a value of $5.7 million – about one-third the value imported in the previous year. After 1971, Volkswagen cargo vans and pickup trucks, the intended targets, "practically disappeared from the U.S. market". While post-1971 Type 2 commercial vans and single-cab and double-cab pickups can be found in the United States today, they are exceedingly rare. Any post-1971 specimen found ostensibly has had its import tariff paid. The "Chicken tax" remains in effect today, even though it is now commonly curtailed by converting passenger vehicles to utility vehicles after they have entered the United States. This practice is ironically exercised by [[Ford Motor Company|Ford]] and [[Chrysler]], two of the companies the tax was meant to protect.

{{-}}

== {{Anchor|T2}}Second generation (T2; 1967–1979) == 
{{Infobox automobile
| name = Volkswagen Type 2 (T2)
| image = 1973-1980 Volkswagen Kombi (T2) van 01.jpg
| production = Aug 1967 – Jul 1979 (Europe and US) 1971–1994 ([[Mexico]]) 1976 – Dec 2013 ([[Brazil]])<ref name=TerminationAutocar /> 1981–1986 ([[Argentina]])
| assembly = [[Hanover]], Germany [[Emden]], Germany [[General Pacheco]], Argentina [[São Bernardo do Campo]], Brazil [[Puebla, Puebla]], Mexico [[Melbourne]], [[Australia]]<ref name=clubvw />
| platform = [[Volkswagen Group T platform#T2|Volkswagen Group T2 platform]]
| class = [[Light commercial vehicle]] ([[M-segment|M]])
| body_style = 4-door [[panel van]] 4-door [[minibus]] 2-door [[pickup truck|pickup]] (regular cab) 3-door [[pickup truck|pickup]] (crew cab)
| layout = [[RR layout]]
| engine = 1.6 [[litre|L]] [[flat-four engine|B4]] ([[petrol engine|petrol]]) 1.7 L B4 ([[petrol engine|petrol]]) 1.8 L B4 ([[petrol engine|petrol]]) 1.8 L [[inline-four engine|I4]] ([[petrol engine|petrol]]) 2.0 L B4 ([[petrol engine|petrol]])
| transmission = 4-speed [[manual transmission|manual]] 3-speed [[automatic transmission|automatic]]
| wheelbase = {{convert|2400|mm|1|abbr=on}}
| length = {{convert|4505|mm|1|abbr=on}}
| width = {{convert|1720|mm|1|abbr=on}}
| height = {{convert|1940|mm|1|abbr=on}}
| weight =
| related =
| designer =
| sp = uk
}}

In late 1967, the second generation of the Volkswagen Type 2 (T2) was introduced. It was built in Germany until 1979. In Mexico, the Volkswagen Kombi and Panel were produced from 1970 to 1994. Models before 1971 are often called the '''T2a''' (or "Early Bay"), while models after 1972 are called the '''T2b''' (or "Late Bay").

[[File:Volkswagen Transporter Pick-up (13936076527).jpg|thumb|left|Volkswagen Transporter Pickup (The Netherlands)]]
[[File:1973-1980 Volkswagen Kombi (T2) van 02.jpg|thumb|left|1973–1980 Volkswagen Kombi (T2) van (Australia)]]

This second-generation Type 2 lost its distinctive split front [[windshield]], and was slightly larger and considerably heavier than its predecessor. Its common nicknames are ''Breadloaf'' and ''Bay-window'', or ''Loaf'' and ''Bay'' for short.<ref>[http://everything2.com/index.pl?node_id=1084792 "Type II Volkswagen (thing)", section "Type 2/T2"] (spells the term "Bread-Loaf")</ref> At 1.6 L and {{convert|35|kW|PS bhp|0|abbr=on}} DIN, the engine was also slightly larger. The battery and electrical system was upgraded to 12 volts, making it incompatible with electric accessories from the previous generation. The new model also did away with the [[swing axle]] rear suspension and transfer boxes previously used to raise ride height. Instead, [[half-shaft]] axles fitted with [[constant velocity joint]]s raised ride height without the wild changes in [[camber angle|camber]] of the Beetle-based swing axle suspension. The updated Bus transaxle is usually sought after by off-road racers using air-cooled Volkswagen components.

The T2b was introduced by way of gradual change over three years. The first models featured rounded bumpers incorporating a step for use when the door was open (replaced by indented bumpers without steps on later models), front doors that opened to 90° from the body, no lip on the front guards, unique engine hatches, and crescent air intakes in the D-[[pillar (car)|pillars]] (later models after the Type 4 engine option was offered, have squared off intakes). The 1971 Type 2 featured a new, 1.6 L engine with dual intake ports on each cylinder head and was DIN-rated at {{convert|37|kW|PS bhp|0|abbr=on}}. An important change came with the introduction of front [[disc brake]]s and new roadwheels with brake ventilation holes and flatter hubcaps. Up until 1972, front indicators are set low on the nose rather than high on either side of the fresh air grille – giving rise to their being nicknamed "Low Lights". 1972's most prominent change was a bigger engine compartment to fit the larger 1.7- to 2.0-litre engines from the [[Volkswagen Type 4]], and a redesigned rear end which eliminated the removable rear apron and introduced the larger late tail lights. The air inlets were also enlarged to accommodate the increased cooling air needs of the larger engines.

In 1971 the 1600cc [[Volkswagen air-cooled engine#T1|Type 1 engine]] as used in the Beetle, was supplemented with the 1700cc [[Volkswagen air-cooled engine#T4|Type 4 engine]] – as it was originally designed for the [[Volkswagen Type 4|Type 4]] (411 and 412) models. European vans kept the option of upright fan Type 1 1600 engine but the 1700 Type 4 became standard for US spec models.

[[File:1968-1973 and 1973-1980 Volkswagen Kombi (T2) vans (2011-01-07).jpg|thumb|left|Pre-facelift ''(left)'' and facelifted ''(right)'' Volkswagen Kombi (T2) vans (Australia)]]

In the Type 2, the [[Volkswagen air-cooled engine#T4|Type 4 engine]] was an option for the 1972 model year onward. This engine was standard in models destined for the US and Canada. Only with the Type 4 engine did an [[automatic transmission]] become available for the first time in the 1973 model year. Both engines displaced 1.7 L, DIN-rated at {{convert|49|kW|PS bhp|0|abbr=on}} with the [[manual transmission]] and {{convert|46|kW|PS bhp|0|abbr=on}} with the automatic. The Type 4 engine was enlarged to 1.8 L and {{convert|50|kW|PS bhp|0|abbr=on}} DIN for the 1974 model year and again to 2.0 L and {{convert|52|kW|PS bhp|0|abbr=on}} DIN for the 1976 model year. The two-litre option appeared in South African manufactured models during 1976, originally only in a comparably well-equipped "Executive" model.<ref name=SAM1076>{{cite journal | ref = SAM1076 | journal = SA Motor | title = Volkswagen 2000L Executive Microbus | page = 37 | last = English | first = Howard | publisher = Scott Publications | location = Cape Town, South Africa | date = October 1976 }}</ref> The 1978 2.0 L now featured hydraulic valve lifters, eliminating the need to periodically adjust the valve clearances as on earlier models. The 1975 and later U.S. model years received [[Robert Bosch GmbH|Bosch]] [[Jetronic#L|L-Jetronic]] electronic fuel injection as standard equipment; 1978 was the first year for electronic ignition, utilizing a hall effect sensor and digital controller, eliminating maintenance-requiring contact-breaker points. As with all Transporter engines, the focus in development was not on power, but on low-end [[torque]]. The Type 4 engines were considerably more robust and durable than the Type 1 engines, particularly in Transporter service.{{Citation needed|date=February 2010}}

In 1972, for the 1973 model year, exterior revisions included relocated front turn indicators, squared off and set higher in the valance, above the headlights. Also, square-profiled bumpers, which became standard until the end of the T2 in 1979, were introduced in 1973. Crash safety improved with this change because of a compressible structure behind the front bumper. This meant that the T2b was capable of meeting US safety standards for passenger cars of the time, though not required of vans. The "VW" emblem on the front valance became slightly smaller.

Later model changes were primarily mechanical. By 1974, the T2 had gained its final shape. Very late in the T2's design life, during the late 1970s, the first prototypes of Type 2 vans with [[four-wheel drive]] (4WD) were built and tested.
<gallery>
File:Vw silverfish.jpg|1979 Volkswagen Type 2 (T2) "Silverfish" last-edition bus. These were a limited edition model to mark the final production of T2 models in Europe
File:Volk bus 1968a.jpg|1968 Volkswagen Type 2 (T2) Hard-Top Westfalia "Cream" bus
File:2005 VW Kombi Silver Limited Edition.jpg|Brazilian Volkswagen Type 2 (T2) – 2005 Limited Edition
File:'77 Volkswagen Kombi Westfalia (Auto classique Salaberry-De-Valleyfield '11).JPG|1977 Volkswagen Kombi Westfalia (North America)
</gallery>

=== T2c ===
[[File:Volkswagen T2 in Brazil.JPG|thumb|T2c in Brazil]]

The '''T2c''', with a roof raised by about {{convert|10|cm|in|abbr=on}} was built starting in the early 1990s for the Mexican, South American and Central American markets. Since 1991, the T2c has been built in México with the water-cooled 1.8 L [[inline-four engine|inline four-cylinder]] {{convert|53|kW|PS bhp|0|abbr=on}} carbureted engine—easily identified by the large, black front-mounted radiator—and since 1995 with the 1.6 L air-cooled engines for the Brazilian market.{{CN|date=February 2016}}

Once production of the original [[Volkswagen Beetle|Beetle]] ended in late 2003, the T2 was the only Volkswagen model with an air-cooled, rear-mounted boxer engine, but then the Brazilian model shifted to a water-cooled engine on 23 December 2005.{{CN|date=February 2016}} There was a 1.6 L {{convert|50|hp|kW PS|0|abbr=on}} water-cooled [[diesel engine]] available from 1981 to 1985, which gave fuel economy of 15 km/l to 18 km/l<ref>{{cite web|url=http://www.angelfire.com/sk2/volksline/kombi/pecas.htm |title=Home page do Volkswagen Kombi – O primeiro portal da Kombi Brasileira |publisher=Angelfire.com |date= |accessdate=19 August 2011}}</ref>—but gave slow performance and its insufficient cooling system led to short engine life.{{CN|date=February 2016}}

The end of the [[Volkswagen air-cooled engine]] on a worldwide basis was marked by a Special Edition Kombi. An exclusive Silver paint job, and limited edition emblems were applied to only 200 units in late 2005, and were sold as 2006 models.{{CN|date=February 2016}}

[[File:Brazilian Kombi pair.jpg|thumb|An air-cooled and a water-cooled VW Kombi (T2), made in Brazil. Model years 2005 and 2006.]]

Stricter [[Vehicle emissions control|emissions regulations]] introduced by the Brazilian government for 2006 forced a shift to a flexible-fuel water-cooled engine{{CN|date=February 2016}} able to [[flexible-fuel vehicle|run on petrol or alcohol]]. Borrowed from the [[Volkswagen Gol]], the engine is a rear-mounted [[List of Volkswagen Group petrol engines#EA111|EA-111 1.4 L 8v Total Flex]] {{convert|1390|cc|1|abbr=on}}, {{convert|58|kW|PS bhp|0|abbr=on}} on petrol, and {{convert|60|kW|PS bhp|0|abbr=on}} when run on [[ethanol]], and {{convert|124|Nm|0|abbr=on}} torque. This version was very successful{{vague|date=February 2016}}, despite the minor changes made to the overall T2-bodied vehicle.{{CN|date=February 2016}} It still included the four-speed transmission, but a new final-drive ratio enabled cruising at {{convert|120|km/h|mph|0|abbr=on}} at 4,100 rpm. Top speed was {{convert|130|km/h|mph|0|abbr=on}}.{{CN|date=February 2016}} {{convert|0|to|100|km/h|mph|0|abbr=on}} acceleration took 22.7 seconds (vs. 29.5 seconds for the last air-cooled version). Other improvements included 6.6% better fuel economy, and nearly 2 [[decibel|dB]] less engine noise.{{CN|date=February 2016}}

The Volkswagen Type 2 is by far the longest model run in Brazil, having been introduced in September 1950 as the Volkswagen "Kombi", a name it has kept throughout production.{{CN|date=February 2016}} Only produced in two versions, bus (nine-seater or 12-seater – a fourth row is added for metro transportation or school bus market) or panel van, it offers only one factory option, a rear window defogger.{{CN|date=February 2016}} {{As of|2009|06}}, the T2 was being built at the Volkswagen Group's [[São Bernardo do Campo]] plant at a rate of 97 per day.{{CN|date=February 2016}}

The production of the Brazilian Volkswagen Kombi ended in 2013 with a production run of 600 Last Edition vehicles.<ref>{{cite web| url= http://www.autoblog.com/2013/08/18/vw-type-2-microbus-production-ending-with-kombi-last-edition/| agency= Auto Express| title= VW Type 2 Microbus production ending with Kombi Last Edition| website= AutoBlog.com | date= 18 August 2013| accessdate= 10 June 2015}}</ref> A [[short film]] entitled "''Os Últimos Desejos da Kombi''" ([[English language|English]]: The Kombi's Last Wishes)was made by [[Volkswagen Brazil]] to commemorate the end of production.<ref>{{cite web |url=http://kombi.vw.com.br |title=Os Últimos Desejos da Kombi |trans-title=Kombi's last wishes |language=Portuguese|publisher=VW |location=Brazil |accessdate=3 April 2014}}</ref>

{{-}}

== Post-Type 2 generations ==

=== {{Anchor|T3}}Third generation (T3; 1979–1992) ===
[[File:Vw transporter t3 luft v sst.jpg|thumb|200px|Volkswagen Type 2 (T3/Vanagon/T25)]]
{{Main|Volkswagen Type 2 (T3)}}

The '''Volkswagen Type 2 (T3)''', also known as T25 in the UK or Vanagon in the United States, the T3 platform was introduced in 1979, and was one of the last new Volkswagen platforms to use an [[air-cooled engine]]. The [[Volkswagen air-cooled engine]] was phased out for a [[water cooling|water-cooled]] [[flat engine|boxer engine]] (still [[rear-engine design|rear-mounted]]) in 1983. Compared to its predecessor the T2, the T3 was larger and heavier, with square corners replacing the rounded edges of the older models. The T3 is sometimes called "the wedge" by enthusiasts to differentiate it from earlier Kombis.

=== {{Anchor|T4}}Fourth generation (T4; 1990–2003) ===
{{Main|Volkswagen Transporter (T4)}}
[[File:VW Eurovan T4a Multivan Allstar.jpg|thumb|200px|Early 1990s Multivan Allstar T4]]

Since 1990, the Transporter in most world markets has been [[front-engine design|front-engined]] and [[water cooling|water-cooled]], similar to other contemporary Volkswagens, almost two decades later than it did for the passenger cars. T4s are marketed as Transporter in Europe. In the United States, Volkswagen Eurovan is the brand name.

=== {{Anchor|T5}}Fifth generation (T5; 2003–2015) ===
{{Main|Volkswagen Transporter (T5)}}
[[File:VW Eurovan T5 Multivan.jpg|thumb|200px|2004 Volkswagen Transporter T5]]

The '''Volkswagen Transporter T5''' range is the fifth generation of [[Volkswagen Commercial Vehicles]] medium-sized [[light commercial vehicle]] and people movers. Launched 6 January 2003, the T5 went into full production in April 2003, replacing the fourth generation range.<ref name=autogenerated1>{{cite web |url=http://www.volkswagen-commercial-vehicles.com/vwcms_publish/vwcms/master_public/virtualmaster/en_vwn/unternehmen/chronikuebersicht/2001-heute.html |title=Volkswagen-Commercial-Vehicles.com |publisher=Volkswagen-Commercial-Vehicles.com |date=5 August 2008 |accessdate=19 October 2010 |deadurl=yes |archiveurl=https://web.archive.org/web/20080522023330/http://www.volkswagen-commercial-vehicles.com/vwcms_publish/vwcms/master_public/virtualmaster/en_vwn/unternehmen/chronikuebersicht/2001-heute.html |archivedate=22 May 2008 |df=dmy-all }}</ref>

Key markets for the T5 are Germany, the United Kingdom, Russia, France and Turkey. It is not sold in the US market because it is classed as a light truck, accruing the 25% [[chicken tax]] on importation. The T5 has a more aerodynamic design. The angle of the [[windshield]] and A-[[pillar (car)|pillar]] is less; this makes for a large [[dashboard]] and small bonnet.

In June 2009, Volkswagen Commercial Vehicles announced the one-millionth T5 rolled off the production line in [[Hanover]].<ref>{{cite web|title=Volkswagen Commercial Vehicles builds one millionth T5|url=http://www.volkswagenag.com/vwag/vwcorp/info_center/en/news/2009/06/vw_commercial_vehicles_builds_one_millionth_t5.html|publisher=[[Volkswagen Group|Volkswagen AG]]|work=volkswagenag.com|date=30 June 2009|accessdate=12 November 2009|deadurl=yes|archiveurl=https://web.archive.org/web/20110720045845/http://www.volkswagenag.com/vwag/vwcorp/info_center/en/news/2009/06/vw_commercial_vehicles_builds_one_millionth_t5.html|archivedate=20 July 2011|df=dmy-all}}</ref>

T5 GP introduced in 2010. Heavily facelifted with some new power plants including the 180 bi-turbo range topper. These new engines saw the demise of the now "dirty" 5 cylinder units.

Late 2015 will see the arrival of the "Neu Sechs", the New 6. The T6 will offer further engine changes in early 2016, but will launch with the previous generation engines. The new engines will see the introduction of Ad-Blu to meet with euro 6 emission compliance. The new 6 was expected by many to be more than just a facelift.

With the T6 now hitting the roads it is very clear it would appear to be just a facelift. New front, new tailgate and a new dash. There are quality improvements, sound deadening, new colours and improved consumption, but many believe VW have missed an opportunity to go back to the top.

=== {{Anchor|T6}}Sixth generation (T6; 2015–present) ===
[[File:VW T6 Multivan Generation Six 2.0 TDI.JPG|VW T6|thumb|right]]

The new T6 launched with the old Euro 5 non AdBlue power-plants, but is offered with a Euro 6 diesel engine with 204bhp and [[Diesel_exhaust_fluid|AdBlue]]. Three further Euro 6 Adblue diesel power-plants with 84ps, 102ps and 150ps are also offered.

There is some debate in the community over whether the T6 is a new model, or simply a face-lift of the T5. There are obvious external changes to the nose and tailgate, while internally there is a new dash in 2 versions. Volkswagen claims refinement to ride, handling and noise levels.

=== Additional developments ===
[[File:BSB Flex cars 118 09 2008 VW Kombi Total Flex with logo blur.jpg|thumb|left|150px|[[Brazil]]ian Air Force 2006 Kombi Total Flex is a [[flexible-fuel vehicle]]]]

In 2001, a [[Volkswagen Microbus Concept]] was created, with design cues from the T1 generation in a spirit similar to the New Beetle nostalgia movement. Volkswagen planned to start selling it in the United States market in 2007, but it was scrapped in May 2004 and replaced with a more cost-effective design to be sold worldwide.
{{clear left}}

== Names and nicknames ==
Like the Beetle, from the beginning, the Type 2 earned many nicknames from its fans. Among the most popular at least in Germany, are '''VW-Bus''' and '''Bulli''' (or '''Bully''') or '''Hippie-van''' or the bus. The Type 2 was meant to be officially named the Bully, but [[Heinrich Lanz]], producer of the [[Lanz Bulldog]] farm tractor, intervened.{{Citation needed|date=November 2009}} The model was then presented as the '''Volkswagen Transporter''' and '''Volkswagen Kleinbus''', but the Bully nickname still caught on.

The official German-language model names '''Transporter''' and '''Kombi''' (''Kombinationskraftwagen'', combined-use vehicle) have also caught on as nicknames. Kombi is not only the name of the passenger variant but also the [[Australasia]]n and [[Brazil]]ian term for the whole Type 2 family, in much the same way that they are all called '''VW-Bus''' in Germany, even the pickup truck variations. In [[Mexico]], the German Kombi was translated as '''Combi''' and became a household word thanks to the vehicle's popularity in [[Mexico City]]'s public transportation system. In [[Peru]], where the term ''Combi'' was similarly adopted, the term '''''Combi Asesina''''' (Murderous Combi) is often used for buses of similar size, because of the notorious recklessness and competition of bus drivers in [[Lima]] to get passengers. In [[Portugal]] it is known as '''''Pão-de-Forma''''' (Breadloaf) because its design resembles a bread baked in a mold. Similarly, in [[Denmark]], the Type 2 is referred to as '''''[[Rugbrød]]''''' ([[Rye bread]]). [[Finland|Finns]] dubbed it '''''Kleinbus''''' (mini-bus), as many taxicab companies adopted it for group transportation; the name Kleinbus has become an appellative for all passenger vans. The vehicle is also known as Kleinbus in [[Chile]].

In the US, however, it is a VW bus, "vee-dub", minibus, hippie-mobile, hippie bus, hippie van, "combie", Microbus, or Transporter to aficionados. The early versions produced before 1967 used a split front windshield (giving rise to the nickname "Splitty"), and their comparative rarity has led to their becoming sought after by collectors and enthusiasts. The next version, sold in the US market from 1968 to 1979, is characterised by a large, curved windshield and is commonly called a "bay-window". It was replaced by the [[Vanagon]], of which only the [[Westfalia]] camper version has a common nickname, "Westy".

It was called '''Volksie Bus''' in South Africa, notable in a series of that country's TV commercials. Kombi is also a generic nickname for vans and minibuses in South Africa, Swaziland, and Zimbabwe, often used as a means of public transportation. In [[Nigeria]] it is called '''Danfo'''.

In the UK, it is known as a "Campervan". In France, it was called a "camping-car" (usually hyphenated) though this has been expanded to include other, often more specialized vehicles in more recent times.

Among VW enthusiasts in countries of the former [[Yugoslavia]], especially in [[Serbia]] and [[Croatia]], VW T2 bus is commonly called a "Terrorist", probably due its cameo appearance in the [[Back to the Future]] film where it is driven by a group of Lybian terrorists.<ref>{{cite web|title=VW bus nicknames throughout the world |work= |first= |last= |date= |url=http://thelatebay.com/index.php?threads/vw-bus-nicknames-throughout-the-world.34945/ }}</ref><ref>{{cite web|title=Legendarni kombi uskoro i na električni pogon |work= |first= |last= |date= |url=http://www.energetika-net.com/vijesti/elektromobilnost/legendarni-kombi-uskoro-i-na-elektricni-pogon-25279 }}</ref><ref>{{cite web|title=VW Kombi odlazi u istoriju |work=B92 |first= |last= |date=17 August 2013 |url=https://www.b92.net/automobili/komentari.php?nav_id=743727 }}</ref>

== Mexican production ==
T2 production began in 1970 at the [[Puebla]] assembly factory.

Offered initially only as a nine-passenger version called the '''Volkswagen Combi''' (Kombi in Brazil), and from 1973 also its cargo van version called the ''Volkswagen Panel'', both variants were fitted with the 1.5 L air-cooled boxer engine and four-speed manual gearbox. In 1974, the 1.6 L {{convert|44|bhp|kW PS|0|abbr=on}} boxer engine replaced the 1.5 previous one, and production continued this way up to 1987. In 1987, the water-cooled 1.8 L {{convert|85|bhp|kW PS|0|abbr=on}} [[inline-four engine|inline four-cylinder]] engine replaced the air-cooled 1.6 L. This new model is recognisable by its black grille (for its engine coolant radiator), bumpers and moldings.

In 1975, Volkswagen de Mexico ordered two specially made [[pickup truck|pickups]] from Germany, one single cab and one double cab, for the Puebla plant. These were evaluated for the possibility of building pickups in Mexico, and were outfitted with every option except the Arctic package, including front and rear fog lights, intermittent wipers, trip odometer, clock, bumper rubber, PVC tilt, and dual doors on the single cab storage compartment. VW de Mexico was interested in having the lights, wiring, brake systems and other parts manufactured in Mexico. Ultimately, VW de Mexico declined to produce pickups, and the pickups were sold to an Autohaus, a Volkswagen dealer in San Antonio, Texas, since they could not be sold in Mexico. By law, no German-made Volkswagens were to be sold in Mexico. These were probably the only pickups that were produced in Germany for Mexican import, and have the "ME" export code on the M-code plate. The green double cab was sold to a new owner in New York, and has been lost track of. The light gray (L345, licht grau) single cab still exists. Pickups were not manufactured in Mexico, nor were they imported into Mexico from Germany, save for these two examples.

In 1988, a luxury variant – the '''Volkswagen Caravelle''' – made its debut in the Mexican market to compete with the [[Nissan Van C22 (Vanette)|Nissan Ichi Van]], which was available in cargo, passenger and luxury versions.

The main differences between the two are that the Caravelle was sold as an eight-passenger version, while the Combi was available as a nine-passenger version, the Caravelle was only painted in metallic colors, while the Combi was only available in non-metallic colors, and the Caravelle was fitted with an AM/FM stereo cassette sound system, tinted windows, velour upholstery, reading lights, mid and rear headrests, and wheel covers from the European T25 model.

In 1991, the {{convert|10|cm|in|abbr=on}} higher roof made its debut in all variants, and the Combi began to be offered in eight- or nine-passenger variants. In 1991, since Mexican anti-pollution regulations required a three-way [[catalytic converter]], a [[Digifant]] [[fuel injection]] system replaced the previous [[carburetor]]. The three variants continued without change until 1994.

In 1994, production ended in [[Mexico]], with models being imported from [[Brazil]]. The Caravelle was discontinued, and both the Combi and the Panel were only offered in white color and finally in 2002, replaced by the T4 '''EuroVan Pasajeros''' and '''EuroVan Carga''', passenger and cargo van in long [[wheelbase]] version, [[straight-five engine|inline five-cylinder]] [[List of discontinued Volkswagen Group petrol engines#2.5 R5 75-85kW|2.5 L 115 bhp]] and five-speed manual gearbox imported from Germany.

== Hippie Van ==
The VW Type 2 became popular during the [[Counterculture of the 1960s]] thanks to its ability to transport a large group of people while requiring cheap maintenance and being easy to work on<ref>{{Cite web |url=https://qz.com/1006112/how-the-volkswagen-van-became-iconic/ |title=The magic recipe that caused hippies to fall in love with the inc incredible, enduring Volkswagen van |first=Chris |last=Ebbert |date=17 June 2017 |website=Quartz |access-date=6 August 2018}}</ref>. The vans were increasingly popular amongst younger crowds, it was big enough to live in allowing many to travel comfortably and was used for long distance traveling such as to music festivals, traveling across the country and to attend anti-war protests. It's design was simple yet spacious and something completely different from what was being seen on the road at the time such as muscle cars and luxury sedans. The vans had a rebellious nature to them and were often times painted in bright colors with extravagant over the top designs allowing them to be easily distinguished while on the road. <ref>{{Cite web |url=https://www.popularmechanics.com/cars/trucks/a26207/volkswagen-microbus-vw-bus/ |title=Peace, Love and the VW Bus |last=Stewart |first=Ben |work=Popular Mechanics |location=US |date=26 April 2017 |access-date=6 August 2018}}</ref> The hippie van still remains iconic for many people today thanks to musicians such as '''[[Bob Dylan]]'''<ref>{{Cite book |url=http://dx.doi.org/10.1093/gmo/9781561592630.article.a2256398 |title=Dylan, Bob |last=Habib |first=Kenneth S. |date=31 January 2014 |publisher=Oxford University Press |series=Oxford Music Online |access-date=6 August 2018}}</ref> who feature one on an album cover <ref>{{Cite news |url=http://www.dailyherald.com/article/20130929/business/709299963/ |title=VW's hippie van ends its long, strange trip |work=Daily Herald |location=US |date=29 September 2013 |access-date=3 August 2018}}</ref> and popular bands such as the Grateful Dead who used them while touring.<ref>{{Cite web|url=https://www.theverge.com/2013/9/26/4772614/last-vw-bus-to-be-produced-this-year|title=VW to end production of iconic hippie bus this year|last=|first=|date=|website=|archive-url=|archive-date=|dead-url=|access-date=}}</ref> But most iconic of all, the music festival Woodstock which was held in the summer of 1969 saw plenty of brightly painted vans transporting excited young crowds.<ref>{{Cite news|url=https://www.adweek.com/brand-marketing/volkswagen-takes-a-trip-back-to-the-1960s-in-nostalgic-ad-saluting-its-free-spirited-owners/|title=Volkswagen Takes a Trip Back to the 1960s in Nostalgic Ad Saluting Its Free-Spirited Owners|access-date=2018-08-05|language=en-US}}</ref>

== See also ==
* [[Van]]
* [[Minibus]]
* [[Volkswagen Bus]]
* [[Volkswagen Transporter]]

== References ==
{{reflist|30em}}

== External links ==
{{Commons category}}

*{{dmoz|Recreation/Autos/Makes_and_Models/Volkswagen/Air_Cooled/Type_2/}}

{{Volkswagen Commercial Vehicles}}
{{Volkswagen Commercial Vehicles (Europe) timeline}}
{{Volkswagen (North America) timeline 1950-1979}}
{{Volkswagen (North America) timeline 1980 to date}}
{{Volkswagen (South America) timeline 1980 to date}}

[[Category:Volkswagen vehicles|Type 2]]
[[Category:Minibuses]]
[[Category:Vans]]
[[Category:Minivans]]
[[Category:Pickup trucks]]
[[Category:Cab over vehicles]]
[[Category:Rear-engined vehicles]]
[[Category:Rear-wheel-drive vehicles]]
[[Category:Automobiles powered by boxer engines]]
[[Category:Cars introduced in 1950]]
[[Category:1950s automobiles]]
[[Category:1960s automobiles]]
[[Category:1970s automobiles]]
[[Category:1980s automobiles]]
[[Category:1990s automobiles]]
[[Category:2000s automobiles]]
[[Category:2010s automobiles]]

Flexography

2018-07-30T20:28:01Z

173.165.237.1: /* Operational overview */

{{Redirect|Flexo|the Futurama character|Flexo (Futurama)}}
[[Image:Flexography-Platecloseup.JPG|thumb|250px|A flexographic printing plate.]]
{{History of printing}}
[[File:Fusion C.jpg|thumb|PCMC's Fusion C Flexographic Printing Press]]

'''Flexography''' (often abbreviated to '''flexo''') is a form of [[printing]] process which utilizes a flexible [[Relief print|relief]] plate. It is essentially a modern version of [[letterpress]] which can be used for printing on almost any type of substrate, including plastic, metallic films, cellophane, and paper. It is widely used for printing on the non-porous substrates required for various types of food packaging (it is also well suited for printing large areas of solid colour).

==History==
In 1890, the first such patented press was built in [[Liverpool]], England by Bibby, Baron and Sons. The water-based ink smeared easily, leading the device to be known as "Bibby's Folly". In the early 1900s, other European presses using rubber printing plates and [[aniline]] oil-based ink were developed. This led to the process being called "aniline printing". By the 1920s, most presses were made in Germany, where the process was called "gummidruck", or rubber printing. In modern-day Germany, they continue to call the process "gummidruck".

During the early part of the 20th century, the technique was used extensively in food packaging in the United States. However, in the 1940s, the [[Food and Drug Administration]] classified aniline dyes as unsuitable for food packaging. Printing sales plummeted. Individual firms tried using new names for the process, such as "Lustro Printing" and "Transglo Printing", but met with limited success. Even after the Food and Drug Administration approved the aniline process in 1949 using new, safe inks, sales continued to decline as some food manufacturers still refused to consider aniline printing. Worried about the image of the industry, packaging representatives decided the process needed to be renamed.

In 1951 Franklin Moss, then the president of the Mosstype Corporation, conducted a poll among the readers of his journal ''The Mosstyper'' to submit new names for the printing process. Over 200 names were submitted, and a subcommittee of the [[Packaging Institute]]'s Printed Packaging Committee narrowed the selection to three possibilities: "permatone process", "rotopake process", and "flexographic process". Postal ballots from readers of ''The Mosstyper'' overwhelmingly chose the last of these, and "flexographic process" was chosen.<ref name=wmich1>{{cite web | last = Fleming | first = Dan | authorlink = | coauthors = | title = Introduction | work = Flexographic printing | publisher = Department of Paper Engineering, Chemical Engineering, and Imaging, Western Michigan University | date = | url = http://www.wmich.edu/pci/flexo/pp1.htm | doi = | accessdate = 31 January 2010 | deadurl = yes | archiveurl = https://web.archive.org/web/20100724201824/http://www.wmich.edu/pci/flexo/pp1.htm | archivedate = 24 July 2010 | df = }}</ref>

===Evolution===
Originally, flexographic printing was rudimentary in quality. Labels requiring high quality have generally been printed using the [[offset printing|offset]] process until recently. Since 1990,<ref name="kipphan976-979">{{Cite book | last = Kipphan | first = Helmut | title = Handbook of print media: technologies and production methods | publisher = Springer | year = 2001 | edition = Illustrated | pages = 976–979 | url = https://books.google.com/books?id=VrdqBRgSKasC | isbn = 3-540-67326-1}}</ref> great advances have been made to the quality of flexographic printing presses, printing plates and printing inks.

The greatest advances in flexographic printing have been in the area of [[photopolymer]] printing plates, including improvements to the plate material and the method of plate creation.

Digital [[direct to plate]] systems have been a good improvement in the industry recently. Companies like Asahi Photoproducts, AV Flexologic, [http://www.dupont.com Dupont], [http://www.platecrafters.com PlateCrafters], MacDermid, [[Kodak]] and [[Esko (company)|Esko]] have pioneered the latest technologies, with advances in fast washout and the latest screening technology.

