Nickel (II) sulfate, or just nickel sulfate, usually refers to the inorganic compound with the formula NiSO4 (H2O) 6. This highly soluble blue-colored salts a common source of the Ni2+ ion for electroplating. Nickel sulfate is used in the laboratory. Columns used in polyhistidine-tagging, useful in biochemistry and molecular biology, are regenerated with nickel sulfate.