Chemical Properties
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.
Chemical Properties
Heavy, Yellow Powder
Physical properties
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.
Occurrence
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.
Uses
In disinfectants, magnets, glass, rubber vulcanization; in fireproofing of papers and polymers; in catalysts.
Preparation
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.
General Description
Bismuth (III) oxide is a yellow, monoclinic crystalline powder. It is insoluble in water and hydroxide solutions but dissolves in acids to form bismuth (III) salts. It can be prepared by heating bismuth in air or by heating hydroxides, carbonates or nitrates of bismuth.
Structure and conformation
Bismuth(III) Oxides are the deeply studied class of bismuth compounds, and they present four different phases. At room temperature, monoclinic α-Bi2O3 is the common stable phase with a polymeric-distorted layered structure composed of pentacoordinate bismuth atoms enclosed into pseudo-octahedral units. At a temperature higher than 710 °C, the α phase is converted into the cubic δ phase, which has a defective structure with random oxygen vacancies. The β phase and several oxygen-rich forms are closely related to the δ phase. In particular, the vacancy structures of highly defected bismuth oxides are some sites filled with O?2 and Bi(III) and Bi (V) sites. Bismuth oxide γ-phase also shows a cubic structure, but it is highly unstable and hard to synthesize without supporting it onto other oxides or metallic species. The other two polymorphic metastable bismuth oxide phases are known as the ω phase, stable at temperatures higher than 800 °C and the ε phase, isolated in 2006 by Cornei and co-workers[1].
References
[1] Mattia Bartoli, Alberto Tagliaferro, Pravin Jagdale. “A Short Review on Biomedical Applications of Nanostructured Bismuth Oxide and Related Nanomaterials.” Materials 13 22 (2020).
