Chemical Properties of Beryllium
|Beryllium is chemically intermediate between magnesium and aluminium. The metal is unaffected by dry air at the ordinary temperature, but burns brilliantly to the oxide when heated. Cold water has very little action on it, though hot water slowly converts it into the hydroxide. Wohler originally stated that water had no action on it at all:12 a surface film of oxide probably protects the metal. Dilute acids dissolve it with evolution of hydrogen. Ammonia does not attack it, but caustic alkalies act on it similarly to aluminium, though some investigators say that the vigour of the attack has been exaggerated. Beryllium sulphate and sulphur dioxide are produced by the action of hot concentrated sulphuric acid. Concentrated nitric acid has hardly any action; at higher dilutions beryllium nitrate is formed and nitric oxide evolved. |
Beryllium partially decomposes silicon tetrachloride at 270°-370° C., and combines directly with fluorine, chlorine, bromine, iodine, and sulphur. Its combination with hydrogen is doubtful; at electric-furnace heat it combines with carbon, boron, and silicon, and above 900° C. with nitrogen.
Compounds of Beryllium
|Beryllium yields only one series of salts, derived from one oxide. Unanimity is not yet absolute, but beryllium is almost universally regarded as BeO, and the salts as containing divalent beryllium. No acid salts are known, but the existence and nature of basic salts have been vexed questions. In 1906, Parsons and Robinson commented on the necessity either of " exact equivalents of anion and cation," or of " excess of the acid component," in preparing " definite crystalline compounds " of beryllium. |
Normal salts of beryllium have an acid reaction in aqueous solution. These aqueous solutions can dissolve relatively large quantities of beryllium oxide. The oxide, or hydroxide, is probably soluble, in the ordinary sense of simple solution, in solid beryllium salts, as camphor is soluble in acetic acid, and also soluble in dissolved beryllium salts, as camphor is soluble in aqueous acetic acid. There is usually very little hydrolysis in dissolved beryllium salts, though the chloride, bromide, iodide, and nitrate are strongly hydrolysed, and the hydrogen ion concentration is reduced virtually to zero by adding very much less beryllia than the solutions will dissolve. Solutions of beryllium hydroxide in aqueous beryllium sulphate are not markedly colloidal, and do not contain beryllium in a complex anion. The solution of the hydroxide also raises the freezing-point and lowers the conductivity.
Residues of very varying basicity are obtained by evaporating solutions of beryllium salts. The basic acetate, and some other basic salts of organic acids, are definite, and remarkably stable, substances. But a large number of the basic salts described are probably indefinite basic phases.
Solutions of beryllium salts are apparently sweet in proportion to their cation concentration.