Laser-etched ceramic [[anilox]] rolls also play a part in the improvement of print quality. Full-color picture printing is now possible, and some of the finer presses available today, in combination with a skilled operator, allow quality that rivals the [[lithography|lithographic]] process. One ongoing improvement has been the increasing ability to reproduce highlight tonal values, thereby providing a workaround for the very high [[dot gain]] associated with flexographic printing.

==Process overview==
'''1. Platemaking'''<ref>Printers' National Environmental Assistance Center: {{cite web|url=http://www.pneac.org/printprocesses/flexography/moreinfo8.cfm |title=Archived copy |accessdate=2009-01-29 |deadurl=no |archiveurl=https://web.archive.org/web/20160304072525/http://www.pneac.org/printprocesses/flexography/moreinfo8.cfm |archivedate=2016-03-04 |df= }}</ref> 
The first method of plate development uses light-sensitive [[polymer]]. A film negative is placed over the plate, which is exposed to ultra-violet light. The polymer hardens where light passes through the film. The remaining polymer has the consistency of chewed gum. It is washed away in a tank of either water or solvent. Brushes scrub the plate to facilitate the "washout" process. The process can differ depending on whether solid sheets of photopolymer or liquid photopolymer are used, but the principle is still the same. The plate to be washed out is fixed in the orbital washout unit on a sticky base plate. The plate is washed out in a mixture of water and 1% dishwasher soap, at a temperature of approximately 40 °C. The unit is equipped with a dual membrane filter. With this the environmental burdening is kept to an absolute minimum. The membrane unit separates photopolymer from the washout water. After addition of absorb gelatine for example, the photopolymer residue can be disposed of as standard solid waste together with household refuse. The recycled water is re-used without adding any detergent.<ref>AV Flexologic B.V.: {{cite web |url=http://www.flexologic.nl/products/plate-making/cosmoline/ |title=Archived copy |accessdate=2015-08-05 |deadurl=no |archiveurl=https://web.archive.org/web/20130908144503/http://www.flexologic.nl/products/plate-making/cosmoline/ |archivedate=2013-09-08 |df= }}</ref>
[[File:Soma OPTIMA - flexographic printing press.jpg|thumb|Flexographic printing press]]
The second method uses a computer-guided laser to etch the image onto the printing plate. Such a direct [[laser engraving]] process is called digital platemaking. Companies such as AV Flexologic, Glunz & Jensen, Xeikon, [[Esko (company)|Esko]], [[Kodak]], Polymount and Screen from The Netherlands are market leaders in manufacturing this type of equipment.

The third method is to go through a molding process. The first step is to create a metal plate out of the negative of our initial image through an exposition process (followed by an acid bath). In the early days the metal used was zinc, leading to the name 'zincos'. Later magnesium was used.This metal plate in relief is then used in the second step to create the mold that could be in [[bakelite]] board or even glass or plastic, through a first molding process. Once cooled, this master mold will press the rubber or plastic compound (under both controlled temperature and pressure) through a second molding process to create the printing plate.

'''2. Mounting''' 
For every colour to be printed, a plate is made and eventually put on a cylinder which is placed in the printing press. To make a complete picture, regardless of printing on flexible film or corrugated paper, the image transferred from each plate has to [[Printing registration|register]] exactly with the images transferred from the other colors. To ensure an accurate picture is made, mounting marks are made on the flexographic plates. These mounting marks can be microdots (down to 0.3 mm) and/or crosses. Special machinery is made for mounting these plates on the printing cylinders to maintain registration. Earle L. Harley invented and patent the Opti-Chek Mounting and Proofing machine enabling the operator to check the registration before going to the press.

'''3. Printing''' 
A flexographic print is made by creating a positive mirrored master of the required image as a [[Three-dimensional space|3D]] [[relief]] in a [[rubber]] or [[polymer]] material. Flexographic plates can be created with analog and digital platemaking processes. The image areas are raised above the non image areas on the rubber or polymer plate. The ink is transferred from the ink roll which is partially immersed in the ink tank. Then it transfers to the [[anilox]] or [[ceramic]] roll (or meter roll) whose texture holds a specific amount of ink since it is covered with thousands of small wells or cups that enable it to meter ink to the printing plate in a uniform thickness evenly and quickly (the number of cells per linear inch can vary according to the type of print job and the quality required).<ref>International Paper - Knowledge center - Flexography: https://web.archive.org/web/20100816235813/http://http//glossary.ippaper.com/default.asp?req=knowledge%2Farticle%2F151</ref> To avoid getting a final product with a smudgy or lumpy look, it must be ensured that the amount of ink on the printing plate is not excessive. This is achieved by using a scraper, called a [[doctor blade]]. The doctor blade removes excess ink from the anilox roller before inking the printing plate. The substrate is finally sandwiched between the plate and the impression cylinder to transfer the image.<ref>Johansson, Lundberg & Ryberg (2003) "A guide to graphic print production", John Wiley & Sons Inc., Hoboken, New Jersey.</ref> The sheet is then fed through a dryer, which allows the inks to dry before the surface is touched again. If a UV-curing ink is used, the sheet does not have to be dried, but the ink is cured by UV rays instead.

===Basic parts of the press===

* ''Unwind and infeed section'' – The roll of stock must be held under control so the web can unwind as needed.
* ''Printing section'' – Single color station including the fountain, anilox, plate and impression rolls.
* ''Drying station'' – High velocity heated air, specially formulated inks and an after-dryer can be used.
* ''Outfeed and rewind section'' – Similar to the unwind segment, keeps web tension controlled.

==Operation==

===Operational overview===
'''1. Fountain roller''' 
The fountain roller transfers ink located in an ink pan to a second roller, an anilox roller.
In modern flexographic printing, the anilox roll is referred to as a type of meter or metering roller.

'''2. Anilox roller''' 
The anilox roll is a unique characteristic of flexography. The anilox roller transfers a uniform thickness of ink to a flexible printing plate. The anilox roll has finely engraved cells with a particular ink capacity, viewable with a microscope. These rollers are responsible for transferring inks to the flexible printing plates mounted on the plate cylinders.

'''3. Doctor blade (optional)''' An optional doctor blade scrapes the anilox roll to ensure that the ink to be delivered to the flexible printing plate is only what is contained within the engraved cells. Doctor blades had predominantly been made of steel, but advanced doctor blades are now made of polymer materials with several different types of beveled edges.

'''4. Plate cylinder''' 
The plate cylinder holds the printing plate, which is made from a soft flexible rubber-like material. Tape, magnets, tension straps and/or ratchets hold the printing plate against the plate cylinder.

'''5. Impression cylinder ''' 
The impression cylinder applies pressure to the plate cylinder where the image is transferred to the image-receiving substrate.
This impression cylinder or "print anvil" is required to apply pressure to the plate cylinder.

===Flexographic printing inks===
The nature and demands of the printing process and the application of the printed product determine the fundamental properties required of [[flexographic ink]]s. Measuring the physical properties of inks and understanding how these are affected by the choice of ingredients is a large part of ink technology. Formulation of inks requires a detailed knowledge of the physical and chemical properties of the raw materials composing the inks, and how these ingredients affect or react with each other as well as with the environment. Flexographic printing inks are primarily formulated to remain compatible with the wide variety of substrates used in the process. Each formulation component individually fulfills a special function and the proportion and composition will vary according to the substrate.

There are five types of inks that can be used in flexography:
solvent-based inks, water-based inks, electron beam (EB) curing inks, ultraviolet (UV) curing inks and two-part chemically-curing inks (usually based on polyurethane isocyanate reactions), although these are uncommon at the moment.<ref>[http://www.encyclopedia.com/doc/1G1-57294024.html]{{dead link|date=June 2014}}</ref> Water based flexo inks with [[particle size]]s below 5 µm may cause problems when [[deinking]] recycled paper.

===Ink controls===
The ink is controlled in the flexographic printing process by the inking unit. The inking unit can be either of [[fountain roll]] system or [[doctor blade]] system. The fountain roll system is a simple old system yet if there is too much or too little ink this system would likely control in a poor way. The doctor blade inside the anilox/ceramic roller uses cell geometry and distribution. These blades ensure that the cells are filled with enough ink.<ref name=autogenerated1>{{Cite book | last = Kipphan | first = Helmut | title = Handbook of print media: technologies and production methods | publisher = Springer | year = 2001 | edition = Illustrated | pages = 401–402| url = https://books.google.com/books?id=VrdqBRgSKasC | isbn = 3-540-67326-1}}</ref>

==Presses==
'''Stack press''' 
Color stations stack up vertically, which makes it easy to access. This press is able to print on both sides of the substrate.

'''Central Impression press''' 
All color stations are located in a circle around the impression cylinder. This press can only print on one side.
Advantage: excellent registry.

'''In-line press''' 
Color stations are placed horizontally. This press prints on both sides, via a turnbar.
Advantage: can print on heavier substrates, such as corrugated boards.
[[File:ELS MAX cutout.jpg|thumb|PCMC's ELS MAX Inline Press]]

==Applications==
Flexo has an advantage over lithography in that it can use a wider range of inks, water based rather than oil based inks, and is good at printing on a variety of different materials like plastic, foil, acetate film, brown paper, and other materials used in packaging. Typical products printed using flexography include brown corrugated boxes, flexible packaging including retail and shopping bags, food and hygiene bags and sacks, milk and beverage cartons, flexible plastics, self-adhesive labels, disposable cups and containers, envelopes and wallpaper. In recent years there has also been a move towards laminates, where two or more materials are bonded together to produce new material with different properties than either of the originals. A number of newspapers now eschew the more common offset lithography process in favour of flexo. Flexographic inks, like those used in [[gravure]] and unlike those used in lithography, generally have a low [[viscosity]]. This enables faster drying and, as a result, faster production, which results in lower costs.

Printing press speeds of up to 750 meters per minute (2000 feet per minute) are achievable now with modern technology high-end printers. Flexo printing is widely used in the [[converting]] industry for printing plastic materials for packaging and other end uses. For maximum efficiency, the flexo presses produce large rolls of material that are then slit down to their finished size on [[slitting]] machines.

==References==
{{Reflist}}

==External links==
{{Commons category|Flexography}}
* [https://web.archive.org/web/20160406194344/http://flexography.org/ Flexographic Technical Association]
* [https://web.archive.org/web/20161013204640/http://www.efia.uk.com/ European Flexographic Industry Association]

[[Category:Packaging]]
[[Category:Relief printing]]

Separator (oil production)

2018-07-13T17:06:15Z

173.165.237.1: /* Separation of water from oil */

{{Use dmy dates|date=June 2013}}
The term '''separator''' in oilfield terminology designates a [[pressure vessel]] used for separating well [[fluid]]s produced from oil and [[gas well]]s into gaseous and [[liquid]] components. A separator for petroleum production is a large vessel designed to separate [[production fluid]]s into their constituent components of [[crude oil|oil]], [[natural gas|gas]] and [[water]]. A separating vessel may be referred to in the following ways: '''Oil and gas separator''', '''Separator''', '''Stage separator''', '''Trap''', '''Knockout vessel''' (Knockout drum, knockout trap, water knockout, or liquid knockout), '''Flash chamber''' (flash vessel or flash trap), '''Expansion separator''' or '''expansion vessel''', '''Scrubber''' (gas scrubber), '''Filter''' (gas filter). These separating vessels are normally used on a producing lease or platform near the wellhead, manifold, or tank battery to separate [[fluid]]s produced from oil and gas wells into oil and gas or liquid and gas. An oil and gas separator generally includes the following essential components and features:

1. A vessel that includes (a) primary separation device and/or section, (b) secondary [[settling|“gravity” settling]] (separating) section, (c) mist extractor to remove small liquid particles from the gas, (d) gas outlet, (e) liquid settling (separating) section to remove gas or vapor from oil (on a three-phase unit, this section also separates water from oil), (f) oil outlet, and (g) water outlet (three-phase unit).

2. Adequate [[volume]]tric liquid capacity to handle liquid surges (slugs) from the wells and/or flowlines.

3. Adequate vessel diameter and height or length to allow most of the liquid to separate from the gas so that the mist extractor will not be flooded.

4. A means of controlling an oil level in the separator, which usually includes a liquid-level controller and a diaphragm motor [[valve]] on the oil outlet.

5. A back pressure valve on the gas outlet to maintain a steady [[pressure]] in the vessel.

6. Pressure relief devices.

Separators work on the principle that the three components have different [[density|densities]], which allows them to stratify when moving slowly with [[natural gas|gas]] on top, [[water]] on the bottom and [[crude oil|oil]] in the middle. Any solids such as sand will also settle in the bottom of the separator. The functions of [[crude oil|oil]] and [[gas]] separators can be divided into the primary and secondary functions which will be discussed later on.

==Classification of oil and gas separators==

===Classification by operating configuration===
Oil and [[gas]] separators can have three general configurations: '''vertical''', '''horizontal''', and '''spherical'''.
Vertical separators can vary in size from 10 or 12 inches in [[diameter]] and 4 to 5 feet seam to seam (S to S) up to 10 or 12 feet in diameter and 15 to 25 feet S to S. Horizontal separators may vary in size from 10 or 12 inches in [[diameter]] and 4 to 5 feet S to S up to 15 to 16 feet in diameter and 60 to 70 feet S to S. Spherical separators are usually available in 24 or 30 inch up to 66 to 72 inch in diameter.
Horizontal oil and [[gas]] separators are manufactured with monotube and dual-tube shells. Monotube units have one [[Cylinder (geometry)|cylindrical]] shell, and dual-tube units have two cylindrical parallel shells with one above the other. Both types of units can be used for two-phase and three-phase service. A monotube horizontal oil and gas separator is usually preferred over a dual-tube unit. The monotube unit has greater area for gas flow as well as a greater oil/gas interface area than is usually available in a dual-tube separator of comparable price. The monotube separator will usually afford a longer retention time because the larger single-tube vessel retains a larger [[volume]] of oil than the dual-tube separator. It is also easier to clean than the dualtube unit.
In cold climates, freezing will likely cause less trouble in the monotube unit because the [[liquid]] is usually in close contact with the warm stream of gas flowing through the separator. The monotube design normally has a lower silhouette than the dual-tube unit, and it is easier to stack them for multiple-stage separation on offshore platforms where space is limited. It was illustrated by Powers ''et al'' (1990)<ref>Powers, Maston L., 1990. Analysis of Gravity Separation in Freewater Knockouts. ''SPE Production Engineering'', [e-journal]5(1). Available through OnePetro database [Accessed 5 April 2011]</ref> that vertical separators should be constructed such that the flow stream enters near the top and passes through a gas/liquid separating chamber even though they are not competitive alternatives unlike the horizontal separators.

===Classification by function===
The three configurations of separators are available for two-phase operation and three-phase operation. In the two-phase units, [[gas]] is separated from the [[liquid]] with the gas and liquid being discharged separately. Oil and gas separators are mechanically designed such that the liquid and gas components are separated from the hydrocarbon steam at specific temperature and pressure according to Arnold ''et al'' (2008).<ref>Arnold, Steward, 2008. Surface Production Operations. Design of Oil handling Sysytems and Facilities. Oxford: Gulf Professional Publishing.</ref> In three-phase separators, well [[fluid]] is separated into gas, oil, and [[water]] with the three fluids being discharged separately. The gas-liquid separation section of the separator is determined by the maximum removal droplet size using the [[Souders–Brown equation]] with an appropriate K factor. The oil-water separation section is held for a retention time that is provided by laboratory test data, pilot plant operating procedure, or operating experience. In the case where the retention time is not available, the recommended retention time for three-phase separator in API 12J is used. The sizing methods by K factor and retention time give proper separator sizes. According to Song ''et al'' (2010),<ref>Joon H. Song, B. E. Jeong, H.J. Kim, S. S. Gil, 2010. Three-Phases Separator Sizing Using Drop Size Distribution. ''In: Offshore Technology Conference, 3–6 May 2010.'' Houston: Dawoo Shipbuilding & Marine Engineering Co., LTD..</ref> engineers sometimes need further information for the design conditions of downstream equipment, i.e., liquid loading for the mist extractor, water content for the crude dehydrator/desalter or oil content for the water treatment.

===Classification by operating pressure===
Oil and [[gas]] separators can operate at pressures ranging from a high vacuum to 4,000 to 5,000 psi. Most oil and gas separators operate in the [[pressure]] range of 20 to 1,500 psi.Separators may be referred to as low pressure, medium pressure, or high pressure. Low-pressure separators
usually operate at pressures ranging from 10 to 20 up to 180 to 225 psi. Medium-pressure separators usually operate at pressures ranging from 230 to 250 up to 600 to 700 psi. High-pressure separators generally operate in the wide pressure range from 750 to 1,500 psi.

===Classification by application===
Oil and [[gas]] separators may be classified according to application as test separator, production separator, low [[temperature]] separator, metering separator, elevated separator, and stage separators (first stage, second stage, etc.).

*'''Test separator:'''

A [[test separator]] is used to separate and to meter the well [[fluid]]s. The test separator can be referred to as a well tester or well checker. Test separators can be vertical, horizontal, or spherical. They can be two-phase or three-phase. They can be permanently installed or portable (skid or trailer mounted). Test separators can be equipped with various types of meters for measuring the oil, [[gas]], and/or [[water]] for potential tests, periodic production tests, marginal well tests, etc.

*'''Production separator:'''

A production separator is used to separate the produced well [[fluid]] from a well, group of wells, or a lease on a daily or continuous basis. Production separators can be vertical, horizontal, or spherical. They can be two-phase or three-phase. Production separators range in size from 12 in. to 15 ft in [[diameter]], with most units ranging from 30 in. to 10 ft in diameter. They range in length from 6 to 70 ft, with most from 10 to 40 ft long.

*'''Low-temperature separator:'''

A low-temperature separator is a special one in which high-pressure well [[fluid]] is jetted into the vessel through a choke or pressure reducing [[valve]] so that the separator [[temperature]] is reduced appreciably below the well-fluid temperature. The temperature reduction is obtained by the [[Joule–Thomson effect]] of expanding well fluid as it flows through the pressure-reducing choke or valve into the separator. The lower [[operating temperature]] in the separator causes condensation of vapors that otherwise would exit the separator in the vapor state. Liquids thus recovered require stabilization to prevent excessive evaporation in the storage tanks.

*'''Metering separator:'''

The function of separating well [[fluid]]s into oil, [[gas]], and [[water]] and metering the liquids can be accomplished in one vessel. These vessels are commonly referred to as metering separators and are available for two-phase and three-phase operation. These units are available in special models that make them suitable for accurately metering foaming and heavy viscous oil.

==Primary functions of oil and gas separators==

Separation of [[crude oil|oil]] from [[gas]] may begin as the [[fluid]] flows through the producing formation into the well bore and may progressively increase through the tubing, flow lines, and surface handling equipment. Under certain conditions, the fluid may be completely separated into [[liquid]] and gas before it reaches the oil and gas separator. In such cases, the separator vessel affords only an "enlargement" to permit gas to ascend to one outlet and liquid to descend to another.

===Removal of oil from gas===

Difference in density of the [[liquid]] and gaseous [[hydrocarbon]]s may accomplish acceptable separation in an [[crude oil|oil]] and [[gas]] separator. However, in some instances, it is necessary to use mechanical devices commonly referred to as "mist extractors" to remove liquid mist from the gas before
it is discharged from the separator. Also, it may be desirable or necessary to use some means to remove non solution gas from the oil before the oil is discharged from the separator.

===Removal of gas from oil===

The physical and chemical characteristics of the [[crude oil|oil]] and its conditions of [[pressure]] and [[temperature]] determine the amount of [[gas]] it will contain in solution. The rate at which the [[gas]] is liberated from a given oil is a function of change in pressure and temperature. The [[volume]] of gas that an oil and gas separator will remove from crude oil is dependent on (1) physical and chemical characteristics of the crude, (2) operating pressure, (3) operating temperature, (4) rate of throughput, (5) size and configuration of the separator, and (6) other factors.

Agitation, heat, special baffling, coalescing packs, and filtering materials can assist in the removal of nonsolution [[gas]] that otherwise may be retained in the [[crude oil|oil]] because of the viscosity and surface tension of the oil. [[Natural gas|Gas]] can be removed from the top of the drum by virtue of being gas. Oil and [[water]] are separated by a [[baffle (in vessel)|baffle]] at the end of the separator, which is set at a height close to the oil-water contact, allowing oil to spill over onto the other side, while trapping water on the near side. The two [[fluid]]s can then be piped out of the separator from their respective sides of the baffle. The produced water is then either injected back into the oil reservoir, disposed of, or treated. The bulk level (gas–liquid interface) and the oil water interface are determined using instrumentation fixed to the vessel. [[Valve]]s on the oil and water outlets are controlled to ensure the interfaces are kept at their optimum levels for separation to occur. The separator will only achieve bulk separation. The smaller droplets of water will not settle by gravity and will remain in the oil stream. Normally the oil from the separator is routed to a [[coalescer]] to further reduce the water content.

===Separation of water from oil===

The production of [[water]] with oil continues to be a problem for engineers and the oil producers. Since 1865 when water was coproduced with hydrocarbons, separation of valuable hydrocarbons from disposable water has challenged and frustrated the oil industry. According to Rehm ''et al'' (1983),<ref>Rehm, S.J., Shaughnessy, R.J., III, C-E Natco, 1983. Enhanced Oil-Water Separation-The Performax Coalescer. ''In: SPE Production Operations Symposium.'' Oklahoma City, Oklahoma 27 February – 1 March 1983. Oklahoma City: Society of Petroleum Engineers of AIME.</ref> innovation over the years has led from the skim pit to installation of the stock tank, to the gunbarrel, to the freewater knockout, to the hay-packed [[coalescer]] and most recently to the Performax Matrix Plate Coalescer, an enhanced gravity settling separator. The history of water treating for the most part has been sketchy and spartan. There is little economic value to the produced water, and it represents an extra cost for the producer to arrange for its disposal. Today oil fields produce greater quantities of water than they produce oil. Along with greater water production are emulsions and dispersions which are more difficult to treat. The separation process becomes interlocked with a myriad of contaminants as the last drop of oil is being recovered from the reservoir. In some instances it is preferable to separate and to remove [[water]] from the well [[fluid]] before it flows through [[pressure]] reductions, such as those caused by chokes and [[valve]]s. Such water removal may prevent difficulties that could be caused [[Downstream (petroleum industry)|downstream]] by the water, such as [[corrosion]] which can be referred to as being a chemical reactions that occurs whenever a gas or liquid chemically attacks an exposed metallic surface.<ref>{{cite web|url=http://www.britannica.com/EBchecked/topic/138721/corrosion |title=Corrosion on Encyclopædia Britannica 2011 – Encyclopædia Britannica Online. Accessed: 04 April 2011.}}</ref> Corrosion is usually accelerated by warm temperatures and likewise by the presence of acids and salts. Other factors that affect the removal of water from oil include hydrate formation and the formation of tight emulsion that may be difficult to resolve into [[crude oil|oil]] and water. The water can be separated from the oil in a three-phase separator by use of chemicals and gravity separation. If the three-phase separator is not large enough to separate
the water adequately, it can be separated in a free-water knockout vessel installed [[Upstream (petroleum industry)|upstream]] or downstream of the separators.

==Secondary functions of oil and gas separators==

===Maintenance of optimum pressure on separator===

For an [[crude oil|oil]] and [[gas]] separator to accomplish its primary functions, [[pressure]] must be maintained in the separator so that the [[liquid]] and gas can be discharged into their respective processing or gathering systems. Pressure is maintained on the separator by use of a gas backpressure [[valve]] on each separator or with one master backpressure valve that controls the pressure on a battery of two or more separators. The optimum pressure to maintain on a separator is the pressure that will result in the highest economic yield from the sale of the liquid and gaseous [[hydrocarbon]]s.

===Maintenance of liquid seal in separator===

To maintain [[pressure]] on a separator, a [[liquid]] seal must be effected in the lower portion of the vessel. This liquid seal prevents loss of [[gas]] with the oil and requires the use of a liquid-level controller and a [[valve]].

==Methods used to remove oil from gas in separators==

Effective oil-gas separation is important not only to ensure that the required export quality is achieved but also to prevent problems in downstream process equipment and compressors. Once the bulk liquid has been knocked out, which can be achieved in many ways, the remaining liquid droplets are separated from by a demisting device. Until recently the main technologies used for this application were reverse-flow cyclones, mesh pads and vane packs. More recently new devices with higher gas-handling have been developed which have enabled potential reduction in the scrubber vessel size. There are several new concepts currently under development in which the fluids are degassed upstream of the primary separator. These systems are based on centrifugal and turbine technology and have additional advantages in that they are compact and motion insensitive, hence ideal for [[Floating production storage and offloading|floating production facilities]].<ref>Stewart, A.C., Chamberlain, N.P., Irshad, M., 1998. A New Approach to Gas–Liquid Separation. ''In: European Petroleum Conference.'' The Hague, Netherlands 20–22 October 1998. The Hague: Kvaerner Paladon Ltd.</ref> Below are some of the ways in which oil is separated from gas in separators.

===Density difference (gravity separation)===
Natural gas is lighter than [[liquid]] [[hydrocarbon]]. Minute particles of liquid hydrocarbon that are temporarily suspended in a stream of natural gas will, by density difference or force of gravity, settle out of the stream of [[gas]] if the velocity of the gas is sufficiently slow. The larger droplets of hydrocarbon will quickly settle out of the gas, but the smaller ones will take longer. At standard conditions of [[pressure]] and [[temperature]], the droplets of liquid hydrocarbon may have a density 400 to 1,600 times that of natural gas. However, as the operating pressure and temperature increase, the difference in density decreases. At an operating pressure of 800 psig, the liquid hydrocarbon may be only 6 to 10 times as dense as the gas. Thus, operating pressure materially affects the size of the separator and the size and type of mist extractor required to separate adequately the liquid and gas. The fact that the liquid droplets may have a density 6 to 10 times that of the gas may indicate that droplets of liquid would quickly settle out of and separate from the gas. However, this may not occur because the particles of liquid may be so small that they tend to "float" in the gas and may not settle out of the gas stream in the short period of time the gas is in the oil and gas separator. As the operating pressure on a separator increases, the density difference between the liquid and gas decreases. For this reason, it is desirable to operate oil and gas separators at as low a pressure as is consistent with other process variables, conditions, and requirements.

===Impingement===
If a flowing stream of [[gas]] containing [[liquid]], mist is impinged against a surface, the liquid mist may adhere to and coalesce on the surface. After the mist coalesces into larger droplets, the droplets will gravitate to the liquid section of the vessel. If the liquid content of the gas is high, or if the mist particles are extremely fine, several successive [[impingement filter|impingement surfaces]] may be required to effect satisfactory removal of the mist.

===Change of flow direction===
When the direction of flow of a [[gas]] stream containing [[liquid]] mist is changed abruptly, inertia causes the liquid to continue in the original direction of flow. Separation of liquid mist from the gas thus can be effected because the gas will more readily assume the change of flow direction and will flow away from the liquid mist particles. The liquid thus removed may coalesce on a surface or fall to the liquid section below.

===Change of flow velocity===
Separation of [[liquid]] and [[gas]] can be effected with either a sudden increase or decrease in gas velocity. Both conditions use the difference in inertia of gas and liquid. With a decrease in velocity, the higher inertia of the liquid mist carries it forward and away from the gas.<ref>changent, 2008. ''Production Separator Principles – sample''[video online] Available at:<https://www.youtube.com/watch?v=vhkcGCUN_Uo&playnext=1&list=PLD23100F9395C2BB0> [Accessed 10 April 2011]</ref> The liquid may then coalesce on some surface and gravitate to the liquid section of the separator. With an increase in gas velocity, the higher inertia of the liquid causes the gas to move away from the liquid, and the liquid may fall to the liquid section of the vessel.

===Centrifugal force===
If a [[gas]] stream carrying [[liquid]] mist flows in a circular motion at sufficiently high velocity, centrifugal force throws the liquid mist outward against the walls of the container. Here the liquid coalesces into progressively larger droplets and finally gravitates to the liquid section below. Centrifugal force is one of the most effective methods of separating liquid mist from gas. However, according to Keplinger (1931),<ref>Keplinger, 1931. Physical Problems in the Separation of Oil and Gas. ''Proceedings of the Oklahoma, University of Tulsa'', Volume VI, pp. 74–75.</ref> some separator designers have pointed out a disadvantage in that a liquid with a free surface rotating as a whole will have its surface curved around its lowest point lying on the axis of rotation. This created false level may cause difficulty in regulating the fluid level control on the separator. This is largely overcome by placing vertical quieting baffles which should extend from the bottom of the separator to above the outlet. Efficiency of this type of mist extractor increases as the velocity of the gas stream increases. Thus for a given rate of throughput, a smaller centrifugal separator will suffice.

==Methods used to remove gas from oil in separators==
Because of higher prices for natural [[gas]], the widespread reliance on metering of [[liquid]] [[hydrocarbon]]s, and other reasons, it is important to remove all nonsolution gas from crude oil during field processing. Methods used to remove gas from crude oil in oil and gas separators are discussed below:

===Agitation===
Moderate, controlled agitation which can be defined as movement of the crude oil with sudden force<ref>{{cite web|url=http://www.thefreedictionary.com/agitate |title=Agitation on The Free Dictionary by Farlex 2011. Accessed: 10 April 2011.}}</ref> is usually helpful in removing nonsolution [[gas]] that may be mechanically locked in the oil by surface tension and oil viscosity. Agitation usually will cause the gas bubbles to coalesce and to separate from the oil in less time than would be required if agitation were not used.

===Heat===
Heat as a form of energy that is transferred from one body to another results in a difference in temperature.<ref>{{cite web|url=http://www.britannica.com/EBchecked/topic/258569/heat |title=Heat on Encyclopædia Britannica 2011 – Encyclopædia Britannica Online. Accessed: 04 April 2011.}}</ref> This reduces surface tension and viscosity of the oil and thus assists in releasing [[gas]] that is hydraulically retained in the oil. The most effective method of heating crude oil is to pass it through a heated-water bath. A spreader plate that disperses the oil into small streams or rivulets increases the effectiveness of the heated-water bath. Upward flow of the oil through the [[water]] bath affords slight agitation, which is helpful in coalescing and separating entrained gas from the oil. A heated-water bath is probably the most effective method of removing foam bubbles from foaming crude oil. A heated-water bath is not practical in most oil and gas separators, but heat can be added to the oil by direct or indirect fired heaters and/or heat exchangers, or heated free-water knockouts or emulsion treaters can be used to obtain a heated-water bath.

===Centrifugal force===
Centrifugal force which can be defined as a fictitious force, peculiar to a particle moving on a circular path, that has the same magnitude and dimensions as the force that keeps the particle on its circular path (the [[centripetal force]]) <ref>{{cite web|url=http://www.britannica.com/EBchecked/topic/102839/centrifugal-force |title=Centrifugal Force on Encyclopædia Britannica 2011 – Encyclopædia Britannica Online. Accessed: 04 April 2011.}}</ref> but points in the opposite direction is effective in separating [[gas]] from oil. The heavier oil is thrown outward against the wall of the vortex retainer while the gas occupies the inner portion of the vortex. A properly shaped and sized vortex will allow the gas to ascend while the [[liquid]] flows downward
to the bottom of the unit.

==Flow measurements in oil and gas separators==
The direction of flow in and around a separator along with other flow instruments are usually illustrated on the [[Piping and instrumentation diagram]], (P&ID). Some of these flow instruments include the Flow Indicator (FI), Flow Transmitter (FT) and the Flow Controller (FC). Flow is of paramount importance in the oil and gas industry because flow, as a major process variable is essentially important in that its understanding helps engineers come up with better designs and enables them to confidently carry out additional research. Mohan ''et al'' (1999) <ref>Ram S. Mohan, Ovadia Shoham, 1999. Design and Development of Gas-Liquid Cylindrical Cyclone
Compact Separators for Three-Phase Flow. ''In: Oil and Gas Conference – Technology Options for Producers' Survival,'' Dallas, Texas 28–30 June 1999. Dallas: DOE and PTTC</ref> carried out a research into the design and development of separators for a three-phase flow system. The purpose of the study was to investigate the complex multiphase [[Fluid dynamics|hydrodynamic]] flow behaviour in a three-phase oil and gas separator. A mechanistic model was developed alongside a [[computational fluid dynamics]] (CFD) simulator. These were then used to carry out a detailed experimentation on the three-phase separator. The experimental and CFD simulation results were suitably integrated with the mechanistic model. The simulation time for the experiment was 20 seconds with the oil specific gravity as 0.885, and the separator lower part length and diameter were 4-ft and 3-inches respectively. The first set of experiment became a basis through which detailed investigations were used to carry out and to conduct similar simulation studies for different flow velocities and other operating conditions as well.

