Bismuth Hexoxide, Bi₂O₆

Bismuth Hexoxide, Bi₂O₆, has been obtained in small quantities by the action of ammonium persulphate or potassium ferricyanide upon a suspension of trioxide in a boiling concentrated solution of alkali hydroxide. Bismuth tetroxide is formed at the same time, and separation may be effected by treatment with warm nitric acid (density 1.2). It may also be obtained by the oxidation of bismuth tetroxide. It is a pale brown, anhydrous substance, which loses oxygen slowly at the ordinary temperature.

Evidence suggesting the existence of another oxide, Bi₄O₇, has been obtained from a study of the electrode Bi/Bi₂O₃ in solutions of sodium hydroxide in the presence of oxidising agents. This oxide does not appear to have been isolated, however.