БЕРИЛЛИЙ

Описание

Beryllium is widely distributed in the earth's crust at trace concentration, 2.8 mg/kg. The element was first discovered by Vauquelin in 1797. Wohler and Bussy in 1828 independently isolated beryllium in the metallic form from its oxide. In nature, beryllium occurs in several minerals, mostly combined with silica and alumina. The most common minerals are beryl, 3BeO•Al2O3•6SiO2; chrysoberyl, BeO•Al2O3; phenacite, 2BeO•SiO2; and bertrandite, 4BeO•2SiO2•H2O. Also, it is found in trace amounts in the ore feldspar, and in volcanic ash. It's abundance in the sea water is estimated in the range 5.6 ppt.

Beryllium oxide is a component of precious stones, emerald, aquamarine and topaz. Beryllium is utilized in nuclear reactors to moderate the velocity of slow neutrons. It is hot-pressed to appropriate shapes and sizes that yield high strength and ductility for its applications.

Химические свойства

Beryllium is a gray shiny metal or powder, or fine granules which resemble powdered aluminum. Beryllium is slightly soluble in water. All beryllium compounds are soluble in water, to some degree. Berylore is the primary source of beryllium, although there are numerous other sources.

Физические свойства

As the first element in group 2 (IIA), beryllium has the smallest, lightest, and most stableatoms of the alkali earth metals. Its melting point is 1278° C, its boiling point is 2970°C, andits density is 1.8477 g/cm³. Its color is whitish-gray.

Происхождение имени

Beryllium was originally known as “glucina” (glucose) from the Greek word glukos, meaning “sugar,” because of the sweet taste of a few of its salt compounds. Later, beryllium was given the Greek name beryllos after the greenish-blue gemstone beryl (emeralds) that was later found to contain the element beryllium.

Вхождение

Since its discovery, beryllium has been classed as the 36th most abundant of the elementsfound in the Earth’s crust. Beryllium’s principle source is a mineral composed of a complex ofberyllium, silicon, and oxygen. It is usually found in deposits as hexagonal crystalline formsin Brazil, Argentina, South Africa, and India as well as in Colorado, Maine, New Hampshire,and South Dakota in the United States. Some deposits have been found in Canada. Manycrystals of the mineral may be very large One chunk that measured 27 feet long length andweighed a 25 tons was found in Albany, Maine in 1969.One method of obtaining beryllium metal is by chemical reduction, whereby berylliumoxide is treated with ammonium fluoride and some other heavy metals to remove impuritieswhile yielding beryllium fluoride. This beryllium fluoride is then reduced at high temperaturesusing magnesium as a catalyst, which results in deposits of “pebbles” of metallic beryllium.Another method for obtaining beryllium metal is by electrolysis of a solution of berylliumchloride (BeCl₂) along with NaCl as an electrolyte in solution that is kept molten but belowthe melting point of beryllium. (₄Be has a relatively high melting point of 2,332.4°F.) Theberyllium metal does not collect at the negative cathode as do metals in other electrolyticcells, but rather beryllium metal pieces are found at the bottom of the cell at the end of theprocess.

Характеристики

Beryllium is one-third as dense as aluminum. Fresh-cut surfaces of the metal oxidize,thus resisting further oxidation, as does aluminum. It is a lightweight, hard, brittle metal. Itcan be machined (rolled, stretched, and pounded) into many shapes and is used to producelightweight alloys.

Использование

Source of neutrons when bombarded with alpha particles according to the equation 94Be + 42He 612C + 10n. This yields about 30 neutrons per million alpha particles. Also as neutron reflector and neutron moderator in nuclear reactors. In beryllium copper and beryllium aluminum alloys (by direct reduction of beryllium oxide with carbon in the presence of Cu or Al). In aerospace, aircraft and satellite structures; x-ray transmission windows; missile parts; nuclear weapons; fuel containers; precision instruments; rocket propellants; navigational systems; heat shields; and mirrors. For fiber optics and cellular network communications systems.

