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The mechanism of electrode processes

J. Heyrovský

Czechoslovak Academy of Sciences, Prague


Abstract: The mechanism of the electrolytic processes can be judged partially from the polarographic waves. In case of complete reversibility of the process, only the no. of electrons can be detd. polarographically from the factor RT/nF (n = no. of electrons) which should agree with the no. of electrons derived from the Ilkovic equation (for the height of the wave). In case of irreversible reactions, the linear relation (π - π0.5)(nF/RT) = ln[(id/i) - 1] is not valid and n is smaller than that detd. from the Ilkovic equation. For this reason studies were made on the behavior of depolarizers, polarized by an a.c. The polarograms shown on the oscillograph indicate exactly both the degree of reversibility and the speed of the electrode processes. The monoelec. depolarizations which are governed only by the diffusion and are undisturbed by the undeformable ions are shown to be the simplest ones. In cases where a chem. reaction proceeds, the transfer of electrons (for instance dissocn. of complex), is retarded by the low rate of the chem. reaction. Dielectronic depolarizations are retarded because one cation or radical is replaced by 2 electrons gradually. A cation excited by the acceptance of an electron is gradually transformed into a stable cation. This process is accompanied by the sepn. between the excited and more stable cations. By this 'step by step' replacement of one ion by two (or more) electrons, the kinetic properties of the reaction enter into the electrode process. It is necessary to distinguish 2 types of electrode processes: (1) electrolytic processes where the electron is transferred instantly on the depolarizer and (2) chem. processes where the depolarizations are governed by the laws of chem. kinetics.

Full paper in Portable Document Format: 810a617.pdf (in Czech)


Chemical Papers 8 (10) 617–625 (1954)

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