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.
