|Other names||Arsenic(III) sulfide
|Molar mass||246.04 g mol-1|
|Density||3.43 g cm-3|
310 °C, 583 K, 590 °F
707 °C, 980 K, 1305 °F
exposure limit (PEL)
|0.01 mg m−3 TWA (as As)|
|Other anions||Arsenic trioxide
|Other cations||Phosphorus trisulfide
|Related compounds||Tetraarsenic tetrasulfide|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)|
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.
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.