Kinetics and Mechanism of Hexachloroiridate(IV) Oxidation of Arsenic(III) in Acidic Perchlorate Solutions

ArticleinCollection of Czechoslovak Chemical Communications 57(7) · July 1992with3 Reads
Impact Factor: 1.14 · DOI: 10.1135/cccc19921451 · Source: OAI


    The kinetics of oxidation of arsenic(III) by hexachloroiridate(IV) at lower acid concentrations and at constant ionic strength of 1.0 mol dm<sup>-3</sup> have been investigated spectrophotometrically. A first-order reaction in [IrCl<sub>6</sub><sup>2-</sup>] and fractional order with respect to arsenic(III) have been observed. A kinetic evidence for the formation of an intermediate complex between the hydrolyzed arsenic(III) species and the oxidant was presented. The results showed that decreasing the [H<sup>+</sup>] is accompanied by an appreciable acceleration of the rate of oxidation. The activation parameters have been evaluated and a mechanism consistent with the kinetic results was suggested.