Behavior of alkali-metal, halide and tetraphenyl ions by sedimentation potential measurement of electrolytes in water-dimethylformamide mixtures

The sedimentation potential(SP) of 10 kinds of electrolytes in Water-Dimeth ylformamide mixtures are measured as a function of DMF composition. By comb ining SP obtained and law of additivity on ionic partial molar volume, limi ting partial molar volumes of the electrolytes are divided into cationic an d anionic parts at each DMF composition. As the result, ionic partial molar volume of Na+ and K+ ions except Na+ ion obtained from NaPh4B shows an inc rease tendency with concentration of DMF in between 15%similar to 45%. In t his case, the change of ionic partial molar volume of K+ ion is bigger than those of Na+ ion. On the contrary, ionic partial molar volume of Cl- and B r- ions except Cl- ion obtained from Ph4PCl shows a decrease tendency with concentration of DMF in the same region. Ionic partial molar volume of Br- ion having alkyl group shows a big change among them. Ionic partial molar v olume of Ph4P(+) and Ph4B(-) ions shows opposite change. From above fact, w e discuss on the basis of ion-water, ion-DMF and ion-ion interactions.