Определение

beryllium: Symbol Be. A grey metallicelement of group 2 (formerly IIA)of the periodic table; a.n. 4; r.a.m.9.012; r.d. 1.85; m.p. 1278°C; b.p.2970°C. Beryllium occurs as beryl(3BeO.Al₂O₃.6SiO₂) and chrysoberyl(BeO.Al₂O₃). The metal is extractedfrom a fused mixture of BeF₂/NaF byelectrolysis or by magnesium reductionof BeF₂. It is used to manufactureBe–Cu alloys, which are used innuclear reactors as reflectors andmoderators because of their low absorptioncross section. Berylliumoxide is used in ceramics and in nuclearreactors. Beryllium and its compoundsare toxic and can causeserious lung diseases and dermatitis.The metal is resistant to oxidation byair because of the formation of anoxide layer, but will react with dilutehydrochloric and sulphuric acids.Beryllium compounds show high covalentcharacter. The element wasisolated independently by F. W?hlerand A. A. Bussy in 1828.

Методы производства

Metallic beryllium is produced by reduction of beryllium halide with sodium, potassium or magnesium. Commercially, it is obtained primarily from its ore, beryl. Beryllium oxide is separated from silica and alumina in ore by melting the ore, quenching the solid solution, and solubilizing in sulfuric acid at high temperatures and pressure. Silica and alumina are removed by pH adjustment. Beryllium is converted to its hydroxide. Alternatively, beryl is roasted with complex fluoride. The products are dissolved in water and then pH is adjusted to produce beryllium hydroxide.
The impure hydroxide obtained above is purified by converting to a double salt, ammonium beryllium fluoride, which subsequently, on thermal decomposition, gives beryllium fluoride. The latter is heated with magnesium metal BERYLLIUM 97 to form pure beryllium metal:
BeF +Mg→Be + MgF2
It finally is purified by either vacuum melting or chelation with an organophosphate reagent followed by liquid-liquid extraction. Beryllium halide alternatively may be reduced to the metal or converted to alloy by electrolysis.

Реакции

Most chemical reactions of beryllium are similar to those of aluminum and, to a lesser extent, magnesium. In general, all the common mineral acids attack beryllium forming their corresponding salts with evolution of hydrogen:
Be + 2HCl → BeCl2 + H2
Cold, concentrated nitric acid, however, has no effect when mixed with the metal.
Reactions with alkalies first produce insoluble beryllium hydroxide with evolution of hydrogen. Excess alkali converts the hydroxide to water-soluble beryllate:
Be(OH)2 + 2NaOH → Na2BeO2 + H2O
Beryllium does not react with oxygen at ordinary temperatures and normal atmosphere. When heated above 700°C, the metal combines with nitrogen, (in an oxygen-free atmosphere) forming beryllium nitride, Be3N2.
Beryllium combines with carbon when heated above 900°C in the absence of air to form beryllium carbide.
2Be + 2C→（>900℃）→Be2C
Beryllium reacts incandescently with fluorine or chlorine, producing beryllium fluoride or chloride.

Общее описание

A grayish-white hard light metal. Denser than water, but the powder may float. May be toxic by inhalation. Will burn if involved in a fire.

Реакции воздуха и воды

Highly flammable. Insoluble in water.

Профиль реактивности

Boron trifluoride reacts with incandescence when heated with alkali metals or alkaline earth metals except magnesium [Merck 11th ed. 1989]. Finely divided or amalgamated metal reacts with HCl, dil HNO3, or dil H2SO4; attacked by strong base with evolution of hydrogen gas [Merck 11th ed. 1989]. BERYLLIUM has been determined experimentally that a mixture of BERYLLIUM with carbon tetrachloride or with trichloroethylene will flash or spark on heavy impact [ASESB Pot. Incid. 39 1968]. The reaction between beryllium and the vapors of phosphorus proceeds with incandescence [Mellor 8:842 1946-47].

Опасность

The elemental metallic form of beryllium is highly toxic, as are most of its compounds.When inhaled, the fumes, dust, or particles of beryllium are highly carcinogenic. Some berylliumcompounds are toxic when they penetrate cuts in the skin (e.g., when an old fluorescenttube breaks). Beryllium oxide when inhaled can result in a fatal disease known as berylliosis(similar to, but more toxic than, silicosis).
As with many other chemicals, beryllium has its positives and negatives. Although it is animportant industrial chemical, the handling of beryllium is best left to experienced workersand laboratory personnel in proper facilities.

