An investigation of the effect that the in-situ solution chemistry would have on the induced-polarization phenomena was carried out by means of laboratory studies of the electrode impedances of metallic and sulfide minerals. Reaction rate theory shows that this effect is largely due to the impedance associated with the diffusion of the ions involved in the charge transfer reaction to and from the reaction sites. This impedance is inversely proportional to the concentration of the reacting ions and inversely proportional to the square root of the frequency. Impedance measurements were made with different concentrations of a variety of ions in order to identify the active ion species. The ion concentrations were controlled by doping and by excursions in Eh and pH. These measurements showed that cupric and sulfide ions are active in the charge transfer reaction and control the electrode impedances whenever their concentrations exceed 10 (super -4) N. None of the other common anions and cations tested appeared active. A background impedance level was found which was relatively insensitive to the solution chemistries tested. These impedances varied somewhat with the type of mineral tested, but generally ran between 2000 and 20,000 Omega -cm 2 at 1 radian/sec. The identity of these background reactions is still an open question.