Beryllium

Beryllium is the chemical elementin the periodic tablethat has the symbol Be and atomic number4. A toxic bivalentelement, beryllium is a steel grey, strong, light-weight yet brittle, alkaline earthmetal, that is primarily used as a hardening agent in alloys(most notably beryllium copper).

Notable characteristics

Beryllium has one of the highest melting pointsof the light metals. The modulus of elasticityof beryllium 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 neutronsare liberated when it is hit by alpha particles, as from radiumor polonium(about 30 neutrons/million alpha particles). At standard temperature and pressuresberyllium resists oxidationwhen exposed to air (although its ability to scratch glass is probably due to the formation of a thin layer of the oxide).

Applications

• Beryllium is used as an alloyingagent in the production of beryllium-copperbecause of its ability to absorb large amounts of heat. Beryllium-copper alloys are used in a wide variety of applications because of their electricaland thermal conductivity, high strength and hardness, nonmagnetic properties, along with good corrosion and fatigue resistance. These applications include the making of spot-weldingelectrodes, 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-raydetection diagnostics to filter out visible light and allow only X-rays to be detected.
• In the field of X-ray lithography beryllium is used for the reproduction of microscopic integrated circuits.
• Because it has a low thermal neutronabsorption cross section, the nuclear power industry uses this metal in nuclear reactorsas a neutron reflector and moderator.
• Beryllium is used in nuclear weapons for similar reasons. For example, the critical massof a plutonium sphere is significantly reduced if the plutonium is surrounded by a beryllium shell.
• Beryllium is sometimes used in neutron sources, in which the beryllium is mixed with an alpha emmiter such as polonium210, radium226, or actinium227.
• Beryllium is also used in the making of gyroscopes, various computerequipment, watch springs and instruments where light-weight, rigidity and dimensional stability are needed.
• Beryllium oxideis 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 lightingtubes, but this use was discontinued because of berylliosisin the workers manufacturing the tubes (see below).
• The James Webb Space Telescope(Beryllium related details from NASA here)will have 18 hexagonal beryllium sections for its mirrors. Because JWST will face a temperature of −240 degrees Celsius (30 kelvin), the mirror is made of beryllium, a material capable of handling extreme cold better than glass. Beryllium contracts and deforms less than glass — and thus remains more uniform — in such temperatures.

History

The name beryllium comes from the Greekberyllos, beryl, from Prakritveruliya, from P?liveuriya; possibly from or simply akin to a Dravidiansource represented by Tamilveiruor, viar, "to whiten, become pale." [1]At one time beryllium was referred to as glucinium (from Greekglykys, sweet), due to the sweet taste of its salts. This element was discovered by Louis Vauquelinin 1798as the oxide in beryland in emeralds. Friedrich Wöhlerand A. A. Bussyindependently isolated the metal in 1828by reacting potassiumand beryllium chloride.

Occurrence

Beryllium is an essential constituent of about 100 out of about 4000 known minerals, the most important of which are bertrandite(Be₄Si₂O₇(OH)₂), beryl(Al₂Be₃Si₆O₁₈), chrysoberyl(Al₂BeO₄), and phenakite(Be₂SiO₄). Precious forms of beryl are aquamarineand emerald. Along with hydrogen, helium, and lithium, some beryllium was created in the big bang.

The most important commercial sources of beryllium and its compounds are beryl and bertrandite. Beryllium metal did not become readily available until 1957. Currently, most production of this metal is accomplished by reducing beryllium fluoridewith magnesiummetal. The price on the US market for vacuum-cast beryllium ingots was 338 US$per pound ($745/kg) in 2001. [2]

BeF₂ + Mg → MgF₂ + Be

Isotopes

Image:Solar Activity Proxies.png

Of beryllium's 10 isotopes, only beryllium-9 is stable. Cosmogenicberyllium-10 is produced in the atmosphereby cosmic rayspallationof oxygenand nitrogen. Because beryllium tends to exist in solutionat pHlevels 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 precipitationquickly becomes more alkaline, beryllium drops out of solution. Cosmogenic beryllium-10 thereby accumulates at the soilsurface, where its relatively long half-life(1.51 million years) permits a long residence time before decaying to boron-10. Beryllium-10 and its daughter products have been used to examine soil erosion, soil formationfrom regolith, the development of lateritic soils, as well as variations in solar activityand the age of ice cores.

