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The e.m.f. of the cell Ag, AgCl(s)| NaCl(m)⋮ NaN3(m)| AgN3(s), Ag in water and water +10, +20, +30 and +40 mass % dioxan has been measured at 5 °C intervals from 5 to 45 °C. The values of the standard potentials of the silver, silver azide electrode have been determined in water and the mixtures at these temperatures. The change in standard thermodynamic quantities (ΔG⊖, ΔH⊖ and ΔS⊖) for the electrode reaction have been evaluated. The thermodynamic parameters for the transfer of HN3 from water to the mixtures have also been evaluated. The results are discussed in terms of the preferential solvation of ions.

Electromotive force measurements on cells without a liquid junction have been used to determine the pK1 and pK2 values, at different temperatures, of DL-malic, maleic and fumaric acids in water and water + 10, + 20, + 30 and + 40 mass percent dioxan. From the temperature coefficients, the thermodynamic quantities ΔG°, ΔH°, ΔS° and ΔC°p of the dissociation processes have been calculated. The results have been discussed with respect to preferential solvation. The distances between the carboxylic groups have been calculated from the ratio of the successive dissociation constants in these media.