Cobalt(II) carbonate dissolves in concentrated HCl or HNO3 when heated, evolving CO2:
CoCO3 + HCl→CoCl2 + CO2 + H2O
It is oxidized by air or weak oxidizing agents, forming cobalt(III) carbonate, Co2(CO3)3. It decomposes on heating, forming the oxides of cobalt with the evolution of CO2.
The compound occurs in nature as the mineral cobalt spar or sphaerocobaltite. It is used in ceramics; in cobalt pigments; as a catalyst; as a temperature indicator; and in the preparation of other cobalt(II) salts. It also is added to soil to provide nutritional supplement in forage for cattle.
Pink rhombohedral crystals; refractive index 1.855; density 4.13 g/cm3; decomposes on heating; insoluble in water and ethanol; soluble in acids.
Cobalt(II) carbonate is prepared by heating cobaltous sulfate, cobaltous chloride or any Co2+ salt with sodium bicarbonate in solution:
CoSO4 + NaHCO3→ CoCO3 + NaHSO4
The compound is moderately toxic by ingestion. (Lewis (Sr.), R. J. 1996. Sax’s Dangerous Properties of Industrial Materials, 9th ed. New York: Van Nostrand Reinhold.)
LD50 oral (rat): 640 mg/kg