Arsenic(III) sulfide (As₂S₃), also known as orpiment, is a specialty chemical primarily used in the production of chalcogenide glasses that transmit infrared radiation, essential for night-vision devices, thermal imaging systems, and optical fibers. It is also employed in the manufacturing of semiconductors, thin-film photovoltaics, and photoresist materials due to its semiconducting and photosensitive properties. In pyrotechnics, it serves as a colorant to produce yellow flames or effects. Historically, it has been used as a yellow pigment (known as king's yellow) in paints, dyes, and enamels. Its application in traditional medicine, such as in some Asian herbal remedies, has been documented, but it is rarely used today due to its high toxicity and carcinogenic risks.