The fact that beryllium-7 and beryllium-8 are unstable has profound cosmological consequences as it means that elements heavier than beryllium could not be produced by nuclear fusion in the Big Bang. Moreover, the nuclear energy levels of beryllium-8 are such that carbon can be produced within stars, thus making life possible. (See triple-alpha processand Big Bang nucleosynthesis).

The shortest-lived known isotope of beryllium is beryllium-13 which decays through neutron emission. It has a half-life of 2.7 × 10^-21 seconds. Be-6 also is also very short-lived with a half-life of 5.0 × 10^-21 seconds.

Precautions

Image:Beryllium OreUSGOV.jpg Beryllium and its salts are toxicsubstances and potentially carcinogenic. Chronic berylliosisis 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 lampsin Massachusetts. Chronic berylliosis resembles sarcoidosisin 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 canceris 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.

Health effects

Beryllium can be harmful if inhaled. The effects depend on period of exposure. If beryllium air levels are high enough (greater than 1000 µg/m³), an acute condition can result, called acute beryllium disease, which resembles pneumonia. Occupational and community air standards are effective in preventing most acute lung damage. Long term exposure to beryllium can increase the risk of developing lung cancer.

Some people (1-15%) become sensitive to beryllium. These individuals may develop an inflammatory reaction in the respiratory system. This condition is called chronic beryllium disease (CBD), and can occur many years after exposure to higher than normal levels of beryllium (greater than 0.2 µg/m³). This disease causes fatigue, weakness, and can cause difficulty in breathing. It can result in anorexia, weight loss, and may also lead to right-side heart enlargement and heart disease in advanced cases. Some people who are sensitized to beryllium may not have any symptoms. The general population is unlikely to develop acute or chronic beryllium disease because ambient air levels of beryllium are normally very low (0.00003-0.0002 µg/m³).

Swallowing beryllium has not been reported to cause effects in humans because very little beryllium is absorbed from the stomach and intestines. Ulcers have been seen in dogs ingesting beryllium in the diet. Beryllium contact with skin that has been scraped or cut may cause rashesor ulcers.

The United States Department of Health and Human Services(DHHS) and the International Agency for Research on Cancer(IARC) have determined that beryllium is a human carcinogen. The U.S. Environmental Protection Agency(EPA) has determined that beryllium is a probable human carcinogen. The EPA has estimated that lifetime exposure to 0.04 µg/m³ beryllium can result in a one in a thousand chance of developing cancer.

There are no studies on the health effects of children exposed to beryllium. It is likely that the health effects seen in children exposed to beryllium will be similar to the effects seen in adults. It is unknown whether children differ from adults in their susceptibility to beryllium. It is unclear whether beryllium is teratogenic.

Beryllium can be measured in the urine and blood. The amount of beryllium in blood or urine may not indicate time or quantity of exposure. Beryllium levels can also be measured in lung and skin samples. Another blood test, the blood beryllium lymphocyte proliferation test (BeLPT), identifies beryllium sensitization and has predictive value for CBD.

Typical levels of beryllium that industries may release into the air are of the order of 0.01 µg/m³, averaged over a 30-day period, or 2 µg/m³ of workroom air for an 8-hour work shift.

References

• Los Alamos National Laboratory – Beryllium

External links

• Computational Chemistry Wiki
• It's Elemental – Beryllium
• IARC Monograph "Beryllium and Beryllium Compounds"
• National Pollutant Inventory - Beryllium and compounds
• WebElements.com – Berylliumaf:Berillium

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It uses material from the http://en.wikipedia.org/wiki/Beryllium Wikipedia article Beryllium.