ION AND SOLVENT TRANSFERS AT HOMOIONIC JUNCTIONS BETWEEN CONCENTRATED ELECTROLYTE-SOLUTIONS

A unified treatment of liquid junction potentials and membrane potentials which accounts for both ionic and solvent transfers at homoionic junctions between ultra concentrated electrolyte solutions, also in terms of the primary hydration parameters and the Stokes-Robinson hydration theory, is described. Application to the determination of cation transference numbers, τ+, water transference numbers, τw, and primary hydration numbers, h, is described as a rational scheme for characterization of concentrated electrolytes as possible new salt bridges for the minimization of liquid junction potentials in electroanalysis. Examples of application of this scheme are presented based on multiple regression analysis of electromotive force measurements of such homoionic concentration cell as Ir | Cl2 | HCl (m2) {norm of matrix} HCl (m1) | Cl2 | Ir and Hg | Hg2SO4 | Li2SO4 (m2) {norm of matrix} Li2SO4 (m1) | Hg2SO4 | Hg, with fixed m1 molality and varied m2 molality. Based on the electromotive force of analogous homoionic transference cells but with interposed membranes, application of the present procedure can be extended to the determination of ion and solvent transport parameters, notably the degree of permselectivity, of membranes for use either as selective sensors in electroanalysis or selective separators in industrial electrochemistry. © 1990 Chapman and Hall Ltd.