The pulp potential of galena, chalcopyrite and pyrite have been measured in parallel with Pt and mineral electrodes by controlling the potential with oxidizing (H2O2 and K2Cr2O7) and reducing (Na2S and Na2S2O4) agents under "free to change conditions" to follow the adaptability of different electrodes to the dynamically changing conditions. It has been determined that while mineral and Pt-electrodes indicated similar potential values in the same environment under acid and reducing conditions, they showed quite different potential values under oxidizing and alkaline conditions. The difference between the measured potentials decreased in the following order: Pt-galena > Pt-chalcopyritc > Pt-pyrite, which is in accordance with the electrochemical activity of minerals. Poisoning of Pt-electrode by Na2S2O4 was observed, whereas no serious poisoning was seen with sulfide ions. (C) 2008 Elsevier B.V. All rights reserved.