Asymmetric potentials in oscillating chemical reaction studied by means of symmetrical electrodes.

Pairs of identical platinum electrodes of variable shape and dimensions were used to investigate the asymmetric electrochemical potentials arising in oscillating systems, as well as the influence of a variety of parameters on the frequency and amplitude of the oscillations. It was found that the typical oscillating potential measured with identical point-electrodes of platinum was independent, within large limits, from the distance between the electrodes. Stirring the solution did not affect the oscillating potential below a certain critical velocity, above which the oscillating potential pattern was destroyed, as well as a colour variations of ferroin. The rather harmonic oscillating pattern at 25 °C was modified when the temperature was increased till complete disappearence above a critical value. Finally, the partial pressure of CO2, a gaseous product of the oscillating reaction, above the solution influenced the amplitude, not the frequency, of the oscillating potential. An increase of the surface of the electrode pair, i.e. passing from the point-electrodes to a pair of platinum grid electrodes, and to a pair of large-surface platinum black electrodes, caused a substantial decrease of the amplitude of the oscillations