The anodic oxidation of ethylxanthate on metal and galena electrodes

Abstract

The products of the electrochemical oxidation of potassium ethylxanthate have been identified by infrared analysis and microanalysis for the constituent elements. The current efficiency for the formation of diethyl dixanthogen depends on the nature of the electrode, and at 0.5 V was found to be 100, 98, 90, c. 50, and 0% for platinum, gold, copper, galena, and lead respectively. The remainder of the current passed at this potential resulted in the formation of the metal xanthate.  Dixanthogen is formed on lead electrodes only at potentials of > 1.0 V, where lead xanthate is unstable with respect to oxides of the metal. The lead xanthate produced on a galena electrode at pH 9.1 involves the release of thiosulphate ions. The formation of lead xanthate by this reaction, followed by its reduction to lead, is shown to change the surface characteristics of a galena electrode to those of lead. However, the formation and reduction of the initial layers which takes place on cycling the electrode potential does not change a galena surface and cannot involve loss of sulphur from the surface to the solution. This supports the conclusion that the chemisorbed xanthate monolayer is first covered by dixanthogen and that lead xanthate forms only when bulk layers are produced.