Arsenic trisulfide

Arsenic trisulfide, also known as orpiment or arsenic(III) sulfide, is a chemical compound. Its chemical formula is As2S3. It has arsenic and sulfide ions in it. The arsenic is in its +3 oxidation state.
Properties.
Arsenic trisulfide is a yellow solid. It is a semiconductor. It has a glass (amorphous) form and a crystalline form. It burns in air to make sulfur dioxide and arsenic trioxide, which makes a highly toxic smoke. Arsenic trisulfide can oxidize on the surface to make a highly toxic layer of arsenic trioxide as well. Arsenic trisulfide is not toxic unless it oxidizes. It does not react with acids.
Occurrence.
Arsenic trisulfide is found as the mineral orpiment.
Preparation.
Arsenic trisulfide is made when an arsenic compound like arsenic trichloride reacts with hydrogen sulfide. It is also made when arsenic and sulfur are heated together. 
Uses.
It was looked at for treating cancer. It was used by the Egyptians as a pigment and cosmetic. It is used in glass.