Arsenites, derived from the acid H3AsO3, such as hydrogen cupric arsenite or " Scheele's green," HCuAsO3, produced by adding to a solution of copper sulphate potassium arsenite, arsenious oxide, and a little ammonia; pyro-arsenites, such as K4As2O5, and metarsenites, K AsO2; also ortho- and meta-thioarsenites, K3AsS3 and KAsS2, are known. They show no signs of isomerism like that of the phosphites and nitrites, and they are doubtless salts of As(OH)3 and 0=As-OH, and the corresponding sulphur acids, although the acids corresponding to the sulphur salts are unknown. Metantimonite of sodium, NaSbO2, and meta-thioantimonite, NaSbS2, are formed by dissolving antimonious oxide, Sb4O6, or the sulphide, Sb2S3, in caustic soda, and precipitating with alcohol.