Kinetics and mechanism of the chlorine dioxide-tetrathionate reaction

The chlorine-dioxide-tetrathionate reaction was studied spectrophotometrically in the pH range 4.55-5.55 at 25.0 +/- 0.2 degreesC and 0.5 M ionic strength adjusted with sodium acetate as a buffer component. The stoichiometry was found to be S4O62- + 4.ClO2 + 5H(2)O --> 4SO(4)(2-) + ClO3- + 3Cl(-) + 10H(+) with small deviations at high excess of chlorine dioxide with no chloride ion initially present. The initial presence of chloride not only affects the stoichiometry but also accelerates the reaction. A 14-step mechanism, including four known and two newly proposed intermediates, is suggested to describe the observed behavior of the system.