Aspen Physical Property System - Physical Property Models

Specifically,
The long range interaction term for the logarithm of the activity coefficient of
component I is computed as the sum of the individual segment contributions.
Activity coefficients given by Eq. 65 are already normalized for molecular
components as well as for ionic components with the infinite-dilution aqueous
solution reference state.
References
Pitzer, K.S., J.M. Simonson, "Thermodynamics of Multicomponent, Miscible,
Ionic Systems: Theory and Equations," J. Phys. Chem., 1986, 90, 3005-3009.
2 Thermodynamic Property Models 127
(62)
(63)
(64)
(65)
Robinson, R.A., Stokes, R.H., Electrolyte Solutions, 2nd revised edition,
Dover, 1970.
Rashig, A.A., Honig, B., "Reevaluation of the Born Model of Ion Hydration," J.
Phys. Chem., 1985, 89, 5588.
NRTL-SAC Flory-Huggins Term
We use the Flory-Huggins term to describe the combinatorial term:
(66)
(67)
where G ex,FH is the Flory-Huggins term for the excess Gibbs energy, �I is the
segment fraction of component I, and rI is the number of all conceptual
segments in component I:
(68)
(69)