It takes a high polish. In its magnetic properties and chemical activity it resembles iron and cobalt, the elements preceding it in group VIII of the periodic table . It is a fairly good conductor of heat and electricity. In its familiar compounds nickel is bivalent, although it assumes other valences. It also forms a number of complex compounds.
Most nickel compounds are blue or green.
Nickel dissolves slowly in dilute acids but, like iron, becomes passive when treated with nitric acid. Finely divided nickel adsorbs hydrogen. Commercially, the most important compound is the sulfate, which is used in electroplating, as a mordant in dyeing, in preparation of other nickel compounds, and in paints, varnishes, and ceramics. Pure wrought nickel in the form of sheets and wire has many uses. Finely divided nickel is used as a catalyst, e.g., in the hydrogenation of oils.