Kinetics of the reaction between chlorite and hexacyanoferrate(II) in aqueous solution; evidence for an interfacial redox reaction

Abstract

The kinetics of oxidation of [Fe(CN)₆]^4– by chlorite have been studied spectrophotometrically at 25.0 °C in buffered aqueous solutions of pH 4.8–6.7. With hexacyanoferrate(II) in considerable excess, the rate equation is –d[ClO₂^–]/dt= 0.25d[Fe^III]/dt=E[ClO₂^–][Fe^II]/(D+[Fe^III]). The value of D is affected by [H⁺], buffer concentration, and the material of the surface of the optical cell in which reaction takes place; E is affected by [H⁺] only. These observations are interpreted in terms of a reaction mechanism in which the first stage, a reversible electron transfer, can occur both in homogeneous solution and at the interface between the optical cell and the solution.