INVESTIGATION OF POSSIBLE BASIC CHARACTER IN NITROGEN TRIFLUORIDE BY VAPOR-PRESSURE MEASUREMENTS ON THE SYSTEMS NF3-BF3 AND NF3-HC1

The vapour pressure of liquid mixtures of nitrogen trifluoride and boron trifluoride has been measured at 158.95 K as a function of composition. The system shows large positive deviations from Raoult's law. The excess Gibbs energy of mixing, GE, for the equimolar mixture is 636 J mol-1. Far from the vapour pressure measurements giving any evidence for acid-base association (which would give a negative, or at least a reduced positive, value of GE), the observed positive deviations are considerably larger than might have been expected. The actual GE for the equimolar mixture is almost three times the value calculated on one of the most reliable of current theories. The system NF3HCl is even more imperfect, the two liquids being only partially miscible between nitrogen and trifluoride mole fractions of ∼0.1 and 0.9. © 1979.