Molybdenum trisulphide, MoS3, is obtained by saturating a solution of an alkaline molybdate with sulphuretted hydrogen and adding a mineral acid.
Bismuth combines directly with sulphur to form a disulphide, B12S2, and a trisulphide, B12S3, the latter compound being formed when the sulphur is in excess.
Bismuth trisulphide, B12S3, constitutes the mineral bismuthite, and may be prepared by direct union of its constituents, or as a brown precipitate by passing sulphuretted hydrogen into a solution of a bismuth salt.
Bismuth forms compounds similar to the trisulphide with the elements selenium and tellurium.
When heated in a current of hydrogen it is transformed into the colourless disulphide, whilst if the heating be carried out in a current of nitrogen it yields the trisulphide, Rb 2 S 3 H 2 0.