Study of Interactions between Amino Acids and Zinc Chloride in Aqueous Solutions through Volumetric Measurements at T = (288.15 to 318.15) K

Densities, ρ, of glycine, dl-α-alanine, dl-α-amino-n-butyric acid, l-valine, and l-leucine in aqueous and in mixed aqueous solutions of zinc chloride, (0.1, 0.5, 1.0, and 1.5) mol·kg−1, have been determined by using a vibrating-tube digital densimeter at (288.15, 298.15, 308.15, and 318.15) K. These data have been used to calculate the apparent molar volumes, V2,ϕ, of the studied amino acids. The partial molar volumes, V20, at infinite dilution are evaluated and further used to obtain the corresponding transfer volumes, ΔtV0 for amino acids from water to aqueous zinc chloride solutions. Partial molar expansibilities, V0E, hydration numbers, nH, interaction coefficients, and side chain group contributions of amino acids have also been calculated. The ΔtV0 values for the studied amino acids are positive, and these values increase with an increase in the concentration of zinc chloride as well as with temperature. The parameters obtained from the volumetric study are used to understand various mixing effects due to the interactions between amino acids and zinc chloride in aqueous solutions.