EXCESS-ENTHALPIES AND EXCESS HEAT-CAPACITIES OF THE TERNARY-SYSTEM ETHANOL PLUS N,N-DIMETHYLFORMAMIDE PLUS TETRAHYDROFURAN AT 298.15 K

Excess enthalpies and excess heat capacities at 298.15 K for the terna ry system ethanol+dimethylformamide+ tetrahydrofuran were determined b y means of a flow calorimetric apparatus built in our laboratory. Expe rimental data were described with a Redlich-Kister type equation and c ompared with those of other ternary systems previously studied (ethano l+tetrahydrofuran+cyclohexane, ethanol+dimethylformamide+cyclohexane, dimethylformamide+tetrahydrofuran+cyclohexane). A peculiar behaviour w as observed for mixtures containing dimethylformamide, namely the nega tive Values of both H-E and C-p(E) ternary contributions. A satisfacto ry prediction of experimental H-E data is provided by the UNIQUAC mode l, while UNIFAC (Dortmund, Germany) clearly fails probably owing to an unsufficient definition of interaction parameters involving dimethylf ormamide.