COBALT(III) OXIDE BLACK

Description

Neither the oxide Co2O3 nor the hydroxide Co(OH)3 is definitely established. The oxidation of cobalt(II) hydroxide in aqueous suspension with, for example, peroxides, or the destruction of a cobalt(III) complex with alkali gives a brown or black powder Co2O3.aq which upon drying at 150° yields the monohydrate Co2O3.H2O; this is probably best formulated as CoO(OH). When heated further in attempts to dehydrate it, the "monohydrate" begins to evolve oxygen (as well as water) at 300° with the formation of black Co3O4. When heated to 100° in air cobalt(II) hydroxide is converted to dark brown CoO(OH).

Chemical properties

Steel-gray or black powder.Soluble in concentrated acids; insoluble in water.

Physical properties

Grayish black powder; density 5.18 g/cm³; decomposes at 895°C; insoluble in water; soluble in concentrated mineral acids.

The Uses of COBALT(III) OXIDE BLACK

Pigment, coloring enamels, glazing pottery.

The Uses of COBALT(III) OXIDE BLACK

Cobaltic oxide (Co2O3) is also known as cobalt oxide or cobalt black. It is dark gray to black and is used in pigments, ceramic glazes, and semiconductors.

Definition

Sometimes incorrectly called cobalt peroxide.

Preparation

Cobalt(III) oxide is prepared by heating cobalt compounds at low temperatures in air.

Safety Profile

: Moderately toxic by intraperitoneal and subcutaneous routes. Questionable carcinogen. Violent reaction with hydrogen peroxide. The oxide increases the sensitivity of nitroalkanes (e.g., nitromethane, nitroethane, and 1 nitropropane) to heat or detonation. See also COBALT COMPOUNDS.