Tungstate

The tungstate ion is WO₄²⁻.

A tungstate (compound) is a compound containing the tungstate ion, or more complicated polymeric ions. Tungstates are salts of tungstic acid.

See the for a list of tungstates.

Occurrence

Tungstates occur naturally with . Powellite is a mineral form of calcium molybdate containing a small extent of tungstate, and scheelite is a mineral form of calcium tungstate containing a small extent of molybdate. Wolframite is manganese and iron tungstate, and all these are valuable sources of tungsten.

Chemical and physical properties

Solutions of tungstates, like those of , give intensely blue solutions of complex tungstate(V,VI) analoguous to the molybdenum blues when reduced by most organic materials. Therefore it could be used to trace paths of solutes in chromatography in which the solute (usually organic if used for this purpose) is colourless.

Tungstate can also be used as an oxidizing agent in the oxidation of cyclohexene. The tungstate can be constantly regenerated through the presence of hydrogen peroxide.

Unlike chromate, tungstate is not a good oxidizer, but like chromate, it polymerizes in acid and depolymerizes back to tungstates in alkaline solutions.

References