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Bismuth(III) oxide is the compound produced by heating the metal, or its carbonate, in air. It is definitely a basic oxide, dissolving readily in acid solutions, and unlike the arsenic or antimony compounds, not amphiprotic in solution, although it forms stoichiometric addition compounds on heating with oxides of a number of other metals. It exists in three modifications, white rhombohedral, yellow rhombohedral, and gray-black cubical. Bismuth(II) oxide, BiO, has been produced by heating the basic oxalate.

Heavy, Yellow Powder

Yellow monoclinic crystal or powder; density 8.90 g/cm³; melts at 817°C; vaporizes at 1,890°C; insoluble in water; soluble in acids.

Bismuth trioxide occurs in nature as mineral bismite. The oxide is used in fireproofing of papers and polymers; in enameling cast iron ceramic; and in disinfectants.

In disinfectants, magnets, glass, rubber vulcanization; in fireproofing of papers and polymers; in catalysts.

Bismuth trioxide is commercially made from bismuth subnitrate. The latter is produced by dissolving bismuth in hot nitric acid. Addition of excess sodium hydroxide followed by continuous heating of the mixture precipitates bismuth trioxide as a heavy yellow powder. Also, the trioxide can be prepared by ignition of bismuth hydroxide.