Applicability of the galvanostatic single-pulse method: Cd2+/Cd(Hg) electrode in M Na2SO4, NaClO4 and KCl

Abstract

The conditions that must be met experimentally in order to obtain reliable io-values for fast reactions with the galvanostatic single pulse method are examined. Distinction must be made between the conditions for systems with low ksh-values, high ksh-values and the intermediate case. This is demonstrated by experiment with the Cd2+/Cd(Hg) electrode in M Na2SO4, NaClO4 and KCl, the rate constants being 0·063, 0·5 and >5 cm/s respectively. The maximum obtainable ksh-value with the galvanostatic single pulse method is about 5 cm/s, provided the value of the double layer capacitance is known. If the latter must be determined with pulse methods in the presence of the electroactive species, the limit is about 1 cm/s.