LIQUID JUNCTION POTENTIAL BETWEEN DIFFERENT SOLVENTS - COMPONENT DUE TO THE DIFFERENCES IN ELECTROLYTE CONCENTRATIONS AND IONIC MOBILITIES

Among the three components of the liquid junction potential at a junction between different solvents, the component due to the differences in electrolyte concentrations (or activities) on the two sides of the junction and the differences between the cationic and anionic mobilities was investigated. An equation was derived for the component at a junction with the same electrolyte (MX) on the two sides, c1 MX (S1):c2 MX (S2): E(j)(a) = (-RT/F){(t(M1-t(X1)) In(a(MX2)/a(MX1)) + (t(M2) - t(M1) - t(X2) + t(X1))[1 - a(MX1) In(a(MX2/a(MX1))/(a(MX2) - a(MX1)]}, where t represents the ionic transport numbers and a the electrolyte activity. Linear variations of t and a were assumed at the interphase region of the junction. The equation was confirmed experimentally to be approximately valid in many cases and may be used in estimating the component. In some cases, apparent deviations from the equation were observed. The deviations were attributed to the influence of electrolyte concentration, which caused partial decreases in the component due to the solvent-solvent interactions at the junction. Some theoretical and experimental studies were also carried out for a junction with different electrolytes (MX and NY) on the two sides, c1 MX (S1):c2 NY (S2).