Nickel(II) sulfate

Overview
Nickel(II) sulfate or just nickel sulfate, usually refers to the chemical compound with the formula NiSO4.6H2O. This blue salt is a common laboratory source of nickel. It also occurs as the rare mineral Retgersite. The anhydrous salt, NiSO4, a high melting solid, is also known but is less commonly encountered. These nickel(II) compounds are paramagnetic.

Synthesis and structure
Dissolution of nickel hydroxide in sulfuric acid followed by evaporation produces crystals of this salt or the corresponding heptahydrate. X-ray crystallography measurements show that NiSO4.6H2O consists of octahedral [Ni(H2O)6]2+ ions. These ions in turn are hydrogen bonded to sulfate ions. Dissolution of the salt in water gives solutions containing the ion [Ni(H2O)6]2+.

Coordination chemistry
NiSO4.6H2O and related hydrates react with ammonia to give [Ni(NH3)6]SO4 and with ethylenediamine to give [Ni(H2NCH2CH2NH2)3]SO4. The latter is occasionally used as a calibrant for magnetic susceptibility measurements because it has no tendency to hydrate.

Applications
NiSO4.6H2O in combination with boric acid or nickel(II) chloride is used in some electroplating baths.

Safety
Nickel salts are considered carcinogenic.