Abstract The goal of this experimental study was to accurately determine the potential of the copper sulfate electrode (CSE) for use in quantitative electrochemical analysis. The potential of the CSE at 25 °C was found to be 317 mV versus that of the normal hydrogen electrode (NHE), with a slope of 0.17 mV/°C over the range from 5 °C to 45 °C. The determination of the true equilibrium potential of the CSE versus the NHE from laboratory measurements included the estimation of the liquid junction potential (LJP) by means of an electrolyte property model. The value of the LJP was estimated to be −14 mV based on calculated CSE potentials. Direct calculation of the LJP, which should have produced a more accurate result than estimation, failed to do so because the standard assumption of linear concentration variation of all species across the liquid junction was shown to be invalid.