Mechanism and reaction rate of the Karl-Fischer titration reaction: Part II. Rotating ring-disk electrode measurements

Abstract

A platinum disk-platinum ring electrode was used to investigate the kinetics of the oxidation of the monomethyl sulfite ion (which is the oxidizable species in the Karl-Fischer reagent) by triiodide and iodine, generated with controlled current at the disk electrode. The experimental conditions were such, that the technique for measurement of homogeneous pseudo-first order reactions could be used. The results are in reasonable agreement with those of the potentiometric investigations as described in part I. The reaction rate constant of triiodide is approximately 600 1 2 mol −2 s −1; for iodine the rate constant is approximately 7×10 6.