Reexamination of the theory of exaltation of the migration current by preceding electrode reactions

The effect of the preceding current of Hg(CN)₂, CdSO₄, ZnSO₄, and HCl on the K⁺ wave, of Hg(CN)₂ and CuSO₄ on the Cd²⁺ wave, of CdSO₄ on the Zn²⁺ wave, and of Hg(CN)₂ and CdSO₄ on the IO^?₃ wave was investigated. No exaltation of the Cd²⁺ wave was observed and only small variations of the Zn²⁺ and IO^?₃ waves. The increase of the K⁺ waves was roughly in accord with the prediction of the theory of the so-called exaltation of migration currents by preceding electrochemical reactions. However, the exaltation can be explained by concomitant reactions of K-amalgam with water and electrochemical reduction of hydrogen, which are accelerated by other ions (and also by the ions involved in the preceding reactions) and which, consequently, invalidate the equation of the exaltation of migration currents.