Tellurium Disulphide, TeS₂

When hydrogen sulphide is passed into a solution of tellurium dioxide or into an acidified solution of a tellurite at room temperature, a reddish-brown precipitate is obtained Tellurium Disulphide, TeS₂. There has been much doubt expressed, however, as to whether tellurium sulphide is a true compound or merely a mixture of the elements, since the sulphur is extractable by carbon disulphide.

Hageman has shown that below -20° C. the disulphide is stable, but that dissociation takes place at about that temperature, the degree increasing with rise in temperature; the degree of dissociation at any temperature may, of course, be determined by the amount of extractable sulphur present. The stability of the compound is then solely a matter of temperature.

Hageman has also shown that the compound TeS suggested by Snelling does not exist.

The existence of a trisulphide, TeS₃, produced by the action of hydrogen sulphide on a solution of telluric acid, is improbable, the product behaving like a mixture containing free sulphur and tellurium.

Tellurium and sulphur do not combine when fused together, but are miscible in all proportions in the molten condition.

Certain unstable thiotellurites have been prepared by the action of hydrogen sulphide on solutions of alkali tellurites, the most definite being the potassium salt, K₂TeS₃.