Selective solvation of copper(I) thiocyanate in acetonitrile-water mixtures at 30°C

The selective solvation of copper(I) thiocyanate has been studied in water-acetonitrile (AN) mixtures at 30°C by solubility and EMF measurements. The solubility of the salt increases continuously and changes only slightly beyond XAN=0.7 mole fraction. The Gibbs energy of transfer of copper(I) ion from water to mixtures with acetonitrile (determined on the basis of the ferrocene reference method) decreases continuously, while that of the thiocyanate ion increases with the addition of acetonitrile. The solvent transport number Δ of acetonitrile passes through a maximum (Δ=6.4) at XAN=0.25. These results were interpreted as arising due to a heteroselective solvation of the salt, the copper(I) ion being preferentially solvated by acetonitrile and the thiocyanate ion by water in these mixtures. © 1982 Plenum Publishing Corporation.