==Flow calibration in oil and gas separators==
As earlier stated, flow instruments that function with the separator in an oil and gas environment include the flow indicator, flow transmitter and the flow controller. Due to maintenance (which will be discussed later) or due to high usage, these flowmeters do need to be calibrated from time to time.<ref>{{cite web|url=http://www.britannica.com/EBchecked/topic/89464/calibration |title=Calibration on Encyclopædia Britannica 2011 – Encyclopædia Britannica Online. Accessed: 04 April 2011.}}</ref> Calibration can be defined as the process of referencing signals of known quantity that has been predetermined to suit the range of measurements required. Calibration can also be seen from a mathematical point of view in which the flowmeters are standardized by determining the deviation from the predetermined standard so as to ascertain the proper correction factors. In determining the deviation from the predetermined standard, the actual flowrate is usually first determined with '''the use of a master meter''' which is a type of flowmeter that has been calibrated with a high degree of accuracy or '''by weighing the flow so as to be able to obtain a gravimetric reading of the mass flow'''. Another type of meter used is the '''transfer meter'''. However, according to Ting ''et al'' (1989),<ref>Ting, V.C., Halpine, J.C., 1989. Portable Piston Gas Prover for Field Calibration of Flowmeters. ''SPE Production Engineering'', 6(4), pp. 454–458.</ref> transfer meters have been proven to be less accurate if the operating conditions are different from its original calibrated points. According to Yoder (2000),<ref>Jesse Yoder, 2000. Flowmeter Calibration: How, Why, and Where. Control for the Process Industries. Houston: Putman Media.</ref> the types of flowmeters used as '''master meters''' include turbine meters, positive displacement meters, venturi meters, and Coriolis meters. In the U.S., master meters are often calibrated at a flow lab that has been certified by the [[National Institute of Standards and Technology]], (NIST). NIST certification of a flowmeter lab means that its methods have been approved by NIST. Normally, this includes NIST traceability, meaning that the standards used in the flowmeter [[calibration]] process have been certified by NIST or are causally linked back to standards that have been approved by NIST. However, there is a general belief in the industry that the second method which involves the gravimetric weighing of the amount of fluid (liquid or gas) that actually flows through the meter into or out of a container during the calibration procedure is the most ideal method for measuring the actual amount of flow. Apparently, the weighing scale used for this method also has to be traceable to the [[National Institute of Standards and Technology]] (NIST) as well.<ref>Jesse Yoder, 2000. Flowmeter Calibration: How, Why, and Where. Control for the Process Industries. Houston: Putman Media.</ref>
In ascertaining a proper correction factor, there is often no simple hardware adjustment to make the flowmeter start reading correctly. Instead, the deviation from the correct reading is recorded at a variety of flowrates. The data points are plotted, comparing the flowmeter output to the actual flowrate as determined by the standardized National Institute of Standards and Technology master meter or weigh scale.

==Controls, valves, accessories, and safety features for oil and gas separators==

===Controls===

The controls required for oil and [[gas]] separators are [[liquid]] level controllers for oil and oil/water interface (three-phase operation) and gas back-pressure control [[valve]] with pressure controller. Although the use of controls is expensive making the cost of operating fields with separators so high, installations has resulted in substantial savings in the overall operating expense as in the case of the 70 gas wells in the Big Piney, Wyo sighted by Fair (1968).<ref>R. A. Fair, 1968. Gas-field Telemetering and Remote Control, Big Piney, Wyoming. Drilling and Production Practice, 1968. Houston: American Petroleum Institute.</ref> The wells with separators were located above 7,200 ft elevation, ranging upward to 9,000 ft. Control installations were sufficiently automated such that the field operations around the controllers could be operated from a remote-control station at the field office using the [[Distributed Control System]]. All in all, this improved the efficiency of personnel and the operation of the field, with a corresponding increase in production from the area.

===Valves===

The [[valve]]s required for oil and [[gas]] separators are oil discharge control valve, water-discharge control valve (three-phase operation), drain valves, block valves, pressure relief valves, and [[Shut down valve|Emergency Shutdown valves]] (ESD). ESD valves typically stay in open position for months or years awaiting a command signal to operate. Little attention is paid to these valves outside of scheduled turnarounds. The pressures of continuous production often stretch these intervals even longer. This leads to build up or corrosion on these valves that prevents them from moving. For safety critical applications, it must be ensured that the valves operate upon demand.<ref>Sadoun Mutar Bezea Al-Khaledi, Naser Abdulaziz, Dwaipayan Bora, 2011. Replacement of Existing ESD Valves with New SIL Rated ESD Valves: A Case Study of Production Optimization and Enhancement of Process Safety and Integrity in Kuwait Oil Company. ''In: SPE Project and Facilities Challenges Conference'' Doha, Qatar 13–16 February 2011. Doha: Kuwait Oil Company.</ref>

===Accessories===

The accessories required for oil and [[gas]] separators are pressure gauges, [[thermometers]], pressure-reducing regulators (for control gas), level sight glasses, safety head with rupture disk, [[piping]], and tubing.

===Safety features for oil and gas separators===

Oil and [[gas]] separators should be installed at a safe distance from other lease equipment. Where they are installed on offshore platforms or in close proximity to other equipment, precautions should be taken to prevent injury to personnel and damage to surrounding equipment in case the
separator or its controls or accessories fail. The following safety features are recommended for most oil and gas separators.

*'''High- and low-liquid-level controls:'''

High- and low liquid-level controls normally are float-operated pilots that actuate a [[valve]] on the inlet to the separator, open a bypass around the separator, sound a warning alarm, or perform some other pertinent function to prevent damage that might result from high or low [[liquid]] levels in the separator.

*'''High- and low-pressure controls:'''

High- and low pressure controls are installed on separators to prevent excessively high or low pressures from interfering with normal operations. These high- and low-pressure controls can be mechanical, pneumatic, or electric and can sound a warning, actuate a shut-in [[valve]], open a bypass, or perform other pertinent functions to protect personnel, the separator, and surrounding equipment.

*'''High- and low-temperature controls:'''

[[Temperature]] controls may be installed on separators to shut in the unit, to open or to close a bypass to a heater, or to sound a warning should the temperature in the separator become too high or too low. Such temperature controls are not normally used on separators, but they may be appropriate in special cases. According to Francis (1951), low-temperature controls in separators is another tools used by gas producers which finds its application in the high-pressure gas fields, usually referred to as "vapour-phase" reservoirs. Low temperatures obtainable from the expansion of these high-pressure gas streams are utilized to a profitable advantage. A more efficient recovery of the hydrocarbon condensate and a greater degree of dehydration of the gas as compared to the conventional heater and separator installation is a major advantage of low-temperature controls in oil and gas separators.<ref>A. W. Francis, 1951. Low-Temperature Separation as Applied to Gas-Condensate Production. Drilling and Production Practice, 1951. Houston: American Petroleum Institute.</ref>

*'''Safety relief valves:'''

A spring-loaded safety relief [[valve]] is usually installed on all oil and [[gas]] separators. These valves normally are set at the design pressure of the vessel. Safety relief valves serve primarily as a warning, and in most instances are too small to handle the full rated [[fluid]] capacity of the separator. Full-capacity safety relief valves can be used and are particularly recommended when no safety head (rupture disk) is used on the separator.

*'''Safety heads or rupture disks:'''

A safety head or rupture disk is a device containing a thin metal membrane that is designed to rupture when the [[pressure]] in the separator exceeds a predetermined value. This is usually from 1 1/4 to 1% times the design pressure of the separator vessel. The safety head disk is usually selected so that it will not rupture until the safety relief [[valve]] has opened and is incapable of preventing excessive pressure buildup in the separator.

==Operation and maintenance considerations for oil and gas separators==

Over the life of a production system, the separator is expected to process a wide range of produced fluids. With break through from water flood and expanded gas lift circulation, the produced fluid water cut and gas-oil ratio is ever changing. In many instances, the separator fluid loading may exceed the original design capacity of the vessel. As a result, many operators find their separator no longer able to meet the required oil and water effluent standards, or experience high liquid carry-over in the gas according to Power ''et al'' (1990).<ref>Powers, Choi, M.S., 1990. Prediction of Separator Performance Under Changing Field Conditions. ''In: SPE Annual Technical Conference and Exhibition,'' New Orleans, Louisiana 23–26 September 1990. New Orleans: Conoco Inc.</ref> Some operational maintenance and considerations are discussed below:

===Periodic inspection===

In refineries and processing plants, it is normal practice to inspect all [[pressure]] vessels and piping periodically for [[corrosion]] and erosion. In the oil fields, this practice is not generally followed (they are inspected at a predetermined frequency, normally decided by an RBI assessment) and equipment is replaced only after actual failure. This policy may create hazardous conditions for operating personnel and surrounding equipment. It is recommended that periodic inspection schedules for all pressure equipment be established and followed to protect against undue failures.

===Installation of safety devices===

All safety relief devices should be installed as close to the vessel as possible and in such manner that the reaction force from exhausting [[fluid]]s will not break off, unscrew, or otherwise dislodge the safety device. The discharge from safety devices should not endanger personnel
or other equipment.

===Low temperature===

Separators should be operated above hydrate-formation [[temperature]]. Otherwise hydrates may form in the vessel and partially or completely plug it thereby reducing the capacity of the separator. In some instances when the [[liquid]] or [[gas]] outlet is plugged or restricted, this causes the safety [[valve]] to open or the safety head to rupture. Steam coils can be installed in the liquid section of oil and gas separators to melt hydrates that may form there. This is especially appropriate on low-temperature separators.

===Corrosive fluids===

A separator handling corrosive [[fluid]] should be checked periodically to determine whether remedial work is required. Extreme cases of [[corrosion]] may require a reduction in the rated working [[pressure]] of the vessel. Periodic hydrostatic testing is recommended, especially if the fluids being handled are corrosive. Expendable [[anode]] can be used in separators to protect them against [[Electrolyte|electrolytic]] [[corrosion]]. Some operators determine separator shell and head thickness with ultrasonic thickness indicators and calculate the maximum allowable working pressure from the remaining metal thickness. This should be done yearly offshore and every two to four years onshore.

==See also==
*[[Piping and instrumentation diagram]]
*[[Fluid dynamics]]
*[[Computational fluid dynamics]]
*[[Souders–Brown equation]]
*[[Joule–Thomson effect]]
*[[Vapor-liquid separator]]
*[[Natural gas condensate]]
*[[Oil production plant]]
*[[Heat]]
*[[Cyclone separator]]
*[[Valve]]
*[[Stokes' law]]
*[[Safety]]

==External links==
*[https://www.flottweg.com/product-lines/separator/ The Flottweg Separator ] – Parameters and influencing factors for the best possible separation results including Separator video
*[http://www.tradeindia.com/fp473138/Separator-Internals-Oil-Gas-Industry.html/ Pictorial illustration of what the internal structure of an Oil and Gas Separator looks like] – This shows how the Defoaming Internals, Coalescing Internals, Demister Internals – Wiremesh Demister, Vane Mist Eliminators, Desanding Internals, Vortex Breakers and other internal components of a typical separator are arranged in the separator.
*[http://www.enggcyclopedia.com/2011/04/typical-pid-arrangement-3-phase-separator-vessels/ Typical P&ID arrangement for three-phase separator vessels] – [[Piping and instrumentation diagram]] (P&ID) illustrates the direction of flow in and around an Oil and Gas Separator. It likewise shows the connectivity of other instruments e.g. valves, level controller, level indicator, flow indicator, flow transmitter, pressure indicator, pressure transmitter, etc. around the separator.
*[https://www.youtube.com/watch?v=sokGjczdLyI/ Computational fluid dynamics (CFD) simulation illustrating a three-phase oil, gas and water separator] – This illustrates the direction of flow in the separator.
*[http://www.enggcyclopedia.com/calculators/equipment-sizing/2-phase-separator-design-calculator-knock-drum/ Quick calculator for horizontal knock out drum sizing] – Based on settling time required for liquid droplets of a given minimum size to be separated.

==References==
{{reflist}}

{{DEFAULTSORT:Separator (Oil Production)}}
[[Category:Petroleum technology]]
[[Category:Natural gas technology]]
[[Category:Industrial equipment]]

Pressure vessel

2018-07-13T16:09:15Z

173.165.237.1: /* History of pressure vessels */

[[File:Modified Hanson steelwatertank.jpg|upright=1.4|thumb|A pressure vessel constructed of a horizontal steel cylinder.]]
A '''pressure vessel''' is a container designed to hold gases or liquids at a [[pressure]] substantially different from the ambient pressure.

Pressure vessels can be dangerous, and fatal accidents have occurred in the history of their development and operation. Consequently, pressure vessel design, manufacture, and operation are regulated by engineering authorities backed by legislation. For these reasons, the definition of a pressure vessel varies from country to country.

Design involves parameters such as maximum safe operating pressure and temperature, [[safety factor]], corrosion allowance and minimum design temperature (for brittle fracture). Construction is tested using [[nondestructive testing]], such as [[ultrasonic testing]], [[radiography]], and pressure tests. Hydrostatic tests use water, but pneumatic tests use air or another gas. Hydrostatic testing is preferred, because it is a safer method, as much less energy is released if a fracture occurs during the test (water does not rapidly increase its volume when rapid depressurization occurs, unlike gases like air, which fail explosively).

In most countries, vessels over a certain size and pressure must be built to a formal code. In the United States that code is the [[ASME Boiler and Pressure Vessel Code (BPVC)]]. These vessels also require an authorized inspector to sign off on every new vessel constructed and each vessel has a nameplate with pertinent information about the vessel, such as maximum allowable working pressure, maximum temperature, minimum design metal temperature, what company manufactured it, the date, its registration number (through the National Board), and [[ASME]]'s official stamp for pressure vessels (U-stamp). The nameplate makes the vessel traceable and officially an [[ASME]] Code vessel.

== History of pressure vessels ==
[[File:Popular Science Jan 1919 p27 - 10,000psi wrapped fuel tank.JPG|right|thumb|A {{convert|10000|psi|MPa|abbr=on}} pressure vessel from 1919, wrapped with high tensile steel banding and steel rods to secure the end caps.]]
The earliest documented design of pressure vessels was described in 1495 in the book by Leonardo da Vinci, the Codex Madrid I, in which containers of pressurized air were theorized to lift heavy weights underwater.<ref name="Nilsen">Nilsen, Kyle. (2011) [http://hdl.handle.net/10057/3997 "Development of low pressure filter testing vessel and analysis of electrospun nanofiber membranes for water treatment"]</ref> However, vessels resembling those used today did not come about until the 1800s, when steam was generated in boilers helping to spur the [[industrial revolution]].<ref name="Nilsen" /> However, with poor material quality and manufacturing techniques along with improper knowledge of design, operation and maintenance there was a large number of damaging and often fatal explosions associated with these boilers and pressure vessels, with a death occurring on a nearly daily basis in the United States.<ref name="Nilsen" /> Local providences and states in the US began enacting rules for constructing these vessels after some particularly devastating vessel failures occurred killing dozens of people at a time, which made it difficult for manufacturers to keep up with the varied rules from one location to another and the first pressure vessel code was developed starting in 1911 and released in 1914, starting the [[ASME Boiler and Pressure Vessel Code (BPVC)]].<ref name="Nilsen" /> In an early effort to design a tank capable of withstanding pressures up to {{convert|10000|psi|MPa|abbr=on}}, a {{convert|6|in|adj=on}} diameter tank was developed in 1919 that was spirally-wound with two layers of high tensile strength steel wire to prevent sidewall rupture, and the end caps longitudinally reinforced with lengthwise high-tensile rods.<ref>''Ingenious Coal-Gas Motor Tank'', [[Popular Science]] monthly, January 1919, page 27, Scanned by Google Books: https://books.google.com/books?id=HykDAAAAMBAJ&pg=PA13</ref> The need for high pressure and temperature vessels for petroleum refineries and chemical plants gave rise to vessels joined with welding instead of rivets (which were unsuitable for the pressures and temperatures required) and in 1920s and 1930s the BPVC included welding as an acceptable means of construction, and welding is the main means of joining metal vessels today.<ref name="Nilsen" />

There have been many advancements in the field of pressure vessel engineering such as advanced non-destructive examination, phased array ultrasonic testing and radiography, new material grades with increased corrosion resistance and stronger materials, and new ways to join materials such as explosion welding (to attach one metal sheet to another, usually a thin corrosion resistant metal like stainless steel to a stronger metal like carbon steel), friction stir welding (which attaches the metals together without melting the metal), advanced theories and means of more accurately assessing the stresses encountered in vessels such as with the use of Finite Element Analysis, allowing the vessels to be built safer and more efficiently. Today vessels in the USA require BPVC stamping but the BPVC is not just a domestic code, many other countries have adopted the BPVC as their official code. There are, however, other official codes in some countries (some of which rely on portions of and reference the BPVC), Japan, Australia, Canada, Britain, and Europe have their own codes. Regardless of the country nearly all recognize the inherent potential hazards of pressure vessels and the need for standards and codes regulating their design and construction.

==Pressure vessel features==

===Shape of a pressure vessel===
Pressure vessels can theoretically be almost any shape, but shapes made of sections of spheres, cylinders, and cones are usually employed. A common design is a cylinder with end caps called [[head (vessel)|heads]]. Head shapes are frequently either hemispherical or dished (torispherical). More complicated shapes have historically been much harder to analyze for safe operation and are usually far more difficult to construct.

<gallery>
File:Biogasholder and flare.JPG|Spherical gas container.
File:Ресивер хладагента FP-LR-100.png|Cylindrical pressure vessel.
File:Diffuser Head.jpg|Picture of the bottom of an aerosol spray can.
File:ABC Fire Extinguisher.jpg|Fire Extinguisher with rounded rectangle pressure vessel
</gallery>

Theoretically, a spherical pressure vessel has approximately twice the strength of a cylindrical pressure vessel with the same wall thickness,<ref>{{cite book|last=Hearn|first=E.J.|title=Mechanics of Materials 1. An Introduction to the Mechanics of Elastic and Plastic Deformation of Solids and Structural Materials - Third Edition|year=1997|publisher=Butterworth-Heinemann|location=Chapter 9|isbn=0-7506-3265-8|pages=199–203}}</ref> and is the ideal shape to hold internal pressure.<ref name="Nilsen" /> However, a spherical shape is difficult to manufacture, and therefore more expensive, so most pressure vessels are cylindrical with 2:1 semi-elliptical heads or end caps on each end. Smaller pressure vessels are assembled from a pipe and two covers. For cylindrical vessels with a diameter up to 600 mm (NPS of 24 in), it is possible to use seamless pipe for the shell, thus avoiding many inspection and testing issues, mainly the nondestructive examination of radiography for the long seam if required. A disadvantage of these vessels is that greater diameters are more expensive, so that for example the most economic shape of a {{convert|1000|l|cuft}}, {{convert|250|bar|psi|lk=on}} pressure vessel might be a diameter of {{convert|91.44|cm|in|0}} and a length of {{convert|1.7018|m|in|0}} including the 2:1 semi-elliptical domed end caps.

===Construction materials===
[[File:Dawn xenon tank.jpg|thumb|200px|Composite overwrapped pressure vessel with titanium liner.]]

Many pressure vessels are made of steel. To manufacture a cylindrical or spherical pressure vessel, rolled and possibly forged parts would have to be welded together. Some mechanical properties of steel, achieved by rolling or forging, could be adversely affected by welding, unless special precautions are taken. In addition to adequate mechanical strength, current standards dictate the use of steel with a high impact resistance, especially for vessels used in low temperatures. In applications where carbon steel would suffer corrosion, special corrosion resistant material should also be used.

Some pressure vessels are made of [[composite material]]s, such as [[filament winding|filament wound composite]] using [[carbon fiber|carbon fibre]] held in place with a polymer. Due to the very high tensile strength of carbon fibre these vessels can be very light, but are much more difficult to manufacture. The composite material may be wound around a metal liner, forming a [[composite overwrapped pressure vessel]].

Other very common materials include [[polymer]]s such as [[polyethylene terephthalate|PET]] in carbonated beverage containers and [[copper]] in plumbing.

Pressure vessels may be lined with various metals, ceramics, or polymers to prevent leaking and protect the structure of the vessel from the contained medium. This liner may also carry a significant portion of the pressure load.<ref>NASA Tech Briefs, [http://www.techbriefs.com/component/content/article/747 "Making a Metal-Lined Composite Overwrapped Pressure Vessel"], 1 Mar 2005.</ref><ref>Frietas, O., "Maintenance and Repair of Glass-Lined Equipment", Chemical Engineering, 1 Jul 2007.</ref>

Pressure Vessels may also be constructed from concrete (PCV) or other materials which are weak in tension. Cabling, wrapped around the vessel or within the wall or the vessel itself, provides the necessary tension to resist the internal pressure. A "leakproof steel thin membrane" lines the internal wall of the vessel. Such vessels can be assembled from modular pieces and so have "no inherent size limitations".<ref>"High Pressure Vessels",D. Freyer and J. Harvey, 1998</ref> There is also a high order of redundancy thanks to the large number of individual cables resisting the internal pressure.

===Safety features===

====Leak before burst====
Leak before burst describes a pressure vessel designed such that a crack in the vessel will grow through the wall, allowing the contained fluid to escape and reducing the pressure, prior to growing so large as to cause [[fracture]] at the operating pressure.

Many pressure vessel standards, including the ASME Boiler and Pressure Vessel Code {{citation needed|reason=Don't think BPVC requires this, please cite where it says this is required for all vessels to be leak before burst or have fatigue analysis run|date=April 2015}} and the AIAA metallic pressure vessel standard, either require pressure vessel designs to be leak before burst, or require pressure vessels to meet more stringent requirements for [[Fatigue (material)|fatigue]] and fracture if they are not shown to be leak before burst.<ref>ANSI/AIAA S-080-1998, Space Systems - Metallic Pressure Vessels, Pressurized Structures, and Pressure Components, §5.1</ref>

====Safety valves====
[[File:Gasfüllventil.jpg|thumb|200px|Example of a valve used for gas cylinders.]]

As the pressure vessel is designed to a pressure, there is typically a [[safety valve]] or [[relief valve]] to ensure that this pressure is not exceeded in operation.

===Maintenance features===

==== Pressure vessel closures ====
Pressure vessel closures are pressure retaining structures designed to provide quick access to pipelines, pressure vessels, pig traps, filters and filtration systems. Typically pressure vessel closures allow maintenance personnel.

==Uses==
[[File:Methanier aspher LNGRIVERS.jpg|thumb|300px|An LNG carrier ship with four pressure vessels for [[liquefied natural gas]].]]
Pressure vessels are used in a variety of applications in both industry and the private sector. They appear in these sectors as industrial [[compressed air]] receivers and [[domestic hot water storage tank]]s. Other examples of pressure vessels are [[diving cylinder]]s, [[recompression chamber]]s, [[fractional distillation|distillation towers]], [[pressure reactor]]s, [[autoclave]]s, and many other vessels in [[mining]] operations, [[oil refinery|oil refineries]] and [[petrochemical]] plants, [[nuclear reactor]] vessels, [[submarine]] and [[space ship]] habitats, [[pneumatic]] reservoirs, [[hydraulic]] reservoirs under pressure, [[air brake (rail)|rail vehicle airbrake reservoir]]s, [[air brake (road vehicle)|road vehicle airbrake reservoir]]s, and storage vessels for liquified gases such as [[ammonia]], [[chlorine]], and [[liquified petroleum gas|LPG]] ([[propane]], [[butane]]).

A unique application of a pressure vessel is the passenger cabin of an airliner: the outer skin carries both the aircraft maneuvering loads and the [[cabin pressurization]] loads.

<gallery>
File:Water well tank.JPG|A pressure tank connected to a water well and domestic hot water system.
File:Propane tanks large.jpg|A few pressure tanks, here used to hold [[propane]].
File:Bergisch Gladbach - Papiermühle Alte Dombach 07 ies.jpg|A pressure vessel used as a [[Kier (industrial)|kier]].
File:CST-100 pressure vessel.jpg|A pressure vessel used for The Boeing Company’s CST-100 spacecraft.
</gallery>

==Alternatives to pressure vessels==
*[[Natural gas storage]]
*[[Gas holder]]
Depending on the application and local circumstances, alternatives to pressure vessels exist. Examples can be seen in domestic water collection systems, where the following may be used:
*Gravity-controlled systems<ref>{{cite web|first=Doug |last=Pushard |url=http://www.harvesth2o.com/faq.shtml |title=Domestic water collection systems also sometimes able to function on gravity |publisher=Harvesth2o.com |year=2005 |accessdate=2009-04-17}}{{Verify source|date=April 2009}}</ref> which typically consist of an unpressurized [[water tank]] at an elevation higher than the point of use. Pressure at the point of use is the result of the hydrostatic pressure caused by the elevation difference. Gravity systems produce {{convert|0.43|psi|kPa}} per foot of water head (elevation difference). A municipal water supply or pumped water is typically around {{convert|90|psi|kPa}}.
*[[Inline pump controller]]s or [[pressure sensor|pressure-sensitive]] pumps.<ref>{{cite web|first=Doug |last=Pushard |url=http://www.harvesth2o.com/pumps_or_tanks.shtml |title=Alternatives to pressure vessels in domestic water systems |publisher=Harvesth2o.com |date= |accessdate=2009-04-17}}</ref>

==Design==

===Scaling===
No matter what shape it takes, the minimum mass of a pressure vessel scales with the pressure and volume it contains and is inversely proportional to the [[strength to weight ratio]] of the construction material (minimum mass decreases as strength increases<ref>{{cite journal|first=Paul|last=Puskarich|url=http://www.gmic.org/Student%20Contest%20Entries/2007%20Contest%20Entries/26-Paul%20Puskarich%20-%20Glass%20for%20Pipeline%20Systems.pdf|title=Strengthened Glass for Pipleine Systems|date=2009-05-01|format=PDF|publisher=MIT|accessdate=2009-04-17|deadurl=yes|archiveurl=https://web.archive.org/web/20120315184643/http://www.gmic.org/Student%20Contest%20Entries/2007%20Contest%20Entries/26-Paul%20Puskarich%20-%20Glass%20for%20Pipeline%20Systems.pdf|archivedate=2012-03-15|df=}}</ref>).

====Scaling of stress in walls of vessel====

Pressure vessels are held together against the gas pressure due to tensile forces within the walls of the container. The normal (tensile) [[stress (mechanics)|stress]] in the walls of the container is proportional to the pressure and radius of the vessel and inversely proportional to the thickness of the walls.<ref>{{cite book|title=Mechanics of Materials |first1=Ferdinand P. |last1=Beer |first2=E. Russel |last2=Johnston, Jr. |first3=John T. |last3=DeWolf |edition=fourth |chapter=7.9 |page=463 |isbn=9780073659350 |publisher=McGraw-Hill}}</ref> Therefore, pressure vessels are designed to have a thickness proportional to the radius of tank and the pressure of the tank and inversely proportional to the maximum allowed normal stress of the particular material used in the walls of the container.

Because (for a given pressure) the thickness of the walls scales with the radius of the tank, the mass of a tank (which scales as the length times radius times thickness of the wall for a cylindrical tank) scales with the volume of the gas held (which scales as length times radius squared). The exact formula varies with the tank shape but depends on the density, ρ, and maximum allowable stress σ of the material in addition to the pressure P and volume V of the vessel. (See below for the exact equations for the stress in the walls.)

====Spherical vessel====
For a [[sphere]], the minimum mass of a pressure vessel is

:<math>M = {3 \over 2} P V {\rho \over \sigma}</math>,

where:
* <math>M</math> is mass, (kg)
* <math>P</math> is the pressure difference from ambient (the [[gauge pressure]]), (Pa)
* <math>V</math> is volume,
* <math>\rho</math> is the density of the pressure vessel material, (kg/m^3)
* <math>\sigma</math> is the maximum working [[stress (physics)|stress]] that material can tolerate. (Pa)<ref>For a sphere the thickness d = rP/2σ, where r is the radius of the tank. The volume of the spherical surface then is 4πr2d = 4πr3P/2σ. The mass is determined by multiplying by the density of the material that makes up the walls of the spherical vessel. Further the volume of the gas is (4πr3)/3. Combining these equations give the above results. The equations for the other geometries are derived in a similar manner</ref>

Other shapes besides a sphere have constants larger than 3/2 (infinite cylinders take 2), although some tanks, such as non-spherical wound composite tanks can approach this.

====Cylindrical vessel with hemispherical ends====
This is sometimes called a "bullet"{{citation needed|date=March 2014}} for its shape, although in geometric terms it is a [[Capsule (geometry)|capsule]].

For a cylinder with hemispherical ends,
:<math>M = 2 \pi R^2 (R + W) P {\rho \over \sigma}</math>,
where
*R is the radius (m)
*W is the middle cylinder width only, and the overall width is W + 2R (m)<ref>{{Cite web|url=http://www.fxsolver.com/browse/formulas/Mass+of+pressure+Cylindrical+vessel+with+hemispherical+ends(+capsule)|title=Mass of pressure Cylindrical vessel with hemispherical ends( capsule) - calculator - fxSolver|website=www.fxsolver.com|access-date=2017-04-11}}</ref>

====Cylindrical vessel with semi-elliptical ends====
In a vessel with an [[aspect ratio]] of middle cylinder width to radius of 2:1,
:<math>M = 6 \pi R^3 P {\rho \over \sigma}</math>.

====Gas storage====
In looking at the first equation, the factor PV, in SI units, is in units of (pressurization) energy. For a stored gas, PV is proportional to the mass of gas at a given temperature, thus
:<math>M = {3 \over 2} nRT {\rho \over \sigma}</math>. (see [[gas law]])

The other factors are constant for a given vessel shape and material. So we can see that there is no theoretical "efficiency of scale", in terms of the ratio of pressure vessel mass to pressurization energy, or of pressure vessel mass to stored gas mass. For storing gases, "tankage efficiency" is independent of pressure, at least for the same temperature.

So, for example, a typical design for a minimum mass tank to hold [[helium]] (as a pressurant gas) on a rocket would use a spherical chamber for a minimum shape constant, carbon fiber for best possible <math>\rho / \sigma</math>, and very cold helium for best possible <math>M / {pV}</math>.

===Stress in thin-walled pressure vessels===
Stress in a shallow-walled pressure vessel in the shape of a sphere is
:<math>\sigma_\theta = \sigma_{\rm long} = \frac{pr}{2t}</math>,
where <math>\sigma_\theta</math> is hoop stress, or stress in the circumferential direction, <math>\sigma_{long}</math> is stress in the longitudinal direction, ''p'' is internal gauge pressure, ''r'' is the inner radius of the sphere, and ''t'' is thickness of the sphere wall. A vessel can be considered "shallow-walled" if the diameter is at least 10 times (sometimes cited as 20 times) greater than the wall depth.<ref>Richard Budynas, J. Nisbett, Shigley's Mechanical Engineering Design, 8th ed., New York:McGraw-Hill, {{ISBN|978-0-07-312193-2}}, pg 108</ref>

[[File:Reservoir cylindrique sous pression contrainte.svg|thumb|300px|Stress in the cylinder body of a pressure vessel.]]
Stress in a shallow-walled pressure vessel in the shape of a cylinder is
:<math>\sigma_\theta = \frac{pr}{t}</math>,
:<math>\sigma_{\rm long} = \frac{pr}{2t}</math>,

where:
* <math>\sigma_\theta</math> is [[hoop stress]], or stress in the circumferential direction
* <math>\sigma_{long}</math> is stress in the longitudinal direction
* ''p'' is internal gauge pressure
* ''r'' is the inner radius of the cylinder
* ''t'' is thickness of the cylinder wall.

Almost all pressure vessel design standards contain variations of these two formulas with additional empirical terms to account for variation of stresses across thickness, quality control of [[welding|welds]] and in-service [[corrosion]] allowances.
All formulae mentioned above assume uniform distribution of membrane stresses across thickness of shell but in reality, that is not the case. Deeper analysis is given by Lame's theory. The formulae of pressure vessel design standards are extension of Lame's theory by putting some limit on ratio of inner radius and thickness.

For example, the [[ASME Boiler and Pressure Vessel Code (BPVC)]] (UG-27) formulas are:<ref>{{cite book|title=An International Code 2007 ASME Boiler & Pressure Vessel Code|year=2007|publisher=The Americal Society of Mechanical Engineers|url=http://www.asme.org/kb/standards/bpvc-resources}}</ref>

Spherical shells: Thickness has to be less than 0.356 times inner radius
:<math>\sigma_\theta = \sigma_{\rm long} = \frac{p(r + 0.2t)}{2tE}</math>

Cylindrical shells: Thickness has to be less than 0.5 times inner radius
:<math>\sigma_\theta = \frac{p(r + 0.6t)}{tE}</math>
:<math>\sigma_{\rm long} = \frac{p(r - 0.4t)}{2tE}</math>

where ''E'' is the joint efficient, and all others variables as stated above.

The [[factor of safety]] is often included in these formulas as well, in the case of the ASME BPVC this term is included in the material stress value when solving for pressure or thickness.

===Winding angle of carbon fibre vessels===
Wound infinite cylindrical shapes optimally take a winding angle of 54.7 degrees, as this gives the necessary twice the strength in the circumferential direction to the longitudinal.<ref>[http://web.mit.edu/course/3/3.11/www/modules/pv.pdf MIT pressure vessel lecture]</ref>

=== Operation standards ===

Pressure vessels are designed to operate safely at a specific pressure and temperature, technically referred to as the "Design Pressure" and "Design Temperature". A vessel that is inadequately designed to handle a high pressure constitutes a very significant safety hazard. Because of that, the design and certification of pressure vessels is governed by design codes such as the [[American Society of Mechanical Engineers#ASME Boiler and Pressure Vessel Code (BPVC)|ASME Boiler and Pressure Vessel Code]] in North America, the [[Pressure Equipment Directive]] of the [[European Union|EU]] (PED), [[Japanese Industrial Standard]] (JIS), [[Canadian Standards Association|CSA]] B51 in [[Canada]], [[Australian Standards]] in Australia and other [[international standard]]s like [[Lloyd's Register|Lloyd's]], [[Germanischer Lloyd]], [[Det Norske Veritas]], Société Générale de Surveillance (SGS S.A.), [http://www.lr.org/nl/energy/stoomwezen/ Lloyd’s Register Energy Nederland (formerly known as Stoomwezen)] etc.

Note that where the pressure-volume product is part of a safety standard, any incompressible liquid in the vessel can be excluded as it does not contribute to the potential energy stored in the vessel, so only the volume of the compressible part such as gas is used.

