Structure of Silico-Tungstic Acid in Aqueous Solution

The structure of 12-silico-tungstic acid, H4SiW12O40, in aqueous solution has been investigated by x-ray diffraction. The results indicate that 12 tungsten atoms are contained in a monodisperse species with arrangement similar to that found in the crystalline acid. Each tungsten atom has two near tungsten neighbors at each of the distances 3.36 A and 3.71 A.