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 °C and 0.5 M ionic strength adjusted with sodium acetate as a buffer component. The stoichiometry was found to be S 4 O 6 2- + 4 • ClO 2 + 5H 2 O → 4SO 4 2- + ClO 3 - + 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.