EFFECT OF DIFFUSION OF A SPARINGLY SOLUBLE SALT ON EMF OF A CELL WITHOUT TRANSFERENCE

In concentration cells without transference, one of the electrodes usually involves a sparingly soluble salt. When the solubility of this salt in the solution between the electrodes is no longer negligible compared to the concentration of the other electrolyte present, access of the sparingly soluble salt to the other electrode must be prevented. The concentration gradients existing in such a cell cause deviations from the emf measured under equilibrium conditions. An approximate treatment is suggested for the estimation of errors incurred due to diffusion of the sparingly soluble salt. The need for this correction is demonstrated for emf measurements on cells involving non-aqueous ionizing solvents, in which the solubility of metal halides is usually higher than in their aqueous analogues. © 1968.