On the impedance of galvanic cells XIX. The potential dependence of the faradaic impedance in the case of an irreversible electrode reaction; experimental verification for the redox couple Eu3+/Eu2+ In 1 M NaClO4 and The mechanism of the Zn2+/Zn(Hg) reaction in KCl

Abstract

An experimental verification of the theory for the potential dependence of the faradaic impedance in the case of irreversible electrode reactions, described in part XVIII, is presented for the Eu3+/Eu2+ couple in 1 M NaClO4 at a D.M.E. It is shown that two peaks occur in an a.c. polarogram, if both En3+ and Eu2+ are present. A good quantitative agreement exists between the experimentally found- and theoretically calculated-faradaic impedance as a function of electrode potential.

The consequences of the theoretical treatment in part XVIII are discussed for the zinc couple in the presence of surfactants. The a.c. measurements do not prove that the reaction proceeds via univalent zinc, as was concluded earlier. The evidence for the existence of the Zn+ion. published by a number of authors, is discussed and it is concluded that no definite proof for the existence of Zn+ has so far been presented.