Effect of Temperature on Volumetric and Viscometric Properties of Homologous Amino Acids in Aqueous Solutions of Metformin Hydrochloride

Density (rho) and viscosity (eta) are measured for glycine, DL-alpha-alanine DL-alpha-valine, and DL-alpha-leucine in 0.05, 0.10, 0.15 and 0.20 mol.L-1 aqueous metformin hydrochloride at 308.15, 313.15 and 318.15 K. The measured values are used to estimate some important parameters, such as partial molal volume V-phi, standard partial molal volume V-phi(0), transfer volume Delta V-phi(0), hydration number n(H), the second derivative of infinite dilution of partial molal volume with respect to temperature, viz., partial derivative V-2(phi)0/partial derivative T-2, viscosity B-coefficient, variation of B with temperature, viz., dB/dT, free energy of activation per mole of solvent Delta mu(0*)(1) and solute Delta mu(0*)(2) of the amino acids. These parameters are interpreted in terms of solute-solute and solute-solvent interactions and structure making/breaking ability of solutes in the given solution. In addition, V-phi(0), Delta V-phi(0), viscosity B-coefficient, Delta B and Delta mu(0*)(2) are split into group contributions (NH3+COO-) and -CH2 of the amino acids using their linear correlation and their behavior is discussed.