Tungsto-vanadates

Tungsto-vanadates or Vanado-tungstates. Three well-defined series of complex salts containing tungsten and vanadium have been obtained, which are comparable to the molybdo-vanadates in that they probably do not contain either vanadium or tungsten as the nuclear atom of the complex anion. They are obtained (1) by saturation of a solution of a paratungstate with vanadium pentoxide, (2) by the action of acetic acid on solutions of mixed alkali tungstates and vanadates, or (3) by the addition of a paratungstate to a metavanadate. The salts are characteristically coloured and all contain water of constitution. The dichromate-coloured series has the composition 5R^•₂O. 3V₂O₅.6WO₃.xH₂O or , where R^• may be NH₄, K, or Na. The yellowish-red salts have the composition 2R^•₂O.V₂O₅.4WO₃.xH₂O, and salts of the alkali metals, alkaline earth metals, and silver have been prepared. The salts of both these series have properties similar to the paratungstates. The salts of the third series are deep red in colour, have the composition 5R^•₂O.3V₂O₅.14WO₃.xH₂O, and resemble the metatungstates. The ammonium, potassium, caesium, and barium salts have been prepared.