Enthalpic Interaction Coefficients of N-(N- Glycylglycyl)glycine in Aqueous Sodium Chloride and Potassium Chloride Solutions at 298.15 K

The enthalpies of dilution have been measured for N-(N-glycylglycyl)glycine in aqueous sodium chloride and potassium chloride solutions at 298.15 K using a mixing-flow microcalorimeter. The enthalpic interaction coefficients h(2), h(3), and h(4) in the studied aqueous solutions have been calculated according to the McMillan-Mayer model. The results show that the enthalpic pairwise interaction coefficients h(2) of N-(N-glycylglycyl)glycine in both electrolyte solutions are negative and become less negative as the molality of sodium chloride or potassium chloride increases. The value of h(2) in aqueous sodium chloride solutions is less than that in aqueous potassium chloride solutions of the same molality. The effects of the two salts on h(2) are discussed from the point of view of electrostatic and structural interactions.