Silicon Selenide, SiSe₂

When crystalline silicon is heated to a red heat in a current of dry hydrogen selenide reaction takes place with the formation of Silicon Selenide, SiSe₂; the product is a dark, variegated mass, of metallic appearance, and has a very irritating odour. When heated to a dull red heat in a current of air or oxygen it undergoes oxidation with the formation of selenium, but the reaction is only superficial. Water reacts vigorously with the selenide with the production of silica and the liberation of hydrogen selenide. The silica forms a protective coating which hinders the total decomposition of the selenide. The reaction is more complete in the presence of caustic potash, which dissolves both the silica and the hydrogen selenide.