| Chromous Sulphide, CrS, may be obtained by heating chromous chloride in hydrogen sulphide at 440° C., or metallic chromium may be used at very much higher temperatures; it is also obtained by heating chromic sulphide, Cr2S3, in hydrogen, or by interaction of aqueous solutions of a chromous salt and alkali sulphide. It is a black powder, or glistening prisms, of density 3.909 at 14° C. It is obtained in a crystalline form by treating with nitric acid the cubical crystals of the double sulphide, Al2S3.CrS, which result on heating a mixture of aluminium and chromium in hydrogen sulphide, and treating the mass with water. Chromous sulphide is oxidised on heating in air, but is scarcely attacked by acids. |