Transfer Properties of Glycylglycine from Water to Aqueous NaNO3, NaClO4, and Na2SO4 Solutions

Enthalpies of solution and densities of glycylglycine in aqueous solutions of NaNO3, NaClO4, and Na2SO4 were measured at 298.15 K. Standard transfer enthalpies (ΔtrH0), standard transfer partial molar volume (ΔtrVϕ0), and hydration numbers (Nh) have been determined for glycylglycine. All of the ΔtrH0 values are negative in the three salt solutions. The relative order of ΔtrH0 in the same concentration of 1–1 type salts is NaNO3 > NaClO4. The ΔtrH0 in low concentration of Na2SO4 solutions is between the corresponding values in NaNO3 and NaClO4 solutions. With increasing Na2SO4 concentration, the ΔtrH0 values exceed that in NaNO3 solutions. The ΔtrVϕ0 values are positive and vary in the sequence Na2SO4 > NaNO3 > NaClO4. The results were discussed in terms of various interactions.