Aspen Physical Property System - Physical Property Models

160 2 Thermodynamic Property Models
(45)
(46)
(47)
(48)
where xm�0 applies to all molecular components in the solution.
For ionic components with infinite-dilution aqueous solution as reference
state, apply Eq. 18 to get:
(49)
(50)
where and are local interaction contributions to activity
coefficients at infinite dilution aqueous solution:
Long-Range Interaction Term
(51)
(52)
To account for the long-range ion-ion interactions, the Symmetric and
Unsymmetric Electrolyte NRTL models use the symmetric Pitzer-Debye-Hückel
(PDH) formula (Pitzer, 1986):
(53)