Stabilized Ceramic Membrane Electrodes for the Measurement of pH at Elevated Temperatures

The use of a ceramic membrane for the measurement of pH at elevated temperatures is described. The measurement system consists of matched membrane and external pressure‐balanced reference electrodes, both of which have their internal sensing elements at ambient temperature in order to avoid thermal degradation. The pH response of the system has been calibrated using and test solutions whose pH values were determined at various temperatures between 25° and 275°C using an in situ hydrogen electrode. The ceramic membrane has been shown to exhibit a Nernstian pH response, particularly at elevated temperatures, although an "acid error" was observed for weakly acidic environments.