PHASE-SEPARATION OF IONIC FLUIDS - AN EXTENDED EBELING-GRIGO APPROACH

The Ebeling-Grigo (EG) improvement of the mean-spherical approximation (MSA) via the Bjerrum theory of ionic association in the restricted p rimitive model (RPM) is reviewed and extended. We find that, in terms of reduced density and temperature, the critical point (p(c), T-c*) o f the EG approximation (EGA) is located at (0.026, 0.0789), rather tha n the (0.018, 0.0837) quoted by EG. The corrected result is closer to the most recent simulation estimates of the RPM critical point. A furt her improvement is obtained by incorporating the activity coefficient of the associated ionic pair to yield a dipole-ion (DI) contribution. The new approximation, EGA+DI, has a critical point at (0.027, 0.0716) , which is in still better agreement with the simulation estimates. A critical discussion comparing these results with recent simulation res ults and other recent theoretical work is given.