Tungsto-arsenites

By treating solutions of tungstates with arsenious acid the following crystalline compounds have been obtained:

7(NH₄)₂O.2As₂O₃.18WO₃.18H₂O
4BaO.As₂O₃.9WO₃.21H₂O
9Na₂O.8As₂O₃.16WO₃.55H₂O

By addition of small quantities of arsenious oxide to a boiling solution of sodium paratungstate until tungstic acid is no longer precipitated on acidifying with hydrochloric acid, a syrup is obtained which, on treatment with potassium chloride, yields gradually on cooling needle- shaped crystals of a very soluble salt of composition 7K₂O.As₂O₃.18WO₃.24H₂O. If ammonium chloride is used, the salt formed has the composition 3½(NH₄)₂O.As₂O₃.18WO₃.45H₂O. These complex salts resemble metatungstates in their reactions.

Compounds of the following composition have also been described:

10K₂O.As₂O₃.4As₂O₅.21WO₃.26H₂O
10K₂O.14As₂O₃.3P₂O₅.32WO₃.28H₂O
5K₂O.Na₂O.2As₂O₃.2P₂O₅.12WO₃.15H₂O
7K₂O.As₂O₃.4P₂O₅.60WO₃.55H₂O