Molybdo-vanadosilicates

The simple vanado-silicates do not appear to be stable, but a number of molybdo-vanadosilicates have been obtained either by acidifying solutions which contain molybdates, vanadates and silicates, or by addition of vanadium pentoxide to the molybdo-silicates. They form heavy, yellowish-red to brownish-red crystals, which are very easily hydrolysed and are, therefore, not always reproducible. The following isomorphous series has been recognised:

3R₂O.SiO₂.V₂O₅.9MoO₃.xH₂O or ; 3R₂O.SiO₂.V₂O₅.10MoO₃.xH₂O or ; 3R₂O.SiO₂.V₂O₅.11MoO₃.xH₂O; 3R₂O.SiO₂.V₂O₅.15MoO₃.xH₂O.

(R = NH₄ or K; R₂ = Ba.)

Potassium-ammonium double salts have also been prepared. The first two series can be looked upon as derivatives of the co-ordinated silico-acid, H₈[Si^IVO₆]; the last two series cannot be formulated in accordance with Werner's theory.