Excess thermodynamic properties of binary mixtures of N,N-dimethylacetamide with water or water-d2 at temperatures from 277.13 K to 318.15 K

Densities of binary mixtures of N,N-dimethylacetamide (DMA) with water (H2O) or water-d(2) (D2O) were measured at the temperatures from T = 277.13 K to T = 318.15 K by means of a vibrating-tube densimeter. The excess molar volumes V-m(E), calculated from the density data, are negative for the (H2O + DMA) and (D2O + DMA) mixtures over the entire range of composition and temperature. The V-m(E) curves exhibit a minimum at x(DMA) congruent to 0.4. At each temperature, this minimum is slightly deeper for the (D2O + DMA) mixtures than for the corresponding (H2O + DMA) mixtures. The difference between D2O and H2O systems becomes results were correlated using a modified comes smaller when the temperature increases. The V-m(E) results were correlated using a modified Redlich-Kister expansion. The partial molar volume of DMA plotted against x(DMA) goes through a sharp minimum in the water-rich region around x(DMA) congruent to 0.08. This minimum is more pronounced the lower the temperature and is deeper in D2O than in H2O at each temperature. Again, the difference becomes smaller as the temperature increases. The excess expansion factor alpha(E) plotted against x(DMA) exhibit a maximum in the water rich region of the mole fraction scale. At each temperature, this maximum is higher for the (D2O + DMA) mixtures than for the corresponding (H2O + DMA) mixtures, and the difference becomes smaller as the temperature increases. At its maximum, alpha(E) can be even more than 25 per cent of total value of the cubic expansion coefficient alpha in the (H2O + DMA) and (D2O + DMA) mixtures. (C) 2002 Elsevier Science Ltd. All rights reserved.