Cobalt(II) carbonate

Cobalt carbonate is the inorganic compound with the formula CoCO₃. This pink paramagnetic solid is an intermediate in the hydrometallurgical purification of cobalt from its ores. It is an inorganic pigment, and a precursor to catalysts. Cobalt carbonate also occurs as the rare red/pink mineral spherocobaltite.

Preparation and structure

It is prepared by combining solutions of cobalt(II) sulfate and sodium bicarbonate:
This reaction is used in the precipitation of cobalt from an extract of its roasted ores.
CoCO₃ adopts a structure like calcite, consisting of cobalt in an octahedral coordination geometry.

Aqueous solutions of cobalt chloride can be prepared from cobalt carbonate with hydrochloric acid according to this idealized equation:
The reaction of cobalt carbonate and acetylacetone in the presence of hydrogen peroxide gives tris(acetylacetonato)cobalt(III).
Heating the carbonate in air is accompanied by partial oxidation:
The resulting Co₃O₄ converts reversibly to CoO at high temperatures.

Cobalt carbonate is a precursor to cobalt carbonyl and various cobalt salts. It is a component of dietary supplements since cobalt is an essential element. It is a precursor to blue pottery glazes, famously in the case of Delftware.

At least two cobalt carbonate-hydroxides are known: Co₂₂ and Co₆₂₈·H₂O.
The moderately rare spherocobaltite is a natural form of cobalt carbonate, with good specimens coming especially from the Republic of Congo. "Cobaltocalcite" is a cobaltiferous calcite variety that is quite similar in habit to spherocobaltite.
Sodium tris(carbonato)cobalt(III) is a cobalt complex containing three carbonate ligands.

Toxicity has rarely been observed. Animals, including humans, require trace amounts of cobalt, a component of vitamin B12.