KINETICS OF OXIDATION OF SULPHUR-CONTAINING COMPOUNDS BY ALKALINE HEXACYANOFERRATE(III). OXIDATION OF SULPHITE AND THIOSULPHATE IONS

Potassium hexacyanoferrate(III), in alkaline medium, oxidised sulphite to dithionate, and thiosulphate to tetrathionate ions. The rate of the reaction in both cases were dependent on the first powers of the concentrations of substrate and oxidant. in the oxidation of sulphite, the rate was dependent on the first power of the concentration of alkali. In the oxidation of thiosulphate, the rate was independent of the concentration of alkali. The oxidation of sulphite proceeded via a radical species, which underwent dimerisation to give dithionate. In the oxidation of thiosulphate, an one-equivalent electron transfer from the thiosulphate to the hexacyanoferrate(III) ion occurred, giving rise to S(2)O(3)(-)ion, which underwent dimerisation to tetrathionate ions.