Iridium Sesquisulphide, Ir₂S₃

Iridium Sesquisulphide, Ir₂S₃, is formed by passing hydrogen sulphide into a slightly acid solution of a chloriridite at 100° C.

It is a black, colloidal substance, soluble in aqua regia, giving an iridium chloride, and decomposable at high temperatures, yielding metallic iridium.