KINETICS AND MECHANISM OF FORMATION OF CHLORATE ION FROM THE HYPOCHLOROUS ACID CHLORITE ION REACTION AT PH 6-10

The reaction between free chlorine (HOCl/OCl-) and chloritee ion (ClO2-) has been studied in the pH 6.4-10.0 region. The reaction proceeds through the Cl2O2 intermediate followed by a direct reaction of the intermediate with hypochlorous acid to form chlorate ion. Time-concentration profiles were measured for each chlorine species, resulting in both total chlorine and redox balance. Negligibly small amounts of chlorine dioxide are formed above pH7. Indirect evidence suggests that, in this pH region, the formation of any chlorine dioxide is primarily due to the presence of concentration gradients or because of the adventitious presence of catalytic metal ion impurities. Details of the overall reaction mechanism for the formation of chlorate ion are presented.