Effect of temperature on volumetric and isentropic compressibility of glycine in aqueous KCl/NaCl solutions

Density (ρ) and ultrasonic velocity (u) values of glycine in 1.0 M aqueous KCl and 1.0 M aqueous NaCl solutions have been measured as a function of amino acids concentration at T = (298.15, 303.15, 308.15, 313.15, 318.15 and 323.15) K. Using the ρ and u data, the thermodynamic parameters such as partial molal volume (ϕ0v), isentropic compressibility (κs), change in isentropic compressibility (Δκs), relative change (Δκs/κ0) in isentropic compressibility and partial molal isentropic compressibility (ϕ0k), values have been computed. The increase in partial molal volume with temperature is attributed to the volume expansion of hydrated zwitterions. The ϕ0v and ϕ0k values of glycine in 1.0 M aqueous KCl and NaCl solutions are larger than the corresponding values in water. The larger partial molal volumes of glycine in 1.0 M aqueous KCl and NaCl is ascribed to the formation of 'zwitterion-K+/Na+/Cl−' and 'K+/Na+/Cl−-water dipole' aggregates in solutions. The variation of κs, Δκs and Δκs/κ0 with amino acid/zwitterions concentration and temperature is discussed in terms of zwitterions-ions, zwitterions-water dipoles, ion-ion, ion-water dipoles due to intermolecular/interionic interactions occurring in the systems.