beryllium

beryllium

[buh-ril-ee-uhm]
beryllium [from beryl ], metallic chemical element; symbol Be; at. no. 4; at. wt. 9.01218; m.p. about 1,278°C;; b.p. 2,970°C; (estimated); sp. gr. 1.85 at 20°C;; valence +2. Beryllium is a strong, extremely light, high-melting, silver-gray metal with a close-packed hexagonal crystalline structure. It is an alkaline-earth metal in Group 2 of the periodic table. Beryllium is resistant to corrosion; weight for weight, it is stronger than steel, and because of its low density (about 1/3 that of aluminum) it has found extensive use in the aerospace industry.

Beryllium is soluble in hot nitric acid, dilute hydrochloric and sulfuric acids, and sodium hydroxide. Like aluminum and magnesium, which it resembles chemically, it readily forms compounds with other elements; it is not found free in nature. However, like aluminum, it is resistant to oxidation in air, even at a red heat; it is thought to form a protective oxide film that prevents further oxidation. The compounds of beryllium are sweet-tasting and highly toxic; this toxicity has limited the use of beryllium as a rocket fuel, even though it yields more heat on combustion for its weight than any other element.

Beryllium transmits X rays much better than glass or other metals; this property, together with its high melting point, makes it desirable as a window material for high-intensity X-ray tubes. Because beryllium resists attack by liquid sodium metal, it is employed in cooling systems of nuclear reactors that use liquid sodium as the heat-transfer material; because it is a good reflector and absorber of neutrons, it is also used as a shield and as a moderator in nuclear reactors.

The addition of 2% to 3% of beryllium to copper makes a nonmagnetic alloy six times stronger than pure copper. This alloy is used to make nonsparking tools for use in oil refineries and other places where sparks constitute a fire hazard; it is also used for small mechanical parts, such as camera shutters. When beryllium is alloyed with other metals such as aluminum or gold it yields substances with a higher melting point, greater hardness and strength, and lower density than the metal with which it is alloyed.

Beryllium aluminum silicates, especially beryl (of which emerald and aquamarine are varieties), constitute the chief sources of the metal. Although its ores occur widely in North America, Europe, and Africa, the cost of extracting the metal limits its commercial use. Beryllium may be prepared by electrolysis of its fused salts; it is prepared commercially by reduction of the fluoride with magnesium metal.

Beryllium was discovered in 1798 as the oxide beryllia by L. N. Vauquelin, a French chemist. Vauquelin analyzed beryl and emerald at the urging of R. J. Haüy, a French mineralogist, who had noted that their optical properties were identical. Beryllium was first isolated in 1828 independently by F. Wöhler in Germany and W. Bussy in France by fusing beryllium chloride with metallic potassium.

Chemical element, lightest of the alkaline earth metals, chemical symbol Be, atomic number 4. It does not occur uncombined in nature but is found chiefly as the mineral beryl (of which emerald and aquamarine are gemstone varieties). Beryllium metal, particularly in alloys, has many structural and thermal applications; it is used in nuclear reactors. Beryllium has valence 2 in all its compounds, which are generally colourless and taste distinctly sweet. All soluble beryllium compounds are toxic. Beryllium oxide is used in specialized ceramics for nuclear devices, and beryllium chloride is a catalyst for organic reactions.

Learn more about beryllium with a free trial on Britannica.com.

Beryllium is a chemical element with the symbol Be and atomic number 4. A bivalent element, beryllium is a steel grey, strong, light-weight yet brittle alkaline earth metal. It is primarily used as a hardening agent in alloys, most notably beryllium copper. Commercial use of beryllium metal presents technical challenges due to the toxicity (especially by inhalation) of beryllium-containing dusts.

Beryllium is a relatively rare element in both the Earth and the universe, because it is not formed in conventional stellar nucleosynthesis. The element is not known to be necessary or useful for either plant or animal life.

Properties

History

This element was discovered by Louis-Nicolas Vauquelin in 1768 as the oxide in beryl and in emeralds. Friedrich Wöhler and A. A. Bussy independently isolated the metal in 1828 by reacting potassium and beryllium chloride.

