I have placed a proposition of activity coefficient description (in liquid
nonelectrolite mixtures) in
my dissertation, in order to try to correlate
three-component liquid-liquid equilibrium data obtained
with component two-component systems. As a starting point it was established
two-component solution of solute (B) in solvent (A). For very diluted solutions
Henry Law is in force, stating that solute activity (when pure substance, in
mixture conditions of temperature and pressure, is assumed as standard state)
is proportional to solute mole fraction in the solution, so
its activity coefficient is constant. After exchange of
solute concentration to its "local" concentration
(concept introduced during derivation of Wilson equation
(G. M. Wilson, J. Am. Chem. Soc 86 (2), 127, 1964)), I
have obtained the following expression describing solute
activity:
giving the straight line on reciprocal of activity coefficient-concentration (mole fraction) diagram. After using of Gibbs-Duhem equation, following equation on solvent activity has been obtained:
![aAA = KA[(RBA·xA/(xB+RBA·xA)]^RBA, where: aAA = activity of solvent A; KA = constant in given conditions of temperature and pressure, equals 1 in good approximation](grafika/formula2.png)
which is one-parameter equation in good approximation. Foregoing equations have been named EHL (Extended Henry Law) equations.
giving the straight line on reciprocal of activity coefficient-concentration (mole fraction) diagram. After using of Gibbs-Duhem equation, following equation on solvent activity has been obtained:
which is one-parameter equation in good approximation. Foregoing equations have been named EHL (Extended Henry Law) equations.
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