A 2631 (OTTO) Arsenic sulphide, 99%+ Cas 1303-33-9 - used as an inorganic photoresist to fabricate 3-D nanostructures. A 2631 (OTTO) Arsenic sulphide, 99%+ Cas 1303-33-9 - used to make infrared-transmitting glass, pyrotechnics, pigments, linoleum, electrical semiconductors and photoconductors.