In the last few years, many attempts have been made to develop reference electrodes which enable electrochemical measurements even at temperatures up to 300 C and pressures about 100 bar.1–3
Principally, two different types have been chosen for internal, i.e., isothermal and isobaric reference electrodes. One way is to use an electrochemical half-cell known to show a reproducible and stable electrode potential which itself is calibrated against the isothermal standard scale of the hydrogen electrode. The other way is to choose an electrochemical half-cell which is compatible with the bulk solution to avoid any liquid junctions.
Experiments of the first type of half-cell design were carried out with an Ag, AgCl/KCl reference electrode used by many other authors4–9 and the potential of which has been measured by Greeley, et al.10,11 The arrangement of the half-cell was similar to that proposed by Indig and Vermilyea5 to...
