Volumetric, acoustic, and refractometric study of cyclic alanylalanine in aqueous cobalt chloride solutions at temperatures T = (293.15 to 313.15) K

Abstract

Density, refractive index, and speed of sound values of cyclic alanylalanine + aqueous CoCl<inf>2</inf> systems have been reported as a function of concentrations of cyclic alanylalanine and that of CoCl<inf>2</inf> at temperatures T = (293.15, 298.15, 303.15, 308.15, and 313.15) K. The values of partial molar volumes, isentropic compressibilities, and partial molar isentropic compressibilities of the cyclic alanylalanine + aqueous CoCl <inf>2</inf> systems have been calculated from the speed of sound and density data obtained from the experiment at various temperatures. The decreasing value of isentropic compressibility with respect to the molal concentration of cyclic alanylalanine and temperature indicated the presence of strong solute-solvent interaction operative in the present system. The variations in partial molar volumes as well as partial molar isentropic compressibilities have been discussed in terms of ionic, hydrophilic, and hydrophobic interactions present in the system. © 2013 American Chemical Society.