1989 Volume 5 Issue 2 Pages 171-174
The current efficiency for the electrolytic generation of cadmium(II) from an amalgamated cadmium anode was investigated as a function of electrolyte composition and current density. The generation of cadmium(II) proceeded with 100% current efficiency over a wide range of current density, when both sodium chloride and sodium acetate concentrations were higher than 0.1M. Thus, the use of cadmium(II) instead of zinc(II) as a coulometric titrant for complexometry (T. Tanaka et al., Bunseki Kagaku, 33, E9 (1984)) reduced the error in amperometric indication of the end point. With 0.5M sodium chloride-0.5M sodium acetate medium of pH 5.5, high-purity gallium and indium were assayed coulometrically. The method was based on the reaction of the sample metal ion with a known excess of EDTA, the unconsumed EDTA being back-titrated with electrolytically generated cadmium(II). The relative standard deviation of the results was about 0.01% for both metals in the range of 200-300mg.