====List of standards====

* [[EN 13445]]: The current European Standard, harmonized with the [[Pressure Equipment Directive]] (97/23/EC). Extensively used in Europe.
* [[ASME Boiler and Pressure Vessel Code (BPVC)|ASME Boiler and Pressure Vessel Code]] Section VIII: Rules for Construction of Pressure Vessels.
* [[BS 5500]]: Former British Standard, replaced in the UK by [[EN 13445|BS EN 13445]] but retained under the name [[PD 5500]] for the design and construction of export equipment.
* AD Merkblätter: German standard, harmonized with the [[Pressure Equipment Directive]].
* EN 286 (Parts 1 to 4): European standard for simple pressure vessels (air tanks), harmonized with Council Directive 87/404/EEC.
* [[BS 4994]]: Specification for design and construction of vessels and tanks in [[reinforced plastics]].
* ASME PVHO: US standard for [[Pressure Vessels for Human Occupancy]].
* CODAP: French Code for Construction of Unfired Pressure Vessel.
* [[AS/NZS 1200]]: Pressure equipment.<ref>{{cite web|title=AS 1200 Pressure Vessels|url=http://infostore.saiglobal.com/store2/Details.aspx?ProductID=356464|publisher=SAI Global|accessdate=14 November 2011}}{{dead link|date=December 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
* [[AS/NZS 3788:2006]]<ref>{{cite web | url=http://infostore.saiglobal.com/store/details.aspx?ProductID=374650 | title=AS_NZS 3788: 2006 Pressure equipment - In-service inspection | publisher=[[SAI Global]] | accessdate=September 4, 2015}}</ref>
* API 510.<ref>{{cite web|url=http://global.ihs.com/doc_detail.cfm?item_s_key=00010564 |title=Pressure Vessel Inspection Code: In-Service Inspection, Rating, Repair, and Alteration |publisher=API |date=June 2006}}</ref>
* ISO 11439: [[Compressed natural gas]] (CNG) cylinders<ref>.{{cite web|url=http://www.iso.org/iso/catalogue_detail?csnumber=33298 |title=Gas cylinders - High pressure cylinders for the on-board storage of natural gas as a fuel for automotive vehicles |publisher=ISO |date=2006-07-18 |accessdate=2009-04-17}}</ref>
* IS 2825-1969 (RE1977)_code_unfired_Pressure_vessels.
* [[FRP tanks and vessels]].
* AIAA S-080-1998: AIAA Standard for Space Systems - Metallic Pressure Vessels, Pressurized Structures, and Pressure Components.
* AIAA S-081A-2006: AIAA Standard for Space Systems - [[Composite Overwrapped Pressure Vessels]] (COPVs).
* ECSS-E-ST-32-02C Rev.1: Space engineering - Structural design and verification of pressurized hardware
* B51-09 Canadian Boiler, pressure vessel, and pressure piping code.
* HSE guidelines for pressure systems.
* Stoomwezen: Former pressure vessels code in the Netherlands, also known as RToD: Regels voor Toestellen onder Druk (Dutch Rules for Pressure Vessels).

== See also ==
{{div col}}
* [[Tube tool]]
* [[American Society of Mechanical Engineers]] (ASME)
* [[Bottled gas]]
* [[Composite overwrapped pressure vessel]]
* [[Compressed air energy storage]]
* [[Compressed natural gas]]
* [[Demister (vapor)|Demister]]
* [[Fire-tube boiler]]
* [[Gas cylinder]]
* [[Gasket]]
* [[Head (vessel)]]
* [[Minimum design metal temperature]] (MDMT)
* [[Vapor–liquid separator]] or Knock-out drum
* [[Pressure bomb]] – a device for measuring leaf [[water potential]]s
* [[Rainwater harvesting]]
* [[Relief valve]]
* [[Safety valve]]
* [[Shell and tube heat exchanger]]
* [[Vortex breaker]]
* [[Water well]]
* [[Water-tube boiler]]
{{div col end}}

==Notes==
{{reflist}}

==References==
* A.C. Ugural, S.K. Fenster, Advanced Strength and Applied Elasticity, 4th ed.
* E.P. Popov, Engineering Mechanics of Solids, 1st ed.
* Megyesy, Eugene F. "Pressure Vessel Handbook, 14th Edition." PV Publishing, Inc. Oklahoma City, OK

==Further reading==
* Megyesy, Eugene F. (2008, 14th ed.) ''Pressure Vessel Handbook.'' PV Publishing, Inc.: Oklahoma City, Oklahoma, USA. www.pressurevesselhandbook.com Design handbook for pressure vessels based on the ASME code.

== External links ==
{{wiktionary}}
{{commons|Pressure vessel|Pressure vessel}}
*[http://articles.compressionjobs.com/articles/oilfield-101/5130-storage-tanks-vessels-gas-liquids?start=6 Use of pressure vessels in oil and gas industry]
*[http://www.mathalino.com/reviewer/mechanics-and-strength-of-materials/thin-walled-pressure-vessels Basic formulas for thin walled pressure vessels; with examples]
*[http://www.pveng.com/ASME/DesignTools/DesignTools.php Educational Excel spreadsheets for ASME head, shell and nozzle designs]
*[http://www.asme.org/Codes/International_Boiler_Pressure.cfm ASME Boiler and Pressure Vessel website]
*[http://www.asmedl.org/PressureVesselTech Journal of Pressure Vessel Technology]
*[https://web.archive.org/web/20070913004940/http://ec.europa.eu/enterprise/pressure_equipment/ped/index_en.html EU Pressure Equipment Directive website]
*[https://web.archive.org/web/20060623135144/http://ec.europa.eu/enterprise/pressure_equipment/sector_pressure/spv_sector/index.htm EU Simple Pressure Vessel Directive]
*[https://web.archive.org/web/20070111202012/http://ec.europa.eu/enterprise/pressure_equipment/ped/guidelines/guideline2-13_en.html EU Classification]
*[http://oakridgebellows.com/metal-expansion-joints/technical-videos/lugs-on-pipe-and-vessels-new Pressure Vessel attachments http://oakridgebellows.com/metal-expansion-joints/technical-videos/lugs-on-pipe-and-vessels-new]

{{Containers}}

{{Authority control}}

[[Category:Pressure vessels| ]]
[[Category:Gas technologies]]

Gametophyte

2018-05-18T17:07:15Z

173.165.237.1:

[[File:Gametophyte2.png|thumb|Several gametophytes growing in a [[terrarium]].]]

[[File:Pinus embryo in female gametophyte.jpg|thumb|100px|Pine gametophyte (outside) surrounding the embryo (inside)]]
A '''gametophyte''' is a stage in the life cycle of [[plant]]s and [[algae]] that undergoes [[alternation of generations]]. It is a [[haploid]] multicellular organism that develops from a [[haploid]] [[spore]] that has one set of chromosomes. The gametophyte is the [[Sexual reproduction of plants|sexual phase]] in the life cycle of plants and algae. It develops sex organs that produce [[gamete]]s, haploid sex cells that participate in [[fertilization]] to form a diploid zygote in which each cell has two sets of chromosomes. Cell division of the zygote results in a new [[diploid]] multicellular organism, the second stage in the life cycle known as the [[sporophyte]], the function of which is to produce haploid spores by [[meiosis]].

== Algae ==
In some [[multicellular]] [[green algae]] (''[[Ulva lactuca]]'' is one example), [[red algae]] and [[brown algae]] sporophytes and gametophytes may be externally indistinguishable (isomorphic). In ''[[Ulva (genus)|Ulva]]'' the gametes are [[Isogamy|isogamous]], all of one size, shape and general morphology.<ref name=Sadava>{{cite book|last1=Sadava|first1=David|last2=Hillis|first2=David|last3=Heller|first3=H. Craig|last4=Berenbaum|first4=May|title=Life: The Science of Biology, Volume 1|date=2012|publisher=Macmillan|isbn=978-1464141225|edition=10th}}</ref>

== Land plants ==
In [[embryophyte|land plants]], [[anisogamy]] is universal. As in animals, female and male gametes are called, respectively, ''eggs'' and ''sperm.'' In extant land plants, either the sporophyte or the gametophyte may be reduced (heteromorphic).<ref>{{Cite journal|last=Bennici|first=Andrea|date=2008|title=Origin and early evolution of land plants|journal=Communicative & Integrative Biology|volume=1|issue=2|pages=212–218|issn=1942-0889|pmc=2686025|pmid=19513262}}</ref>

=== Bryophytes ===
In [[bryophytes]] ([[mosses]], [[liverworts]], and [[hornworts]]), the gametophyte is the most visible stage of the life cycle. The bryophyte gametophyte is longer lived, nutritionally independent, and the sporophytes are typically attached to the gametophytes and dependent on them.<ref name=Budke>{{cite journal | last1 = Budke | first1 = J.M. | last2 = Goffinet | first2 = B. | last3 = Jones | first3 = C.S. | year = 2013 | title = Dehydration protection provided by a maternal cuticle improves offspring fitness in the moss ''Funaria hygrometrica'' | journal = Annals of Botany | volume = 111| issue = | pages = 781–789| doi = 10.1093/aob/mct033 | pmid=23471009 | pmc=3631323}}</ref> When a moss spore germinates it grows to produce a filament of cells (called the [[protonema]]). The mature gametophyte of mosses develops into leafy shoots that produce sex organs ([[Gametangium|gametangia]]) that produce gametes. Eggs develop in [[Archegonium|archegonia]] and sperm in [[Antheridium|antheridia]].<ref>[[Ralf Reski]] (1998): Development, genetics and molecular biology of mosses. In: Botanica Acta 111, pp 1-15.</ref>

In some bryophyte groups such as many liverworts of the order [[Marchantiales]], the gametes are produced on specialized structures called [[gametophore]]s (or gametangiophores).

=== Ferns ===
In most [[fern]]s, for example, in the [[leptosporangiate fern]] ''[[Dryopteris]]'', the gametophyte is a [[photosynthesis|photosynthetic]] free living [[autotroph]]ic organism called a [[prothallium|prothallus]] that produces gametes and maintains the sporophyte during its early multicellular development. However, in some groups, notably the clade that includes [[Ophioglossaceae]] and ''[[Psilotaceae]]'', the gametophytes are subterranean and subsist by forming [[mycotroph]]ic relationships with fungi.

=== Lycophytes ===

Extant [[Lycopodiophyta|lycophytes]] produce several different types of gametophytes. In the families [[Lycopodiaceae]] and [[Huperziaceae]], gametophytes are subterranean and [[mycotroph]]ic, deriving nutrients from symbiosis with fungi. ''[[Isoetes]]'' and ''[[Selaginella]]'', which are heterosporous, megagametophytes develop inside the megaspores, which crack open at the trilete suture to allow the male gametes to access the egg cells in the archegonia inside. The gametophytes of ''Isoetes'' appear to be similar in this respect to those of the extinct [[Carboniferous]] giant arborescent clubmosses, ''Lepidodendron'' and ''Lepidostrobus''.<ref name="Brack-Hanes">{{cite journal|first=S.D.|last=Brack-Hanes|date=1978|title=On the megagametophytes of two Lepidodendracean cones.|journal=Botanical Gazette|volume=139|pages=140–146|doi=10.1086/336979}}</ref>

=== Seed plants ===
By contrast, in [[Spermatophyta|seed plants]] ([[gymnosperms]] and [[angiosperms]]), gametophytes develop into multicellular organisms while still enclosed within the sporangium.<ref>C.Michael Hogan (2010): [http://www.eoearth.org/article/Fern ''Fern''. Encyclopedia of Earth. National council for Science and the Environment] {{webarchive |url=https://web.archive.org/web/20111109071540/http://www.eoearth.org/article/Fern |date=November 9, 2011 }}. Washington, DC</ref>

Vascular plants that produce only one type of spore are said to be homosporous. They have exosporic gametophytes—that is, the gametophyte is free-living and develops outside of the spore wall. Exosporic gametophytes are normally bisexual, capable of producing both sperm and eggs. In heterosporous vascular plants (plants that produce both microspores and megaspores), the gametophyte develops endosporically, within the spore wall. These gametophytes are unisexual, producing either sperm or eggs but not both.

All vascular plants are sporophyte dominant, and a trend toward smaller and more sporophyte-dependent female gametophytes is evident as land plants evolved towards reproduction by seeds.<ref name="Stewart and Rothwell">{{cite book|first1=W.N.|last1=Stewart|first2=G.W.|last2=Rothwell|title=Palaeobotany and the evolution of plants, second edition.|location=Cambridge, U.K.|publisher=Cambridge University press|isbn=0521382947 }}</ref>

==Heteromorphy==
{{main article|Dioicous|Heterospory}}

In plants with heteromorphic gametophytes, there are two distinct kinds of gametophytes. Because the two gametophytes differ in form and function, they are termed ''heteromorphic'', from ''hetero''- "different" and ''morph'' "form". The egg producing gametophyte is known as a '''megagametophyte''', because it is typically larger, and the sperm producing gametophyte is known as a '''microgametophyte'''. Gametophytes which produce egg and sperm on separate plants are termed [[Dioicous]].

In [[Heterospory|heterosporous]] plants (water ferns, some lycophytes, as well as all gymnosperms and angiosperms), there are two distinct [[sporangium|sporangia]], each of which produces a single kind of spore and single kind of gametophyte. However, not all heteromorphic gametophytes come from heterosporous plants. That is, some plants have distinct egg-producing and sperm-producing gametophytes, but these gametophytes develop from the same kind of spore inside the same sporangium; ''[[Sphaerocarpos]]'' is an example of such a plant.

In the seed plants, the microgametophyte is called [[pollen]]. Seed plant microgametophytes consists of two or three cells when the pollen grains exit the sporangium. The megagametophyte develops within the megaspore of extant seedless vascular plants and within the megasporangium in a cone or flower in seed plants. In seed plants, the microgametophyte (pollen grain) travels to the vicinity of the egg cell (carried by a physical or animal vector), and produces two sperm by mitosis.

In [[gymnosperm]]s the megagametophyte consists of several thousand cells and produces one to several [[archegonia]], each with a single egg cell. The gametophyte becomes a food storage tissue in the seed.<ref>{{cite web|url=http://digimuse.nmns.edu.tw/Default.aspx?Domin=b&tabid=268&Field=v0&ContentType=Study&FieldName=&ObjectId=&Subject=&Language=ENG |title=Vascular Plants :: Description |publisher=Digimuse.nmns.edu.tw |date= |accessdate=2014-07-13 |deadurl=yes |archiveurl=https://web.archive.org/web/20140522044106/http://digimuse.nmns.edu.tw/Default.aspx?Domin=b&tabid=268&Field=v0&ContentType=Study&FieldName=&ObjectId=&Subject=&Language=ENG |archivedate=2014-05-22 |df= }}</ref>

In [[angiosperm]]s, the megagametophyte is reduced to only a few nuclei and cells, and is sometimes called the [[embryo sac]]. A typical embryo sac contains seven cells and eight nuclei, one of which is the egg cell. Two nuclei fuse with a sperm nucleus to form [[endosperm]], which becomes the food storage tissue in the seed.

==See also==
*[[Sporophyte]]
*[[Alternation of generations]]
*[[Archegonium]]
*[[Antheridium]]

==References==
{{reflist}}

{{Botany}}

[[Category:Plant morphology]]
[[Category:Plant anatomy]]
[[Category:Plant reproduction]]

Cartridge heater

2018-04-27T14:09:35Z

173.165.237.1: /* Insulation */

{{refimprove|date=June 2016}}

{{Infobox machine
| name = Cartridge Heater
| image = Types-of-cartridge-heaters.jpg
| caption = From top to bottom: Square cartridge heater, cartridge heater with threaded NPT fitting (tapered threads), "mini" cartridge heater.
| industry = Process heating
}}

A '''cartridge heater''' is a tube-shaped, heavy-duty, industrial [[Joule heating]] element used in the process heating industry, usually custom manufactured to a specific watt density,<ref>http://www.omega.com/prodinfo/cartridgeheaters.html</ref> based on its intended application.<ref>http://www.process-heating.com/Articles/Feature_Article/154bd7dd2f268010VgnVCM100000f932a8c0____</ref> Compact designs are capable of reaching a watt density of up to 50W/cm².<ref>http://www.freek-heaters.com/products/cartridge_heaters/cartridge_heaters.php</ref><ref>http://www.backermarathon.com/products/hotrod/</ref>

==Applications==

Cartridge heaters are found useful in many applications,<ref>http://www.nexthermal.com/product/cartridge-heaters/high-watt-density-cartridge-heaters.aspx</ref> such as:

* Seal bars
*Torpedo heaters for injection molding
* Injection molding manifolds
* Mass spectrometry
* Rubber molding
* Food production
* Immersion tank heating
* HVAC compressors
* Fuel cells
* Semiconductors
* Medical devices
* Sensor measurement devices
* Extrusion
* Die casting
* Hot melt adhesives
* Heat staking / hole punch
* Plastic welding
* Fluid heating

<gallery>
File:Cartridge-heater-cold.jpg|Cold cartridge heater
File:Cartridge-heater-hot.jpg|Hot cartridge heater
</gallery>

==Construction==

Construction of a cartridge heater may be divided in 7 main parts:
* Heating coil
* Insulation
* Sheath
* Sealing
* Termination
* Lead wire type
* Watt density

===Heating coil===

The heating coil is the actual resistance which is where the electrical load occurs. The most common type of metal alloy used for this purpose is a nickel-chromium mixture, also known as [[nichrome]]. The nichrome wire is wound around a ceramic core, and the number of spirals per inch vary according to the requested watt density. Potential from an alternating current source, which can either be 2 phase or 3 phase, flows through the coiled nichrome wire, heating up the wire, which in turn, heats the cartridge heater sheath.

===Insulation===

Insulation is used to prevent the nichrome coil contacting the sheath, an event that would ground the resistance and could produce a catastrophic short-circuit, resulting in a melted sheath and a major equipment failure. Damage can be mitigated by installing a ground fault interrupting circuit. To prevent the coil from touching the sheath, the coil is inserted into the sheath, and immediately filled with [[magnesium oxide]] (MgO). To ensure the MgO fills the empty space between the sheath and the coil, the cartridge heater is filled under vibration.

===Sheath===

The sheath is the part of the cartridge heater which makes contact with the material or substance to be heated. Several metal alloys are used, depending on the type of application, such as highly acidic or corrosive environments. The most common types of sheaths are 304 [[stainless steel]], 316 stainless steel, and incoloy 800. Incoloy has the highest temperature rating, and is considered a [[superalloy]].

===Sealing===

After the cartridge heater has been filled with MgO, a seal is applied to the open end of the cartridge heater (where the nichrome coil was introduced). This prevents the coil and the MgO from coming out, as well as preventing contaminants such as plastic debris, air, or moisture from entering the heater.

===Termination===

Since cartridge heaters are installed in a wide variety of machines, manufacturers must design the heaters to meet certain clearances.<ref>{{cite web |url=http://www.bigchiefheaters.com/insert1h.htm |title=Archived copy |accessdate=2011-03-11 |deadurl=yes |archiveurl=https://web.archive.org/web/20110206013257/http://www.bigchiefheaters.com/insert1h.htm |archivedate=2011-02-06 |df= }}</ref> [dead link] The cartridge heaters might be terminated with the leads coming out straight, or in a right angle. Also, manufacturers must be careful that the leads are not exposed to temperatures higher than the maximum rating for the lead wire. In order to prevent lead wire damage from temperature, movement or contamination, the lead wire can be protected with a metal conduit, braided metal or silicone sleeves.<ref>http://freek-heaters.com/products/cartridge_heaters/options_for_cartridge_heaters.php</ref>

=== Lead wire type ===

Depending on the clearance and the design of the machine where the cartridge heater will be inserted, the type of wire used will vary. [[Fiberglass]] is the commonly used for cartridge heaters and other high temperature applications, such as automotive wiring harnesses and industrial equipment. Other variants used are [[silicone]] impregnated fiber glass and [[silicone rubber]]. It is a type of wire.

==References==
{{Reflist}}
http://www.gimido.com/

==External links==
*[http://www.backermarathon.com/products/cartridge-heaters/ Sheath Materials]
*[http://www.resisten.com.br/resistencia-cartucho/ Resistência Cartucho]
*[https://www.sinowellmetal.com/galvanized-steel-coil Galvanized Steel Coil]
*[https://hengze-steel.com/product/galvalume-steel-coil/ Galvalume Steel Coil]

[[Category:Heating]]

Cartridge heater

2018-04-27T14:08:33Z

173.165.237.1: /* Insulation */

{{refimprove|date=June 2016}}

{{Infobox machine
| name = Cartridge Heater
| image = Types-of-cartridge-heaters.jpg
| caption = From top to bottom: Square cartridge heater, cartridge heater with threaded NPT fitting (tapered threads), "mini" cartridge heater.
| industry = Process heating
}}

A '''cartridge heater''' is a tube-shaped, heavy-duty, industrial [[Joule heating]] element used in the process heating industry, usually custom manufactured to a specific watt density,<ref>http://www.omega.com/prodinfo/cartridgeheaters.html</ref> based on its intended application.<ref>http://www.process-heating.com/Articles/Feature_Article/154bd7dd2f268010VgnVCM100000f932a8c0____</ref> Compact designs are capable of reaching a watt density of up to 50W/cm².<ref>http://www.freek-heaters.com/products/cartridge_heaters/cartridge_heaters.php</ref><ref>http://www.backermarathon.com/products/hotrod/</ref>

==Applications==

Cartridge heaters are found useful in many applications,<ref>http://www.nexthermal.com/product/cartridge-heaters/high-watt-density-cartridge-heaters.aspx</ref> such as:

* Seal bars
*Torpedo heaters for injection molding
* Injection molding manifolds
* Mass spectrometry
* Rubber molding
* Food production
* Immersion tank heating
* HVAC compressors
* Fuel cells
* Semiconductors
* Medical devices
* Sensor measurement devices
* Extrusion
* Die casting
* Hot melt adhesives
* Heat staking / hole punch
* Plastic welding
* Fluid heating

<gallery>
File:Cartridge-heater-cold.jpg|Cold cartridge heater
File:Cartridge-heater-hot.jpg|Hot cartridge heater
</gallery>

==Construction==

Construction of a cartridge heater may be divided in 7 main parts:
* Heating coil
* Insulation
* Sheath
* Sealing
* Termination
* Lead wire type
* Watt density

===Heating coil===

The heating coil is the actual resistance which is where the electrical load occurs. The most common type of metal alloy used for this purpose is a nickel-chromium mixture, also known as [[nichrome]]. The nichrome wire is wound around a ceramic core, and the number of spirals per inch vary according to the requested watt density. Potential from an alternating current source, which can either be 2 phase or 3 phase, flows through the coiled nichrome wire, heating up the wire, which in turn, heats the cartridge heater sheath.

===Insulation===

Insulation is used to prevent the nichrome coil contacting the sheath. If such event happened, it would ground the resistance and potentially produce a catastrophic short-circuit, resulting in a melted sheath and a major equipment failure. Damage can be mitigated by installing a ground fault interrupting circuit. To prevent the coil from touching the sheath, the coil is inserted into the sheath, and immediately filled with [[magnesium oxide]] (MgO). To ensure the MgO fills the empty space between the sheath and the coil, the cartridge heater is filled under vibration.

===Sheath===

The sheath is the part of the cartridge heater which makes contact with the material or substance to be heated. Several metal alloys are used, depending on the type of application, such as highly acidic or corrosive environments. The most common types of sheaths are 304 [[stainless steel]], 316 stainless steel, and incoloy 800. Incoloy has the highest temperature rating, and is considered a [[superalloy]].

===Sealing===

After the cartridge heater has been filled with MgO, a seal is applied to the open end of the cartridge heater (where the nichrome coil was introduced). This prevents the coil and the MgO from coming out, as well as preventing contaminants such as plastic debris, air, or moisture from entering the heater.

===Termination===

Since cartridge heaters are installed in a wide variety of machines, manufacturers must design the heaters to meet certain clearances.<ref>{{cite web |url=http://www.bigchiefheaters.com/insert1h.htm |title=Archived copy |accessdate=2011-03-11 |deadurl=yes |archiveurl=https://web.archive.org/web/20110206013257/http://www.bigchiefheaters.com/insert1h.htm |archivedate=2011-02-06 |df= }}</ref> [dead link] The cartridge heaters might be terminated with the leads coming out straight, or in a right angle. Also, manufacturers must be careful that the leads are not exposed to temperatures higher than the maximum rating for the lead wire. In order to prevent lead wire damage from temperature, movement or contamination, the lead wire can be protected with a metal conduit, braided metal or silicone sleeves.<ref>http://freek-heaters.com/products/cartridge_heaters/options_for_cartridge_heaters.php</ref>

=== Lead wire type ===

Depending on the clearance and the design of the machine where the cartridge heater will be inserted, the type of wire used will vary. [[Fiberglass]] is the commonly used for cartridge heaters and other high temperature applications, such as automotive wiring harnesses and industrial equipment. Other variants used are [[silicone]] impregnated fiber glass and [[silicone rubber]]. It is a type of wire.

==References==
{{Reflist}}
http://www.gimido.com/

==External links==
*[http://www.backermarathon.com/products/cartridge-heaters/ Sheath Materials]
*[http://www.resisten.com.br/resistencia-cartucho/ Resistência Cartucho]
*[https://www.sinowellmetal.com/galvanized-steel-coil Galvanized Steel Coil]
*[https://hengze-steel.com/product/galvalume-steel-coil/ Galvalume Steel Coil]

[[Category:Heating]]

Ammonium polyphosphate

2018-03-20T15:09:46Z

173.165.237.1:

{{Chembox

| ImageFile = Ammoniumpolyphosphat.svg
| ImageSize =
| ImageAlt =

| IUPACName =
| OtherNames = Exolit AP 422, FR CROS 484, APP

| Section1 = {{Chembox Identifiers
| CASNo = 68333-79-9
| PubChem =
| SMILES =
}}
| Section2 = {{Chembox Properties
| Formula = [NH4PO3]n(OH)23; bulk density = 0,7 g/cm3
| MeltingPt =
| BoilingPt =
| Solubility =
}}
| Section3 = {{Chembox Hazards
| MainHazards =
| FlashPt =
| AutoignitionPt =
}}
}}
'''Ammonium polyphosphate''' commercially produced by [[Clariant]], (former business area of [[Hoechst AG]]), Budenheim and other sources is an inorganic salt of [[polyphosphoric acid]] and [[ammonia]] containing both chains and possibly branching. Its chemical formula is [NH4 PO3]n(OH)2 showing that each [[monomer]] consists of an [[orthophosphate]] radical of a [[phosphorus]] atom with three [[oxygen]]s and one negative charge neutralized by an [[ammonium]] [[cation]] leaving two bonds free to [[polymerize]]. In the branched cases some monomers are missing the ammonium anion and instead link to three other monomers.

The properties of ammonium polyphosphate depend on the number of monomers in each molecule and to a degree on how often it branches. Shorter chains (n<100) are more water sensitive and less thermally stable than longer chains (n>1000),<ref>[http://www.sinoharvest.com/products/Ammonium-Polyphosphate.shtml]</ref> but short polymer chains (''e.g.'' pyro-, tripoly-, and tetrapoly-) are more soluble and show increasing solubility with increasing chain length.<ref>{{cite patent|US|4041133}}</ref>

Ammonium polyphosphate can be prepared by reacting concentrated phosphoric acid with ammonia. However, iron and aluminum impurities, soluble in concentrated phosphoric acid, form gelatinous precipitates or "sludges" in ammonium polyphosphate at pH between 5 and 7.<ref>{{cite patent|US|4721519}}</ref> Other metal impurities such as copper, chromium, magnesium, and zinc form granular precipitates.<ref>{{cite patent|US|3044851}}</ref> However, depending on the degree of polymerization, ammonium polyphosphate can act as a [[chelating agent]] to keep certain metal ions dissolved in solution.<ref>[https://books.google.com/books?id=GP1caeWDUWkC&pg=PA51&lpg=PA51&dq=precipitation+ammonium+polyphosphate+solution&source=bl&ots=rVZdLjLDMq&sig=qyKpG82yckoQV6YoQEcgwhbR8Lo&hl=en&ei=BFDgS7eOGo_ENriY-Z4H&sa=X&oi=book_result&ct=result&resnum=10&ved=0CDkQ6AEwCQ#v=onepage&q=precipitation%20ammonium%20polyphosphate%20solution&f=false]</ref>

Ammonium polyphosphate is used as a food additive, [[emulsifier]], ([[E number]]: E545) and as a [[fertilizer]].

Ammonium polyphosphate (APP) is also used as a [[flame retardant]] in many applications such as paints and coatings, and in a variety of polymers: the most important ones are [[polyolefin]]s, and particularly polypropylene, where APP is part of intumescent systems.<ref>Weil, E.D., Levchik, S.V. Flame retardants for plastics and textiles, p. 16. Hanser Publishers, Munich, Germany, 2009</ref> Compounding with APP-based flame retardants in polypropylene is described in.<ref>[http://www.mindfully.org/Plastic/Flame/Ammonium-Polyphosphate-FlameApr02.htm As a flame retardant]</ref> Further applications are thermosets, where APP is used in unsaturated polyesters and gel coats (APP blends with synergists), epoxies and polyurethane castings (intumescent systems). APP is also applied to flame retard [[polyurethane]] foams.

Ammonium polyphosphates as used as flame retardants in polymers have long chains and a specific crystallinity (Form II). They start to decompose at 240 °C to form ammonia and phosphoric acid. The phosphoric acid acts as an acid catalyst in the dehydration of carbon-based poly-alcohols, such as cellulose in wood. The phosphoric acid reacts with alcohol groups to form heat-unstable phosphate [[ester]]s. The esters decompose to release carbon dioxide and regenerate the phosphoric acid catalyst. In the gas phase, the release of non-flammable carbon dioxide helps to dilute the oxygen of the air and flammable decomposition products of the material that is burning. In the condensed phase, the resultant carbonaceous char helps to shield the underlying polymer from attack by oxygen and radiant heat.<ref>{{Cite patent|US|4515632}}</ref> Use as an [[intumescent]] is achieved when combined with starch-based materials such as pentaerythritol and melamine as expanding agents. The mechanisms of intumescence and the mode of action of APP are described in a series of publications.<ref>Camino, G.; Luda, M.P. Mechanistic study of intumescence, p. 48 f, in Le Bras, M.; Camino, G.; Bourbigot, S.; Delobel, R. Eds., Fire retardancy of polymers; The use of intumescence, The Royal Society of Chemistry, Cambridge, UK, 1998</ref><ref>Bourbigot, S.; Le Bras, M. Intumescence flame retardants and char formation, p. 139 f, in Troitzsch, J. Ed. Plastics flammability handbook, 3rd Ed., Hanser Publishers, Munich, 2004</ref>

==References==
{{reflist}}

==External links==
*{{cite patent|US|2950961}}
*{{cite patent|US|4211546}}
*[http://www.specialchem4polymers.com/tc/ammonium-polyphosphate/index.aspx?id=description specialchem4polymers.com]

[[Category:Food additives]]
[[Category:Polymers]]
[[Category:Ammonium compounds]]

Fiat Bravo and Brava

2018-02-08T19:44:40Z

173.165.237.1: /* HGT Abarth */

{{Redirect|Fiat Bravo|the 2007 Bravo|Fiat Bravo (2007)|the car marketed in the United States as the Fiat Brava from 1978|Fiat 131}}
{{Use dmy dates|date=April 2014}}
{{Infobox automobile
| image = Trequartiantoq5.jpg
| caption = Fiat Bravo
| name = Fiat Bravo Fiat Brava
| aka = Fiat Bravissimo (Japan)
| production = 1995–2001
| predecessor = [[Fiat Tipo]]
| class = [[Small family car]] ([[C-segment|C]])
| assembly = [[Cassino, Italy|Cassino]], Piedimonte San Germano, [[Italy]]<ref name="bravo-guide.co.uk">{{cite web|url=http://www.bravo-guide.co.uk/press.htm|title=Fiat Press Information|accessdate=12 November 2008|publisher=Bravo-guide.co.uk}}</ref> [[Bursa]], [[Turkey]] (Brava only) [[Tychy]], [[Poland]]<ref>[http://www.auto-press.net/a:10-million-vehicles-produced-in-the-former-FSM-and-Fiat-Auto-Poland-factories 10 million vehicles produced in the former FSM and Fiat Auto Poland factories]</ref>
| body_style = 3-door [[hatchback]] (Bravo) 5-door [[fastback]] (Brava)
| layout = [[FF layout]]
| platform = [[Type Two platform]] ''(Tipo Due)''<ref>{{cite web|url=http://fiat-tipo-portugal.com/curiosidades.htm|title=Curiosidades Tipo|archiveurl=https://web.archive.org/web/20120305183446/http://fiat-tipo-portugal.com/curiosidades.htm|archivedate=5 March 2012|publisher=Fiat Tipo Portugal|accessdate=30 December 2013}}</ref>
| engine =
| transmission =
| successor = [[Fiat Stilo]]
| wheelbase = {{convert|2540|mm|in|1|abbr=on}}
| length = {{convert|4020|mm|in|1|abbr=on}} (Bravo) {{convert|4190|mm|in|1|abbr=on}} (Brava)
| width = {{convert|1750|mm|in|1|abbr=on}}
| height = {{convert|1420|mm|in|1|abbr=on}}
| weight =
| related = [[Fiat Marea]] [[Fiat Multipla]]
| designer = Centro Stile Fiat (1992)<ref>{{cite web|url=http://lexpansion.lexpress.fr/actualite-economique/megane-bravo-compte-a-rebours-pour-un-double-lancement_1349366.html|title= MEGANE, BRAVO COMPTE A REBOURS POUR UN DOUBLE LANCEMENT}} MEGANE, BRAVO COMPTE A REBOURS POUR UN DOUBLE LANCEMENT 18th September 1995.</ref>
}}

The '''Fiat Bravo''' and '''Fiat Brava''' (Type 182) are [[small family car]]s produced by the Italian automaker [[Fiat]] from 1995 to 2001. They were effectively two versions of the same car, the Bravo a three-door [[hatchback]] and the Brava a five-door [[fastback]].

