General representation of a solution with several components

General representation of a solution with several components 

Still with the aim of having mathematical expressions for the representation of the solution, Redlich and Kister offered a representation that provides an expansion of the excess Gibbs energy, a pure-substance reference in the same state of segregation as the solution (reference (I)), the equivalent of ihe Margules expansion for the activity coefficients. For a two-component solution, the pol5momial expansion up to order m is written  

The coefficients parameters which reflect atomic interactions. 

Because the exponents k are odd and even integers, it is internationally agreed to write the differences (x, -X2) in alphabetical order of the chemical symbols of the components, written as subscripts next to the molar fractions. 

For a solution containing a given number of components, relation [2.10] becomes  

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