High Performance Liquid Chromatography Study on the Kinetics and Mechanism of Chlorite-Thiosulfate Reaction in Slightly Alkaline Medium

Chlorite-thiosulfate reaction was studied by high performance liquid chromatography under slightly alkaline solution by monitoring the concentration of thiosulfate and tetrathionate simultaneously during the course of reaction. It is demonstrated that various polythionates are formed and the composition of polythionates mainly depends on pH. Initial rate studies have revealed that the formal kinetic order of hydrogen ion is unambiguously unity but that of chlorite ion is significantly larger, while that of thiosulfate is lower than one. A 10-step kinetic model is proposed with seven fitted and three fixed parameters by simultaneous evaluation of kinetic data taking all the important characteristics of the measured kinetic curves into account. It is also enlightened that higher formal kinetic order of chlorite and lower kinetic order of thiosulfate than unity is an inherent feature of the system and may explain the systematic deviation between the measured and the calculated data encountered in previous studies.