Densities and volumetric properties of (acetonitrile + an amide) binary mixtures at temperatures between 293.15 K and 318.15 K

The densities of binary mixtures of acetonitrile (ACN) with formamide (FA), N,N-dimethylformamide (DMF), N-methylacetamide (NMA), and N,N  -dimethylacetamide (DMA), including those of pure liquids, over the entire composition range were measured at temperatures (293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K and atmospheric pressure. From the experimental data, the excess molar volume, VmE, and partial molar volumes, V¯m,1 and V¯m,2, were calculated over whole composition range. The variation of these parameters with composition and temperature of the mixtures has been discussed in terms of molecular interaction in these mixtures. The VmE values were found negative for all the mixtures and at each temperature studied, indicating the presence of specific interactions between ACN and amide molecules. The extent of negative deviations in VmE values follows the order: FA > NMA > DMA > DMF. It is observed that the VmE values depend upon the positions of methyl groups in these amide molecules.