Experimental Studies of the Liquid Junction Potential between Electrolyte Solutions in Different Solvents. I. Water–Organic Solvent Junctions

The liquid junction potential (ljp) between water and organic solvents was investigated by measuring the emfs of cells with free-diffusion junctions of various electrolyte solutions. In most experiments, the concentration of the electrolyte on one side of a junction was kept much larger than that on the other side (c MX in S⁄⁄c′ M′X′ in S′; S or S′ is H2O and c>>c′; thus the ljp was mainly determined by MX. The ljp may practically be expressed by the sum of Ej,ion (concn)(I), Ej,ion (ion-solv.)(II), and Ej,solv. (III). I and II are contributions from ionic species: I is the concentration term, which can be estimated approximately from the Henderson equation, and II is the term due to the difference in ionic solvations in S and S′. III is the contribution from the transfer of solvent molecules. The sum of II and III for the case in which S=H2O is approximately equal in absolute value but opposite in sign to that for the case in which S′=H2O. The change of II with the anion X− is in linear relation with fre...