Conductance studies over a range of relative permittivities

16 Conductance studies over a range of relative permittivities 

One of the most important smdies involves the dependence of the molar conductivity on the solvent. The solvent is characterised by its chemical nature, its macroscopic relative permittivity and viscosity. Smdies carried out in non-aqueous solvents and/or mixed solvents one of whose components is often water, allow conductance smdies to be made over a range of relative permittivities and viscosities. The dependence of A°, ATassoc and a on relative permittivity has furnished a vast amount of data which is of fundamental importance in conductance smdies. In particular, the relation between ATassoc and e, has given considerable insight into the correctness or otherwise of the various models developed to describe the ion pair. 

Smdies in mixed solvents and non-aqueous solvents are outside the scope of this book. But they indicate conclusively that the primitive model used by Fuoss and Onsager up to 1978 is wrong, and that a new model needs to be developed. 

The model and theory, like that of the Debye-Htickel treatment of non-ideality, were based on consideration of long range electrostatic coulombic interactions only. The model was most likely to be inadequate because it did not take into account specific short range interactions corresponding to ion-ion, ion-solvent, and solvent-solvent interactions. 

For the ion-ion interactions, Fuoss indicated that a fruitful line of enquiry would be that of working downwards from 

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See also in sourсe #XX -- [ ]

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