Densities, partial molar volumes, and heat capacities of glycine, L-alanine, and L-leucine in aqueous magnesium chloride solutions at different temperatures

The apparent molar volumes (V-2,V-phi) have been determined for glycine, L-alanine, and L-leucine in water and in aqueous magnesium chloride solutions with concentrations approximate to (0.05 to 0.80) mol(.)kg(-1) by measuring the densities at (288.15, 298.15, and 308.15) K. The apparent molar heat capacities (C-p2,C-phi) have also been determined for glycine and L-alanine in aqueous magnesium chloride solutions with concentrations (0.05 to 0.40) mol(.)kg(-1) by measuring heat capacities in the temperature range (298.15 to 328.15) K. These properties show a peculiar dependence upon the concentration of magnesium chloride. The standard partial molar volumes at infinite dilution (V-2(infinity)) obtained from these data have been used to calculate the partial molar volumes of transfer of amino acids from water to aqueous magnesium chloride solutions at infinite dilution (Delta(t)V(2)(infinity)), which are positive for the presently studied amino acids at all temperatures and concentrations. The partial molar expansibilities (partial derivativeV(2)(infinity)/partial derivativeT)(p) at infinite dilution and the (partial derivative(2)V(2)(infinity)/partial derivativeT(2))(p) have also been determined from the V-2(infinity) data at various concentrations of the salt. The volumetric interaction parameters have been calculated from Delta(t)V(2)(infinity) data. The results have been discussed in terms of various interactions operating in these systems.