The Ag/AgCl electrode is often used as a reference electrode in high temperature aqueous electrochemical studies because it has good thermal stability. It is also relatively resistant to attack by high acidity or chloride concentration. Jones and Masterson cite instances in their review1 where the Ag/AgCl electrode was used successfully in 275 C (527 F) 1N HC12 and in 200 C (392 F) saturated NaCl.3
These reports encouraged a test of Ag/AgCl as a reference electrode in stress corrosion cracking (SCC) experiments involving stainless steel in 200 to 300 C (392 to 572 F) 35% MgCl2.4 Unfortunately, the electrode proved unstable and appeared to come to act ultimately as a hydrogen electrode even at the lower temperature limit. The tendency of the AgCl electrode to assume the hydrogen potential at elevated temperatures has been noted before,5 and it is reasonable that this tendency...
