In order to study the corrosion of materials for use in nuclear reactor systems, it is desirable to measure and control the potential of electrodes in aqueous solutions at approximately 289 C (552 F). Several schemes have been used to connect an external room temperature calomel electrode to a corroding electrode contained in a pressure vessel at elevated temperatures and pressures. Bacarella and Sutton1 used a salt bridge constructed from Teflon tubing which contained an asbestos wick and the test solution. The tubing was passed out of an autoclave through a pressure seal to an external calomel electrode. Wilde2 used a Luggin tip and capillary to contain the electrolyte which was connected to an external calomel electrode. This salt bridge was also fabricated from Teflon except for the pressure seal which was a porous cellulose plug.
External reference electrodes have the disadvantage that streaming potentials and thermal junction...
