HEAT-CAPACITIES AND VOLUMES OF NAI IN MIXTURES OF DIMETHYLFORMAMIDE AND SEVERAL NONELECTROLYTES

Heat capacities and densities of solutions of NaI in mixtures of N,N-dimethylformanide (DMF) with isobutanol, formamide, acetone, tetrahydrofuran, ethylene glycol, 2-methoxyethanol, n-propanol and benzo-15-crown-5-ether have been measured at 25°C. The apparent molar volumes of NaI in mixtures of DMF with isobutanol, formamide, ethylene glycol, n-propanol, and 2-methoxyethanol increase with the amount of these non-electrolytes, while in the systems containing acetone, tetrahydrofuran and benzo-15-crown-5 ether a decrease is observed. The apparent molar heat capacity of NaI in the system containing the crown ether is higher than that in pure DMF. In all other cases Cp,φ{symbol} of NaI decreases with the amount of non-electrolyte. Finally, the non-ideal contributions to heat capacity and volume as a result of the interaction between pairs of unlike solutes, respectively cXY and vXY with X=NaI and Y=non-electrolyte, are calculated. © 1990 Plenum Publishing Corporation.