Compressibility Studies of Some Copper(I), Silver(I), and Tetrabutylammonium Salts in Acetonitrile plus Adiponitrile Binary Mixtures

Ultrasonic velocities and densities of some copper(1), silver(I), and tetrabutylammonium salts have been measured in the concentration range of (0.002 to 0.28) in in binary mixtures of acetonitrile (AN) + adiponitrile (ADN) containing 1.0, 0.9, 0.8, 0.7, 0.6, and 0.5 mol fraction of AN at 298.15 K. The isentropic compressibility (K-s) and apparent molal isentropic compressibility (K-s,K-phi) in various solvent systems have been calculated by using ultrasonic velocity (a) and partial molal volume (V-phi) data, respectively. Limiting apparent molal isentropic compressibilities (u) for various salts have been evaluated from ic, versus in /2 plots and split into the contributions of individual ions (K-s,phi(o))(+/-). The (K-s,phi(o)) values for copper(I) and silver(I) ions are found to be negative over the entire solvent composition range which indicates strong solvation of these ions. The (K-s,phi(o)), values becoming more and more negative with an increase in the ADN composition shows that the extent of solvation increases with an increase in ADN composition. The large and positive (k(s,phi)(o)) values for Bu4N+ and Ph4B- indicate some special type of interaction with the solvent molecules, which increases with the increase of ADN composition in the mixture.