Electrode processes at mercury in the far cathodic potential region II. The reduction of Li+ and mM Na+ from aqueous 1 M LiCl solution

Abstract

The reduction of Li+ ions in 1 M concentration and the reduction of Na+ ions in mM concentration in aqueous solution, has been studied at the dropping mercury electrode, using d.c. polarography and electrode impedance measurements, as a function of frequency and electrode potential. The reduction of Li+ was found to be quasireversible (kfsh=0.08±0.04 cm s−1). The reduction process was accompanied by an irreversible secondary process as was found previously for K+ and Na+ reductions. This is attributed to the reaction of the alkali metal amalgam with water. The error in potentiometric measurements of the standard potential of the lithium/lithium ion couple has been calculated (21 mV). The reversibility of the Na+ reaction was confirmed by the measurements in mM concentration. The presence of the irreversible reaction due to water reduction was detected over the entire polarographic reduction range of the Na+ ion. This irreversible reaction was found to be in agreement with the theory developed for the process in the presence of 1 M alkali metal ions.