Etymology

The name beryllium comes from the Greek βήρυλλος, bērullos, beryl, from Prakrit veruliya, from Pāli veḷuriya; akin or perhaps akin to Tamil veḷiru or, viḷar, "to become pale," in reference to the pale semiprecious gemstone beryl. At one time beryllium was referred to as glucinium (with the accompanying chemical symbol "Gl), the name coming from the Greek word for sweet, due to the sweet taste of its salts.

== Applications ==

Mechanical

  • Due to its stiffness, light weight, and dimensional stability over a wide temperature range, Beryllium metal is used in the defense and aerospace industries as light-weight structural materials in high-speed aircraft, missiles, space vehicles, and communication satellites. For example, many high-quality liquid fueled rockets use nozzles of pure Be, an example being the Saturn V.
  • Beryllium is used as an alloying agent in the production of beryllium copper, which contains up to 2.5% beryllium. Beryllium-copper alloys are used in a wide variety of applications because of their combination of high electrical and thermal conductivity, high strength and hardness, nonmagnetic properties, along with good corrosion and fatigue resistance. These applications include the making of spot-welding electrodes, springs, non-sparking tools and electrical contacts.
  • Due to its non-magnetic properties, Beryllium-based tools are often used by military naval EOD-personnel when working on or around sea-mines, as these often have fuses that detonate on direct magnetic contact or when influenced by a magnetic field.
  • Beryllium was also used in Jason pistols which were used to strip paint from the hulls of ships. In this case, beryllium was alloyed to copper and used as a hardening agent.
  • In the telecommunications industry, tools made of beryllium are used to tune the highly magnetic klystrons used for high power microwave applications.
  • Many high-energy particle physics collision experiments such as the Large Hadron Collider, the Tevatron, the SLAC and others contain beam pipes made of beryllium. The low density allows collision products to reach the surrounding detectors without significant interaction, the stiffness allows a powerful vacuum to be produced within the pipe to minimize interaction with gases, its thermal stability allows it to function correctly at temperatures of only a few Kelvin, and its diamagnetic nature keeps it from interfering with the complex multipole magnet systems used to steer and focus the particle beams.
  • Beryllium copper is used in electrical spring contacts.
  • Beryllium is used in gyroscopes, computer equipment, watch springs and instruments where light-weight, rigidity and dimensional stability are needed.
  • The James Webb Space Telescope will have 18 hexagonal beryllium sections for its mirrors. Because JWST will face a temperature of −240 degrees Celsius (33 kelvins), the mirror is made of beryllium, capable of handling extreme cold better than glass. Beryllium contracts and deforms less than glass — and remains more uniform — in such temperatures. For the same reason, the optics of the Spitzer Space Telescope are entirely built of beryllium metal.
  • Beryllium has been used in tweeter and mid-range audio loudspeaker construction as an alternative to titanium and aluminium, largely due to its lower density and greater rigidity.
  • In 1968 Porsche employed Beryllium brake discs in the 909 hill-climb spyder.

Radiation

  • Thin sheets of beryllium foil are used as windows in X-ray detectors to filter out visible light and allow only X-rays to be detected.
  • Sheets of beryllium ranging from thick down to thick are used as the output window in x-ray tubes, allowing x-rays to leave the tube while keeping a vacuum on the inside of the tube.
  • In the field of X-ray lithography beryllium is used for the reproduction of microscopic integrated circuits.
  • Because of its low atomic number beryllium is almost transparent to energetic electrically charged particles. Therefore it is used to build the beam pipe around the collision region in collider particle physics experiments. Notably all four main detector experiments at the Large Hadron Collider accelerator (ALICE, ATLAS, CMS, LHCb) use a beryllium beam-pipe.

Nuclear

Acoustics

  • Beryllium's characteristics (low weight and high rigidity) make it useful as a material for high-frequency drivers. Until recently, most beryllium tweeters used an alloy of beryllium and other metals due to beryllium's high cost, but some high end audio companies manufacture pure beryllium tweeters or speakers using these tweeters. Because beryllium is many times more expensive than titanium, hard to shape due to its brittle nature, and toxic, these tweeters are limited to high-end and PA applications.

