Thiotungstate isopolyanions: an electrometric study

The stoichiometry of the various polyanions formed during the reaction between sodium thiotungstate and sulphuric acid has been investigated by pH and conductance measurements, which have revealed the formation of different polymerized species, viz. (W4SI5)6−, (W2S7)2−, and possibly (W4S13)2− in the vicinity of pH 6.2, 4.4, and 2.7 respectively. The formation of (W4S13)2− is, however, not evidenced by the pH investigations. It was observed that at higher hydrogen ion concentration (pH < 2.4), thiotungstate decomposes into hydrated tungsten trisulphide.