Trichromium Disilicide, Cr₃Si₂

Trichromium Disilicide, Cr₃Si₂, is obtained by fusing a mixture of copper silicide with 4 per cent, of its weight of chromium in an electric furnace, and digesting the resulting mass alternately with 50 per cent, nitric acid and 10 per cent, caustic soda solution. It has also been prepared by prolonged heating at 1200° C. of pure chromium powder in contact with silicon tetrachloride. It yields long quadratic prisms, of density 5.6 at 0° C. It is hard enough to scratch glass, but not quartz. It is stable in air at ordinary temperatures, but is oxidised superficially at 1100° C. It becomes incandescent in chlorine at 400° C., and forms silicon and chromic chlorides; bromine attacks it slowly at red heat. It is not attacked by sulphuric or nitric acids; warm concentrated hydrochloric acid, or gaseous hydrogen chloride, gives chromous chloride; hydrofluoric acid also defcsanposes it. When fused with alkali carbonates, the alkali silicate and chromium sesquioxide are produced.