Hydrated Antimony Trioxide

Hydrated Antimony Trioxide has not been obtained by direct methods, but three substances, obtained by indirect methods, have been described as ortho-, pyro- and meta-antimonious acids, respectively, with the formulae H₃SbO₃, H₄Sb₂O₅ and HSbO₂. The first, which may also be regarded as antimony hydroxide, is obtained by the action of dilute sulphuric acid on a double tartrate of antimony and barium. The substance, formerly known as pyro-antimonious acid, which is obtained when antimony trisulphide is heated with a solution of potassium hydroxide, and copper sulphate then added to the mixture, was subsequently shown to be ortho-antimonic acid, H₃SbO₄. The substance described as meta-antimonious acid, HSbO₂, is obtained by the decomposition of a double tartrate of potassium and antimony, using an alkali carbonate, phosphate or acetate.

There is, however, no conclusive evidence for the existence of these hydrated forms of antimony trioxide. No evidence for the existence of definite hydrates has been obtained from dehydration curves, and it seems probable that the various substances described are colloidal modifications of hydrated antimony trioxide differing in fineness of division.