The Bravo name was revived in January 2007, with the all new [[Fiat Bravo (2007)|Fiat Bravo]], a replacement of the [[Fiat Stilo|Stilo]]. The new version is available only with five doors. The name Brava was also used in the United States in the 1980s on the earlier [[Fiat 131]].

==History==
{{Multiple image
| align = left
| direction = horizontal
| image1 = Fiat Bravo 1.9 TD.jpg
| width1 = 170px
| caption1 = 3 door Fiat Bravo
| image2 = Fiat Bravo 1998 rear.jpg
| width2 = 170px
| caption2 = 3 door Fiat Bravo
}}
{{Multiple image
| align = left
| direction = horizontal
| image3 = Fiat Brava front 20080318.jpg
| width3 = 170px
| caption3 = 5 door Fiat Brava
| image4 = Fiat Brava rear 20080318.jpg
| width4 = 170px
| caption4 = 5 door Fiat Brava rear
}}

The Bravo and the Brava were replacements for [[Fiat|Fiat's]] successful, but ageing [[Fiat Tipo|Tipo]] model. The two cars were very different in styling detail and driving experience, the Bravo chassis being tuned for more precise handling, whilst the Brava was tuned for better comfort.

Even the interior trim and many of the body colours were unique to either one version or the other. Both cars had a two star safety rating on EuroNCAP. The cars came with all new engines, the base model using a 1.4 L twelve valve engine producing {{convert|80|PS|kW|0|abbr=on}}.

Three other [[gasoline|petrol]] engines were available: the {{convert|103|PS|kW|0|abbr=on}} 1.6 L 16 valve; the {{convert|113|PS|kW|0|abbr=on}} 1.8 L 16 valve engine and the top of the range 2.0 L twenty valve inline five unit used in the HGT model, which produced {{convert|147|PS|kW|0|abbr=on}} and which could take the car to a maximum speed of {{convert|213|km/h|mph|abbr=on}}, later in 1999 the 155 HGT model replaced the older model, power rising to {{convert|155|PS|kW|0|abbr=on}}.

Two [[turbodiesel]] engines were also available: both were 1.9 L four cylinder units, one producing {{convert|75|PS|kW|0|abbr=on}} and the other making {{convert|100|PS|kW|0|abbr=on}}. The Bravo/Brava was voted [[European Car of the Year]] on its launch.<ref>{{cite web|title=Rewind to 1996: Fiat Bravo/Brava. |url=http://www.quicks.co.uk/news/2013/rewind-1996-fiat-bravo-brava/ |publisher=Quicks |accessdate=23 January 2014 |deadurl=yes |archiveurl=https://web.archive.org/web/20140117191846/http://www.quicks.co.uk/news/2013/rewind-1996-fiat-bravo-brava/ |archivedate=17 January 2014 |df=dmy }}</ref>

In August 1996, the Bravo/Brava chassis spawned [[sedan (car)|saloon]] and [[station wagon|estate]] versions, badged [[Fiat Marea]], a car which was aimed at [[Ford Mondeo]] and [[Opel Vectra|Opel/Vauxhall Vectra]] buyers, which won praise for its large [[Trunk (automobile)|boot]].

Another car based on the Bravo/Brava underpinnings was launched in January 1999: the curious looking [[Fiat Multipla]], a six seater [[compact MPV]]. In 1999, the Bravo/Brava received a mild makeover, and it was discontinued in October 2001, being replaced by the all new [[Fiat Stilo]].

The cars were advertised as being silent, futuristic, economical and offering "The Choice". Fiat's Italian adverts said "Fiat Bravo. Fiat Brava. La Scelta." which roughly translates to "Fiat Bravo. Fiat Brava. The Choice", hinting to the fact that they're very similar cars but you can select between a sporty three door [[hatchback]] or a practical five door [[fastback]]. <ref>https://www.youtube.com/watch?v=flgNCrXaeA0</ref>

The Bravo and Brava were criticised as being a bit "futuristic" for their time, some reviewers really liked the way they looked, while others thought they were a bit odd. Peter Davis, Fiat's Styling Center director at the time, said that they started working on the Bravo and Brava right after they had finished working on the Coupe and the Barchetta, so they had the steam built up. He mentioned that they wanted to push the design to the limit, break the rules and discover every angle of the car, distinguishing it from the competitors.<ref>https://www.youtube.com/watch?v=jPi1CtWncKw</ref>

[[Jeremy Clarkson]] reviewed the Fiat Bravo and Brava in 1995, on the old format of ''[[Top Gear (1977 TV series)|Top Gear]]'', stating that "This is how an ordinary car can look like, if you put a bit of effort into it". He also stated : "I'm in a three door hatchback which you can buy for less than £10,000, and I'm having fun, and it's only got a 1.4 litre engine! A good looking car, that's nice to drive and cheap to run too." He also mentioned that the car feels rigid, there are no squeaks or rattles, and all the switches inside have a quality feel.<ref>https://www.youtube.com/watch?v=jPi1CtWncKw</ref>

==Makeover==
The Bravo/Brava received a mild makeover in 1999.

The 1.4L 12v engine was dropped in favour of the 1.2 16v unit from the [[Fiat Punto]], the 2.0L 20V engine of the HGT model gained VVT and VIS systems upping the power from {{convert|147|PS|kW|0|abbr=on}} to {{convert|155|PS|kW|0|abbr=on}}, the dashboard was redesigned and improved across all trim levels, the grilles of the cars were redesigned, the A/C unit was swapped with the automatic one from the [[Fiat Coupé]], and other small details about the cars were changed throughout the range of trims. The 1.9 [[turbodiesel]] was phased out in favour of 1.9 JTD diesel units (now with and {{convert|105|PS|kW|0|abbr=on|disp=or}}), to give even better economy and refinement. In the Greek market, all later model Bravas received the rear deck spoiler as standard.

==Special editions==

* '''Anniversaire''': introduced in 1997 for both cars, with only 1,100 pieces, celebrating Fiat's win of ''Car of the Year 1996'' for the Bravo/Brava duo, for the Western Europe market. It was a 1.6 16v Sx version, with metallic paint, electrically adjustable and heated mirrors, fog lights, front passenger airbag, ABS and a CD player instead of the Tape player.

* '''Evening Vale''': introduced in March 2000 for the Brava for the Western Europe market. It was a 1.2 16V/1.6 16V/1.9 JTD SX version, with special 14" wheel trims and automatic A/C.

* '''Formula''': introduced in 2001, for the Bravo, for the United Kingdom. It was a 1.2 16V SX version with the GT Trim's 15" wheels, GT's rear spoiler, electrically adjustable and heated mirrors, fog lights, CD Player and remote central locking.

* '''Limited Edition''': onwards from 2000, for the Hungarian market. Available for the 1.2 16V and 1.6 16V versions, it featured metallic paint, electrically adjustable and heated mirrors, fog lights, a passenger airbag and automatic A/C. The 1.6 16V also featured ABS.

* '''Special Edition''': limited Edition, but only for the Bravo.

* '''Steel''': last Bravo/Brava models, a "farewell" of October 2001 for the Western European market, before the duo was discontinued. Offered in 1.2 16v, 1.6 16v and 1.9 JTD Sx models, it featured Metallic Gray/Black/Blue paint, GT's 15" alloy wheels (Bravo) or Special 14" Wheel Trims (Brava), GT's rear spoiler, darkened rear lights (Bravo), "Steel" logo in the C column, electrically adjustable and heated mirrors, fog lights, passenger airbag, automatic A/C, CD Player, GT's steering wheel and shift knob wrapped in leather, two tone black/blue seats, white GT cluster and silver gt console and dash trim.

* '''Suite''': available only for the 1.6/1.8/1.9 JTD Bravo GT for the Swiss market, in Blue or Black metallic colours, featuring special seven spoke 15" alloy wheels, the GT's rear spoiler, '''Suite''' logo in the C-Column, front passenger airbag, side airbags, electrically adjustable and heated mirrors, fog lights, automatic A/C, remote central locking, a high quality four speaker CD player with a CD Changer, GT leather wrapped steering wheel and shift knob, silver center console and dash trim and a full leather interior in cream, dark brown, dark blue or black.

* '''Trofeo''': available only for the 1.2 Bravo Sx, for Western European markets, for 2000. Similar to the "Formula", it featured metallic Gray/Blue/Black/Sprint Blue/Sky Blue paint, GT's 15" alloy wheels painted with special gray paint, GT's rear spoiler, Trofeo written on the front wings, electrically adjustable and heated mirrors, fog lights, automatic A/C, GT's leather shift knob and steering wheel, white GT's cluster, silver center console and dash trim, blue/black two tone seats and door trim.

* '''Yellow''': Hungarian 1.2 16v Sx Bravo, featuring the GT's alloy wheels, electrically adjustable and heated mirrors, fog lights and only available in a distinct yellow.<ref>http://www.fiatbravo.hu/leirasok/view.php?id=96</ref>

==HGT Abarth==
In the end of 1999, Fiat introduced the [[Abarth]] accessories for the Bravo, available were more aggressive wheels and bodykit, performance was the same as the 2.0 HGT model. It was produced from 2000 to 2002.

==Engines==
{| class="wikitable" cellpadding="0" style="text-align:center; font-size:90%;"
|-
!Model 995:2003
!Engine
!Displacement
!Power
!Torque
!Note
!0-100km/h (Bravo - Brava)
|-
!colspan="7"|Petrol engines
|-
|'''1.4 S/SX'''||[[straight-4|I4]]||1,370 cc|| {{convert|80|PS|kW hp|0|abbr=on}} at 6000 rpm|| {{convert|112|Nm|lb·ft|0|abbr=on}} at 2750 rpm|| Until 1999|| 13.7s - 13.9s
|-
|'''80 SX/HSX'''||[[straight-4|I4]]||1,242 cc|| {{convert|82|PS|kW hp|0|abbr=on}} at 5500 rpm|| {{convert|113|Nm|lb·ft|0|abbr=on}} at 4250 rpm|| From 1999|| 12.5s - 13.0s
|-
|'''100 SX/HSX/ELX'''||[[straight-4|I4]]||1,581 cc|| {{convert|103|PS|kW hp|0|abbr=on}} at 5750 rpm|| {{convert|144|Nm|lb·ft|0|abbr=on}} at 4000 rpm|| - || 11.0s - 11.5s
|-
|'''115 ELX/HLX/GT'''||[[straight-4|I4]]||1,747 cc|| {{convert|113|PS|kW hp|0|abbr=on}} at 6100 rpm|| {{convert|154|Nm|lb·ft|0|abbr=on}} at 4400 rpm|| - || 10.0s - 10.3s
|-
|'''HGT'''||[[straight-5|I5]]||1,998 cc|| {{convert|147|PS|kW hp|0|abbr=on}} at 6100 rpm|| {{convert|186|Nm|lb·ft|0|abbr=on}} at 4500 rpm||Bravo only, Until 1999|| 8.5s
|-
|'''155 HGT'''||[[straight-5|I5]]||1,998 cc|| {{convert|155|PS|kW hp|0|abbr=on}} at 6500 rpm|| {{convert|186|Nm|lb·ft|0|abbr=on}} at 3750 rpm||Bravo only, From 1999|| 8.0s
|-
!colspan="7"|Diesel engines
|-
|'''1.9 D SX'''||[[straight-4|I4]]||1,929 cc||{{convert|65|PS|kW hp||abbr=on}} at 4600 rpm||{{convert|119|Nm|lbft||abbr=on}} at 2000 rpm|| - || 17.8s - 17.8s
|-
|'''TD 75 SX'''||[[straight-4|I4]]||1,910 cc||{{convert|75|PS|kW hp||abbr=on}} at 4200 rpm||{{convert|147|Nm|lbft||abbr=on}} at 2750 rpm|| - || 15.1s - 15.5s
|-
|'''TD 100 SX/ELX'''||[[straight-4|I4]]||1,910 cc||{{convert|100|PS|kW hp||abbr=on}} at 4200 rpm||{{convert|200|Nm|lbft||abbr=on}} at 2250 rpm|| - || 10.8s - 11.0s
|-
|'''JTD 105 SX/ELX/GT'''||[[straight-4|I4]]||1,910 cc||{{convert|105|PS|kW hp||abbr=on}} at 4000 rpm||{{convert|200|Nm|lbft||abbr=on}} at 1500 rpm||From 1999|| 10.4s - 10.6s
|-
|'''JTD 100 SX/ELX/GT'''||[[straight-4|I4]]||1,910 cc||{{convert|100|PS|kW hp||abbr=on}} at 4000 rpm||{{convert|200|Nm|lbft||abbr=on}} at 1500rpm||From 2001 to 2003|| 10.4s - 10.6s
|}

==Brazil==
The Brava was produced until 2003 in Brazil for the home market and export, but in the former, the engines available were:

* Brava Sx/Elx 1.6 16v {{convert|106|PS|kW|0|abbr=on}}
* Brava HGT 1.8 16v ({{convert|127|PS|kW|0|abbr=on}} or {{convert|132|PS|kW|0|abbr=on}})

==References==
{{Reflist}}

==External links==
*{{Commons category-inline|Fiat Bravo}}
*{{Commons category-inline|Fiat Brava}}

{{Fiat}}
{{Modern European Fiat vehicles}}

{{DEFAULTSORT:Fiat Bravo Brava}}
[[Category:Fiat vehicles|Bravo Brava]]
[[Category:Compact cars]]
[[Category:Euro NCAP small family cars]]
[[Category:Hatchbacks]]
[[Category:1990s automobiles]]
[[Category:2000s automobiles]]
[[Category:Cars introduced in 1995]]
[[Category:Hot Hatch]]
[[Category:Cars of Turkey]]
[[Category:Front-wheel-drive vehicles]]

Ulmus minor 'Atinia'

2018-01-31T17:10:54Z

173.165.237.1: /* Description */

{{DISPLAYTITLE:''Ulmus minor'' 'Atinia'}}
{{Infobox cultivar
| name = ''Ulmus minor'' 'Atinia'
| species = ''[[Ulmus minor]]''
| cultivar = 'Atinia'
| image = Ulmus-minor-atinia-brighton-south-east-entrance-to-preston-park.jpg
| image_caption = English Elm, Brighton, 1992
| origin = Italy
}}

The '''[[Field Elm]]''' [[cultivar]] '''''Ulmus minor'' 'Atinia'''',<ref name=coleman2016>{{cite journal|first1=M.|last1=Coleman|first2=S.W.|last2=A’Hara|first3=P.R.|last3=Tomlinson|first4=P.J.|last4=Davey|date=2017|journal=New Journal of Botany|title=Elm clone identification and the conundrum of the slow spread of Dutch Elm Disease on the Isle of Man|volume=6|issue=2-3|pages=79-89}}</ref> commonly known as the '''English Elm''', formerly '''Common Elm''' and '''Horse May''',<ref name = Davey>{{cite book|first=Frederick Hamilton|last=Davey|title=Flora of Cornwall|year=1909|pages=401|url=https://babel.hathitrust.org/cgi/pt?id=mdp.39015069772864;view=2up;seq=508}} Republished 1978 by EP Publishing, Wakefield. {{ISBN|0-7158-1334 X}}</ref> and more lately the '''Atinian Elm'''<ref>{{Cite web | title = A Reappraisal of British Elms based on DNA Evidence | author-last = Adams | author-first = Ken | work = Essex botany and mycology groups| date = 2006 | accessdate = 2017-02-23 | url = https://web.archive.org/web/20160304071455/http://www.s231645534.websitehome.co.uk/dna__elm_origins.htm}}</ref> was, before the spread of [[Dutch elm disease]], the most common field elm in central southern England, though not native there, and one of the largest and fastest-growing [[deciduous]] [[tree]]s in Europe. [[R. H. Richens]] noted that there are elm-populations in north-west Spain, in northern Portugal and on the Mediterranean coast of France that "closely resemble the English Elm" and appear to be "trees of long standing" in those regions rather than recent introductions.<ref>Richens, R. H., ''Elm'' (Cambridge, 1983), p.18, p.90</ref><ref>[http://www.icnf.pt/portal/florestas/aip/resource/img/arv-mon-pt/1-031-antig.jpg/view Specimen of tree labelled ''U. procera'' in Portugal, icnf.pt]</ref> [[Augustine Henry]] had earlier noted that the supposed English Elms planted extensively in the [[Royal Palace of Aranjuez|Royal Park at Aranjuez]] from the late 16th century onwards, specimens said to have been introduced from England by [[Philip II of Spain|Philip II]]<ref name="Richens, R. H. 1983 p.276">Richens, R. H., ''Elm'' (Cambridge, 1983), p.276</ref> and "differing in no respects from the English Elm in England", behaved as native trees in Spain. He suggested that the tree "may be a true native of Spain, indigenous in the alluvial plains of the great rivers, now almost completely deforested".<ref name=Elwes>Elwes, H. J. & Henry, A. (1913). ''[http://fax.libs.uga.edu/QK488xE4/1f/trees_of_britain_and_ireland_vol_7.pdf The Trees of Great Britain & Ireland]''. Vol. VII. 1848–1929. Republished 2004 Cambridge University Press, {{ISBN|9781108069380}}</ref>

Richens believed that English Elm was a particular clone of the variable species ''[[Ulmus minor]]'', referring to it as ''Ulmus minor'' var. ''vulgaris''.<ref name=Richens>[https://books.google.com/books?id=0g49AAAAIAAJ&pg=PA279&lpg=PA279&dq=ulmus+wyssotzky&source=bl&ots=ZOBXkCNqaj&sig=4u_Wan9HOmHkEgc8ssTvxyd1iQ4&hl=en&ei=dnQySsz7IYWOjAfvt7X9CQ&sa=X&oi=book_result&ct=result&resnum=10#v=onepage&q=ulmus%20wyssotzky&f=false Richens, R. H., ''Elm'', Cambridge University Press, 1983]</ref> A 2004 survey of genetic diversity in Spain, Italy and the UK confirmed that English Elms are indeed genetically identical, clones of a single tree, said to be [[Columella]]'s 'Atinian Elm',<ref name = Gil>{{cite journal|journal=Nature|last=Gil|first=L.|display-authors=etal|date=2004|title=English Elm is a 2,000-year-old Roman Clone|volume=431|pages=1053|publisher=Nature Publishing Group|location=London|url=https://www.researchgate.net/profile/Carmen_Collada/publication/8207367_Phylogeography_English_elm_is_a_2000-year-old_Roman_clone/links/0fcfd5142d377aef97000000/Phylogeography-English-elm-is-a-2-000-year-old-Roman-clone.pdf}}.</ref> once widely used for [[training vines]], and assumed to have been brought to the British Isles by [[Ancient Rome|Romans]] for that purpose.<ref>[http://www.treecouncil.org.uk Tree News, Spring/Summer 2005, Publisher Felix Press]</ref> Thus, despite its name, the origin of the tree is widely believed to be Italy,<ref name=Gil/><ref>{{cite news | url = http://news.bbc.co.uk/2/hi/science/nature/3959561.stm | title = English elm 'brought by Romans' | publisher = BBC | accessdate= 2008-12-21 | date=2004-10-28}}</ref> though the clone is no longer found there and has not yet been identified further east.<ref name=Heybroek>Heybroek, Hans M, 'The elm, tree of milk and wine' (2013), sisef.it/iforest/contents/?id=ifor1244-007</ref>

Dr Max Coleman of the [[Royal Botanic Garden, Edinburgh]] writes (2009): "The advent of DNA fingerprinting has shed considerable light on the question. A number of studies have now shown that the distinctive forms that [[Ronald Melville|Melville]] elevated to species and Richens lumped together as field elm are single clones, all genetically identical, that have been propagated by vegetative means such as cuttings or root suckers. This means that enigmatic British elms such as ... English Elm have turned out to be single clones of field elm."<ref>Max Coleman, ed.: ''Wych Elm'' ([[Royal Botanic Garden Edinburgh]] publication, 2009; {{ISBN|978-1-906129-21-7}}); p. 22</ref> Most floras and field guides, however, do not list English Elm as a form of ''Ulmus minor'', but rather as ''Ulmus procera''.

==Synonyms (chronological)==
<section begin=Synonymy />
*''Ulmus sativa'' Mill.<ref name = miller1768>{{cite book|first=Philip|last=Miller|volume=3|edition=8|pages=674|year=1768|title=The gardeners dictionary|url=https://archive.org/stream/gardenersdictio3mill#page/674/mode/1up}}</ref>
*''Ulmus campestris'' L. var. ''vulgaris'' Aiton <ref name = aiton1789>{{cite book|first=William|last=Aiton|volume=1|pages=319|year=1789|title=Hortus Kewensis|url=https://archive.org/stream/mobot31753000624095#page/319/mode/1up}}</ref>
*''Ulmus procera'' Salisb.<ref name = salisbury1796>{{cite book|first=Richard Anthony|last=Salisbury|pages=391|year=1796|title=Prodromus stirpium in horto ad Chapel Allerton vigentium|url=https://archive.org/stream/mobot31753000639358#page/391/mode/1up}}</ref>
*''Ulmus atinia'' J. Walker <ref name = walker1808>{{cite book|first=John|last=Walker|pages=70-72|year=1808|title=Essays on natural history and rural economy|url=https://archive.org/stream/essaysonnatural00walkgoog#page/n80/mode/1up}}</ref>
*''Ulmus surculosa'' Stokes<ref name=Stokes>{{cite book|first=Jonathan|last=Stokes|pages=35|volume=2|year=1812|title=A botanical materia medica|url=https://archive.org/stream/b21299687_0002#page/35/mode/2up}}</ref>
*[''Ulmus suberosa'' Smith, Loudon, Lindley - disputed]
*''Ulmus minor'' Mill. var. ''vulgaris'' (Aiton) Richens <ref name = richens1977>{{cite journal|journal=Taxon|title=New Designations in Ulmus minor Mill.|first=Richard Hook|last=Richens|volume=26|pages=583-584|date=1977}}</ref>
*''Ulmus minor'' Mill. subsp. procera (Salisb.) Franco.<ref name = anjardbot>{{cite journal|journal=Anales del Jardín Botánico de Madrid|title=Notas Breves|first=João Manuel Antonio|last=do Amaral Franco|volume=50|issue=2|pages=259|date=1992|url=http://www.rjb.csic.es/jardinbotanico/ficheros/documentos/pdf/anales/1992/Anales_50(2)_259_266.pdf}}</ref>
*''Ulmus procera'' 'Atinia' <ref name = heybroek2003>{{cite journal|journal=Mitteilungen der Deutschen Dendrologischen Gesellschaft|title=Die vierte deutsche Ulme? Ein Baum mit Geschichte|first=Hans|last=Heybroek|volume=88|pages=117-119|date=2003}}</ref>
<section end=Synonymy />

==Description==
The tree often exceeded 40 m (about 130 feet) in height with a trunk < 2 m (6.5 feet) [[diameter at breast height|d.b.h]].<ref name=Bean>Bean, W. J. (1981). ''Trees and shrubs hardy in Great Britain''. Murray, London.</ref> The largest specimen ever recorded in England, at [[Forthampton]] Court, near [[Tewkesbury]], was 46 m (151 feet) tall.<ref name=Elwes/> While the upper branches form a fan-shaped crown, heavy more horizontal boughs low on the bole often give the tree a distinctive 'figure-of-eight' silhouette. The small, reddish-purple hermaphrodite apetalous flowers appear in early spring before the leaves. The [[leaf|leaves]] are dark green, almost [[leaf shape|orbicular]], < 10 cm long, without the pronounced [[leaf shape|acuminate]] tip at the apex typical of the genus. They flush a lighter green in April, about a month earlier than most [[Field Elm]]. Since the tree does not produce long shoots in the canopy, it does not develop the markedly pendulous habit of some Field Elm. The bark of old trees is scaly, unlike the vertically-furrowed bark of ancient Field Elm. The bark of English Elm [[Basal shoot|suckers]], like that of [[Ulmus × hollandica 'Major'|Dutch Elm]] suckers and of some Field Elm, can be corky, but Dutch Elm suckers may be distinguished from English by their straighter, stouter twigs, bolder 'herringbone' pattern, and later flushing.

The tree does not produce fertile [[seed]] as it is female-sterile, and natural regeneration is entirely by [[root]] [[Basal shoot|suckers]].<ref name=Richens/><ref name=White>White, J. & More, D. (2002). ''Trees of Britain & Northern Europe''. Cassell, London</ref> Seed production in England was often unknown in any case.<ref name=Hanson>{{cite book | last=Hanson | first=M. W. | title=Essex elm | publisher=Essex Field Club | location=London | year=1990 | isbn=978-0-905637-15-0 | url=http://www.essexfieldclub.org.uk/portal/p/Archive/s/109/o/0001|access-date=2017-10-24}}</ref> By the late 19th century, urban specimens in Britain were often grafted on to [[wych elm]] root-stock to eliminate suckering; [[Augustine Henry|Henry]] noted that this method of propagation seldom produced good specimens.<ref name = Elwes/>
<gallery>
File:English Elm at Powderham.jpg|English Elm at [[Powderham Castle|Powderham]], before 1913
File:Ulmus minor 'Procera'.jpg|English Elm, 1904
File:Bark of Ulmus minor 'Procera'.jpg|Bark of English Elm
Image:Umvvulgaris-WC-2003.jpg|Leaves from a specimen tree in Sussex, England (2009)
File:Leaves of Ulmus minor 'Procera', short shoots of old trees.jpg|Dried short-shoot leaves of mature trees in Edinburgh (August)
Image:Elm Leaves - geograph.org.uk - 990660.jpg|Juvenile leaves in hedgerow
</gallery>

==Pests and diseases==
Owing to its homogeneity, the tree has proven particularly susceptible to [[Dutch elm disease]], but immature trees remain a common feature in the English countryside courtesy of the ability to sucker from roots. After about 20 years, these suckers too become infected by the fungus and killed back to ground level. English Elm was the first elm to be [[genetically engineered]] to resist disease, at the [[University of Abertay Dundee]].<ref>{{cite news| url=https://www.theguardian.com/print/0,3858,4246134-103690,00.html | work=The Guardian | location=London | title=Scientists modify elm to resist disease that killed millions of trees in Britain | first=James | last=Meek | date=2001-08-28 | accessdate=2010-05-26}}</ref> It was an ideal subject for such an experiment, as its sterility meant there was no danger of its introgression into the countryside.

In the United States, English Elm was found to be one of the most preferred elms for feeding by the Japanese Beetle ''[[Popillia japonica]]''.<ref name="Miller, b">Miller, F., Ware, G. and Jackson, J. (2001). [http://www.bioone.org/doi/full/10.1603/0022-0493%282001%29094%5B0445%3APOTCEU%5D2.0.CO%3B2 Preference of Temperate Chinese Elms (Ulmuss spp.) for the Feeding of the Japanese Beetle (Coleoptera: Scarabaeidae)]. ''Journal of Economic Entomology'' 94 (2). pp 445-448. 2001. Entom. Soc.of America.</ref>

The leaves of the English Elm in the UK are mined by ''[[Stigmella ulmivora]]''.

==Uses==
{|class="toccolours" style="float: right; margin-left: 1em; margin-right: 2em; font-size: 85%; background:#dbf7c5; color:black; width:30em; max-width: 40%;" cellspacing="5"
|style="text-align: left;" |
... He liked to be alone, feeling his soul heavy with its own fate. He would sit for hours watching the elm trees standing in rows like giants, like warriors across the country. The Earl had told him that the Romans had brought these elms to Britain. And he seemed to see the spirit of the Romans in them still. Sitting there alone in the spring sunshine, in the solitude of the roof, he saw the glamour of this England of hedgerows and elm trees, and the labourers with slow horses slowly drilling the sod, crossing the brown furrow, and the chequer of fields away to the distance.

|-
|style="text-align: left;" | – From '''[[D. H. Lawrence]]''', ''[[The Ladybird]]'' (1923).<ref>D. H. Lawrence, ''The Ladybird'' (Penguin edition, 1960, p.69)</ref>
|}

The English Elm was once valued for many purposes, notably as water pipes from hollowed trunks, owing to its resistance to rot in saturated conditions. It is also very resilient to crushing damage and these two properties led to its widespread use in the construction of jetties, timber piers and lock gates, etc. It was used to a degree in furniture manufacture but not to the same extent as oak, because of its greater tendency to shrink, swell and split, which also rendered it unsuitable as the major timber component in shipbuilding and building construction. The wood has a density of around 560 kg per cubic metre.<ref>[http://www.nichetimbers.co.uk/native-hardwood/elm/ Elm]. Niche Timbers. Accessed 19-08-2009.</ref>

However, English Elm is chiefly remembered today for its aesthetic contribution to the English countryside. In 1913 [[Henry John Elwes|Henry Elwes]] wrote that "Its true value as a landscape tree may be best estimated by looking down from an eminence in almost any part of the valley of the Thames, or of the Severn below Worcester, during the latter half of November, when the bright golden colour of the lines of elms in the hedgerows is one of the most striking scenes that England can produce".<ref name="Elwes"/>

==Cultivation==
The introduction of the Atinian elm to Spain from Italy is recorded by the Roman agronomist [[Columella]].<ref name=Columella>Columella, Lucius Junius Moderadus (c.A D 50) ''De re rustica'', v.6</ref> It has also been identified by [[Hans M. Heybroek|Heybroek]] as the elm grown in the vineyards of the Valais, or Wallis, canton of Switzerland.<ref>[http://bioportal.naturalis.nl/nba/result?nba_request=http%253A%252F%252Fapi.biodiversitydata.nl%252Fv0%252F%252Fmultimedia%252Fget-multimedia-object-for-specimen-within-result-set%252F%253FunitID%253DL.4214289_01561868738%2526searchID%253Dee1907d7492a3dc38517675f48665771#prettyPhoto/0/ bioportal.naturalis.nl L.4214289 ''Ulmus procera'' 'Atinia']</ref><ref>[http://bioportal.naturalis.nl/nba/result?nba_request=http%253A%252F%252Fapi.biodiversitydata.nl%252Fv0%252F%252Fmultimedia%252Fget-multimedia-object-for-specimen-within-result-set%252F%253FunitID%253DL.4214286_045192863%2526searchID%253D4a86b5774a96e8e07acb4bfb8d61b890#prettyPhoto/0/ bioportal.naturalis.nl L.4214286 ''Ulmus procera'' 'Atinia']</ref><ref>[http://bioportal.naturalis.nl/nba/result?nba_request=http%253A%252F%252Fapi.biodiversitydata.nl%252Fv0%252F%252Fmultimedia%252Fget-multimedia-object-for-specimen-within-result-set%252F%253FunitID%253DL.4214283_1471483012%2526searchID%253D8bb8e372f5b13df1b296916ed3946ef0#prettyPhoto/0/ bioportal.naturalis.nl L.4214283 ''Ulmus procera'' 'Atinia']</ref> Although there is no record of its introduction to Britain from Spain, it has long been believed<ref>Loudon, John Claudius, ''Arboretum et fruticetum Britannicum; or, The trees and shrubs of Britain'', Vol. 3 (1838)</ref> that the tree arrived with the [[Ancient Rome|Romans]], a hypothesis supported by the discovery of pollen in an excavated Roman vineyard. It is likely the tree was used also as a source of leaf hay.<ref name="Heybroek"/> Elms said to be English Elm, and reputedly brought to Spain from England by [[Philip II of Spain|Philip II]], were planted extensively in the [[Royal Palace of Aranjuez|Royal Park at Aranjuez]] and the [[Buen Retiro Park|Retiro Park, Madrid]] from the late 16th century onwards (see '''Hybrids''' below).<ref name=Richens/><ref>Elwes, H. J., & Henry, A., The Trees of Great Britain & Ireland (Private publication, Edinburgh, 1913), Vol. VII, p.1908</ref>

More than a thousand years after the departure of the Romans from Britain, English Elm found far greater popularity, as the preferred tree for planting in the new [[Common Hawthorn|hawthorn]] hedgerows appearing as a consequence of the [[Enclosure]] movement, which lasted from 1550 to 1850. In parts of the [[Severn Valley]], the tree occurred at densities of over 1000 per square kilometre, so prolific as to have been known as the 'Worcester Weed'.<ref name=Wilkinson>Wilkinson, G. (1984). ''Trees in the Wild and Other Trees and Shrubs''. Stephen Hope Books. {{ISBN|0-903792-05-2}}.</ref> In the eastern counties of England, however, hedgerows were usually planted with local [[Field Elm]], or with suckering [[Ulmus × hollandica|hybrids]].<ref>Richens, R. H., ''Elm'' (Cambridge, 1983), Ch.14</ref> When elm became the tree of fashion in the 18th and 19th centuries, avenues and groves of English Elm were often planted, among them the elm-groves in [[The Backs]], [[Cambridge]].<ref>Photographs of English Elm in The Backs in ''101 Views of Cambridge'', Rock Bros. Ltd., c.1900</ref>

English Elm was introduced into Ireland,<ref>Elwes, H. J. & Henry, A. (1913). ''The Trees of Great Britain & Ireland'', Vol.7, p.1920 [http://fax.libs.uga.edu/QK488xE4/1f/trees_of_britain_and_ireland_vol_7.pdf]</ref> and as a consequence of Empire has been cultivated in eastern North America and widely in south-eastern Australia and New Zealand. It is still commonly found in Australia and New Zealand, where it is regarded at its best as a street or avenue tree.<ref name=Auckland>{{cite journal|first1=Mike|last1=Wilcox|first2=Chris|last2=Inglis|journal=Auckland Botanical Society Journal|title=Auckland's elms|volume=58|issue=1|date=2003|pages=38-45|publisher=Auckland Botanical Society|url=http://bts.nzpcn.org.nz/bts_pdf/ABJ58%281%292003-38-45-Elms.pdf}}</ref><ref>Lefoe, Gregory K., 'Elm Trees', emelbourne.net.au</ref><ref>[http://vhd.heritage.vic.gov.au/vhd/heritagevic#search:simple:user:list:database|places:ulmus:1 Victorian Heritage Database]</ref> It was also planted as a street tree on the American West Coast, notably in [[St Helena, California]],<ref name=Dreistadt>Dreistadt, S, Dahlsten, D. L., and Frankie, G. W. (1990). Urban Forests and Insect Ecology. ''BioScience''. Vol. 40, No. 3 (March 1990). pp. 192 - 198. University of California Press.</ref> and it has been planted in South Africa.<ref name=Troup>[[Robert Scott Troup|Troup]], R. S. (1932). ''Exotic forest trees in the British Empire''. Oxford Clarendon Press. ASIN: B0018EQG9G</ref>
<gallery>
Image:Preston Church, Brighton - geograph.org.uk - 1546696.jpg|[[St Peter's Church, Preston Village, Brighton]], with English Elms regrowing after lopping (1951) (Photo: Les Whitcomb)
Image:English elm in east sussex.jpg|English Elms in hedgerow, [[Alfriston]], East Sussex (1996)
Image:Ulmus minor atinia brighton preston park.jpg|Hourglass-shaped English Elm, Preston Park, Brighton (1992)
Image:PP-5-71990 (25).JPG|English Elm, Preston Park, Brighton (2004)
Image:Brighton Museum - geograph.org.uk - 1169622.jpg|Winter silhouette of English Elm, Brighton (2009)
Image:Elm trees on Royal Parade, Parkville, Melbourne.jpg|English Elms on [[Royal Parade, Melbourne|Royal Parade, Parkville]], Melbourne (2012)
File:Cootamundra Adams Street.JPG|English Elms in [[Cootamundra, New South Wales]], one trimmed for power line (2015)
</gallery>

==Notable trees==
Mature English Elms are now only very rarely found in the UK beyond Brighton (see below) and Edinburgh. One large tree survives in [[Leicester]] in Cossington Street Recreation Ground. Several survive in [[Edinburgh]] (2015): one in [[Rosebank Cemetery]] (girth 3 metres), one in Founders Avenue, [[Fettes College]], and one in [[Inverleith Park]] (east avenue), while a majestic open-grown specimen (3 metres) in Claremont Park, [[Leith Links]], retains the dense fan-vaulted crown iconic in this cultivar. There is an isolated mature English Elm in the cemetery at [[Dervaig]], Isle of Mull, Scotland.

