This paper deals with the densities of aqueous solutions of N-methylacetamide (NMA) in the range of concentrations x (starting from 0.0095 to 0.699) at T = 278.15, 288.15, 298.15, 308.15, 323.15, and 333.15 K and p = 10, 25, 50, 75, and 100 MPa. A modified Tate equation was used to correlate the experimental density data. The obtained absolute average deviation between the densities measured and calculated by the Tate equation was about 0.02%. The volumetric properties of the solution calculated from the density, such as molar isothermal compressions, KT,m, and molar isobaric thermal expansions, EP,m, were considered depending on the concentration, temperature, and pressure. Some volumetric characteristics were also obtained for an infinitely diluted aqueous solution of N-methylacetamide: the limiting partial molar volumes, V2∞, the limiting partial molar isothermal compressions, KT,2∞, and the limiting partial molar isobaric expansions, EP,2∞. The results obtained are discussed taking into account the solute–solvent and solute–solute interactions. A tendency of N-methylacetamide molecules to self-associate in water was found, and increases in pressure and temperature lead to the weakening of the interaction between NMA molecules.
