Beryllium compound

Beryllium Carbide. Beryllium carbide [506-66-17, Be2C, maybe prepared by heating a mixture of beryllium oxide and carbon to 1950—2000°C, 

Beryllium carbide slowly hydroly2es to beryllium oxide and methane in the presence of atmospheric moisture although months may be requited to complete the reaction. Any carbon contained in beryllium metal is present as the carbide because the solubiUty of carbon in beryllium is extremely low. 

The crystal stmcture of beryUium carbide is cubic, density = 2.44 g/mL. The melting point is 2250—2400°C and the compound dissociates under vacuum at 2100°C (1). This compound is not used industhaUy, but Be2C is a potential first-waU material for fusion reactors, one on the very limited Ust of possible candidates (see Fusion energy). 

Beryllium Carbonates. BeryUium carbonate tetrahydrate [60883-64-9] BeCO 4H2O, has been prepared by passing carbon dioxide through an aqueous suspension of beryUium hydroxide. It is unstable and is obtained only when the solution is under carbon dioxide pressure. BeryUium oxide carbonate [66104-25-4] is precipitated when sodium carbonate is added to a beryUium salt solution. Carbon dioxide is evolved. The precipitate appears to be a mixture of beryUium hydroxide and the normal carbonate, BeCO, and usuaUy contains two to five molecules of Be(OH)2 for each BeCO.  

Beryllium Halides. The properties of the fluoride differ sharply from those of the chloride, bromide, and iodide. BeryUium fluoride is essentiaUy an ionic compound, whereas the other three haUdes are largely covalent. The fluoroberyUate anion is very stable. 

Crystal Structure, Mechanical and Thermal Properties Tables 4.1-94 -4.1-99. 

Beryllium selenide BeSe n F4Zm fee Zinc blende Fig. 4.1-131 

Beryllium selenide BeSe a = 0.51520 (23) RT Epitaxial film, X-ray diffraction 

---

Electrolytic Processes. The electrolytic procedures for both electrowinning and electrorefining beryUium have primarily involved electrolysis of the beryUium chloride [7787-47-5], BeCl2, in a variety of fused-salt baths. The chloride readUy hydrolyzes making the use of dry methods mandatory for its preparation (see Beryllium compounds). For both ecological and economic reasons there is no electrolyticaUy derived beryUium avaUable in the market-place. 

Beryllium is principally consumed in the metallic form, either as an alloy constituent or as the pure metal. Consequendy, there is no industry associated with beryllium compounds except for beryllium oxide, BeO, which is commercially important as a ceramic material. BeO powder is available at 154/kg in 1991. 

Beryllium compounds (except aluminium beryllium silicates) Bis(chloromethyl)ether (BCME)... 

Beryllium compounds with the exception of aluminium beryllium silicates Cadmium oxide Cadmium sulphate... 

Tnglycidyl isocyanurate, beryllium and beryllium compounds Cancer epidemiology m coal tar pitch volatile-associated industries Cobalt and cobalt compounds... 

Beryllium Compounds - Includes any unique chemical substance that contains beryllium as part of that chemical s infrastructure. 

Procedure. Prepare a solution containing 10 jug of beryllium in 50 mL. (CARE Beryllium compounds are toxic.) Use beryllium sulphate, BeS04,4H20. To... 

Beryllium compounds are very toxic and must be handled with great caution. Their properties are dominated by the highly polarizing character of the Be2+ ion and its small size. The strong polarizing power results in moderately covalent compounds, and its small size limits to four the number of groups that can attach to the ion. These two features together are responsible for the prominence of the... 

Beryllium compounds have a pronounced covalent character, and the structural... 

Self-Test 14.7A Explain why beryllium compounds have covalent characteristics. 

Beryllium and beryllium compounds Insoluble chromium (VI) compounds Mustard gas (B,B -Dichlorodiethyl sulphide)... 

The glasses used by Steenbock in his original compositions were mixtures of calcium aluminosilicates and beryllium silicates but, as Dreschfeld reported in 1907, subsequent developments moved away from the use of beryllium compounds. Published chemical analyses in the period to 1916 (Voelker, 1916a Greve, 1913 Watts, 1915) confirmed Dreschfeld s statement. In the following we shall refer to these as oxide glasses. 

Because of numerous similarities in their properties and reactions, aluminum and beryllium will be described together even though they are in different groups of the periodic table. Although it is not completely understood, there is some indication that the accumulation of aluminum in the brain may have some relationship to Alzheimer s disease, and beryllium compounds are extremely toxic. 

The structure of dimethylberyllium is similar to that of trimethylaluminum except for the fact that the beryllium compound forms chains, whereas the aluminum compound forms dimers. Dimethylberyllium has the structure shown in Figure 12.3. The bridges involve an orbital on the methyl groups overlapping an orbital (probably best regarded as sp3) on the beryllium atoms to give two-electron three-center bonds. Note, however, that the bond angle Be-C-Be is unusually small. Because beryllium is a Lewis acid, the polymeric [Be(CH3)2] is separated when a Lewis base is added and adducts form. For example, with phosphine the reaction is... 

Only three beryllium compounds have been structurally characterized, the three-coordinate monomers [Be(SMes )2(thf)]73 and [Be(SMes )(SCgH3-2,6-Mes2)(OEt2)]74 and the four-coordinate [ Be(SPh)2(py)(NH3) 2(18-crown-6)] (7).75... 

This review is timely because of the likely increase in the use of beryllium compounds in the coming years. There is therefore a need for improved knowledge of beryllium chemistry, especially in relation to aqueous solutions. There is little doubt that fear has played a part in the relative underdevelopment of beryllium chemistry now that the hazards are better understood it should be possible to make good progress. 

There is little hazard to the aqueous environment, as beryllium compounds are scarcely soluble in the pH range of natural waters. 

Beryllium (Be), 3 637-661. See also Beryllium compounds analysis, 3 645-647 chemical reactions, 3 639-640 in coal, 6 718-719 commercial grades, 3 644t economic aspects, 3 644-645 effect on copper resistivity, 7 676t fabrication, 3 642-644 in galvanic series, 7 805t handling, 3 647... 

---