Nickel Hypophosphite, NiH₄(PO₂)₂

Nickel Hypophosphite, NiH₄(PO₂)₂.6H₂O, may be obtained by double decomposition of nickel sulphate and barium hypophosphite solutions, or by dissolving nickel hydroxide in hypophosphorous acid. From the solution thus obtained the hexahydrated salt crystallises out in green regular octahedra.

On warming the solution to 100° C. metallic nickel is deposited in consequence of partial decomposition. On raising the moistened crystals to 120° C. the salt is completely reduced.