Nickel Pyrophosphate, Ni₂P₂O₇

Nickel Pyrophosphate, Ni₂P₂O₇.6H₂O, results as a green amorphous powder on adding sodium pyrophosphate solution to one of a nickel salt. It is soluble in excess of the former reagent, in mineral acids, and in aqueous ammonia. It may be obtained in the crystalline form by dissolving in sulphurous acid and reprecipitating by boiling. The anhydrous salt is obtained by igniting the double ammoniacal orthophosphate. Its density at 25° C. is 3.93.

Several thiophosphates of nickel have been prepared.