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Nickel Tungstates

The anhydrous normal salt is obtained in well-defined, brown, lustrous, translucent, rhombic prisms, of density 6.88, by fusing together sodium tungstate, sodium chloride, and nickel chloride. The hydrates, NiWO4.3H2O and NiWO4.6H2O, are obtained by precipitation as light green powders which yield the anhydrous salt on heating.

The acid tungstates, NiO.2WO3.5H2O, NiO.2WO3.7H2O, and NiO.3WO3.4H2O, are described by Lefort.

Nickel paratungstate, 3NiO.7WO3.14H2O, is obtained as a light green precipitate when solutions of a nickel salt and an acid tungstate of sodium are mixed.

The salt, 4NiO.10WO3.34H2O, obtained in a similar manner to the barium salt, is a greenish-white powder.

By the addition of a nickel salt to a large excess of alkali paratungstate, Rosenheim has prepared well-defined crystalline salts, corresponding to the ferri-tungstates, for which he suggests the formulae: Na3H7[Ni(WO4)6].18H2O, or Na3NiH5[H2(WO4)6].18H2O, and (NH4)3H7[Ni(WO4)6].7.5H2O, or (NH4)3NiH5[H2(WO4)6].7.5H2O.

Complex salts containing trivalent nickel, and of composition 3(NH4)2O.Ni2O3.16WO3.22H2O and 2(NH4)2O.Ni2O3.8WO3.14H2O, are obtained by boiling hydrated nickel dioxide with an ammoniacal ammonium paratungstate solution.

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