Nickel sulfate (Nickelous sulfate), green crystal, square crystal system. There are three kinds of water without, six water and seven water. The commodity is mostly hexahydrate, there are two variants of α-type and β-type, the former is blue tetragonal crystal, the latter is green monoclinic crystal. When heated to 103°C, six crystalline waters are lost. Easily soluble in water, slightly soluble in ethanol, methanol, its aqueous solution is acidic, slightly soluble in acid, ammonia water. Toxic.