Densities have been measured for glycylglycine, glycyl-L-valine and glycyl-L-leucine in aqueous solutions of 0.5, 1.0, 1.5 and 2.0 mol•kg－1 sodium acetate at 298.15 K. The apparent molar volumes, standard partial molar volumes ( ), standard partial molar volumes of transfer for the dipeptide from water to aqueous sodium acetate solutions (DtV$), the hydration number and volumetric interaction coefficients have been calculated. Both the and DtV$ for the glycyl dipeptides increase with increasing molality of sodium acetate. The interactions between charged center or glycyl units of the peptide and ions dominate those between alkyl groups of the peptide and the ions. The interaction between the peptides and sodium acetate is mainly pairwise. The results were interpreted successfully by the cosphere overlap model. Using the values of the amino acids, the standard partial molar volumes of peptide were estimated. Excellent agreement between the calculated values and the experimental values of the peptides was observed.

Key words: glycyl dipeptide, sodium acetate, standard partial molar volume, standard partial molar volume of transfer