Nickel Sulfate Hexahydrate: Nickel Dissolved in Sulphuric Acid, Crystallised Warm

Nickel sulfate, the turquoise salt of the nickel-plating bath, forms when nickel dissolves in sulphuric acid. Its common six-water crystals grow only between about 31 and 54 °C, so keep the dish warm while it crystallises. It is a carcinogen and a strong skin allergen: gloves, goggles and a mask, and no dust. The picture: nickel sulfate hexahydrate crystals.