ABSTRACT
Potentiometry has been an essential tool for experimental studies of electrolytes since the earliest quantitative work in the field. As direct measures of salt chemical potential, potentiometric data have provided an ideal complement to isopiestic measurements, which determine water activity. Experimentally simpler, because elaborate precautions for eliminating oxygen are not necessary, the glass electrode method can provide detailed activity coefficient data more rapidly, and can work under some circumstances where the hydrogen electrode cannot be used. The final criterion, absence of side reactions, is the most difficult to satisfy and is the primary cause of experimental errors with amalgam electrodes. A word should be said about alkaline earth amalgams. Although some of the basic activity coefficient data for the alkaline earth chlorides were first obtained using amalgam electrodes, these have been supplanted by more accurate isopiestic and ion-selective membrane electrode data.
