The Fuoss-Onsager equation for associated electrolytes

The 1957 Fuoss-Onsager equation can be adapted to take account of association of ions to form ion pairs and to account for incomplete dissociation of weak electrolytes. Chemically these are two different types of situation, but physically they are the same, viz. some of the ions are removed from solution by formation of ion pairs, or by formation of undissociated molecular species. The physical manifestation is that not all of the solute will be able to conduct the current, and so the observed conductance will be lower than that predicted by the 

Fuoss-Onsager 1957 equation. Fuoss later modified his treatment to include the possibility that some ion pairs are conducting (see Section 12.17). 

The equation for fully dissociated electrolytes in compact form and ignoring higher order 

If removal of ions from the solution of electrolyte at a stoichiometric concentration, Cstoich occurs then  

The expression for formation of the weak acid, association, can also be written in terms of the fraction dissociated, a. 

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Determination of A°, Afassodation and a using the Fuoss-Onsager equation for associated electrolytes... 

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