Compounds

  • Beryllium is an effective p-type dopant in III-V compound semiconductors. It is widely used in materials such as GaAs, AlGaAs, InGaAs, and InAlAs grown by molecular beam epitaxy (MBE).
  • Beryllium oxide is useful for many applications that require the combined properties of an electrical insulator an excellent heat conductor, with high strength and hardness, with a very high melting point. Beryllium oxide is frequently used as an insulator base plate in high-power transistors in RF transmitters for telecommunications. Beryllium oxide is also being studied for use in increasing the thermal conductivity of uranium dioxide nuclear fuel pellets.
  • 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).

See also Beryllium compounds.

Occurrence on Earth

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 aquamarine, bixbite and emerald.

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 fluoride with magnesium metal. The price on the US market for vacuum-cast beryllium ingots was 338 US$ per pound ($745/kg) in 2001.

BeF2 + Mg → MgF2 + Be

See also Beryllium minerals.

Isotopes

''see also Isotopes of beryllium

Of beryllium's isotopes, only 9Be is stable. Cosmogenic 10Be is produced in the atmosphere by cosmic ray spallation of oxygen and nitrogen. Because beryllium tends to exist in solutions below about pH 5.5 (and rainwater above many industrialized areas can have a pH less than 5), it will dissolve and be transported to the Earth's surface via rainwater. As the precipitation quickly becomes more alkaline, beryllium drops out of solution. Cosmogenic 10Be thereby accumulates at the soil surface, where its relatively long half-life (1.51 million years) permits a long residence time before decaying to 10B. 10Be and its daughter products have been used to examine soil erosion, soil formation from regolith, the development of lateritic soils, as well as variations in solar activity and the age of ice cores. It is also formed in nuclear explosions by a reaction of fast neutrons with 13C in the carbon dioxide in air, and is one of the historical indicators of past activity at nuclear test sites.

The fact that 7Be and 8Be 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. However, Fred Hoyle showed that the energy levels of 8Be and 12C favour carbon production by the triple-alpha process in helium burning stars, thus making life possible. (See also Big Bang nucleosynthesis).

7Be decays by electron capture, therefore its decay rate is dependent upon its electron configuration - a rare occurrence in nuclear decay.

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

The exotics 11Be and 14Be are known to exhibit a nuclear halo.

Precautions

According to the International Agency for Research on Cancer (IARC), beryllium and beryllium compounds are Category 1 carcinogens; they are carcinogenic to both animals and humans. 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. It occasionally killed early workers in nuclear weapons design, such as Herbert Anderson.

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 highly toxic 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.

A successful test for beryllium on different surface areas has been recently developed. The procedure uses fluorescence when beryllium is bound to sulfonated hydroxybenzoquinoline to detect up to 10 times lower than the recommended limit for beryllium concentration in the work place. Fluorescence increases with increasing beryllium concentration. The new procedure has been successfully tested on a variety of surfaces.

Inhalation

Beryllium can be harmful if inhaled and the effects depend on period of exposure. If beryllium concentrations in air are high enough (greater than ), 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. The more common and serious health hazard from beryllium today is chronic beryllium disease (CBD), discussed below. It continues to occur in industries as diverse as metal recycling, dental laboratories, alloy manufacturing, nuclear weapons production, defense industries, and metal machine shops that work with alloys containing small amounts of beryllium.

Chronic beryllium disease (CBD)

Some people (1-15%) become sensitive to beryllium. These individuals may develop an inflammatory reaction that principally targets the respiratory system and skin. This condition is called chronic beryllium disease (CBD), and can occur within a few months or many years after exposure to higher than normal levels of beryllium (greater than ). This disease causes fatigue, weakness, night sweats and can cause difficulty in breathing and a persistent dry cough. 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 disease is treatable, but not curable with traditional drugs and medicine. CBD occurs when the body's immune system recognizes beryllium particles as foreign material and mounts an immune system attack against the particles. Because these particles are typically inhaled into the lungs, the lungs become the major site where the immune system responds, they become inflamed and fill with large numbers of white blood cells that accumulate wherever beryllium particles are found. These cells form balls around the beryllium particles called “granulomas.” When enough of these develop, they interfere with the normal function of the organ. Over time, the lungs become stiff and lose their ability to help transfer oxygen from the air into the bloodstream. Patients with CBD develop difficulty inhaling and exhaling sufficient amounts of air, and the amount of oxygen in their bloodstreams falls. Treatment of such patients includes use of oxygen and medicines that try to suppress the immune system’s over-reaction to beryllium. A class of immunosuppressive medicines called glucocorticoids (example: prednisone) is most commonly used as treatment. 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).

