Indium(III) Sulfide

Indium(III) sulfide is the inorganic compound with the formula In₂S₃. Three different structures ("polymorphs") are known: yellow, α-In₂S₃ has a defect cubic structure, red β-In₂S₃ has a defect spinel, tetragonal, structure, and γ-In₂S₃ has a layered structure. The red, β, form is considered to be the most stable form at room temperature, although the yellow form may be present depending on the method of production. Like related covalent solids, In₂S₃ is insoluble in all solvents. It is attacked by acids and by sulfide. It is slightly soluble in Na2S.

Indium sulfide was the first indium compound ever described, being reported in 1863. Reich and Richter determined the existence of indium as a new element from the sulfide precipitate.