The Cu II−Cu I−Cu 0(Hg) system in the presence of benzotriazole : Part II. A chronocoulometric investigation

Abstract

Both the oxidation of Cu 0 at dropping amalgam electrodes immersed in solutions of benzotriazole (BTA) and the reduction of Cu II at a dropping mercury electrode from BTA solutions have been investigated by the single potential-step chronocoulometric technique. The dependence of the charge Q(t) flowing as a consequence of a given potential jump E i→ E f upon the initial and final potentials E i and E f, as well as upon the time t elapsed from the instant of the potential jump provides direct evidence for the presence of a single adsorbed monolayer of a Cu I compound on a mercury electrode immersed in a Cu II solution containing BTA, at applied potentials positive to ≈−0.4 V/SCE. Analogous measurements carried out at dropping amalgam electrodes reveal the presence of a single adsorbed monolayer of a Cu I compound, or else of an adsorbed multilayer, depending on the potential range investigated. The results of the chronocoulometric measurements are in agreement with those of the polarographic measurements of Part I.