Some of the most significant remaining stands are to be found overseas, notably in Australia where they line the streets of [[Melbourne]], protected by [[geography]] and [[quarantine]] from [[disease]].<ref name=Spencer>Spencer, R., Hawker, J. and Lumley, P. (1991). ''Elms in Australia''. Australia: Royal Botanic Gardens, Melbourne. {{ISBN|0-7241-9962-4}}</ref><ref>[http://2.bp.blogspot.com/-ehIbJgZ3HMM/UL4roHacROI/AAAAAAAAMFw/4B7LsC65cbA/s1600/IMG_3909.jpg Photograph of English Elm in Melbourne, 2.bp.blogspot.com]</ref> An avenue of 87 English Elms, planted c.1880, lines the entrance to the winery of [[Rutherglen wine region|All Saints Estate, Rutherglen]], [[Victoria (Australia)|Victoria]];<ref>English Elm avenue, All Saints Estate, Rutherglen, allsaintswine.com.au [http://www.allsaintswine.com.au/the-estate/our-history], rutherglenvic.com [http://www.rutherglenvic.com/attractions/all-saints-estate], 2bustickets.blogspot.co.uk [http://2bustickets.blogspot.co.uk/2009/11/rutherglen-to-beechworth.htm] l</ref> a double avenue of 400 English Elms, planted in 1897 and 1910–15, lines [[Royal Parade, Melbourne|Royal Parade, Parkville]], Melbourne.<ref>English Elm in Melbourne, emelbourne.net.au [http://www.emelbourne.net.au/biogs/EM00514b.htm], gardendrum.com [http://gardendrum.com/2014/06/25/save-melbournes-elms-as-a-citizen-forester/]</ref><ref>English Elm in Victoria, Victorian Heritage Database, [http://vhd.heritage.vic.gov.au/vhd/heritagevic#search:simple:user:list:database|places:ulmus procera:1]
[http://vhd.heritage.vic.gov.au/vhd/heritagevic#search:simple:user:list:database|places:ulmus procera:2]</ref><ref>[https://www.flickr.com/photos/30554196@N06/8749101117 English Elms on Royal Parade, Melbourne, flickr.com]</ref> A large free-standing English Elm in [[Traralgon]], Victoria, shows the 'un-English' growth-form<ref>English Elm in Traralgon, Victoria, vhd.heritage.vic.gov.au [http://vhd.heritage.vic.gov.au/images/vhr/150154.jpg] [http://vhd.heritage.vic.gov.au/vhd/heritagevic#detail_places;70701]</ref> of the tree in tropical latitudes.<ref>[http://www.resistantelms.co.uk/english-elm/ 'The growth and ultimate form of English Elm', resistantelms.co.uk]</ref> However, many of the Australian trees, now over 100 years old, are succumbing to old age, and are being replaced with new trees raised by material from the older trees budded onto Wych Elm ''[[Ulmus glabra]]'' rootstock.<ref name=Fitzgibbon>Fitzgibbon, J. (2006) Royal Parade Elm Replacement. ''Elmwatch'', Vol. 16 No. 1, March 2006</ref> In New Zealand a "massive individual" stands at 36 Mt Albert Road, Auckland.<ref name=Auckland/> In the United States, several fine trees survive at Boston Common, Boston, and in [[New York City]],<ref>[http://centralpark-ny.com/assets/trees/English-ElmcPB040384.jpg English Elm in Central Park, New York, centralpark-ny.com]</ref> notably the [[Hangman's Elm]] in [[Washington Square Park]],<ref name=Barnard>Barnard, E. S. (2002). ''New York City Trees''. Columbia University Press</ref> while in Canada four 130-year English Elms, inoculated against disease, survive on the Back Campus field of the [[University of Toronto]].<ref>Photograph of English Elms in University of Toronto: Janet Harrison, nativeplantwildlifegarden.com [http://nativeplantwildlifegarden.com/dirt-to-turf/]</ref>
<gallery>
Image:Crystal Palace Great Exhibition tree 1851.png|One of three English Elms (lower branches removed) around which the Crystal Palace was built for the [[The Great Exhibition|Great Exhibition]], 1851<ref>Clouston, B., Stansfield, K., eds., ''After the Elm'' (London, 1979), p.55</ref>
Image:Crystal Palace interior.jpg|A coloured lithograph of the same tree (1851)
Image:English Elm avenue.jpg|English Elm avenue in [[Fitzroy Gardens, Melbourne]] (2006)
Image:Hangman's Elm by David Shankbone.jpg|[[Hangman's Elm]], [[Washington Square Park]], New York (2007)
Image:Large English Elm at West Point, NY 4 Sep 2009.jpg|One of two large English Elms near [[Trophy Point]] at [[United States Military Academy|West Point, NY]] (2009)
Image:Barns at Upper Swell - geograph.org.uk - 1718618.jpg|The [[Swell, Gloucestershire|Upper Swell]] elms (2010) currently undergoing tests by the [[Conservation Foundation, UK|Conservation Foundation]]<ref>The Conservation Foundation's Great British Elm Experiment map of parent trees: [http://www.conservationfoundation.co.uk/content.php?id=178]</ref>
File:Ulmus minor 'Procera'. Claremont Park, Edinburgh.jpg|One of the last old English Elms in Edinburgh (2016)
</gallery>

===Brighton and the 'cordon sanitaire'===
Although the English Elm population in Britain was almost entirely destroyed by Dutch elm disease, mature trees can still be found along the south coast Dutch Elm Disease Management Area in [[East Sussex]]. This 'cordon sanitaire', aided by the prevailing south westerly onshore winds and the topographical niche formed by the [[South Downs]], has saved many mature elms. Amongst these are possibly the world's oldest surviving English Elms, known as the 'Preston Twins' in [[Preston Park, Brighton|Preston Park]], both with trunks exceeding 600 cm in circumference (2.0 m [[d.b.h.]]) though the larger tree lost two limbs in August 2017 following high winds.<ref name="dail_Euro">{{Cite web | title = Europe's biggest elm tree splits in two and crashes to the ground | author = | work = Mail Online | date = 21 August 2017 | accessdate = 2017-08-22 | url = http://www.dailymail.co.uk/news/article-4810562/Europe-s-biggest-elm-tree-splits-two.html }}</ref><ref name="thea_Scra">{{Cite web | title = Scramble to save the oldest elm in world | author = | work = The Argus | date = 22 August 2017 | accessdate = 2017-08-22 | url = http://www.theargus.co.uk/NEWS/15486732.Scramble_to_save_the_oldest_elm_in_world/ }}</ref>

<gallery>
Image:DED control notice.jpg|Sign on A27 road, Brighton, England
Image:World Champion English elm.JPG|The oldest known English Elms in the UK, the 'Preston Twins', Brighton, 2008
File:English Elm Preston Park Brighton.jpg|The larger of the twins, 2006
</gallery>

==Cultivars==
A small number of putative [[cultivar]]s have been raised since the 18th and early 19th centuries,<ref name=Green>{{cite journal |last=Green |first=Peter Shaw |authorlink=Peter Shaw Green |date=1964 |title=Registration of cultivar names in Ulmus|url=https://archive.org/stream/arnoldiaarno_21#page/40/mode/2up/|journal=Arnoldia |volume=24|pages=41–80 |number=6–8 |publisher=[[Arnold Arboretum]], [[Harvard University]] |access-date=16 February 2017}}</ref> three of which are now almost certainly lost to cultivation:
[[Ulmus 'Acutifolia'|'Acutifolia']], [[Ulmus minor 'Variegata'|'Atinia Variegata']], [[Ulmus 'Folia Aurea'|'Folia Aurea']], [[Ulmus 'Pyramidalis'|'Pyramidalis']].
Though usually listed as an English Elm cultivar, ''Ulmus'' [[Ulmus 'Louis van Houtte'|'Louis van Houtte']] "cannot with any certainty be referred to as ''Ulmus procera'' [ = 'Atinia'] " (W. J. Bean).<ref name=Bean/>

==Hybrids, hybrid cultivars, and mutations==
Crossability experiments conducted at the [[Arnold Arboretum]] in the 1970s apparently succeeded in hybridizing English Elm with [[Ulmus glabra|''U. glabra'']] and [[Ulmus rubra|''U. rubra'']], both also [[protogynous]] species. However, the same experiments also shewed English Elm to be self-compatible which, in the light of its proven female-sterility, must cast doubt on the identity of the specimens used.<ref name=Hans>Hans, A. S. (1981). Compatibility and Crossability Studies in Ulmus. ''Silvae Genetica'' 30, 4 - 5 (1981).</ref> A similar doubt must hang over [[Augustine Henry|Henry]]'s observation that the 'English Elms' at [[Royal Palace of Aranjuez|Aranjuez]] (see '''Cultivation''' above) "produced every year fertile seed in great abundance",<ref>Elwes, H. J. & Henry, A. (1913). ''The Trees of Great Britain & Ireland'', Vol.7, p.1908 [http://fax.libs.uga.edu/QK488xE4/1f/trees_of_britain_and_ireland_vol_7.pdf]</ref> seed said to have been taken "all over Europe", presumably in the hope that it would grow into trees like the royal elms of Spain.<ref>Wilkinson, Gerald, ''Epitaph for the Elm'' (London, 1978), p.115</ref> Given that English Elm is female-sterile, the Aranjuez elms either were not after all English Elm, or, by the time Henry collected seed from them, English Elms there had been replaced by intermediates or by other kinds. At higher altitudes in Spain, Henry noted, such as in Madrid and Toledo, the 'English Elm' did not set fertile seed.<ref>Elwes, H. J. & Henry, A. (1913). ''The Trees of Great Britain & Ireland'', Vol.7, p.1908</ref>

The 2004 study, which examined "eight individuals classified as English Elm" collected in Lazio, Spain and Britain, noted "slight differences among the [[Amplified fragment length polymorphism|AFLP fingerprinting]] profiles of these eight samples, attributable to somatic mutations".<ref name = Gil/> Since 'Atinia', though female infertile, is an efficient producer of pollen and should be capable of acting as a pollen parent, it is compatible with the 2004 findings that, in addition to a core population of genetically virtually identical trees deriving from a single clone, there exist intermediate forms of ''U. minor'' of which that clone was the pollen parent. These might be popularly or even botanically regarded as 'English Elm', though they would be genetically distinct from it; and in these, the female infertility could have gone. The "smooth-leaved form" of English Elm mentioned by Richens (1983),<ref name = Richens/> and the "northern form" mentioned by [[Oliver Rackham]] (1986) as having been introduced to Massachusetts,<ref>[[Rackham, Oliver]], ''The History of the Countryside'' (London, 1986)</ref> are possible examples of 'Atinia' mutations or intermediates.

==In art and photography==
The elms in the [[Suffolk]] landscape-paintings and drawings of [[John Constable]] were not English Elm but "most probably [[Ulmus × hollandica|East Anglian hybrid elms]] ... such as still grow in the same hedges" in [[Dedham Vale]] and [[East Bergholt]],<ref>R. H. Richens, ''Elm'', p.166, 179</ref> while his [[Flatford Mill]] elms were [[field elm|''U. minor'']].<ref>Richens, R. H., ''Elm'' (Cambridge 1983), p.173; p.293, note 26</ref> Constable's''Study of an elm tree'' (c.1821) is, however, thought to depict the bole of an English Elm with its bark "cracked into parched-earth patterns".<ref>'Elm' by Robert Macfarlane, vam.ac.uk/content/articles/m/memory-maps-elm-by-robert-macfarlane/</ref> Among artists who depicted English Elms were [[Edward Seago]]<ref>Edward Seago, ''Elm Trees near Cookham'', telegraph.co.uk/comment/letters/8571179/Last-chance-to-save-the-surviving-English-elms.html</ref> and [[James Duffield Harding]]. English Elm features in oil paintings by the contemporary artist [[David Shepherd (artist)|David Shepherd]], either as the main subject (''Majestic elms'' [http://www.davidshepherd.com/davidshepherd-original-majesticelms.html]) or more often as the background to nostalgic evocations of farming scenes.<ref>English Elm in David Shepherd landscapes, davidshepherd.com/davidshepherd-farm.html</ref>

Among classic photographs of English Elm are those by Edward Step and Henry Irving in ''Wayside and Woodland Trees, A pocket guide to the British sylva'' (1904).<ref>Step, Edward, ''Wayside and Woodland Trees'', Plate 36, gutenberg.org/files/34740/34740-h/34740-h.htm</ref>
<gallery>
File:Constable - Study of an Elm Tree - c1821.jpeg|Constable, ''Study of an elm tree'' (c.1821)
File:James Duffield Harding - The Great Exhibition of 1851 - Google Art Project.jpg|'Figure-of-eight' shaped English Elms, Hyde Park: [[James Duffield Harding]]'s ''The Great Exhibition of 1851''
Image:PSM V65 D491 The cam near trinity college cambridge university.png|''The Cam near Trinity College, Cambridge'' (unknown artist): a grove of mainly English Elm on the [[The Backs|Backs]]<ref>Photographs of English Elms on the Backs in ''101 Views of Cambridge'', Rock Bros Ltd, c.1900</ref>
</gallery>

==Accessions==

===North America===
*[[Longwood Gardens]]. Acc. no. L-2507.
*[[Morton Arboretum]]. Acc. nos. 211-40, 756-60, 351-70.

===Europe===
*[[Brighton & Hove]] City Council, [[NCCPG]] Elm Collection.<ref>{{cite web|title=List of plants in the {elm} collection|publisher=Brighton & Hove City Council|access-date=23 September 2016|url=http://www.brighton-hove.gov.uk/content/leisure-and-libraries/parks-and-green-spaces/list-plants-collection}}</ref> UK champion: Preston Park, 15 m high (storm damaged), 201 cm [[d.b.h.]] in 2001.<ref name=Johnson>Johnson, Owen (ed.) (2003). ''Champion Trees of Britain & Ireland''. Whittet Press, {{ISBN|978-1-873580-61-5}}.</ref> Brighton & Hove has some 700 trees; the most notable examples are at Preston Park, South Victoria Gardens, Royal Pavilion Gardens, The Level, Holmes Avenue, University of Sussex Campus; Preston Road (A23) and Hanover Crescent.
*[[Grange Farm Arboretum]], [[Sutton St James]], [[Spalding, Lincolnshire|Spalding]], [[Lincolnshire]], England. Acc. no. 518.
*[[Royal Botanic Garden Edinburgh]], as ''Ulmus procera''. Acc. no. 20081448.<ref name=Royal>Royal Botanic Garden Edinburgh. (2017). ''List of Living Accessions: Ulmus'' [http://elmer.rbge.org.uk/bgbase/livcol/bgbaselivcol.php?cfg=bgbase/livcol/bgbaselivcol.cfg&startrow=26]</ref>
*[[Strona Arboretum]], University of Life Sciences, [[Warsaw]], Poland. No details available.
*[[University of Copenhagen]], Botanic Garden. One specimen, no details available.
*[[Westonbirt Arboretum]],<ref>http://www.forestry.gov.uk/forestry/infd-62qk8w</ref> [[Tetbury]], [[Gloucestershire|Glos.]], England. Four trees, listed as ''U. minor'' var. ''vulgaris''; no acc. details available.

===Australasia===
*[[Avenue of Honour]], [[Ballarat]], Australia. Details not known.
*[[Eastwoodhill Arboretum]],<ref>[http://www.eastwoodhill.org.nz/gardens--collection/collection.aspx?Type=Collection&L=U ] {{webarchive |url=https://web.archive.org/web/20081014075735/http://www.eastwoodhill.org.nz/gardens--collection/collection.aspx?Type=Collection&L=U |date=October 14, 2008 }}</ref> [[Gisborne, New Zealand|Gisborne]], New Zealand. 12 trees, details not known.
*Waite Arboretum,<ref>{{cite web|url=http://www.waite.adelaide.edu.au/arboretum/ |title=Waite Arboretum | Waite Arboretum |publisher=Waite.adelaide.edu.au |date=2003-01-21 |accessdate=2012-11-02}}</ref> [[University of Adelaide]], [[Adelaide]], Australia. No details available.

==See also==
[[The Elm and the Vine]]

==References==
{{Reflist}}

==External links==
*[http://www.forestry.gov.uk/pdf/FCBK042.pdf/$FILE/FCBK042.pdf Jobling & Mitchell, 'Field Recognition of British Elms', Forestry Commission Booklet]
*http://redwood.mortonarb.org/PageBuilder?cid=2&qid= Morton Arboretum Catalogue 2006
*[http://www.s231645534.websitehome.co.uk/dna__elm_origins.htm Adams, K., 'A Reappraisal of British Elms based on DNA Evidence' (2006)]
*[http://www.sisef.it/iforest/contents/?id=ifor1244-007 Heybroek, Hans M, 'The elm, tree of milk and wine' (2013)]
* {{Naturalis Biodiversity Center |id=L.4214471 |name=Ulmus procera Salisb.}} [[Samara (fruit) |Samara]] of ''U. procera'', [[Hunsdon]] (Kew Herbarium specimen)

{{Elm species, varieties, hybrids, hybrid cultivars and species cultivars |state=collapsed}}

[[Category:Ulmus]]
[[Category:Ornamental trees]]
[[Category:Flora of Great Britain]]
[[Category:Flora of Portugal]]
[[Category:Flora of Spain]]
[[Category:Trees of Europe]]
[[Category:Field elm cultivar]]
[[Category:Ulmus articles with images]]

Ulmus minor 'Atinia'

2018-01-31T17:10:40Z

173.165.237.1: /* Description */

{{DISPLAYTITLE:''Ulmus minor'' 'Atinia'}}
{{Infobox cultivar
| name = ''Ulmus minor'' 'Atinia'
| species = ''[[Ulmus minor]]''
| cultivar = 'Atinia'
| image = Ulmus-minor-atinia-brighton-south-east-entrance-to-preston-park.jpg
| image_caption = English Elm, Brighton, 1992
| origin = Italy
}}

The '''[[Field Elm]]''' [[cultivar]] '''''Ulmus minor'' 'Atinia'''',<ref name=coleman2016>{{cite journal|first1=M.|last1=Coleman|first2=S.W.|last2=A’Hara|first3=P.R.|last3=Tomlinson|first4=P.J.|last4=Davey|date=2017|journal=New Journal of Botany|title=Elm clone identification and the conundrum of the slow spread of Dutch Elm Disease on the Isle of Man|volume=6|issue=2-3|pages=79-89}}</ref> commonly known as the '''English Elm''', formerly '''Common Elm''' and '''Horse May''',<ref name = Davey>{{cite book|first=Frederick Hamilton|last=Davey|title=Flora of Cornwall|year=1909|pages=401|url=https://babel.hathitrust.org/cgi/pt?id=mdp.39015069772864;view=2up;seq=508}} Republished 1978 by EP Publishing, Wakefield. {{ISBN|0-7158-1334 X}}</ref> and more lately the '''Atinian Elm'''<ref>{{Cite web | title = A Reappraisal of British Elms based on DNA Evidence | author-last = Adams | author-first = Ken | work = Essex botany and mycology groups| date = 2006 | accessdate = 2017-02-23 | url = https://web.archive.org/web/20160304071455/http://www.s231645534.websitehome.co.uk/dna__elm_origins.htm}}</ref> was, before the spread of [[Dutch elm disease]], the most common field elm in central southern England, though not native there, and one of the largest and fastest-growing [[deciduous]] [[tree]]s in Europe. [[R. H. Richens]] noted that there are elm-populations in north-west Spain, in northern Portugal and on the Mediterranean coast of France that "closely resemble the English Elm" and appear to be "trees of long standing" in those regions rather than recent introductions.<ref>Richens, R. H., ''Elm'' (Cambridge, 1983), p.18, p.90</ref><ref>[http://www.icnf.pt/portal/florestas/aip/resource/img/arv-mon-pt/1-031-antig.jpg/view Specimen of tree labelled ''U. procera'' in Portugal, icnf.pt]</ref> [[Augustine Henry]] had earlier noted that the supposed English Elms planted extensively in the [[Royal Palace of Aranjuez|Royal Park at Aranjuez]] from the late 16th century onwards, specimens said to have been introduced from England by [[Philip II of Spain|Philip II]]<ref name="Richens, R. H. 1983 p.276">Richens, R. H., ''Elm'' (Cambridge, 1983), p.276</ref> and "differing in no respects from the English Elm in England", behaved as native trees in Spain. He suggested that the tree "may be a true native of Spain, indigenous in the alluvial plains of the great rivers, now almost completely deforested".<ref name=Elwes>Elwes, H. J. & Henry, A. (1913). ''[http://fax.libs.uga.edu/QK488xE4/1f/trees_of_britain_and_ireland_vol_7.pdf The Trees of Great Britain & Ireland]''. Vol. VII. 1848–1929. Republished 2004 Cambridge University Press, {{ISBN|9781108069380}}</ref>

Richens believed that English Elm was a particular clone of the variable species ''[[Ulmus minor]]'', referring to it as ''Ulmus minor'' var. ''vulgaris''.<ref name=Richens>[https://books.google.com/books?id=0g49AAAAIAAJ&pg=PA279&lpg=PA279&dq=ulmus+wyssotzky&source=bl&ots=ZOBXkCNqaj&sig=4u_Wan9HOmHkEgc8ssTvxyd1iQ4&hl=en&ei=dnQySsz7IYWOjAfvt7X9CQ&sa=X&oi=book_result&ct=result&resnum=10#v=onepage&q=ulmus%20wyssotzky&f=false Richens, R. H., ''Elm'', Cambridge University Press, 1983]</ref> A 2004 survey of genetic diversity in Spain, Italy and the UK confirmed that English Elms are indeed genetically identical, clones of a single tree, said to be [[Columella]]'s 'Atinian Elm',<ref name = Gil>{{cite journal|journal=Nature|last=Gil|first=L.|display-authors=etal|date=2004|title=English Elm is a 2,000-year-old Roman Clone|volume=431|pages=1053|publisher=Nature Publishing Group|location=London|url=https://www.researchgate.net/profile/Carmen_Collada/publication/8207367_Phylogeography_English_elm_is_a_2000-year-old_Roman_clone/links/0fcfd5142d377aef97000000/Phylogeography-English-elm-is-a-2-000-year-old-Roman-clone.pdf}}.</ref> once widely used for [[training vines]], and assumed to have been brought to the British Isles by [[Ancient Rome|Romans]] for that purpose.<ref>[http://www.treecouncil.org.uk Tree News, Spring/Summer 2005, Publisher Felix Press]</ref> Thus, despite its name, the origin of the tree is widely believed to be Italy,<ref name=Gil/><ref>{{cite news | url = http://news.bbc.co.uk/2/hi/science/nature/3959561.stm | title = English elm 'brought by Romans' | publisher = BBC | accessdate= 2008-12-21 | date=2004-10-28}}</ref> though the clone is no longer found there and has not yet been identified further east.<ref name=Heybroek>Heybroek, Hans M, 'The elm, tree of milk and wine' (2013), sisef.it/iforest/contents/?id=ifor1244-007</ref>

Dr Max Coleman of the [[Royal Botanic Garden, Edinburgh]] writes (2009): "The advent of DNA fingerprinting has shed considerable light on the question. A number of studies have now shown that the distinctive forms that [[Ronald Melville|Melville]] elevated to species and Richens lumped together as field elm are single clones, all genetically identical, that have been propagated by vegetative means such as cuttings or root suckers. This means that enigmatic British elms such as ... English Elm have turned out to be single clones of field elm."<ref>Max Coleman, ed.: ''Wych Elm'' ([[Royal Botanic Garden Edinburgh]] publication, 2009; {{ISBN|978-1-906129-21-7}}); p. 22</ref> Most floras and field guides, however, do not list English Elm as a form of ''Ulmus minor'', but rather as ''Ulmus procera''.

==Synonyms (chronological)==
<section begin=Synonymy />
*''Ulmus sativa'' Mill.<ref name = miller1768>{{cite book|first=Philip|last=Miller|volume=3|edition=8|pages=674|year=1768|title=The gardeners dictionary|url=https://archive.org/stream/gardenersdictio3mill#page/674/mode/1up}}</ref>
*''Ulmus campestris'' L. var. ''vulgaris'' Aiton <ref name = aiton1789>{{cite book|first=William|last=Aiton|volume=1|pages=319|year=1789|title=Hortus Kewensis|url=https://archive.org/stream/mobot31753000624095#page/319/mode/1up}}</ref>
*''Ulmus procera'' Salisb.<ref name = salisbury1796>{{cite book|first=Richard Anthony|last=Salisbury|pages=391|year=1796|title=Prodromus stirpium in horto ad Chapel Allerton vigentium|url=https://archive.org/stream/mobot31753000639358#page/391/mode/1up}}</ref>
*''Ulmus atinia'' J. Walker <ref name = walker1808>{{cite book|first=John|last=Walker|pages=70-72|year=1808|title=Essays on natural history and rural economy|url=https://archive.org/stream/essaysonnatural00walkgoog#page/n80/mode/1up}}</ref>
*''Ulmus surculosa'' Stokes<ref name=Stokes>{{cite book|first=Jonathan|last=Stokes|pages=35|volume=2|year=1812|title=A botanical materia medica|url=https://archive.org/stream/b21299687_0002#page/35/mode/2up}}</ref>
*[''Ulmus suberosa'' Smith, Loudon, Lindley - disputed]
*''Ulmus minor'' Mill. var. ''vulgaris'' (Aiton) Richens <ref name = richens1977>{{cite journal|journal=Taxon|title=New Designations in Ulmus minor Mill.|first=Richard Hook|last=Richens|volume=26|pages=583-584|date=1977}}</ref>
*''Ulmus minor'' Mill. subsp. procera (Salisb.) Franco.<ref name = anjardbot>{{cite journal|journal=Anales del Jardín Botánico de Madrid|title=Notas Breves|first=João Manuel Antonio|last=do Amaral Franco|volume=50|issue=2|pages=259|date=1992|url=http://www.rjb.csic.es/jardinbotanico/ficheros/documentos/pdf/anales/1992/Anales_50(2)_259_266.pdf}}</ref>
*''Ulmus procera'' 'Atinia' <ref name = heybroek2003>{{cite journal|journal=Mitteilungen der Deutschen Dendrologischen Gesellschaft|title=Die vierte deutsche Ulme? Ein Baum mit Geschichte|first=Hans|last=Heybroek|volume=88|pages=117-119|date=2003}}</ref>
<section end=Synonymy />

==Description==
The tree often exceeded 40 m (about 130 feet) in height with a trunk < 2 m (6.5 feet)[[diameter at breast height|d.b.h]].<ref name=Bean>Bean, W. J. (1981). ''Trees and shrubs hardy in Great Britain''. Murray, London.</ref> The largest specimen ever recorded in England, at [[Forthampton]] Court, near [[Tewkesbury]], was 46 m (151 feet) tall.<ref name=Elwes/> While the upper branches form a fan-shaped crown, heavy more horizontal boughs low on the bole often give the tree a distinctive 'figure-of-eight' silhouette. The small, reddish-purple hermaphrodite apetalous flowers appear in early spring before the leaves. The [[leaf|leaves]] are dark green, almost [[leaf shape|orbicular]], < 10 cm long, without the pronounced [[leaf shape|acuminate]] tip at the apex typical of the genus. They flush a lighter green in April, about a month earlier than most [[Field Elm]]. Since the tree does not produce long shoots in the canopy, it does not develop the markedly pendulous habit of some Field Elm. The bark of old trees is scaly, unlike the vertically-furrowed bark of ancient Field Elm. The bark of English Elm [[Basal shoot|suckers]], like that of [[Ulmus × hollandica 'Major'|Dutch Elm]] suckers and of some Field Elm, can be corky, but Dutch Elm suckers may be distinguished from English by their straighter, stouter twigs, bolder 'herringbone' pattern, and later flushing.

The tree does not produce fertile [[seed]] as it is female-sterile, and natural regeneration is entirely by [[root]] [[Basal shoot|suckers]].<ref name=Richens/><ref name=White>White, J. & More, D. (2002). ''Trees of Britain & Northern Europe''. Cassell, London</ref> Seed production in England was often unknown in any case.<ref name=Hanson>{{cite book | last=Hanson | first=M. W. | title=Essex elm | publisher=Essex Field Club | location=London | year=1990 | isbn=978-0-905637-15-0 | url=http://www.essexfieldclub.org.uk/portal/p/Archive/s/109/o/0001|access-date=2017-10-24}}</ref> By the late 19th century, urban specimens in Britain were often grafted on to [[wych elm]] root-stock to eliminate suckering; [[Augustine Henry|Henry]] noted that this method of propagation seldom produced good specimens.<ref name = Elwes/>
<gallery>
File:English Elm at Powderham.jpg|English Elm at [[Powderham Castle|Powderham]], before 1913
File:Ulmus minor 'Procera'.jpg|English Elm, 1904
File:Bark of Ulmus minor 'Procera'.jpg|Bark of English Elm
Image:Umvvulgaris-WC-2003.jpg|Leaves from a specimen tree in Sussex, England (2009)
File:Leaves of Ulmus minor 'Procera', short shoots of old trees.jpg|Dried short-shoot leaves of mature trees in Edinburgh (August)
Image:Elm Leaves - geograph.org.uk - 990660.jpg|Juvenile leaves in hedgerow
</gallery>

==Pests and diseases==
Owing to its homogeneity, the tree has proven particularly susceptible to [[Dutch elm disease]], but immature trees remain a common feature in the English countryside courtesy of the ability to sucker from roots. After about 20 years, these suckers too become infected by the fungus and killed back to ground level. English Elm was the first elm to be [[genetically engineered]] to resist disease, at the [[University of Abertay Dundee]].<ref>{{cite news| url=https://www.theguardian.com/print/0,3858,4246134-103690,00.html | work=The Guardian | location=London | title=Scientists modify elm to resist disease that killed millions of trees in Britain | first=James | last=Meek | date=2001-08-28 | accessdate=2010-05-26}}</ref> It was an ideal subject for such an experiment, as its sterility meant there was no danger of its introgression into the countryside.

In the United States, English Elm was found to be one of the most preferred elms for feeding by the Japanese Beetle ''[[Popillia japonica]]''.<ref name="Miller, b">Miller, F., Ware, G. and Jackson, J. (2001). [http://www.bioone.org/doi/full/10.1603/0022-0493%282001%29094%5B0445%3APOTCEU%5D2.0.CO%3B2 Preference of Temperate Chinese Elms (Ulmuss spp.) for the Feeding of the Japanese Beetle (Coleoptera: Scarabaeidae)]. ''Journal of Economic Entomology'' 94 (2). pp 445-448. 2001. Entom. Soc.of America.</ref>

The leaves of the English Elm in the UK are mined by ''[[Stigmella ulmivora]]''.

