These complexes are analogous to the molybdo-vanadosilicates, and are prepared as yellowish-red to red crystals by the action of vanadates on the silico-tungstates, or by the action of hydrofluosilicic acid on the tungsto-vanadates. The following series has been recognised
3R2O.SiO2.V2O5.9WO3 xH2O;
3R2O.SiO2.V2O5.10WO3.xH2O;
7R2O.2SiO2.3V2O5.18WO3.xH2O.
(R = NH4 or K; R2 = Ba.)
Double salts have also been isolated.
Several of the natural ores of vanadium consist of complex silicates, e.g. ardennite and roscoelite. |