Thallic sulphide, Tl₂S₃

Thallic sulphide, Tl₂S₃, is not precipitated from a thallic salt by hydrogen sulphide, thallous sulphide and sulphur being produced. It may, however, be prepared by fusing thallium with excess of sulphur and removing excess of the latter by distillation. It is a black solid, hard and brittle below 12°, soft and plastic above that temperature. It dissolves in warm dilute sulphuric acid with the evolution of hydrogen sulphide, no sulphur separating as such.

With thallous sulphide, thallic sulphide forms a series of solid solutions. The compound potassium thallium sulphide, Tl₂S₃.K₂S, is obtained by fusing together thallous sulphate (1 pt.) with sulphur (6 pts.) and potassium carbonate (6 pts.), and washing the fused mass with water. It is a reddish- brown, crystalline solid, insoluble in water.