Chromic Sulphide, Cr₂S₃

Chromic Sulphide, Cr₂S₃, is formed when dry hydrogen sulphide is passed over chromium sesquioxide at 440° C.. or over heated chromium sesquichloride, excess of sulphur being removed with carbon disulphide. It may also be obtained by the action of carbon disulphide upon heated chromic oxide, Cr₂O₃, or potassium dichromate. Another method consists in heating the sesquioxide, or metallic chromium, in carbon disulphide vapour.

Chromic sulphide is a brownish-black, lustrous amorphous powder, of density 3.538 at 14° C. When heated in air it gives sulphur dioxide and chromium sesquioxide, while in hydrogen it yields chromous sulphide. It is attacked and oxidised by nitric acid, aqua regia, and fused potassium nitrate. Compounds of chromic sulphide with sulphides of other metals have been described. Regarding chromic sulphide as the thioanhydride of thiochromous acid, H₂Cr₂S₄, these compounds may be described as thiochromites.