Thermodynamic behaviour of mixtures. Part 1.—Mixtures of pyridine with β-picoline, γ-picoline, isoquinoline, benzene and cyclohexane at 25 °C

Abstract

Ultrasonic velocities (u) and densities (ρ) of mixtures of pyridine (Py) with β-picoline, γ-picoline, isoquinoline, benzene and cyclohexane have been measured over the whole composition range at 25 °C. From u and ρ data, various intermolecular interaction parameters such as Wada's constant (W), the molar sound velocity (u_m) and the solvation number of the co-solvent (N_c) have been calculated for these binary systems. The partial molar volumes (V⁰) and isentropic compressibilities (κ⁰_s) at infinite dilution have also been computed for all the cosolvents as well as for Py. The variation of the excess properties V^E and κ^E_s shows that Py–β-picoline and Py–γ-picoline have mild excess contributions in comparison to all other Py–co-solvent systems. The excess contributions for Py–isoquinoline and Py–benzene have been attributed to the strong specific interactions and that of Py–cyclohexane to the strong dispersive forces that operate between the components of the binary mixtures.