Densities and solubilities of glycylglycine and glycyl-l-alanine in aqueous electrolyte solutions

Solubilities of glycylglycine and glycyl-l-alanine in aqueous electrolyte solutions containing 0–6 molal NaCl, 0–1 molal Na2SO4, and 0–1 molal (NH4)2SO4, have been determined experimentally at 298.15 K and atmospheric pressure. The solubility of glycylglycine and glycyl-l-alanine in pure water is 1.74 and 4.78 mol/kg of water, respectively. The solubility of glycylglycine in salt solutions of NaCl, Na2SO4, and (NH4)2SO4 show a moderate salting-in effect. The solubility of glycyl-l-alanine show a minor or no salting-in effect at low salt concentrations and a moderate salting-out effect at higher salt concentrations in NaCl and Na2SO4, and in (NH4)2SO4 the solubility is almost constant. The densities of the solutions have been determined experimentally, and the volume expansions by dissolving salt and dipeptide in water have been calculated.