Study of intermolecular interactions in binary liquid mixtures through ultrasonic speed measurement

Density rho, and ultrasonic speed u, have been measured in pure benzyl alcohol (BA), cyclohexane, toluene and chlorobenzene and in their binary mixtures with BA as common component at 308 K. From these experimental data, isentropic compressibility K-s, intermolecular free length L-f, acoustic impedance Z, molecular association R-A, molar sound speed R-m, excess isentropic compressibility K-s(E), excess free length L-f(E), excess acoustic impedance Z(E), and excess ultrasonic speed u(E) are calculated for all the three binary liquid mixtures, over the entire composition range, The variations of these parameters, particularly the sign and magnitude of excess functions, with composition of the mixtures suggest dipole-induced-dipole interaction between BA and cyclohexane, and weak to medium-strength pi-H bond between BA and chlorobenzene/toluene molecules. Theoretical values of ultrasonic speed in binary liquid mixtures are calculated using different theories and empirical relations. The relative merits of these theories and relations have been discussed.