Activity measurements in aqueous mixed electrolyte solutions—III. HClCaCl 2 mixtures of constant total ionic strength

Abstract

Emf measurements have been made in cells without liquid junction of the type H 2/H X ( m 1), M X n ( m 2)/AgCl, Ag . . (I) containing mixtures of HCl and CaCl 2 in different proportions, but at constant total ionic strength (I = 2, 1, 0.5). The measurements have been carried out at 5°C intervals over the temperature range 5–35°C. AgAgCl electrodes prepared by two different methods (thermal and thermoelectrolytic) were used of which the thermoelectrolytic electrodes were found to give more consistent results. The results when extrapolated properly lead to E° values at the different temperatures which agree well with those reported in literature. The application of the Pitzer method leads to the calculation of the ionic interaction coefficients α 12 and α 21, at the different constant ionic strengths. The nature of variation of these α's with the total mixture ionic strength at different temperatures has been considered.