Small Deviations from Symmetric Ideal SI Solutions

SMALL DEVIATIONS FROM SYMMETRIC IDEAL (SI) SOLUTIONS 

Any solution of two components can be viewed as a SI solution, with a correction term which takes into account the extent of dissimilarity between the two components. More precisely, we can integrate relation (4.93) to obtain 

The superscript S on serves to indicate that this particular activity coefficient is for symmetric ideal behavior, and should be distinguished from other activity coefficients introduced later which have different meanings. 

In the general case, (4.116) is not expected to be useful, since we know nothing about the analytical dependence of q or Aab on composition. We therefore confine ourselves to a discussion of first-order deviations from SI solutions. 

We recall that SI solutions are characterized by the condition Aab = 0-It is therefore natural to measure deviations from similarity by the parameter Aab- % first-order deviations from SI solutions, we refer to the 

Small Deviations from Symmetric Ideal (SI) Solutions 

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