Промышленное использование

Among structural metals, beryllium (symbolBe) has a unique combination of properties. Ithas low density (two thirds that of aluminum),high modulus per weight (five times that ofultrastrength steels), high specific heat, highstrength per density, excellent dimensionalstability, and transparency to x-rays. Berylliumis expensive, however, and its impactstrength is low compared to values for mostother metals.
Beryllium is a steel-gray lightweight metal,used mainly for its excellent physical propertiesrather than its mechanical properties. Except formagnesium (Mg), it is the lightest in weight ofcommon metals, with a density of 1855 kg/m3.It also has the highest specific heat (1833J/kg K) and a melting point of 1290°C. It isnonmagnetic, has about 40% the electrical conductivityof copper, a thermal conductivity of190 W/m K, high permeability to x-rays, andthe lowest neutron cross section of any metalhaving a melting point above 500°C.

Возможный контакт

Beryllium is used extensively in manufacturing electrical components, chemicals, ceramics, nuclear reactors; in the aerospace industry; and X-ray tubes. Beryllium and Compounds 423 A number of alloys are produced in which beryllium is added to yield greater tensile strength, electrical conductivity, and resistance to corrosion and fatigue. The metal is used as a neutron reflector in high-flux test reactors. Human exposure occurs mainly through inhalation of beryllium dust or fumes by beryllium ore miners, beryllium alloy makers and fabricators; phosphor manufacturers; ceramic workers; missile technicians; nuclear reactor workers; electric and electronic equipment workers; and jewelers. The major source of beryllium exposure of the general population is thought to be the burning of coal. Approximately 250,000 pounds of beryllium is released from coal and oil-fired burners. EPA estimates the total release of beryllium to the atmosphere from point sources is approximately 5500 pounds per year. The principal emissions are from beryllium copper alloy production. Approximately 721,000 persons living within 12.5 mi (20 km) of point sources are exposed to small amounts of beryllium (median concentration 0.005 μ/m3). Levels of beryllium have been reported in drinking water supplies and in small amounts in food.

Канцерогенность

Beryllium and beryllium compounds are known to be human carcinogens based on sufficient evidence of carcinogenicity from studies in humans. Beryllium and beryllium compounds were first listed in the Second Annual Report on Carcinogens as reasonably anticipated to be human carcinogens based on sufficient evidence of carcinogenicity from studies in experimental animals. The listing was revised to known to be human carcinogens in the Tenth Report on Carcinogens in 2002.

Экологическая судьба

Beryllium compromises the immune system. Enzymes catalyzed by magnesium or calcium can be inhibited by beryllium; succinic dehydrogenase is activated. Beryllium exposure leads to a deficiency in lung carbon monoxide diffusing capacity. Hypercalcemia (excess of calcium in the blood) can occur.
Because of the toxicity of beryllium vapor and dust, all operations should be carried out in properly ventilated rooms, and with vented equipment. Source exhaust has been found to be most  effective. In the presence of poorly controlled high workplace concentrations, finedust masks with filters of the specific safety level must be worn.

Перевозки

UN1567: Beryllium powder, Hazard class: 6.1; Labels: 6.1—Poisonous material, 4.1—Flammable solid.

Структура и конформация

The space lattice of Beryllium belongs to the hexagonal system, and its close-packed hexagonal lattice has constants of a = 0.228 nm, c = 0.3977 nm (188 ℃).

Несовместимости

Beryllium metal reacts with strong acids; alkalis (forming combustible hydrogen gas), oxidizable materials. Forms shock sensitive mixtures with some chlorinated solvents, such as carbon tetrachloride and trichloroethylene. Incompatible with caustics, chlorinated hydrocarbons, oxidizers, molten lithium.

Утилизация отходов

For beryllium (powder), waste should be converted into chemically inert oxides using incineration and particulate collection techniques. These oxides should be returned to suppliers if possible. Recovery and recycling is an alternative to disposal for beryllium scrap and pickle liquors containing beryllium.