where E is the equilibrium cell potential, E is the equilibrium cell potential at standard conditions minus the overpotential at the copper cathode, γ’s are the activity coefficients, and PH2 is the hydrogen gas pressure. In the analysis which follows, it is assumed that the hydrogen gas is at standard conditions. Physical chemistry texts such as Atkins (8) provide a detailed discussion of electrochemical cells and the application of the Nernst equation. As shown in eq 1, decreasing hydrogen ion activity by increasing ionic strength or hydrogen ion concentration by dilution with water will reduce the equilibrium cell potential. In order to explore the effect of dilution and salt addition, a series of experiments at different dilutions and salt concentrations was carried out. The internal resistance is determined using