Arsenic Production
Arsenic Production
Arsenic-containing ores are exposed to oxidizing roasting after which As2O3 is extracted. The following sublimation yields a product with 98% purity. Almost all arsenic compounds in industry are produced from As2O3 including metallic arsenic wich is reduced by carbonaceous deoxidizers, such as charcoal. Arsenic is purified by sublimation. High-purity arsenic which is used in semiconductors is obtained from AsH3 or AsCl3, previously refined, by chemical deposition form gaseous phase. Arsine (arsenic hydride) is decomposed 300-400°C in H2 or Argon current. Chloride is deoxidized by high-purity H2, which is refined by diffusion through palladium alloys. Arsenic of highest purity is obtained by distillation and crystallization at temperature 815-850°C and under pressure 4-6 MPa. Arsen for semiconductors must not contain impurities, such as silicon, sulphur, oxygen, etc. more than 10-5 - 10-6 % by mass of each element.