Enthalpies of dilution of glycine, l-alanine and l-serine in aqueous potassium chloride solutions

The dilution enthalpies of glycine, l-alanine and l-serine in aqueous potassium chloride solutions of various molalities have been determined using LKB-2277 flow microcalorimetry at 298.15 K. The homogeneous enthalpic interaction coefficients over the whole range of aqueous potassium chloride solutions investigated have been calculated according to the excess enthalpy concept. It is found that pairwise enthalpic interaction coefficients h2 of glycine and l-serine are all negative and become less negative with increasing of the molalities of potassium chloride, while pairwise enthalpic interaction coefficients h2 of l-alanine are positive on which the influence of potassium chloride is not obvious. The results are interpreted from the point of view of solute-solute interactions involved by solvent effects.