Theory of chronopotentiometry with cylindrical electrodes: II. Application of theoretical transition time relation in reduction of ferric iron and hydrogen ion

Abstract

The theoretical equation (see ref. I) for the transition time, based on cylindrically symmetrical diffusion as the sole means of mass transfer, has been further verified by studying the reduction of +3 iron to the +2 state and the reduction of hydrogen ion to hydrogen at a platinum, wire electrode. Transition time data for ferric iron reduction agree excellently with the theoretical values over a wide range of current densities. Agreement between observed and theoretical transition times in the reduction of hydrogen ion has also been demonstrated, but, because of the extraordinarily large diffusion coefficient of hydrogen ion, an awkwardly large number of terms in the series expansion of the theoretical equation is necessary at relatively large transition times. Empirically it was found that iτ 1 2 /C is very nearly a linear function of τ 1 2 , and this simple empirical relation is more convenient than the theoretical equation in practical applications of chronopotentiometry.