==Uses==
{|class="toccolours" style="float: right; margin-left: 1em; margin-right: 2em; font-size: 85%; background:#dbf7c5; color:black; width:30em; max-width: 40%;" cellspacing="5"
|style="text-align: left;" |
... He liked to be alone, feeling his soul heavy with its own fate. He would sit for hours watching the elm trees standing in rows like giants, like warriors across the country. The Earl had told him that the Romans had brought these elms to Britain. And he seemed to see the spirit of the Romans in them still. Sitting there alone in the spring sunshine, in the solitude of the roof, he saw the glamour of this England of hedgerows and elm trees, and the labourers with slow horses slowly drilling the sod, crossing the brown furrow, and the chequer of fields away to the distance.

|-
|style="text-align: left;" | – From '''[[D. H. Lawrence]]''', ''[[The Ladybird]]'' (1923).<ref>D. H. Lawrence, ''The Ladybird'' (Penguin edition, 1960, p.69)</ref>
|}

The English Elm was once valued for many purposes, notably as water pipes from hollowed trunks, owing to its resistance to rot in saturated conditions. It is also very resilient to crushing damage and these two properties led to its widespread use in the construction of jetties, timber piers and lock gates, etc. It was used to a degree in furniture manufacture but not to the same extent as oak, because of its greater tendency to shrink, swell and split, which also rendered it unsuitable as the major timber component in shipbuilding and building construction. The wood has a density of around 560 kg per cubic metre.<ref>[http://www.nichetimbers.co.uk/native-hardwood/elm/ Elm]. Niche Timbers. Accessed 19-08-2009.</ref>

However, English Elm is chiefly remembered today for its aesthetic contribution to the English countryside. In 1913 [[Henry John Elwes|Henry Elwes]] wrote that "Its true value as a landscape tree may be best estimated by looking down from an eminence in almost any part of the valley of the Thames, or of the Severn below Worcester, during the latter half of November, when the bright golden colour of the lines of elms in the hedgerows is one of the most striking scenes that England can produce".<ref name="Elwes"/>

==Cultivation==
The introduction of the Atinian elm to Spain from Italy is recorded by the Roman agronomist [[Columella]].<ref name=Columella>Columella, Lucius Junius Moderadus (c.A D 50) ''De re rustica'', v.6</ref> It has also been identified by [[Hans M. Heybroek|Heybroek]] as the elm grown in the vineyards of the Valais, or Wallis, canton of Switzerland.<ref>[http://bioportal.naturalis.nl/nba/result?nba_request=http%253A%252F%252Fapi.biodiversitydata.nl%252Fv0%252F%252Fmultimedia%252Fget-multimedia-object-for-specimen-within-result-set%252F%253FunitID%253DL.4214289_01561868738%2526searchID%253Dee1907d7492a3dc38517675f48665771#prettyPhoto/0/ bioportal.naturalis.nl L.4214289 ''Ulmus procera'' 'Atinia']</ref><ref>[http://bioportal.naturalis.nl/nba/result?nba_request=http%253A%252F%252Fapi.biodiversitydata.nl%252Fv0%252F%252Fmultimedia%252Fget-multimedia-object-for-specimen-within-result-set%252F%253FunitID%253DL.4214286_045192863%2526searchID%253D4a86b5774a96e8e07acb4bfb8d61b890#prettyPhoto/0/ bioportal.naturalis.nl L.4214286 ''Ulmus procera'' 'Atinia']</ref><ref>[http://bioportal.naturalis.nl/nba/result?nba_request=http%253A%252F%252Fapi.biodiversitydata.nl%252Fv0%252F%252Fmultimedia%252Fget-multimedia-object-for-specimen-within-result-set%252F%253FunitID%253DL.4214283_1471483012%2526searchID%253D8bb8e372f5b13df1b296916ed3946ef0#prettyPhoto/0/ bioportal.naturalis.nl L.4214283 ''Ulmus procera'' 'Atinia']</ref> Although there is no record of its introduction to Britain from Spain, it has long been believed<ref>Loudon, John Claudius, ''Arboretum et fruticetum Britannicum; or, The trees and shrubs of Britain'', Vol. 3 (1838)</ref> that the tree arrived with the [[Ancient Rome|Romans]], a hypothesis supported by the discovery of pollen in an excavated Roman vineyard. It is likely the tree was used also as a source of leaf hay.<ref name="Heybroek"/> Elms said to be English Elm, and reputedly brought to Spain from England by [[Philip II of Spain|Philip II]], were planted extensively in the [[Royal Palace of Aranjuez|Royal Park at Aranjuez]] and the [[Buen Retiro Park|Retiro Park, Madrid]] from the late 16th century onwards (see '''Hybrids''' below).<ref name=Richens/><ref>Elwes, H. J., & Henry, A., The Trees of Great Britain & Ireland (Private publication, Edinburgh, 1913), Vol. VII, p.1908</ref>

More than a thousand years after the departure of the Romans from Britain, English Elm found far greater popularity, as the preferred tree for planting in the new [[Common Hawthorn|hawthorn]] hedgerows appearing as a consequence of the [[Enclosure]] movement, which lasted from 1550 to 1850. In parts of the [[Severn Valley]], the tree occurred at densities of over 1000 per square kilometre, so prolific as to have been known as the 'Worcester Weed'.<ref name=Wilkinson>Wilkinson, G. (1984). ''Trees in the Wild and Other Trees and Shrubs''. Stephen Hope Books. {{ISBN|0-903792-05-2}}.</ref> In the eastern counties of England, however, hedgerows were usually planted with local [[Field Elm]], or with suckering [[Ulmus × hollandica|hybrids]].<ref>Richens, R. H., ''Elm'' (Cambridge, 1983), Ch.14</ref> When elm became the tree of fashion in the 18th and 19th centuries, avenues and groves of English Elm were often planted, among them the elm-groves in [[The Backs]], [[Cambridge]].<ref>Photographs of English Elm in The Backs in ''101 Views of Cambridge'', Rock Bros. Ltd., c.1900</ref>

English Elm was introduced into Ireland,<ref>Elwes, H. J. & Henry, A. (1913). ''The Trees of Great Britain & Ireland'', Vol.7, p.1920 [http://fax.libs.uga.edu/QK488xE4/1f/trees_of_britain_and_ireland_vol_7.pdf]</ref> and as a consequence of Empire has been cultivated in eastern North America and widely in south-eastern Australia and New Zealand. It is still commonly found in Australia and New Zealand, where it is regarded at its best as a street or avenue tree.<ref name=Auckland>{{cite journal|first1=Mike|last1=Wilcox|first2=Chris|last2=Inglis|journal=Auckland Botanical Society Journal|title=Auckland's elms|volume=58|issue=1|date=2003|pages=38-45|publisher=Auckland Botanical Society|url=http://bts.nzpcn.org.nz/bts_pdf/ABJ58%281%292003-38-45-Elms.pdf}}</ref><ref>Lefoe, Gregory K., 'Elm Trees', emelbourne.net.au</ref><ref>[http://vhd.heritage.vic.gov.au/vhd/heritagevic#search:simple:user:list:database|places:ulmus:1 Victorian Heritage Database]</ref> It was also planted as a street tree on the American West Coast, notably in [[St Helena, California]],<ref name=Dreistadt>Dreistadt, S, Dahlsten, D. L., and Frankie, G. W. (1990). Urban Forests and Insect Ecology. ''BioScience''. Vol. 40, No. 3 (March 1990). pp. 192 - 198. University of California Press.</ref> and it has been planted in South Africa.<ref name=Troup>[[Robert Scott Troup|Troup]], R. S. (1932). ''Exotic forest trees in the British Empire''. Oxford Clarendon Press. ASIN: B0018EQG9G</ref>
<gallery>
Image:Preston Church, Brighton - geograph.org.uk - 1546696.jpg|[[St Peter's Church, Preston Village, Brighton]], with English Elms regrowing after lopping (1951) (Photo: Les Whitcomb)
Image:English elm in east sussex.jpg|English Elms in hedgerow, [[Alfriston]], East Sussex (1996)
Image:Ulmus minor atinia brighton preston park.jpg|Hourglass-shaped English Elm, Preston Park, Brighton (1992)
Image:PP-5-71990 (25).JPG|English Elm, Preston Park, Brighton (2004)
Image:Brighton Museum - geograph.org.uk - 1169622.jpg|Winter silhouette of English Elm, Brighton (2009)
Image:Elm trees on Royal Parade, Parkville, Melbourne.jpg|English Elms on [[Royal Parade, Melbourne|Royal Parade, Parkville]], Melbourne (2012)
File:Cootamundra Adams Street.JPG|English Elms in [[Cootamundra, New South Wales]], one trimmed for power line (2015)
</gallery>

==Notable trees==
Mature English Elms are now only very rarely found in the UK beyond Brighton (see below) and Edinburgh. One large tree survives in [[Leicester]] in Cossington Street Recreation Ground. Several survive in [[Edinburgh]] (2015): one in [[Rosebank Cemetery]] (girth 3 metres), one in Founders Avenue, [[Fettes College]], and one in [[Inverleith Park]] (east avenue), while a majestic open-grown specimen (3 metres) in Claremont Park, [[Leith Links]], retains the dense fan-vaulted crown iconic in this cultivar. There is an isolated mature English Elm in the cemetery at [[Dervaig]], Isle of Mull, Scotland.

Some of the most significant remaining stands are to be found overseas, notably in Australia where they line the streets of [[Melbourne]], protected by [[geography]] and [[quarantine]] from [[disease]].<ref name=Spencer>Spencer, R., Hawker, J. and Lumley, P. (1991). ''Elms in Australia''. Australia: Royal Botanic Gardens, Melbourne. {{ISBN|0-7241-9962-4}}</ref><ref>[http://2.bp.blogspot.com/-ehIbJgZ3HMM/UL4roHacROI/AAAAAAAAMFw/4B7LsC65cbA/s1600/IMG_3909.jpg Photograph of English Elm in Melbourne, 2.bp.blogspot.com]</ref> An avenue of 87 English Elms, planted c.1880, lines the entrance to the winery of [[Rutherglen wine region|All Saints Estate, Rutherglen]], [[Victoria (Australia)|Victoria]];<ref>English Elm avenue, All Saints Estate, Rutherglen, allsaintswine.com.au [http://www.allsaintswine.com.au/the-estate/our-history], rutherglenvic.com [http://www.rutherglenvic.com/attractions/all-saints-estate], 2bustickets.blogspot.co.uk [http://2bustickets.blogspot.co.uk/2009/11/rutherglen-to-beechworth.htm] l</ref> a double avenue of 400 English Elms, planted in 1897 and 1910–15, lines [[Royal Parade, Melbourne|Royal Parade, Parkville]], Melbourne.<ref>English Elm in Melbourne, emelbourne.net.au [http://www.emelbourne.net.au/biogs/EM00514b.htm], gardendrum.com [http://gardendrum.com/2014/06/25/save-melbournes-elms-as-a-citizen-forester/]</ref><ref>English Elm in Victoria, Victorian Heritage Database, [http://vhd.heritage.vic.gov.au/vhd/heritagevic#search:simple:user:list:database|places:ulmus procera:1]
[http://vhd.heritage.vic.gov.au/vhd/heritagevic#search:simple:user:list:database|places:ulmus procera:2]</ref><ref>[https://www.flickr.com/photos/30554196@N06/8749101117 English Elms on Royal Parade, Melbourne, flickr.com]</ref> A large free-standing English Elm in [[Traralgon]], Victoria, shows the 'un-English' growth-form<ref>English Elm in Traralgon, Victoria, vhd.heritage.vic.gov.au [http://vhd.heritage.vic.gov.au/images/vhr/150154.jpg] [http://vhd.heritage.vic.gov.au/vhd/heritagevic#detail_places;70701]</ref> of the tree in tropical latitudes.<ref>[http://www.resistantelms.co.uk/english-elm/ 'The growth and ultimate form of English Elm', resistantelms.co.uk]</ref> However, many of the Australian trees, now over 100 years old, are succumbing to old age, and are being replaced with new trees raised by material from the older trees budded onto Wych Elm ''[[Ulmus glabra]]'' rootstock.<ref name=Fitzgibbon>Fitzgibbon, J. (2006) Royal Parade Elm Replacement. ''Elmwatch'', Vol. 16 No. 1, March 2006</ref> In New Zealand a "massive individual" stands at 36 Mt Albert Road, Auckland.<ref name=Auckland/> In the United States, several fine trees survive at Boston Common, Boston, and in [[New York City]],<ref>[http://centralpark-ny.com/assets/trees/English-ElmcPB040384.jpg English Elm in Central Park, New York, centralpark-ny.com]</ref> notably the [[Hangman's Elm]] in [[Washington Square Park]],<ref name=Barnard>Barnard, E. S. (2002). ''New York City Trees''. Columbia University Press</ref> while in Canada four 130-year English Elms, inoculated against disease, survive on the Back Campus field of the [[University of Toronto]].<ref>Photograph of English Elms in University of Toronto: Janet Harrison, nativeplantwildlifegarden.com [http://nativeplantwildlifegarden.com/dirt-to-turf/]</ref>
<gallery>
Image:Crystal Palace Great Exhibition tree 1851.png|One of three English Elms (lower branches removed) around which the Crystal Palace was built for the [[The Great Exhibition|Great Exhibition]], 1851<ref>Clouston, B., Stansfield, K., eds., ''After the Elm'' (London, 1979), p.55</ref>
Image:Crystal Palace interior.jpg|A coloured lithograph of the same tree (1851)
Image:English Elm avenue.jpg|English Elm avenue in [[Fitzroy Gardens, Melbourne]] (2006)
Image:Hangman's Elm by David Shankbone.jpg|[[Hangman's Elm]], [[Washington Square Park]], New York (2007)
Image:Large English Elm at West Point, NY 4 Sep 2009.jpg|One of two large English Elms near [[Trophy Point]] at [[United States Military Academy|West Point, NY]] (2009)
Image:Barns at Upper Swell - geograph.org.uk - 1718618.jpg|The [[Swell, Gloucestershire|Upper Swell]] elms (2010) currently undergoing tests by the [[Conservation Foundation, UK|Conservation Foundation]]<ref>The Conservation Foundation's Great British Elm Experiment map of parent trees: [http://www.conservationfoundation.co.uk/content.php?id=178]</ref>
File:Ulmus minor 'Procera'. Claremont Park, Edinburgh.jpg|One of the last old English Elms in Edinburgh (2016)
</gallery>

===Brighton and the 'cordon sanitaire'===
Although the English Elm population in Britain was almost entirely destroyed by Dutch elm disease, mature trees can still be found along the south coast Dutch Elm Disease Management Area in [[East Sussex]]. This 'cordon sanitaire', aided by the prevailing south westerly onshore winds and the topographical niche formed by the [[South Downs]], has saved many mature elms. Amongst these are possibly the world's oldest surviving English Elms, known as the 'Preston Twins' in [[Preston Park, Brighton|Preston Park]], both with trunks exceeding 600 cm in circumference (2.0 m [[d.b.h.]]) though the larger tree lost two limbs in August 2017 following high winds.<ref name="dail_Euro">{{Cite web | title = Europe's biggest elm tree splits in two and crashes to the ground | author = | work = Mail Online | date = 21 August 2017 | accessdate = 2017-08-22 | url = http://www.dailymail.co.uk/news/article-4810562/Europe-s-biggest-elm-tree-splits-two.html }}</ref><ref name="thea_Scra">{{Cite web | title = Scramble to save the oldest elm in world | author = | work = The Argus | date = 22 August 2017 | accessdate = 2017-08-22 | url = http://www.theargus.co.uk/NEWS/15486732.Scramble_to_save_the_oldest_elm_in_world/ }}</ref>

<gallery>
Image:DED control notice.jpg|Sign on A27 road, Brighton, England
Image:World Champion English elm.JPG|The oldest known English Elms in the UK, the 'Preston Twins', Brighton, 2008
File:English Elm Preston Park Brighton.jpg|The larger of the twins, 2006
</gallery>

==Cultivars==
A small number of putative [[cultivar]]s have been raised since the 18th and early 19th centuries,<ref name=Green>{{cite journal |last=Green |first=Peter Shaw |authorlink=Peter Shaw Green |date=1964 |title=Registration of cultivar names in Ulmus|url=https://archive.org/stream/arnoldiaarno_21#page/40/mode/2up/|journal=Arnoldia |volume=24|pages=41–80 |number=6–8 |publisher=[[Arnold Arboretum]], [[Harvard University]] |access-date=16 February 2017}}</ref> three of which are now almost certainly lost to cultivation:
[[Ulmus 'Acutifolia'|'Acutifolia']], [[Ulmus minor 'Variegata'|'Atinia Variegata']], [[Ulmus 'Folia Aurea'|'Folia Aurea']], [[Ulmus 'Pyramidalis'|'Pyramidalis']].
Though usually listed as an English Elm cultivar, ''Ulmus'' [[Ulmus 'Louis van Houtte'|'Louis van Houtte']] "cannot with any certainty be referred to as ''Ulmus procera'' [ = 'Atinia'] " (W. J. Bean).<ref name=Bean/>

==Hybrids, hybrid cultivars, and mutations==
Crossability experiments conducted at the [[Arnold Arboretum]] in the 1970s apparently succeeded in hybridizing English Elm with [[Ulmus glabra|''U. glabra'']] and [[Ulmus rubra|''U. rubra'']], both also [[protogynous]] species. However, the same experiments also shewed English Elm to be self-compatible which, in the light of its proven female-sterility, must cast doubt on the identity of the specimens used.<ref name=Hans>Hans, A. S. (1981). Compatibility and Crossability Studies in Ulmus. ''Silvae Genetica'' 30, 4 - 5 (1981).</ref> A similar doubt must hang over [[Augustine Henry|Henry]]'s observation that the 'English Elms' at [[Royal Palace of Aranjuez|Aranjuez]] (see '''Cultivation''' above) "produced every year fertile seed in great abundance",<ref>Elwes, H. J. & Henry, A. (1913). ''The Trees of Great Britain & Ireland'', Vol.7, p.1908 [http://fax.libs.uga.edu/QK488xE4/1f/trees_of_britain_and_ireland_vol_7.pdf]</ref> seed said to have been taken "all over Europe", presumably in the hope that it would grow into trees like the royal elms of Spain.<ref>Wilkinson, Gerald, ''Epitaph for the Elm'' (London, 1978), p.115</ref> Given that English Elm is female-sterile, the Aranjuez elms either were not after all English Elm, or, by the time Henry collected seed from them, English Elms there had been replaced by intermediates or by other kinds. At higher altitudes in Spain, Henry noted, such as in Madrid and Toledo, the 'English Elm' did not set fertile seed.<ref>Elwes, H. J. & Henry, A. (1913). ''The Trees of Great Britain & Ireland'', Vol.7, p.1908</ref>

The 2004 study, which examined "eight individuals classified as English Elm" collected in Lazio, Spain and Britain, noted "slight differences among the [[Amplified fragment length polymorphism|AFLP fingerprinting]] profiles of these eight samples, attributable to somatic mutations".<ref name = Gil/> Since 'Atinia', though female infertile, is an efficient producer of pollen and should be capable of acting as a pollen parent, it is compatible with the 2004 findings that, in addition to a core population of genetically virtually identical trees deriving from a single clone, there exist intermediate forms of ''U. minor'' of which that clone was the pollen parent. These might be popularly or even botanically regarded as 'English Elm', though they would be genetically distinct from it; and in these, the female infertility could have gone. The "smooth-leaved form" of English Elm mentioned by Richens (1983),<ref name = Richens/> and the "northern form" mentioned by [[Oliver Rackham]] (1986) as having been introduced to Massachusetts,<ref>[[Rackham, Oliver]], ''The History of the Countryside'' (London, 1986)</ref> are possible examples of 'Atinia' mutations or intermediates.

==In art and photography==
The elms in the [[Suffolk]] landscape-paintings and drawings of [[John Constable]] were not English Elm but "most probably [[Ulmus × hollandica|East Anglian hybrid elms]] ... such as still grow in the same hedges" in [[Dedham Vale]] and [[East Bergholt]],<ref>R. H. Richens, ''Elm'', p.166, 179</ref> while his [[Flatford Mill]] elms were [[field elm|''U. minor'']].<ref>Richens, R. H., ''Elm'' (Cambridge 1983), p.173; p.293, note 26</ref> Constable's''Study of an elm tree'' (c.1821) is, however, thought to depict the bole of an English Elm with its bark "cracked into parched-earth patterns".<ref>'Elm' by Robert Macfarlane, vam.ac.uk/content/articles/m/memory-maps-elm-by-robert-macfarlane/</ref> Among artists who depicted English Elms were [[Edward Seago]]<ref>Edward Seago, ''Elm Trees near Cookham'', telegraph.co.uk/comment/letters/8571179/Last-chance-to-save-the-surviving-English-elms.html</ref> and [[James Duffield Harding]]. English Elm features in oil paintings by the contemporary artist [[David Shepherd (artist)|David Shepherd]], either as the main subject (''Majestic elms'' [http://www.davidshepherd.com/davidshepherd-original-majesticelms.html]) or more often as the background to nostalgic evocations of farming scenes.<ref>English Elm in David Shepherd landscapes, davidshepherd.com/davidshepherd-farm.html</ref>

Among classic photographs of English Elm are those by Edward Step and Henry Irving in ''Wayside and Woodland Trees, A pocket guide to the British sylva'' (1904).<ref>Step, Edward, ''Wayside and Woodland Trees'', Plate 36, gutenberg.org/files/34740/34740-h/34740-h.htm</ref>
<gallery>
File:Constable - Study of an Elm Tree - c1821.jpeg|Constable, ''Study of an elm tree'' (c.1821)
File:James Duffield Harding - The Great Exhibition of 1851 - Google Art Project.jpg|'Figure-of-eight' shaped English Elms, Hyde Park: [[James Duffield Harding]]'s ''The Great Exhibition of 1851''
Image:PSM V65 D491 The cam near trinity college cambridge university.png|''The Cam near Trinity College, Cambridge'' (unknown artist): a grove of mainly English Elm on the [[The Backs|Backs]]<ref>Photographs of English Elms on the Backs in ''101 Views of Cambridge'', Rock Bros Ltd, c.1900</ref>
</gallery>

==Accessions==

===North America===
*[[Longwood Gardens]]. Acc. no. L-2507.
*[[Morton Arboretum]]. Acc. nos. 211-40, 756-60, 351-70.

===Europe===
*[[Brighton & Hove]] City Council, [[NCCPG]] Elm Collection.<ref>{{cite web|title=List of plants in the {elm} collection|publisher=Brighton & Hove City Council|access-date=23 September 2016|url=http://www.brighton-hove.gov.uk/content/leisure-and-libraries/parks-and-green-spaces/list-plants-collection}}</ref> UK champion: Preston Park, 15 m high (storm damaged), 201 cm [[d.b.h.]] in 2001.<ref name=Johnson>Johnson, Owen (ed.) (2003). ''Champion Trees of Britain & Ireland''. Whittet Press, {{ISBN|978-1-873580-61-5}}.</ref> Brighton & Hove has some 700 trees; the most notable examples are at Preston Park, South Victoria Gardens, Royal Pavilion Gardens, The Level, Holmes Avenue, University of Sussex Campus; Preston Road (A23) and Hanover Crescent.
*[[Grange Farm Arboretum]], [[Sutton St James]], [[Spalding, Lincolnshire|Spalding]], [[Lincolnshire]], England. Acc. no. 518.
*[[Royal Botanic Garden Edinburgh]], as ''Ulmus procera''. Acc. no. 20081448.<ref name=Royal>Royal Botanic Garden Edinburgh. (2017). ''List of Living Accessions: Ulmus'' [http://elmer.rbge.org.uk/bgbase/livcol/bgbaselivcol.php?cfg=bgbase/livcol/bgbaselivcol.cfg&startrow=26]</ref>
*[[Strona Arboretum]], University of Life Sciences, [[Warsaw]], Poland. No details available.
*[[University of Copenhagen]], Botanic Garden. One specimen, no details available.
*[[Westonbirt Arboretum]],<ref>http://www.forestry.gov.uk/forestry/infd-62qk8w</ref> [[Tetbury]], [[Gloucestershire|Glos.]], England. Four trees, listed as ''U. minor'' var. ''vulgaris''; no acc. details available.

===Australasia===
*[[Avenue of Honour]], [[Ballarat]], Australia. Details not known.
*[[Eastwoodhill Arboretum]],<ref>[http://www.eastwoodhill.org.nz/gardens--collection/collection.aspx?Type=Collection&L=U ] {{webarchive |url=https://web.archive.org/web/20081014075735/http://www.eastwoodhill.org.nz/gardens--collection/collection.aspx?Type=Collection&L=U |date=October 14, 2008 }}</ref> [[Gisborne, New Zealand|Gisborne]], New Zealand. 12 trees, details not known.
*Waite Arboretum,<ref>{{cite web|url=http://www.waite.adelaide.edu.au/arboretum/ |title=Waite Arboretum | Waite Arboretum |publisher=Waite.adelaide.edu.au |date=2003-01-21 |accessdate=2012-11-02}}</ref> [[University of Adelaide]], [[Adelaide]], Australia. No details available.

==See also==
[[The Elm and the Vine]]

==References==
{{Reflist}}

==External links==
*[http://www.forestry.gov.uk/pdf/FCBK042.pdf/$FILE/FCBK042.pdf Jobling & Mitchell, 'Field Recognition of British Elms', Forestry Commission Booklet]
*http://redwood.mortonarb.org/PageBuilder?cid=2&qid= Morton Arboretum Catalogue 2006
*[http://www.s231645534.websitehome.co.uk/dna__elm_origins.htm Adams, K., 'A Reappraisal of British Elms based on DNA Evidence' (2006)]
*[http://www.sisef.it/iforest/contents/?id=ifor1244-007 Heybroek, Hans M, 'The elm, tree of milk and wine' (2013)]
* {{Naturalis Biodiversity Center |id=L.4214471 |name=Ulmus procera Salisb.}} [[Samara (fruit) |Samara]] of ''U. procera'', [[Hunsdon]] (Kew Herbarium specimen)

{{Elm species, varieties, hybrids, hybrid cultivars and species cultivars |state=collapsed}}

[[Category:Ulmus]]
[[Category:Ornamental trees]]
[[Category:Flora of Great Britain]]
[[Category:Flora of Portugal]]
[[Category:Flora of Spain]]
[[Category:Trees of Europe]]
[[Category:Field elm cultivar]]
[[Category:Ulmus articles with images]]

Porsche Cayenne

2018-01-12T15:25:30Z

173.165.237.1: /* Third generation (2018–present) */ transmission incorrect

{{Infobox automobile
|name = Porsche Cayenne
|image = 2014 Porsche Cayenne (92A MY14) GTS wagon (2015-08-07) 01.jpg
|aka =
|manufacturer = [[Porsche|Porsche AG]]
|production = 2002-present
|model_years = 2003–present
|assembly = {{ubl |[[Bratislava]], [[Slovakia]] |([[Volkswagen Bratislava Plant]]) |(body assembly, paint, engine, gearbox, drivetrain, under chassis, wheels) |[[Leipzig]], [[Germany]] |(interior, finishing, inspection)}}
|class = [[Mid-size]] [[Luxury car|luxury]] [[crossover SUV]]
|body_style = 5-door [[Sport utility vehicle|SUV]]
|layout = [[Front-engine design|Front engine]], [[four-wheel drive]]
|platform = [[Volkswagen Group PL71 platform]]
|related = {{ubl |[[Volkswagen Touareg]] |[[Audi Q7]]}}
}}

The '''Porsche Cayenne''' (Type 9PA [Designated 955 in online forums, not recognized by Porsche Cars AG]) is a [[mid-size car|mid-size]] [[luxury car|luxury]] [[Crossover (automobile)|crossover]] [[sport utility vehicle]] produced by the German manufacturer [[Porsche]] since 2002, with [[North America]]n sales beginning in 2003. It is the first [[V8 engine|V8-engined]] vehicle built by Porsche since 1995, when the [[Porsche 928]] was discontinued. It is also Porsche's first off road Varient [[sports car]] since its [[Porsche Super|Super]] and [[Porsche Junior|Junior]] tractors of 1950s, and the first Porsche with four doors. Since 2008, all engines have featured direct injection technology.

The second-generation Cayenne (Type 92A) was unveiled at the 2010 [[Geneva Motor Show]] in March following an online reveal. Although the Cayenne shares its platform, body frame and doors with the similar [[Volkswagen Touareg]] and [[Audi Q7]], all other aspects of vehicle design, tuning and production are done in-house at Porsche. The second generation received a [[Facelift (automotive)|facelift]] in 2014 with minor external changes, and introduced a new plug-in E-Hybrid version, with its public launch at the [[Paris Motor Show]].<ref>{{cite web|title=Facelifted Porsche Cayenne revealed ahead of Paris motor show launch|url=http://www.autocar.co.uk/car-news/paris-motor-show/facelifted-porsche-cayenne-revealed-ahead-paris-motor-show-launch|website=Autocar|accessdate=28 July 2014|date=23 July 2014}}</ref>

== First generation (2002–2010) ==
{{Infobox automobile
|name = First generation (9PA) Chassis E1
|image = 2003-2006 Porsche Cayenne (9PA) S wagon 01.jpg
|production = 2002–2010
|typ = 9PA
|model_years = 2003–2010
|wheelbase = {{convert|2855|mm|in|1|abbr=on}}
|length = {{convert|4780|mm|in|1|abbr=on}} Turbo: {{convert|4783|mm|in|1|abbr=on}}
|width = {{convert|1928|mm|in|1|abbr=on}}
|height = {{convert|1700|mm|in|1|abbr=on}}
|engine = 3.2 [[Liter|L]] {{Convert|240|hp|kW|0|abbr=on}} [[VR6]] 3.6 L {{Convert|290|hp|kW|0|abbr=on}} [[VR6]] 4.5 L {{Convert|340|hp|kW|0|abbr=on}} [[V8 engine|V8]] (S) 4.5 L {{Convert|450|hp|kW|0|abbr=on}} [[V8 engine|V8]] [[Twin-turbo|TT]] (Turbo) 4.5 L {{Convert|521|hp|kW|0|abbr=on}} [[V8 engine|V8]] Twin-turbo|TT]] (Turbo S) 3.0 L {{Convert|240|hp|kW|0|abbr=on}} [[V6]] [[Turbo-diesel]] 3.6 L {{Convert|290|hp|kW|0|abbr=on}} [[VR6]] 4.8 L {{Convert|385|hp|kW|0|abbr=on}} [[V8 engine|V8]] (S) 4.8 L {{Convert|405|hp|kW|0|abbr=on}} [[V8 engine|V8]] (GTS) 4.8 L {{Convert|493|hp|kW|-1|abbr=on}} [[V8 engine|V8]] Twin-turbo|TT]] (Turbo) 4.8 L {{Convert|542|hp|kW|-1|abbr=on}} [[V8 engine|V8]] [[Twin-turbo|TT]] (Turbo S)
|transmission = 6-speed [[automatic transmission|automatic]] 6-speed [[manual transmission|manual]]
|drag coefficient = 0.39 Cd (2006 models), .35 (2008 models)
}}

The Porsche Cayenne entered the market with mixed anticipation. However, it soon proved that it was the performance vehicle among SUVs and was praised for its excellent handling and powerful engines.<ref>{{cite web|url=http://www.jbcarpages.com/porsche/cayenne/2004/|title=2004 Porsche Cayenne Review|publisher=JB car pages|accessdate=2011-04-03}}</ref> The lineup initially consisted of the V8-powered Cayenne S and Cayenne Turbo. Later in the model cycle, VR6 and diesel-powered versions joined the lineup.

The base model is powered by a 3.2-L [[VR6 engine]] producing {{convert|250|PS|kW|0|abbr=on}}; modifications in the exhaust manifold allow power to peak at 6700 rpm. Acceleration from 0 to 60 mph (97 km) is approx 7.5 seconds with manual transmission and 8.1 seconds with the Tiptronic S.
[[File:2009 Porsche Cayenne (9PA MY09) 3.6 wagon (2015-07-16) 02.jpg|thumb|left|Facelift Porsche Cayenne 3.6 (Australia)]]
===Cayenne S===
[[File:2003-2006 Porsche Cayenne (9PA) S wagon 02.jpg|thumb|left|Pre–facelift Porsche Cayenne S (Australia)]]
The S is powered by an 8-cylinder engine with a dry-sump lubrication system and variable valve timing. The Cayenne S engine produces {{convert|340|PS|kW|0|abbr=on}} and {{convert|310|lbft|abbr=on}} of torque. Acceleration from 0–60 mph is 7.1 seconds and the top speed is 150 mph.<ref name="2004specs">{{cite web|url=http://www.jbcarpages.com/porsche/cayenne/2004/specs/|title=2004 Porsche Cayenne Specs|publisher=JB car pages|accessdate=2011-04-03}}</ref>

Introduced only for 2006 (Pre-GTS concept), a special distinctive '''Cayenne S Titanium Edition''' Wagon (9PA), a 1 Year exclusive, limited production SUV featuring a lightweight steel body (it is lighter than the Cayenne S), titanium-painted accented body parts, side lower rocker body panels, 4 sports chrome tailpipes, 19" titanium painted alloy wheels, bi-xenon headlights, two-tone interior upholstery, Porsche PCM w/ trip computer navigation, MP3 audio and Bose cabin surround sound. Exhaust tone is aggressive and deep, even at idle. This sporty design S(Ti) is also powered by an alloy 4.5L V8 engine with a dry-sump lubrication system and variable valve timing. The Cayenne S(Ti) engine produces healthy 340 PS (250 kW) and 310 lb·ft (420 N·m) of torque. Acceleration is quicker from 0–60 mph at sub 6.8 seconds and the top speed is 150+ mph. It featured sport tuned suspension, and includes a low-range case, a locking differential and six-speed automatic Tiptronic transmission (See Turbo & Turbo S).[3]

===Cayenne GTS===
The GTS is powered with a {{convert|405|PS|kW|0|abbr=on}} 4.8-L V8 and features a sport suspension and {{convert|21|in|mm|sing=on}} wheels. It is lighter than the Cayenne S and has an aerodynamic body kit. The Porsche Cayenne GTS has a 0 to {{convert|100|km/h|mph|0|abbr=on}} time of 5.7 seconds. A six-speed [[manual transmission]] is also offered.<ref>{{cite web|url=http://www.automoblog.net/2008/02/15/porsche-cayenne-gts/ |archive-url=https://web.archive.org/web/20080828065726/http://www.automoblog.net/2008/02/15/porsche-cayenne-gts/ |dead-url=yes |archive-date=2008-08-28 |title=Porsche Cayenne GTS at the Chicago Auto Show |publisher=Automoblog.net |date=2008-02-15 |accessdate=2010-10-03}}</ref>

===Cayenne Turbo and Turbo S===
[[File:2007 Porsche Cayenne Turbo - Flickr - The Car Spy (25).jpg|thumb|left|Porsche Cayenne Turbo (UK; facelift)]]
The first-generation Cayenne Turbo had {{convert|450|PS|kW|0|abbr=on}}, and accelerated from 0 to {{convert|100|km/h|mph|abbr=on}} in 5.3 seconds.<ref name="2004specs"/> A Turbo S version was built in 2006 to compete with the Mercedes-Benz ML 63 AMG. The Cayenne Turbo and Turbo S included a low-range case, a locking differential, and the height-adjustable, off-road suspension. The S was powered by a twin-turbocharged 4.5-L V8 that produced {{convert|521|PS|kW|0|abbr=on}} and {{Convert|720|Nm|lb·ft|abbr=on}} of torque; Acceleration from 0–60 mph (96 km/h) was 5.0 seconds and the top speed was 171 miles per hour; It featured a six-speed [[automatic transmission|automatic]] Tiptronic transmission.

