Kinetics and Mechanism of Oxidation of Arsenic(III) by Chloramine-T

Department of Chemistry, Andhra University, Waltair Manuscript received 21 February 1979, revised 21 November 1979, accepted 31 December 1979 The kinetics of oxidation of arsenic (III) by chloramine-T has been studied in an alkaline medium. The reaction is first order both in the substrate and in the oxidant. An inverse first order dependence on [OH-] has been observed. The effect of varying the ionic strength on the reaction rate is found to be negligible. A decrease in the dielectric constant of the medium increases the rate. The energy and entropy of activation for the oxidation process are 42.7 KJ mo1-1 and -109.3 JK-1 (at 273°K) respectively. The proposed mechanism involves an interaction between AsO(OH)2 ion and p-toluene sulphocbloramide in the rate determining step