Excess enthalpies and excess heat capacities of the ternary system ethanol + N,N-dimethylformamide + tetrahydrofuran at 298.15 K

Excess enthalpies and excess heat capacities at 298.15 K for the ternary system ethanol + dimethylformamide + tetrahydrofuran were determined by means of a flow calorimetric apparatus built in our laboratory. Experimental data were described with a Redlich-Kister type equation and compared with those of other ternary systems previously studied (ethanol + tetrahydrofuran + cyclohexane, ethanol + dimethylformamide + cyclohexane, dimethylformamide + tetrahydrofuran + cyclohexane). A peculiar behaviour was observed for mixtures containing dimethylformamide, namely the negative values of both H E and C p E ternary contributions. A satisfactory prediction of experimental H E data is provided by the UNIQUAC model, while UNIFAC (Dortmund, Germany) clearly fails probably owing to an unsufficient definition of interaction parameters involving dimethylformamide.