Nickel Borates

Several borates of nickel have been described. The tetraborate, NiO.4B₂O₃.10H₂O, is obtained by slow evaporation of a solution of nickel carbonate in boric acid. The precipitate first formed becomes crystalline gradually, yielding small brilliant and clear green crystals; soluble in cold water, but becoming turbid at 40° C.

On fusing nickel chloride or carbonate with molecular proportions of potassium hydrogen fluoride and boric oxide, green prisms of 3NiO.B₂O₃ are obtained. They are not attacked by hot water, but dissolve in acids.

A diborate, NiO.2B₂O₃.6H₂O, has also been obtained.

Nickel borate has been recommended as a catalyst in the hydrogenation of unsaturated oils, but its action is attributable to nickel liberated by the hydrogen, and not to any inherent catalytic power of the borate itself. It offers no advantage over nickel oxide.