Ingestion

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 their diet.

Dermatological effects

Beryllium can cause contact dermatitis. Beryllium contact with skin that has been scraped or cut may cause rashes, ulcers, or bumps under the skin called granulomas.

Effects on children

There are no studies on the health effects of children exposed to beryllium, although individual cases of CBD have been reported in children of beryllium workers from the 1940s. 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.

Detection in the body

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. While such measurements may help establish that exposure has occurred, other tests are used to determine if that exposure has resulted in health effects. A blood test, the blood beryllium lymphocyte proliferation test (BeLPT), identifies beryllium sensitization and has predictive value for CBD. The BeLPT has become the standard test for detecting beryllium sensitization and CBD in individuals who are suspected of having CBD and to help distinguish it from similar conditions such as sarcoidosis. It is also the main test used in industry health programs to monitor whether disease is occurring among current and former workers who have been exposed to beryllium on the job. The test can detect disease that is at an early stage, or can detect disease at more advanced stages of illness as well. The BeLPT can also be performed using cells obtained from a person's lung by a procedure called "bronchoscopy."

Industrial release and occupational exposure limits

Typical levels of beryllium that industries may release into the air are of the order of , averaged over a 30-day period, or of workroom air for an 8-hour work shift. Compliance with the current U.S. Occupational Safety and Health Administration (OSHA) permissible exposure limit for beryllium of has been determined to be inadequate to protect workers from developing beryllium sensitization and CBD. The American Conference of Governmental Industrial Hygienists (ACGIH), which is an independent organization of experts in the field of occupational health, has proposed a threshold limit value (TLV) of in a 2006 Notice of Intended Change (NIC). This TLV is 40 times lower than the current OSHA permissible exposure limit, reflecting the ACGIH analysis of best available peer-reviewed research data concerning how little airborne beryllium is required to cause sensitization and CBD. Because it can be difficult to control industrial exposures to beryllium, it is advisable to use any methods possible to reduce airborne and surface contamination by beryllium, to minimize the use of beryllium and beryllium-containing alloys whenever possible, and to educate people about the potential hazards if they are likely to encounter beryllium dust or fumes.

See also

Notes

References

  • Los Alamos National Laboratory – Beryllium
  • Burrell, AK. Ehler, DS. McClesky, TM. Minogue, EM. Taylor, TP. Development of a New Fluorescence Method for the Detection of Beryllium on Surfaces. Journal of ASTM International (JAI). 2005. Vol 2: Issue 9. http://www.astm.org/cgi-bin/SoftCart.exe/JOURNALS/JAI/PAGES/JAI13168.htm?E+mystore
  • Infante PF, Newman LS. "Commentary: Beryllium exposure and Chronic Beryllium Disease." Lancet 2004; 415-16.
  • Newman LS. "Beryllium." Chemical & Engineering News, 2003; 36:38.
  • Kelleher PC, Martyny JW, Mroz MM, Maier LA, Ruttenber JA, Young DA, Newman LS. "Beryllium particulate exposure and disease relations in a beryllium machining plant." J Occup Environ Med 2001; 43:238-249.
  • Mroz MM, Balkissoon R, Newman LS. "Beryllium." In: Bingham E, Cohrssen B, Powell C (eds.) Patty’s Toxicology, Fifth Edition. New York: John Wiley & Sons 2001, 177-220.
  • Beryllium and Compounds: TLV Chemical Substances Draft Documentation, Notice of Intended Change ACGIH Publication #7NIC-042

External links

Search another word or see berylliumon Dictionary | Thesaurus |Spanish
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature