Nickel(II) sulfate, or just nickel sulfate, usually refers to the chemical compound with the formula NiSO4. This highly soluble blue-coloured salt is a common source of the Ni2+ ion for electroplating.
Several sulfate salts of nickel(II) are known, all being paramagnetic. These salts differ with respect to their hydration or subtle structural details. The common tetragonal hexahydrate crystallizes from aqueous solution between 30.7 and 53.8 °C. Below these temperatures, a heptahydrate crystallises and above these temperatures an orthorhombic hexahydrate forms. The yellow anhydrous form, NiSO4, is a high melting solid. This material produced by heating the hydrates above 330 °C. It decomposes at still higher temperatures to nickel oxide.
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