Temperature Effect on Transference Numbers for KCl in Ethanol–Water Mixtures

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Abstract
Cation-transference numbers were determined by the moving boundary method for 0.02 mol dm−3 KCl in 5-, 10-, 15-, 20-, and 30 mol% ethanol–water mixtures at 15 and 35 °C. The cation-transference number has a maximum around 10 mol% of ethanol at each temperature studied, and becomes larger with decreasing temperature in the solvent of the same composition. From the temperature dependence of the transference number, the differences in the activation energy of transport between K+ and Cl− ions were estimated, and it was found that the activation energy of the K+ ion is less than that of the Cl− ion and the difference becomes larger in the range of 5–20 mol% of ethanol. These results are discussed in terms of structural effects and ion-solvent interactions.