NiCO3

Nickel(II) carbonate, with the chemical formula NiCO3, is an inorganic salt formed by nickel in the +2 oxidation state and carbonate ions. It is commonly referred to as nickel carbonate and is used mainly as a laboratory reagent and as a precursor to other nickel compounds. In solid form it is typically described as a pale green material.

NiCO3 crystallizes in a calcite-type structure and, like many metal carbonates, is sparingly soluble in water. It decomposes upon heating to nickel oxide and carbon dioxide, and it reacts with acids to release carbon dioxide and form soluble nickel(II) salts. The compound can exist as a hydrate, NiCO3·xH2O, when prepared or stored under certain conditions.

Preparation methods for NiCO3 include precipitation from solutions of nickel(II) salts, such as nickel sulfate, by adding carbonate sources (for example, Na2CO3 or (NH4)2CO3). It can also be generated by converting nickel hydroxide with carbon dioxide: Ni(OH)2 + CO2 → NiCO3 + H2O. In solution, carbonate ions bind nickel(II) to form the solid, which can then be separated by filtration and dried.

Natural occurrence is rare, but minerals with the same composition exist, notably gaspeite, (Ni,Mg,Fe)CO3, which occurs in carbonatite rocks and can be found in meteorites. Gaspeite is of interest to mineral collectors and researchers studying nickel-bearing carbonate minerals.

Safety considerations for NiCO3 reflect the broader hazards of nickel compounds: exposure to dust can be irritating, and nickel compounds are regarded as potentially carcinogenic with strict handling advised. Use appropriate protective equipment and work in well-ventilated areas.