GERMANIUM  (

symbol Ge, atomic weight 72.5); one of the metallic elements included in the same natural family as carbon, silicon, tin and lead . It was discovered in 1886 by C . Winkler in argyrodite, a mineral found at Freiberg in Saxony . On examination of the metal and its salts it was shown to be identical with the hypothetical element eka,silicon, whose properties had been predicted by D . Mendeleeff many years previously . The element is of extremely rare occurrence, being met with only in argyrodite and, to a very small extent, in euxenite . It may be obtained from argyrodite by heating the mineral in a current of hydrogen; or by heating the dioxide to redness with carbon . _ It forms grey coloured octahedra of specific gravity 5'496 at 20° C., melting at 900° C.; it burns at a red heat, is insoluble in hydrochloric acid, but dissolves in aqua regia, and is also soluble in molten alkalis . Two oxides of germanium are known, the dioxide, GeO2, being obtained by roasting the sulphide and treatment with nitric acid . It is a white powder, very slightly soluble in water, and possesses acid properties . By heating with a small quantity of magnesium it is converted into germanious oxide, GeO . By heating the metal with chlorine, germanic chloride, GeC14j is obtained as a colourless fuming liquid boiling at 86-87° C., it is decomposed by water forming a hydrated germanium dioxide .

Germanium dichloride, GeC12, and germanium

chloroform, GeHCI3, have also been described . Germanium compounds on fusion with alkaline carbonates and sulphur form salts known as thiogermanates . If excess of a mineral acid be added to a solution of an alkaline thiogermanate a white precipitate of germanium disulphide, GeS2, is obtained . It can also be obtained by passing sulphuretted hydrogen through a solution of the dioxide in hydrochloric acid . It is appreciably soluble in water, and also in solutions of the caustic alkalis and alkaline sulphides . By heating the disulphide in a current of hydrogen, germanious sulphide, GeS, is formed . It sublimes in thin plates of a dark colour and metallic lustre, and is soluble in solutions of the caustic alkalis . Alkyl compounds of germanium such as germanium tetra-ethyl, Ge(C2H5)4, a liquid boiling at 16o° C., have been obtained . The germanium salts are most readily recognized by the white precipitate of the disulphide, formed in acid solutions, on passing sulphuretted hydrogen . The atomic weight of the element was determined by C . Winkler by analysis of the pure chloride GeC14, the value obtained being 7232, whilst Lecoq de Boisbaudran (Comptes rendus, 1886, 103, 452), by a comparison of the lines in the spark spectrum of the element, deduced the value 72.3 .