In 1979, the author published a paper describing two high temperature/pressure Ag/AgCl electrodes which were resistant to the contaminating effects of H2 and H2S.1 The external model, which operates at full system pressure but at ambient temperatures, has been successfully used in the nuclear, petroleum, and geothermal industries. However, electrode life is a strong function of the rate and magnitude of the pressure fluctuations in the system. This technical note describes a design which results in a significant improvement in electrode life.
The external reference electrode suffers from a thermal liquid junction potential (TLJP) and the development of the Soret Effect (thermodiffusion of the electrolyte). Two papers1,2 have been published which indicate that the TLJP rapidly stabilizes and that the Soret effect is extremely slow to develop (when KCl is used). Consequently, the potential of the external reference electrode can be placed on the hydrogen...
