of a species in a solution represents the relation between the real fugacity and the fugacity corresponding to an ideal solution (calculated via Lewis-Randall rule).
These solvent heats of vaporization values, derived from the experimentally determined activity coefficients
, can be compared with the ones estimated employing the Watson model  as a kind of consistency test, in order to check the goodness of the experimental data.
Hence, the VLE model itself is valid at low acid gas partial pressures even though the parameters of the activity coefficient
model were not fitted in this range (Kundu, 2004).
The extrapolation method of Harned and Ehlers, which expressed the activity coefficient
in eq (1) by the Debye-Huckel limiting law, was used to obtain all of the potentials except those given in the last column.
Table-5: (b) Weight fraction activity coefficient
a|1a of with alcohols and alkanes systems for poly(ABM%71-co-AN).
In the electroneutral mixture method of the COSMO-RS, in order to estimate the activity coefficient
([gamma]), a mixture of ILs and solute was treated as ternary system (1: 1 IL, cation + anion + solute) that can be converted into a binary system.
where [[gamma].sub.i] is the activity coefficient
of component i in the ternary mixture of the composition [x.sub.i], [x.sub.j], [x.sub.k], and
[a.sup.C.sub.i] = [[omega].sub.i][[OMEGA].sup.C.sub.i] it follows that, for the elastic contribution, the activity is equal to the activity coefficient
[a.sup.el.sub.i] = [[OMEGA].sup.el.sub.i].
Dependences of the activity coefficient
upon temperature and composition of the investigated system alloy can be calculated within the framework of the Redlich--Kister model .
The activity coefficient
of an adsorbed ion represents the degree of freedom that it has to leave the adsorbed state towards the unitary standard state of maximum freedom, and therefore reflects the heterogeneity of the exchange process (Goulding 1983).
, because of the change of ion environment, the change of activity coefficient
and liquid junction potential error could modify the ion data as Na[HCO.sub.3] is substituted for NaCl.
The weight fraction activity coefficient
(1) of the solute at infinite dilution can be calculated from following relation .