The effect of electrochemical potential on the adsorption of potassium ethyl xanthate (KEX) on gold, silver and their alloys of different compositions has been studied in borate solutions of pH 9.2, using FT-IR reflection spectroscopy, cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). The results show that (EX)2 and AgEX are the oxidation products formed on pure gold and silver, respectively. Both voltammetry and IR reaction spectroscopy show that the onset of these oxidation reactions occurs near the reversible potentials for the EX−/(EX)2 and EX−/AgEX couples. On gold-silver alloys, AgEX is formed first during the anodic scan, followed by (EX)2 formation. The potential at which xanthate is oxidized is reduced significantly, depending on the amount of silver present in a gold—silver alloy. Thus, the presence of silver in gold allows the xanthate flotation to be achieved at lower potentials than with pure gold. Both the IR and XPS spectra show evidence for the formation of unknown surface species at low potentials.