Ring disc electrodes: Part 6. - Second-order reactions

The size of the ring current observed when a reagent generated on the disc electrode reacts rapidly with a reagent of comparable concentration in the bulk of the solution, has been calculated and shown to be in good agreement with experiment.² Depending on the second-order rate constant for the reaction, more or less of the disc reagent will penetrate through the bulk reagent to the ring electrode. An approximate theory is developed, using the method of moments and a reaction layer treatment, which relates the size of the ring current to the second-order rate constant. The method seems capable of measuring a wide range of homogeneous second-order rate constants with an upper limit of 10⁸ l. M^-1 sec^-1. It is also demonstrated for any particular electrode and for any particular placing of the reaction zone that the kinetic collection efficiency is only a function of (ka^∞ω^-1D^1/3v-^1/3).