The rest potential of sulphide electrodes was examined from both thermodynamic and kinetic aspects. The kinetic aspect has been found to be necessary for the interpretation of the establishment of the mixed potential in polyelectrode system, to which most sulphide systems belong. The pyrrhotite electrode system was studied by measuring the rest potential while changing the concentrations of ferrous ion, hydrogen ion and hydrogen sulphide in the electrolyte, and the composition of pyrrhotite. A mixed potential of pyrrhotite consisting of the reaction S (in pyrrhotite) + 2H⁺ + 2e ⃗ H₂S as a cathodic process and the reaction Fe (in pyrrhotite) ⃗ Fe⁺⁺ + 2e as an anodic process accounts for the dependence of the rest potential on those ionic species in the electrolyte and the composition of pyrrhotite electrodes. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate