Enthalpies of Dilution of N-Glycylglycine in Aqueous Sodium Chloride and Potassium Chloride Solutions at 298.15 K

Abstract

The enthalpies of dilution of N-glycylglycine in aqueous sodium chloride and potassium chloride solutions have been determined by using flow microcalorimetry at 298.15 K. The homogeneous enthalpic interaction coefficients (h2, h3, h4) in the range of sodium chloride and potassium chloride molality, (0 to 0.6) mol·kg−1, have been calculated according to the McMillan−Mayer theory. It shows that the enthalpic pairwise interaction coefficients h2 of N-glycylglycine in both electrolyte solutions are negative, and the value of h2 in aqueous sodium chloride solutions is less than that in aqueous potassium chloride solutions of the same molality. The values of h2 for N-glycylglycine in aqueous solutions of sodium chloride pass through a minimum at about 0.10 mol·kg−1, while the corresponding values of h2 in aqueous potassium chloride solutions become less negative with an increase in the molality of potassium chloride. The results are discussed in terms of the solute−solute and solute−solvent interactions.