Tungstic acid often in concludes with yellow tungstic acid, white tungstic acid and metatungstic acid ect.. Metatungstic acid is a kind of poly tungsten acid, the only one compound in all the tungstic acid which has the confirmed structure, the colorless crystal. It belongs to 12-poly-tungstic acid with the sample formula of H6[H2(W3O10)4]•nH2O, wherein n can be 10 or 23, the density of 3.93 g/ cm3, will be decomposed under 50℃, very big solubility of 88.57 g/100 cm3 in water (25℃).
Metatungstic acid is always generated by conversion of metatungstate, the commonly used preparation method. Metatungstic acid is an important compound which is developed at the end of 1970s, and mainly used for catalyst. Metatungstic acid can prepared from ammonium paratungstate, and also can be obtained from microcrystalline powdery white tungstic acid, and many of other metatungstate, including kinds of metal salts and multi-carbon ammonium salts ect.. can be generated directly or indirectly from microcrystalline powdery white tungstic acid.
As a kind of poly tungsten acid, metatungstic acid can be got by conversion of other poly tungsten acid. It can firstly get decamethylene tungstate by dpolymerization of raw material of white tungstic acid in the aqueous solution of polyvinyl alcohol, and then changing the acidity and other environment factors to convert to hexahydrophthalic acid, which is metatungstic acid.