Polarographic studies on the oxidation reactions of vanadium(II) by chlorate ion and nitrite ion

Abstract

Polarographic techniques were applied to elucidate the reaction mechanism for the oxidatinn of vanadium(II) by chlorate ion and nitrite ion. With chlorate ion, the measurement of the decreasing diffusion current by the oxidation gave a rate constant 24.4 l mol −1 s −1 in accordance with that obtained by other methods. A kinetic study showed the reaction to contain a slow rate subsequent reaction path, probably the oxidation of vanadium(II) by vanadium(IV). The rate constant could also be evaluated by applying Koutecky's equation to the catalytic wave, giving a smaller value: 19 l mol −1 s −1 . From Kalousek's polarograms, the reaction was found to proceed mainly by way of a one-electron oxidation step, but some contribution of a two-electron step was observed. For the oxidation by nitrite ion, d.c. polarography was used to follow the reaction and to determine the amount of vanadium(III) produced, showing a complicated mechanism. The measurement of Kalousek's polarograms supported the view that the reaction proceeds by way of a two-electron oxidation step.