pH Measurements of High Temperature Aqueous Environments with Stabilized‐Zirconia Membranes

A pH sensor has been developed for precise pH measurements of high temperature aqueous solutions based on a yttria‐stabilized zirconia (9% ) membrane electrode with a solid‐state internal element. In these investigations, the use of calculated pH values in evaluating the performance of the sensor has been eliminated. The excellent one‐to‐one correlation obtained between the potential of the sensor and a hydrogen reference electrode measured against a , reference electrode confirms that the pH sensor behaves in a Nernstian manner. The sensor is capable of withstanding high temperatures and pressures and is unaffected by hydrogen and oxygen gases and chloride ion concentration. The electrode remains stable over long periods of time, thus showing its potential use in monitoring the pH of waters in nuclear reactors, geothermal brines, and other high temperature aqueous systems.