NiSO4

Nickel(II) sulfate, NiSO4, is an inorganic salt that occurs primarily as hydrates. The most common form is the blue heptahydrate, NiSO4·7H2O, while the anhydrous salt and lower hydrates exist as white or pale-colored solids. In aqueous solution, NiSO4 dissociates to Ni2+ and SO4^2-, producing blue-green solutions characteristic of Ni2+.

It is prepared commercially by reacting nickel oxide, nickel sulfide, or nickel carbonate with sulfuric acid, followed by crystallization and drying. The mineral goslarite, NiSO4·7H2O, is a naturally occurring form of nickel sulfate.

NiSO4 is a major source of Ni2+ for electroplating, electroforming, and nickel chemistry. It serves as a starting material for diverse nickel compounds, catalysts, and laboratory reagents.

Soluble nickel salts, including nickel sulfate, are toxic and can cause irritation or sensitization on contact. Inhalation of nickel sulfate dust or mist is associated with increased cancer risk; handling requires appropriate protective equipment, good ventilation, and proper waste management.