In 2008 an updated Turbo model, featuring a larger 4.8-L engine, was revealed at the Beijing auto show. It produced {{convert|50|PS|kW|0|abbr=on}} more power, and now accelerated from 0–60 mph (96 km/h) in 4.9 seconds.<ref>{{cite web|url=http://www.jbcarpages.com/porsche/cayenne/2008/specs/|title=2008 Porsche Cayenne Specs|publisher=JB car pages|accessdate=2011-04-03}}</ref> Also revealed with the new Turbo was a new {{convert|550|hp|adj=on}} Turbo S. Acceleration from 0–60 mph is 4.7 seconds and it has optional ceramic composite brakes.

===Cayenne Diesel===
Porsche has sold a diesel version of the Cayenne powered by a 3.0-L [[V6]] TDI engine since February 2009.<ref>{{cite web|last=Tan |first=Paul |url=http://paultan.org/archives/2008/11/21/porsche-cayenne-tdi-diesel-in-february-2009/|title=Porsche Cayenne TDI diesel in February 2009|publisher=Paultan.org|date= |accessdate=2010-10-03}}</ref> The engine is rated at {{convert|240|PS|kW hp|0|abbr=on}} and {{convert|550|Nm|lbft||abbr=on}} of torque. The car was unveiled in 2009 Geneva Motor Show.<ref>{{cite web|last=Abuelsamid |first=Sam |url=http://www.autobloggreen.com/2009/02/19/geneva-preview-porsche-to-publicly-debut-cayenne-diesel/ |title=Geneva Preview: Porsche to publicly debut Cayenne diesel |publisher=Autobloggreen.com |date=2009-02-19 |accessdate=2010-10-03}}</ref> The diesel can accelerate from 0–60 mph in 9.2 seconds.

===Cayenne S Transsyberia===
Originally a racing vehicle for [[Transsyberia rally]], only 26 were built.<ref>{{cite web|last=Nunez |first=Alex |url=http://www.autoblog.com/2007/04/15/porsche-cayenne-s-transsyberia-factory-built-rally-goodness/ |title=Porsche Cayenne S Transsyberia: factory-built rally machine |publisher=Autoblog.com |date=2007-04-15 |accessdate=2010-10-03}}</ref>

The street version was later built to commemorate Porsche's victory in [[Transsyberia rally]]. It is a variant with the {{Convert|405|hp|kW|0|abbr=on}} direct-inject 4.8-L V8 from the Cayenne GTS. Sales began in January 2009, with a production run of 600 road vehicles.<ref>{{cite web|last=Neff |first=John |url=http://www.autoblog.com/2008/09/08/paris-preview-porsche-cayenne-s-transsyberia-special-edition/ |title=Paris Preview: Porsche Cayenne S Transsyberia special edition |publisher=Autoblog.com |date=2008-09-08 |accessdate=2010-10-03}}</ref>

===Cayenne GTS Porsche Design Edition 3 (2010)===
In May 2009,<ref>{{cite web|url=http://www.porsche.com/usa/aboutporsche/pressreleases/pag/archive2009/quarter1/?pool=international-de&id=2009-03-25 |title=New Porsche Cayenne GTS Porsche Design Edition 3 |publisher=Porsche.com |date=2009-03-25 |accessdate=2010-10-03}}</ref> a limited edition version based on Cayenne GTS was introduced, designed by [[Porsche Design]] Studio and included a Porsche Design chronograph Type P’6612. Production was limited to 1000 units, 100 in the USA.<ref>{{cite web|last=Neff |first=John |url=http://www.autoblog.com/2009/03/25/limited-edition-cayenne-gts-porsche-design-edition-iii-to-hit-th/ |title=Limited-edition Cayenne GTS Porsche Design Edition 3 to hit the streets |publisher=Autoblog.com |date=2009-03-25 |accessdate=2010-10-03}}</ref>

===Engines===
{{Unreferenced section|date=December 2016}}
{| class="wikitable"
|-
! Model !! Production period !! Engine !! Power (PS, torque)@rpm
|-
|Cayenne||2003-2007||{{convert|3189|cc|L cuin|1|abbr=on}} V6||{{convert|250|PS|kW hp||abbr=on}}@6000, {{convert|310|Nm|lbft||abbr=on}}@2500
|-
|Cayenne 3.6||2007-2010||{{convert|3598|cc|L cuin|1|abbr=on}} V6||{{convert|290|PS|kW hp||abbr=on}}@6200, {{convert|385|Nm|lbft||abbr=on}}@3000
|-
|Cayenne S ||2002-2007 ||{{convert|4511|cc|L cuin|1|abbr=on}} V8||{{convert|340|PS|kW hp||abbr=on}}@6000, {{convert|420|Nm|lbft||abbr=on}}@2500
|-
|Cayenne S(Ti) Titanium Edition||2006||{{convert|4511|cc|L cuin|1|abbr=on}} V8||{{convert|340|PS|kW hp||abbr=on}}@6000, {{convert|420|Nm|lbft||abbr=on}}@2500
|-
|Cayenne S||2007-2010||{{convert|4806|cc|L cuin|1|abbr=on}} V8||{{convert|385|PS|kW hp||abbr=on}}@6200, {{convert|500|Nm|lbft||abbr=on}}@3500
|-
|Cayenne S Transsyberia||2009||{{convert|4806|cc|L cuin|1|abbr=on}} V8||{{convert|405|PS|kW hp||abbr=on}}@6500, {{convert|500|Nm|lbft||abbr=on}}@3500
|-
|Cayenne GTS||2008-2010||{{convert|4806|cc|L cuin|1|abbr=on}} V8||{{convert|405|PS|kW hp||abbr=on}}@6500, {{convert|500|Nm|lbft||abbr=on}}@3500
|-
|Cayenne GTS Porsche Design Edition 3||2009-2009||{{convert|4806|cc|L cuin|1|abbr=on}} V8||{{convert|405|PS|kW hp||abbr=on}}@6500, {{convert|500|Nm|lbft||abbr=on}}@3500
|-
|Cayenne Turbo||2002-2007||{{convert|4511|cc|L cuin|1|abbr=on}} twin turbo V8||{{convert|450|PS|kW hp||abbr=on}}@6000, {{convert|620|Nm|lbft||abbr=on}}@2250
|-
|Cayenne Turbo||2007-2010||{{convert|4806|cc|L cuin|1|abbr=on}} twin turbo V8||{{convert|500|PS|kW hp||abbr=on}}@6000, {{convert|700|Nm|lbft||abbr=on}}@4500
|-
|Cayenne Turbo S||2006-2007||{{convert|4511|cc|L cuin|1|abbr=on}} twin turbo V8||{{convert|520|PS|kW hp||abbr=on}}@5500, {{convert|720|Nm|lbft||abbr=on}}@2750
|-
|Cayenne Turbo S||2008-2010||{{convert|4806|cc|L cuin|1|abbr=on}} twin turbo V8||{{convert|550|PS|kW hp||abbr=on}}@6000, {{convert|750|Nm|lbft||abbr=on}}@2250
|-
|Cayenne Diesel||2009-2010||{{convert|2967|cc|L cuin|1|abbr=on}} V6||{{convert|240|PS|kW hp||abbr=on}}@4000, {{convert|550|Nm|lbft||abbr=on}}@2000
|}

==Second generation (2011–2017)==
{{Infobox automobile
|name = Second generation (92A) Chassis E2
|image = 2010-2011 Porsche Cayenne (92A MY11) S wagon (2011-08-03) 01.jpg
|production = 2010-2017
|model_years = 2011-2017
|engine = '''petrol''' [[List of Volkswagen Group petrol engines#3.0 V6 24v TFSI 213-245kW|3.0]] [[Supercharger|S/C]] [[V6 engine|V6]] 333[[Pferdestärke|PS]] [[List of Volkswagen Group petrol engines#3.6 VR6 24v FSI 191-220kW EA390|3.6]] [[VR6 engine#VR6|VR6]] 300PS [[List of Porsche engines#Porsche Cayenne .28957.29 engines|4.8]] [[V8 engine|V8]] 400PS / 420PS [[List of Porsche engines#Porsche Cayenne .28957.29 engines|4.8]] [[Turbocharger|T]] V8 500PS / 550PS '''diesel''' [[List of Volkswagen Group diesel engines#3.0 V6 24v TDI CR 150.E2.80.93195 kW|3.0 V6]] 250PS [[List of Volkswagen Group diesel engines#4.2 V8 TDI CR 235-257kW|4.1 V8]] 385 PS
|transmission = 6-Speed [[ZF Friedrichshafen|ZF]] Manual <ref>{{cite web |url=http://www.zf.com/ap/content/en/china/corporate_cn/news_events_cn/news_cn/news_detail_cn.jsp?newsId=21970412|title=ZF Technology Helps "Company Cars of the Year 2013" Gain a Podium Place|accessdate=17 November 2013}}</ref> 8-Speed [[Aisin Seiki Co.|Aisin]] Tiptronic S Automatic<ref>{{cite web |url=http://editorial.autos.msn.com/article.aspx?cp-documentid=962259|title=Porsche Goes Green|accessdate=18 May 2010}}</ref>
|wheelbase = {{convert|2895|mm|in|1|abbr=on}}
|length = {{convert|4846|mm|in|1|abbr=on}} (2010-14) {{convert|4855|mm|in|1|abbr=on}}(2014-)
|width = {{convert|1938|mm|in|1|abbr=on}} (2010-14) {{convert|1939|mm|in|1|abbr=on}}(2014-)
|height = {{convert|1705|mm|in|1|abbr=on}}
|weight = 2085 kg to 2215 kg (DIN)
}}
The second-generation Porsche Cayenne went on sale in April–May 2010 as a 2011 model, with an official debut at the 2010 [[Geneva Motor Show]]. In preparation for the unveiling, the Cayenne production facility in Leipzig, Germany, closed in December 2009 to commence factory retooling for the new model, a process that took 2–3 months.{{cn|date=December 2016}}

[[File:2010-2011 Porsche Cayenne (92A MY11) S wagon (2011-08-03) 02.jpg|thumb|left|Porsche Cayenne S (Australia; pre-facelift)]]
[[File:2015 Porsche Cayenne V6 Disel Triptonic S 3.0 Front.jpg|thumb|left|Porsche Cayenne V6 Diesel (UK; facelift)]]
[[File:2015 Porsche Cayenne V6 Disel Triptonic S 3.0 Rear.jpg|thumb|left|Porsche Cayenne V6 Diesel (UK; facelift)]]
The 2011 Porsche Cayenne is larger than its predecessors, but features a more slanted rear window, less upright windshield, a more sloping roofline, door-mounted mirrors, smaller windows at the rear of the vehicle, headlights inspired by the [[Porsche Carrera GT|Carrera GT]], taillights that extend onto the car's tailgate, [[LED]] [[daytime running lamp|daytime running lights]] and a vastly redesigned interior modeled after the [[Porsche Panamera|Panamera]].<ref>{{cite web|url=http://www.jbcarpages.com/porsche/cayenne/2008/|title=2008 Porsche Cayenne Review|publisher=JB car pages|accessdate=2011-04-03}}</ref> The 2011 Cayenne is almost {{Convert|250|kg|abbr=on}} lighter than the previous models due to extensive use of aluminum and magnesium, making it more fuel efficient than the previous lineup.<ref name="2011specs">{{cite web|url=http://www.jbcarpages.com/porsche/cayenne/2011/specs/|title=2011 Porsche Cayenne Specs & Features|publisher=JB car pages|accessdate=2011-04-03}}</ref> Despite its lower stance, the new vehicle's off-road capabilities have been retained without compromising the street performance-oriented layout and design. {{Citation needed|date=February 2010}}. In addition to a diesel offering, a hybrid version is available.<ref>{{cite web|url=http://www.jbcarpages.com/porsche/cayenne/2011/|title=2011 Porsche Cayenne Review|publisher=JB car pages|accessdate=2011-04-03}}</ref> Also, model year 2013 - 2016 diesel Porsche Cayennes are included in the [[Volkswagen emissions scandal]].

Standard features of the 2011 Porsche Cayenne include air conditioning with dual-zone climate controls, interior air filter, tilt/telescopic leather-wrapped steering wheel with radio controls, cruise control, leather upholstery, eight-way power front seats, outside-temperature indicator, and universal garage door opener in the base model. The Cayenne S adds a power sunroof and memory for the driver's seat.<ref name="2011specs"/> The Cayenne GTS added an optional rearview camera, keyless access and start, and memory system. Finally, the most upscale Cayenne Turbo and Turbo S added a navigation system with voice recognition, optional four-zone climate controls, heated rear seats, premium sound system with six-disc CD changer.<ref>{{cite web|author=Cayenne S or Turbo? - Page 2 - MBWorld.org Forums says: |url=http://streetcars.co.za/2009/03/2010-porsche-cayenne-suv-spy-shots/ |title=2010 Porsche Cayenne SUV - SPY SHOTS |publisher=StreetCars |date=2009-03-16 |accessdate=2009-07-09}}</ref>

The Cayenne's naturally aspirated and turbocharged V8 engines are shared with the Panamera and have been upgraded for faster acceleration times with more horsepower and torque, as well as more powerful direct-injection technology to improve efficiency. The base Cayenne model Cayenne is tuned to offer 300 hp.{{cn|date=December 2016}}
[[File:Porsche Cayenne GTS and Porsche Hybrid Drive.jpg|thumb|left|Porsche Cayenne [[hybrid vehicle drivetrain|hybrid drivetrain]]]]
The Cayenne comes powered by a 3.6-L VR6 engine producing {{Convert|300|PS|kW hp|0|abbr=on}}, the Cayenne S features the same 4.8-L V8 in the Panamera S models producing {{Convert|400|PS|kW hp|0|abbr=on}} and the Cayenne Turbo comes with Panamera Turbo's 4.8-L twin turbo V8 producing {{Convert|500|PS|kW hp|0|abbr=on}}.<ref name="2011specs"/> The Cayenne S Hybrid uses an Volkswagen-sourced 3.0-L V6 engine producing {{Convert|333|PS|kW hp|0|abbr=on}} paired with a nickel metal hydride battery capable of {{Convert|47|PS|kW hp|0|abbr=on}} for a total of {{Convert|380|PS|kW hp|0|abbr=on}}.<ref>{{cite web|url=http://www.jbcarpages.com/porsche/cayenne/2011/specs2/|title=2011 Porsche Cayenne Hybrid Specs & Features|publisher=JB car pages|accessdate=2011-04-03}}</ref> A manual gearbox serves as the standard transmission system on the base Cayenne, with all other models featuring an eight-speed Tiptronic as standard equipment. The low-range transfer case found in the previous generation has been removed. All vehicles will feature about 10% less weight than their predecessors, 70 kg worth of standard equipment in excess of that found on the current model and a more heavily contoured rear bench.{{cn|date=December 2016}}

Available [[Porsche Dynamic Chassis Control]] ([[PDCC]]) [[active anti-roll bar]]s,<ref>{{cite web|url=http://www.porsche.com/international/models/cayenne/cayenne-turbo/chassis/porsche-dynamic-chassis-control-pdcc/|title=Porsche Dynamic Chassis Control (PDCC) - Chassis - Cayenne Turbo - Dr. Ing. h.c. F. Porsche AG|work=Porsche AG - Dr. Ing. h.c. F. Porsche AG}}</ref> [[Adaptive air suspension]] and [[Porsche Active Suspension Management]] (PASM).

In September 2012 Porsche announced the Cayenne S Diesel.<ref>{{cite web|url=http://www.porsche.com/uk/aboutporsche/pressreleases/pag/archive2012/quarter3/?pool=international-de&id=2012-09-12|title=Cayenne S Diesel: a measure of efficiency}}</ref> This model is fitted with the Volkswagen 4.1-L V8 TDI engine. In October 2012, Porsche confirmed the addition of a new Cayenne Turbo S.<ref>{{cite web|url=http://www.autoweek.com/article/20121011/losangeles/121019961|title=2013 Porsche Cayenne Turbo S model confirmed|work=autoweek.com}}</ref>

In July 2014, Porsche launched a facelifted Cayenne range, with minor exterior alterations and new power-train options, including a plug-in E-Hybrid and downsizing of the S model's 4.8-L V8 to a turbocharged 3.6-L V6.{{cn|date=December 2016}}

===Hybrid===

At the [[Frankfurt Motor Show#2005|IAA 2005]], Porsche announced it would produce a [[hybrid vehicle|hybrid]] version of the Cayenne before 2010 (Porsche Cayenne Hybrid). Two years later, at the [[Frankfurt Motor Show#2007|IAA 2007]], Porsche presented a functioning Cayenne Hybrid and demonstration model of the drivetrain.{{cn|date=December 2016}}

Notable modifications to this car include an electric vacuum pump and hydraulic steering pump, allowing the car to function even when the engine is deactivated. A 288-volt [[nickel metal hydride]] battery is placed under the boot floor, occupying the space normally used for a spare tire.<ref>{{cite web|url=http://www.edmunds.com/insideline/do/Features/articleId=121999/First |archive-url=https://web.archive.org/web/20080922184208/http://www.edmunds.com/insideline/do/Features/articleId%3D121999/First |dead-url=yes |archive-date=2008-09-22 |title=Look: Porsche Cayenne Hybrid |publisher=Edmunds |date=2007-08-06 |accessdate=2010-10-03 |df= }}</ref>

The production version, called the S Hybrid, was launched in 2010, with a 3.0-L petrol V6 linked with an electric motor to achieve {{CO2}} emissions of 193 g/km.<ref>{{cite web|title=Porsche Cayenne S Hybrid|url=http://www.autoexpress.co.uk/porsche/cayenne/17788/porsche-cayenne-s-hybrid|website=Auto Express|accessdate=28 July 2014|date=3 April 2010}}</ref> The S Hybrid was launched in the U.S. market in November 2010.<ref>{{cite web|url=http://www.insideline.com/porsche/cayenne/2011/2011-porsche-cayenne-s-hybrid-on-sale-in-november.html |title=2011 Porsche Cayenne S Hybrid on Sale in November |publisher=Insideline.com |date=2010-10-28 |accessdate=2011-04-24}}</ref>

===Plug-in hybrid===
[[File:2017 Porsche Cayenne S E-Hybrid Platinum WAS 2017 1807.jpg|thumb|upright|Porsche Cayenne S E-Hybrid charging port.]][[File:Porsche Cayenne S e-hybrid badge SAO 2016 9492.jpg|thumb|Porsche badge for its [[plug-in hybrid]] variants.]]

In July 2014, Porsche announced the launch of the Porsche Cayenne S E-Hybrid, a [[plug-in hybrid]] with an [[all-electric range]] between {{Convert|18|and|36|km|abbr=on}} under the [[New European Driving Cycle]] (NEDC) standard. The plug-in model displaced the Cayenne S Hybrid from the line up, and it is part of the revised range. The Cayenne S E-Hybrid is the first plug-in hybrid in the premium [[SUV]] segment, allowing Porsche to become the first automaker with three production plug-in hybrid models.<ref name=CayennePHEV>{{cite web|url=http://www.greencarcongress.com/2014/07/20140724-cayenne.html|title=Porsche introducing new plug-in Cayenne S E-Hybrid SUV; third plug-in from Porsche|author=Porsche Press Release|publisher=Green Car Congress|date=2014-07-24|accessdate=2014-07-27}}</ref> Deliveries in Germany were scheduled to begin in October 2014.<ref name=CayenneGER>{{cite news|url=http://www.kfz-betrieb.vogel.de/neuwagen/handel/articles/453657/?cmp=nl-125|title=Neuer Porsche Cayenne kommt im Oktober|language=German|trans-title=New Porsche Cayenne comes in October|author=Martin Achter|work=KFZ-Betrieb |date=2014-07-24|accessdate=2014-07-27}}</ref> Sales in the U.S. began in November 2014.<ref name=USPEVsales112014>{{cite web|url=http://insideevs.com/november-2014-plug-electric-vehicle-sales-report-card/|title=November 2014 Plug-In Electric Vehicle Sales Report Card |author=Jay Cole|publisher=InsideEVs.com|date=2014-12-03|accessdate=2014-12-04}}</ref>

;EPA fuel economy ratings
The following are the official [[EPA]] ratings of the Cayenne S E-Hybrid compared with the others models of the 2015 line up available in the U.S.:

{|class="wikitable" style="margin: 1em auto 1em auto"
|-
! rowspan="2"| Vehicle || rowspan="2"|Model year|| rowspan="2"|Operating mode ([[all-electric range|AER]])|| colspan="3"|[[U. S. Environmental Protection Agency|EPA]] [[fuel economy in automobiles|fuel economy]] ratings<ref name=EPAratings>{{cite web|url=http://www.fueleconomy.gov/feg/Find.do?action=sbs&id=35896&id=35594&id=35792&id=35895|title=Compare Side-by-Side - 2015 Porsche Cayenne S E-Hybrid, 2015 Porsche Cayenne Diesel, 2015 Porsche Cayenne S and 2015 Porsche Cayenne Turbo|publisher=Fueleconomy.gov|author=[[U. S. Environmental Protection Agency]] and [[U.S. Department of Energy]]|date=2014-12-05|accessdate=2014-12-05}}</ref>
|- style="text-align:center;"
! Combined || City||Highway
|-style="text-align:center;"
| rowspan="2" align=left|Porsche Cayenne S E-Hybrid||rowspan="2"| 2015||Electricity and gasoline (14 mi)||47 [[Miles per gallon gasoline equivalent|mpg-e]] (69 kWh/100 mi)||-||-
|- style="text-align:center;"
|Gasoline only||22 mpg ||- || -
|-style="text-align:center;"
|align=left|Porsche Cayenne Diesel||2015||Diesel only||23 mpg || 20 mpg || 29 mpg
|-style="text-align:center;"
|align=left|Porsche Cayenne S||2015||Gasoline only|| 20 mpg || 17 mpg || 24 mpg
|-style="text-align:center;"
|align=left|Porsche Cayenne Turbo||2015||Gasoline only|| 17 mpg || 14 mpg|| 21 mpg
|-
|}

===Engines===
{{Unreferenced section|date=December 2016}}
{| class="wikitable"
|-
! Model !! Production period !! Engine !! Power (PS, torque)@rpm!! Emissions {{CO2}}
|-
|Cayenne||2010-2014||{{convert|3598|cc|L cuin|1|abbr=on}} VR6||{{convert|300|PS|kW hp||abbr=on}}@6300, {{convert|400|Nm|lbft||abbr=on}}@3000||236 g/km
|-
|Cayenne||2014-2018||{{convert|3598|cc|L cuin|1|abbr=on}} VR6||{{convert|300|PS|kW hp||abbr=on}}@6300, {{convert|400|Nm|lbft||abbr=on}}@3000||215 g/km
|-
|Cayenne S||2010-2014||{{convert|4806|cc|L cuin|1|abbr=on}} V8||{{convert|400|PS|kW hp||abbr=on}}@6500, {{convert|500|Nm|lbft||abbr=on}}@3500|| 245 g/km
|-
|Cayenne S||2014-2018||{{convert|3604|cc|L cuin|1|abbr=on}} twin turbo V6||{{convert|420|PS|kW hp||abbr=on}}@6000, {{convert|500|Nm|lbft||abbr=on}}@1350|| 223 g/km
|-
|Cayenne S Hybrid||2010-2014||{{convert|2995|cc|L cuin|1|abbr=on}} V6||{{convert|333|PS|kW hp||abbr=on}}@5250, {{convert|440|Nm|lbft||abbr=on}}@3000|| 193 g/km
|-
|Cayenne S E-Hybrid||2014-2018||{{convert|2995|cc|L cuin|1|abbr=on}} V6||{{convert|416|PS|kW hp||abbr=on}}@5500, {{convert|590|Nm|lbft||abbr=on}}@3000|| 79 g/km
|-
|Cayenne GTS||2010-2014||{{convert|4806|cc|L cuin|1|abbr=on}} V8||{{convert|420|PS|kW hp||abbr=on}}@6500, {{convert|515|Nm|lbft||abbr=on}}@3500|| 251 g/km
|-
|Cayenne GTS||2015-2018||{{convert|3604|cc|L cuin|1|abbr=on}} twin turbo V6||{{convert|440|PS|kW hp||abbr=on}}@6000, {{convert|600|Nm|lbft||abbr=on}}@1600|| 228 g/km
|-
|Cayenne Turbo||2010-2014||{{convert|4806|cc|L cuin|1|abbr=on}} twin turbo V8||{{convert|500|PS|kW hp||abbr=on}}@6000, {{convert|700|Nm|lbft||abbr=on}}@2250|| 270 g/km
|-
|Cayenne Turbo||2014-2018||{{convert|4806|cc|L cuin|1|abbr=on}} twin turbo V8||{{convert|520|PS|kW hp||abbr=on}}@6000, {{convert|750|Nm|lbft||abbr=on}}@2250|| 261 g/km
|-
|Cayenne Turbo S||2010-2014||{{convert|4806|cc|L cuin|1|abbr=on}} twin turbo V8||{{convert|550|PS|kW hp||abbr=on}}@6000, {{convert|750|Nm|lbft||abbr=on}}@2250|| 270 g/km
|-
|Cayenne Turbo S||2015-2018||{{convert|4806|cc|L cuin|1|abbr=on}} twin turbo V8||{{convert|570|PS|kW hp||abbr=on}}@6000, {{convert|800|Nm|lbft||abbr=on}}@2500|| 267 g/km
|-
|Cayenne Diesel||2010-2011||{{convert|2967|cc|L cuin|1|abbr=on}} V6||{{convert|240|PS|kW hp||abbr=on}}@4000, {{convert|550|Nm|lbft||abbr=on}}@2000||
|-
|Cayenne Diesel||2011-2014||{{convert|2967|cc|L cuin|1|abbr=on}} V6||{{convert|245|PS|kW hp||abbr=on}}@4000, {{convert|550|Nm|lbft||abbr=on}}@1750|| 189 g/km
|-
|Cayenne Diesel||2012-2018||{{convert|2967|cc|L cuin|1|abbr=on}} V6||{{convert|262|PS|kW hp||abbr=on}}@4000, {{convert|580|Nm|lbft||abbr=on}}@1750|| 173 g/km
|-
|Cayenne S Diesel||2014-2018||{{convert|4134|cc|L cuin|1|abbr=on}} V8||{{convert|385|PS|kW hp||abbr=on}}@3750, {{convert|850|Nm|lbft||abbr=on}}@2000|| 209 g/km
|}

===Guinness World Record===
On 1 May 2017, a 2017 Porsche Cayenne S Diesel set the [[Guinness World Records|Guinness World Record]] for heaviest aircraft pulled by a production car. The Cayenne towed a 285 ton [[Air France]] [[Airbus A380]] to a distance of 42 meters, breaking the previous 2013 record of a [[Nissan Patrol]] towing a 170 ton [[Ilyushin Il-76]] to a distance of 50 meters.<ref>{{cite news |url=https://sg.news.yahoo.com/porsche-cayenne-tows-airbus-a380-062112301.html |title=Porsche Cayenne tows Airbus A380 to set Guinness World Record |author=Tadeo, Patrick Everett |publisher=[[Carmudi]]/[[Yahoo! News]] |date=2 May 2017 |accessdate=3 May 2017}}</ref> After the attempt Porsche repeated the test using a petrol-powered Cayenne Turbo S with 800 Nm of [[torque]], 50 Nm less than the S Diesel, in an effort to prove the Cayenne's remarkable ability.<ref>{{Cite news|url=https://www.cnet.com/roadshow/news/watch-porsche-cayenne-tow-airbus-a380-earn-world-record/|title=Watch a Porsche Cayenne tow an Airbus A380, earn a world record - Roadshow|work=Roadshow|access-date=2017-05-08|language=en}}</ref>

==Third generation (2018–present)==
{{infobox automobile
|name = Third generation (9Y0)
|image=Porsche Cayenne, IAA 2017 (1Y7A2256).jpg
|caption=Porsche Cayenne (Third Generation)
|model_years=2018–present (Europe) 2019–present (US&Canada)
|production=2017–present
|designer=Michael Mauer
| engine = '''Petrol:''' 3.0 L [[Audi]] [[V6 engine|V6]] [[Turbocharger|Turbo]] [[Gasoline direct injection|FSI]] 2.9 L [[Audi]] [[V6 engine|V6]] [[Twin-turbo]] [[Gasoline direct injection|FSI]] 4.0 L Audi-Porsche [[V8 engine|V8]] [[Twin-turbo]]
| transmission = 8-speed ZF automatic
|related=[[Volkswagen Touareg#Third generation (2018–present)|Volkswagen Touareg]] [[Audi Q7#4M|Audi Q7]] [[Audi Q8]] [[Bentley Bentayga]] [[Audi A4#B9|Audi A4]] [[Audi A5#Second generation (2016–present)|Audi A5]] [[Audi A8#D5|Audi A8]] [[Porsche Panamera#Second generation (2017–present)|Porsche Panamera]] [[Lamborghini Urus]]
}}
The third-generation Porsche Cayenne was revealed online on August 29, 2017 as a 2019 model, based on the [[Volkswagen Group MLB platform]].<ref name=2018engines>{{cite web|url=https://newsroom.porsche.com/en/products/porsche-cayenne-world-premiere-livestream-suv-third-generation-14073.html|title=World premiere of the new Cayenne in Zuffenhausen |author=Porsche|publisher=Porsche|date=2017-08-29|accessdate=2017-08-30}}</ref>

===Engines===

All engines of the third generation models are turbocharged.<ref name=2018engines>{{cite web|url=https://newsroom.porsche.com/en/products/porsche-cayenne-world-premiere-livestream-suv-third-generation-14073.html|title=World premiere of the new Cayenne in Zuffenhausen |author=Porsche|publisher=Porsche|date=2017-08-29|accessdate=2017-08-30}}</ref>

{| class="wikitable"
|-
! Model !! Production period !! Engine !! Power (PS, torque)@rpm!! Emissions {{CO2}}
|-
|Cayenne||2019-||{{convert|2995|cc|L cuin|1|abbr=on}} V6||{{convert|340|PS|kW hp||abbr=on}}@5300-6400, {{convert|450|Nm|lbft||abbr=on}}@1340-5300||205 g/km
|-
|Cayenne S||2019-||{{convert|2894|cc|L cuin|1|abbr=on}} V6||{{convert|440|PS|kW hp||abbr=on}}@5700-6600, {{convert|550|Nm|lbft||abbr=on}}@1800-5500|| 209 g/km
|-
|Cayenne Turbo||2019-||{{convert|3996|cc|L cuin|1|abbr=on}} V8||{{convert|558|PS|kW hp||abbr=on}}@5750, {{convert|770|Nm|lbft||abbr=on}}@1960|| 272-267 g/km
|-
|}

==See also==
{{portal|Cars}}
*[[List of hybrid vehicles]]
*[[Lohner-Porsche Mixte Hybrid]], the first hybrid in history.

==References==
{{reflist|30em}}

===Bibliography===
*{{cite book|last1=Becker|first1=Clauspeter|last2=Warter|first2=Stefan|title=Porsche Cayenne|year=2002|publisher=Delius Klasing Verlag|location=Bielefeld|isbn=3-7688-1403-3}} {{en icon}}
*{{cite web|last1=Morris|first1=Raymond|title=2014 Porsche Cayenne Platinum Edition Review|url=http://www.izmostudio.com/design-reviews/2014-porsche-cayenne-platinum-edition-review|website=izmoStudio|accessdate=24 August 2014}}

==External links==

{{Commons category|Porsche Cayenne}}
{{Commonscat |Porsche 92A Cayenne S Hybrid}}
{{Commons category|Porsche 92A Cayenne S e-hybrid}}

*[http://www.porsche.com/international/models/cayenne/ Cayenne models at official website]

{{Porsche vehicles}}
{{Porsche modern timeline}}

{{Authority control}}
[[Category:Porsche vehicles|Cayenne]]
[[Category:Luxury crossover sport utility vehicles]]
[[Category:Luxury sport utility vehicles]]
[[Category:Hybrid sport utility vehicles]]
[[Category:Plug-in hybrid vehicles]]
[[Category:All-wheel-drive vehicles]]
[[Category:2000s automobiles]]
[[Category:2010s automobiles]]
[[Category:Cars introduced in 2002]]
[[Category:Cars introduced in 2010]]