Silicon Disulphide, SiS₂

Silicon Disulphide, SiS₂, can be prepared by passing the vapour of carbon disulphide over a heated mixture of silica and carbon, but is best obtained by heating to a red heat an intimate mixture of amorphous silicon with three times its weight of powdered sulphur, and subliming the product under reduced pressure. It is also formed by the dry distillation of the thiochloride:

2SiSCl₂ = SiS₂ + SiCl₄,

and by adding lithium silicide to molten sulphur.

Silicon disulphide forms white silky needles, which may be sublimed in an inert atmosphere, but which burn to silica and sulphur dioxide when heated in air. Moisture decomposes this compound, forming silica and hydrogen sulphide; chlorine forms chlorides of sulphur and silicon; fused sodium sulphide yields sodium thiosilicate, Na₂SiS₃, so that silicon disulphide, SiS₂, is thiosilicic anhydride.