Preparations of Nikel Compounds

Nickel carbonate usually occurs as a light green crystalline solid or a brown powder. It dissolves in ammonia and dilute acids but is insoluble in hot water. It exhibits vigorous reaction with iodine, hydrogen sulphide or a mixture of barium oxide and air. It decomposes on heating before melting occurs.

Ni + F₂ 55°C /slow → NiF₂
Ni + Cl₂ EtOH/ 20°C → NiCl₂
Ni + Br₂ red heat → NiBr₂
NiCl₂ + 2NaI → NiI₂ + 2NaCl

Nickel carbonyl is a colorless, volatile, liquid. It is soluble in alcohol, benzene, and nitric acid but only slightly soluble in water, and insoluble in dilute acids and alkalis. Upon heating or in contact with acid or acid fumes, nickel carbonyl emits toxic carbon monoxide gas, a property exploited in preparation of nickel metal. When exposed to heat or flame the compound explodes and it can react violently with air, oxygen and bromine.

Identification of nickel compounds can be achieved by employing the use of an organic reagent dimethylglyoxine. This compound forms a red flocculent precipitate on addition to a solution of a nickel compound.