Construction and Calibration of an Internal Silver/Silver Chloride Reference Electrode for Supercritical Fluid Studies

Abstract An internal silver/silver chloride (0.1 M KCl) reference electrode was constructed and calibrated versus a hydrogen electrode under supercritical conditions. Solutions used for the calibration were 0.1 and 1.0 M HCl. An extrapolation method is discussed for calculating the mean ionic activity coefficients of HCl at elevated conditions. The standard potential of the reference electrode can be expressed as E° = 0.4597 − 0.0006087T (volts) for temperatures from 300 to 750 K and pressures from 200 to 280 atm.