Cobalt(II,III) oxide
Tricobalttetraoxid
Black solid
Fixed
6.07 g · cm -3
895 ° C
> 900 ° C ( decomposition)
Insoluble in water
Risk
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Cobalt ( II, III) -oxide is a chemical compound of cobalt and oxygen. The black solid is one of several oxides of cobalt and belongs to the group of spinels.
Production and representation
Cobalt (II, III ) oxide is formed by heating the cobalt (II ) oxide in the air at 400 to 500 ° C.
Properties
Cobalt (II, III ) oxide is a mixed-valence compound with divalent and trivalent cobalt ions and the more accurate formula Co2 Co3 O4 2 (CoO Co2O3 * ). The compound has a spinel structure, in which in a cubic close packing of O2 - one-eighth of all tetrahedral sites and half of the octahedral sites are occupied by cobalt ions ions. The Co2 ions thereby occupy the tetrahedral sites, the Co3 ions the octahedral sites. The crystals have the space group, the lattice parameters a = 809 pm. In the unit cell contains eight formula units.
From about 900 ° C decomposes cobalt (II, III ) oxide to cobalt (II ) oxide. Reducing agents such as coke or the aluminum compound is reduced to elemental cobalt.
Cobalt (II, III ) oxide is insoluble in hydrochloric acid, nitric acid, and aqua regia, but soluble in concentrated sulfuric acid and potassium hydrogen sulfate in the melt.
Use
Cobalt (II, III ) oxide is an important intermediate in the production of metallic cobalt. By roasting and leaching is recovered first, cobalt ( II, III ) oxide, cobalt ores of different (usually sulfides or arsenides ). This can now be reduced with carbon or aluminothermically the element.
Cobalt (II, III ) oxide can be used to form nitric acid as a catalyst for the oxidation of ammonia. This is significantly cheaper than the platinum alloys normally used. However, a disadvantage is the far lower selectivity of cobalt (II, III ) oxide catalysts.
Other cobalt compounds such as is the cobalt (II, III ) oxide, a blue pigment for coloring ceramics.
Safety
Cobalt (II, III ) oxide is considered to be Carcinogenic and Mutagenicity.