Preparation of nickel(II) sulfamate dihydrate
10 g of sulfamic acid are dissolved in 100 ml of warm water and nickel carbonate is added in small portions until no more dissolves with evolution of carbon dioxide. The solution is filtered by suction, two crystals of the acid are added, and the mixture is evaporated to a green oil on the steam bath. After cooling, the residue is triturated with acetone until solid.
Inorganic laboratory preparations, by G. G. Schlessinger, 39-40, 1962