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General |
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|---|---|
| Name | Dinitrogen oxide |
| Chemical formula | N2O |
| Appearance | Colourless gas |
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Physical |
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| Formula weight | 44.0 amu |
| Melting point | 182 K (-91 °C) |
| Boiling point | 185 K (-88 °C) |
| Density | 1.2 ×103 kg/m3 (liquid) |
| Solubility | 0.112 g in 100g water |
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Thermochemistry |
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| ΔfH0gas | 82.05 kJ/mol |
| ΔfH0liquid | ? kJ/mol |
| ΔfH0solid | ? kJ/mol |
| S0gas, 1 bar | 219.96 J/mol·K |
| S0liquid, 1 bar | ? J/mol·K |
| S0solid | ? J/mol·K |
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Safety |
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| Inhalation | See main text. May cause asphyxiation without warning. |
| Skin | Hazardous when cryogenic or compressed. |
| Eyes | Hazardous when cryogenic or compressed. |
| More info | Hazardous Chemical Database |
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SI units were used where possible. Unless otherwise stated, standard conditions were used. | |
Nitrous oxide, also known as dinitrogen oxide or dinitrogen monoxide, is a chemical compound with chemical formula N2O. Under room conditions it is a colourless non-flammable gas, with a pleasant slightly sweet odor. It is commonly known as laughing gas due to the exhilarating effects of inhaling it. It is used in surgery and dentistry for its anaesthetic and analgesic effects.
Chemistry
History
The gas was discovered by Joseph Priestley in 1772. Humphry Davy in the 1790s tested the gas on himself and some of his friends, including the poets Samuel Taylor Coleridge and Robert Southey. They soon realised that nitrous oxide considerably dulled the sensation of pain, even if the inhaler were still semi-conscious, and so it came into use as an anaesthetic, particularly by dentists, who do not typically have access to the services of an anesthesologist and who may benefit from a patient who can respond to verbal commands.
Uses
Inhalant effects — laughing gas
Nitrous oxide is a dissociative which causes (by some accounts) euphoria, dizziness, and, in some cases, a mild aphrodisiac effect. It can also result in mild nausea or lingering dizziness if too much is inhaled in too short a time. The anaesthetic function of nitrous oxide is not completely understood, but it is thought that the gas interacts with the plasma membranes of nerve cells in the brain and thus affects the communication among such cells at their synapses.
Some people use nitrous oxide for its psychological effects (in this context it is sometimes referred to as "hippie crack"). While the gas itself is not toxic, death can result if it is inhaled in such a way that not enough oxygen is breathed in. Long-term use in large quantities has been associated with symptoms similar to vitamin B12 deficiency: anemia and neuropathy. It can be habit-forming, mainly because of its short-lived effect and ease of access. Its use is thus restricted in many districts. In California, for instance, inhalation of nitrous oxide "for the purpose of causing euphoria, or for the purpose of changing in any manner, one’s mental processes," is a criminal offense. (See, Cal. Pen. Code, Sec. 381b.) The Center for Cognitive Liberty & Ethics, a nonprofit law and policy center in the United States, contends that such laws are unconstitional "prior restraints on speech" and constitute "cognitive censorship."
Aerosol propellant
The gas is licensed for use as a food additive, specifically as an aerosol propellant. Its most common uses in this context are in aerosol whipped cream canisters and as an inert gas used to displace staleness-inducing oxygen when filling packages of potato chips and other similar snack foods.
The gas is excellently soluble in fatty compounds. In aerosol whipped cream, it is dissolved in the fatty cream until it leaves the can, when it becomes gaseous and thus creates foam.
Car racing
In car racing, nitrous oxide (often just "nitrous" or "nitro" in this context) is sometimes injected into the intake manifold (or just prior to the intake manifold) to increase power: even though the gas itself is not flammable, it delivers more oxygen than atmospheric air by breaking down at elevated temperatures, thus allowing the engine to burn more fuel and air. Additionally, since nitrous oxide is stored as a liquid, the evaporation of liquid nitrous oxide in the intake manifold causes a large drop in intake charge temperature. This results in a smaller, denser charge, and can reduce detonation, as well as increase power available to the engine.
The same technique was used during World War II to boost the power of aircraft engines, particularly by the Luftwaffe which had less access to fuel with high octane ratings than did the Royal Air Force and United States Air Force.
It is very important with nitrous oxide augmentation of internal combustion engines to maintain temperatures and fuel levels so as to prevent preignition, or detonation (sometimes referred to as knocking or pinging).
Rocket motors
Nitrous oxide can be used as an oxidiser in a rocket engine. This has the advantages over other oxidisers that it is non-toxic and, due to its stability at room temperature, easy to store and relatively safe to carry on a flight.
Nitrous oxide has notably been the oxidiser of choice in several hybrid rocket designs (using solid fuel with a liquid or gaseous oxidiser). The combination of nitrous oxide with hydroxy-terminated polybutadiene fuel has been used by SpaceShipOne and others.
Nitrous oxide pollution
Nitrogen oxides, nitrous oxide included, are greenhouse gases 270 times more potent than carbon dioxide.