17:2-Tungstophosphates

17:2-Tungstophosphates, (P₂O₅:WO₃ = 1:17) - By carefully neutralising a solution of 9-tungstophosphoric acid, or by treating a solution of an alkali 9-tungstophosphate with the corresponding alkali hydrogen carbonate, salts of this series are obtained. The potassium salt, 5K₂O.P₂O₅.17WO₃.22H₂O, yields white satiny needles. The ammonium salt, 5(NH₄)₂O.P₂O₅.17WO₃.16H₂O, forms tabular crystals. A silver salt, of composition 5Ag₂O.P₂O₅.17WO₃.20H₂O, is obtained in small tabular crystals by double decomposition. The constitution of these salts is not yet determined.

Other series containing less tungstic acid have also been described; for example, 6-tungstophosphoric acid and its salts, 2R^•₂O.P₂O₅.12WO₃.xH₂O, and 7:2-tungstophosphates, 3R^•₂O.P₂O₅.7WO₃.xH₂O. The work on these series is, however, inconclusive.