Conductivity Measurements of Alkali Metal Thiocyanates
in Water-Methanol Mixtures
Eiji KUBOTA* and Sanaki HORIMOTO
Department of Chemistry, Faculty of Science, Shinshu University;
The conductivity of several alkali metal thiocyanates in water-methanol mixtures was measured at 25 °C. The data were analyzed using the Lee-Wheaton theory for symmetrical electrolytes to obtain ion association constant, KA, limiting molar conductivity, Λ0, and limiting ionic molar conductivity, λ0±. In all the solvent systems, calculated λ0+ values of the alkali metal ions increase in the order Li+<Na+<K+
<Rb+<Cs+. The λ0± values of the alkali metal ions and thiocyanate ion showed a minimum when the molar fraction of methanol was ca. 0.4. The changes in λ0± of these alkali metal ions and thiocyanate ion with the molar fraction of methanol agree with the change in the viscosity of the solvent or the heat of mixing of water-methanol mixtures. These alkali metal thiocyanates form little or no ion aggregated in water and water-methanol mixtures. These alkali metal thiocyanates were KA=15--24 dm3 mol−1 in methanol.
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