Molybdenum Sesquisulphide, Mo₂S₃

When the disulphide, compressed into small bars, is heated in an electric furnace, a metallic mass is produced which consists of the Molybdenum Sesquisulphide, Mo₂S₃, contaminated with metallic molybdenum. On removal of the latter with aqua regia, there are obtained steel-grey needles, of density 5.9, which are readily reduced to the metal by heating in hydrogen, or converted to the disulphide by heating in sulphur-vapour.