Mercurous Metatungstate, Hg₂W₄O₁₃

Mercurous Metatungstate, Hg₂W₄O₁₃.25H₂O (?), is obtained, according to Scheibler, on adding mercurous nitrate to the free acid or to an alkali metatungstate, as a white bulky precipitate which shrinks considerably on drying and assumes a lemon-yellow colour. Friedheim, however, was only able to obtain the paratungstate by this means, while Copaux by treating concentrated metatungstic acid with mercurous nitrate solution obtained crystals in which the ratio Hg₂O:WO₃ was equal to 1.7:4. A compound of composition 9Hg₂O.24WO₃.N₂O₅.29H₂O was also obtained. This may be formulated as Hg^•₈H₂[H₂(W₂O₇)₆].HgNO₃.12.5H₂O, which is of interest in that the metatungstic acid exhibits a higher basicity than is usual.