Beryllium
Beryllium is a chemical element in the periodic table that has the symbol Be and atomic number 4. A toxic bivalent element, Beryllium is a steel grey, strong, light-weight yet brittle, alkaline earth metal, that is primarily used as a hardening agent in alloys (most notably, beryllium copper).
Notable Characteristics
Beryllium has one of the highest melting points of the light metals. The modulus of elasticity of this light metal is approximately 1/3 greater than that of steel. It has excellent thermal conductivity, is nonmagnetic and resists attack by concentrated nitric acid. It is highly permeable to X-rays, and neutrons are liberated when it is hit by alpha particles, as from radium or polonium (about 30 neutrons/million alpha particles). At standard temperature and pressures beryllium resists oxidation when exposed to air (although its ability to scratch glass is probably due to the formation of a thin layer of the oxide).
Uses
- Beryllium is used as an alloying agent in the production of beryllium copper (Be has the ability to absorb large amounts of heat). Beryllium-copper alloys are used in a wide variety of applications because of their electrical and thermal conductivity, high strength and hardness, nonmagnetic properties, along with good corrosion and fatigue resistance. These applications include that making of: spot-welding electrodes, springs, non-sparking tools and electrical contacts.
- Due to their stiffness, light weight, and dimensional stability over a wide temperature range, beryllium-copper alloys are also used in the defense and aerospace industries as light-weight structural materials in high-speed aircraft, missiles, space vehicles and communication satellites.
- Thin sheets of beryllium foil are used with X-ray detection diagnostics to filter out visible light and allow only X-rays to be detected.
- In the field of X-ray lithography beryllium is being used for the reproduction of microscopic integrated circuits.
- Because it has a low thermal neutron absorption cross section, the nuclear power industry uses this metal in nuclear reactors as a neutron reflector and moderator.
- Beryllium is also used in the making of gyroscopes, various computer equipment, watch springs and instruments where light-weight, rigidity and dimensional stability are needed.
- Beryllium oxide is useful for many applications that require an excellent heat conductor, with high strength and hardness, with a very high melting point, and that acts as an electrical insulator.
- Beryllium compounds were once used in fluorescent lighting tubes, but this use was discontinued because of berylliosis in the workers manufacturing the tubes (see below).
History
The name beryllium comes from the Greek beryllos, beryl. At one time beryllium was referred to as glucinium (from Greek glykys, sweet), due to the sweet taste of its salts. This element was discovered by Vauquelin in 1798 as the oxide in beryl and in emeralds. Friedrich Wöhler and A. A. Bussy independently isolatated the metal in 1828 by reacting potassium on beryllium chloride.
Sources
Beryllium is found in 30 different minerals, the most important of which are bertrandite, beryl, chrysoberyl, and phenacite. Precious forms of beryl are Aquamarine and emerald. The most important commercial sources of Beryllium and its compounds are beryl and bertrandite. Currently, most production of this metal is accomplished by reducing beryllium fluoride with magnesium metal. Beryllium metal did not become readily available until 1957.
Isolation
BeF2 + Mg --> MgF2 + Be
Isotopes
Beryllium has only one stable isotope, Be-9. Cosmogenic beryllium (Be-10) is produced in the atmosphere by cosmic ray spallation of oxygen and nitrogen. Because beryllium tends to exist in solution at pH levels less than about 5.5 (and most rainwater has a pH less than 5), it will enter into solution and be transported to the Earth's surface via rainwater. As the precipitation quickly becomes more alkaline, Be drops out of solution. Cosmogenic Be-10 thereby accumulates at the soil surface, where its relatively long half-life (1.5 million years -- Ma) permits a long residence time before decaying to Be-9. Be-10 and its daughter products have been used to examine soil erosion, soil formation from regolith, and the development of lateritic soils.
Precautions
Beryllium and its salts are toxic substances and potentially carcinogenic.
Chronic berylliosis is a pulmonary and systemic granulomatous disease caused by exposure to beryllium. Acute beryllium disease in the form of chemical pneumonitis was first reported in Europe in 1933 and in the United States in 1943. Cases of chronic berylliosis were first described in 1946 among workers in plants manufacturing fluorescent lamps in Massachusetts. Chronic berylliosis resembles sarcoidosis in many respects, and the differential diagnosis is often difficult.
Although the use of beryllium compounds in fluorescent lighting tubes was discontinued in 1949, potential for exposure to beryllium exists in the nuclear and aerospace industries and in the refining of beryllium metal and melting of beryllium-containing alloys, the manufacturing of electronic devices, and the handling of other beryllium-containing material.
Early researchers tasted beryllium and its various compounds for sweetness in order to verify its presence. Modern diagnostic equipment no longer necessitates this highly risky procedure and no attempt should be made to ingest this substance. Beryllium and its compounds should be handled with great care and special precautions must be taken when carrying out any activity which could result in the release of beryllium dust (lung cancer is a possible result of prolonged exposure to beryllium laden dust).
This substance can be handled safely if certain procedures are followed. No attempt should be made to work with beryllium before familiarization with correct handling procedures.
External Link Resources:
WebElements.com - Beryllium
EnvironmentalChemistry.com - Beryllium