Electrolytes interionic interactions

The first accurate calculation of the activity coefficient based on energetic effects of inter-ionic interactions in solvents was carried out by -> Debye and -> Huckel in 1923 by assuming that all the deviations from ideality at low concentrations of electrolyte were due to interionic interactions (- Debye-Huckel theory) with this it is possible to show that... 

For dilute electrolyte solutions, Lewis and Randall observed that the mean activity coefficient of a strong electrolyte does not depend on the kind of ion, but only on the concentration and charge numbers of all ions present in solution. So, the individual properties of the ions are not decisive for interionic interactions in dilute electrolyte solutions. These observations paved the way for the introduction of the concept of ionic strength / ... 

This type of study, still in its infancy, is important if it provides new insight into the short-range forces in electrolyte solutions because classical measurements can only give limited information. A new picture of the contact ion pair emerges and emphasis is placed on the role of solvent structure in interionic interactions an emphasis which is being recognised as essential if models are to be extended beyond the limited sphere in continuum picture of the very dilute solution. ... 

Both Kohlrausch s law and the Debye-Hiickel-Onsager equations break down as the concentration of the electrolyte increases above a certain value. As already mentioned, the reason for this breakdown is that as eoncentration inereases the average separation between cation and anion decreases, so that there is more interionic interaction. 

The values of the individual ionic Vj at finite concentrations are not known as accurately, contrary to those at infinite dilution, Vi° . This is due to interionic interactions causing the additivity of the individual volumes to breaks down. According to Redlich and Meyer (1964) the apparent molar volumes of electrolytes can be expressed as ... 

Aqueous electrolyte solutions are not restricted to moderate temperatures and low pressures. They can exist and have been investigated to and far beyond the critical temperature of pure water and to pressures of several kilobars. Research on equilibria in electrolyte solutions in such a wide range gives valuable scientific information on intermolecular and interionic interaction and kinetic phenomena in dense fluids. Practical applications of the unusual combinations of properties of dense supercritical fluids can also be anticipated. 

Now, the degree to which these interactions affect the properties of solutions will depend on the mean distance apart of the ions, i.e., on how densely the solution is populated with ions, because the interionic fields are distance dependent. This ionic population density will in turn depend on the nature of the electrolyte, i.e., on the extent to which the electrolyte gives rise to ions in solution. 

Where no is the solvent viscosity and n solution viscosity, C is the bulk concentration and A is a constant dependent on interionic attraction and B a constant dependent on ion-solvent interaction and is a function of the ionic mobility. The concentration of non-exchange electrolyte in the pore system of a membrane is determined by a distribution equilibrium, dependent on the width of the pore. The higher the concentration of the outside solution, the greater is the concentration of non-exchange electrolyte in the pore system of a poorly hydrated ionic membrane film. 

Chirodiastaltic interactions occurring at sohd/liquid interfaces involve differences in the lattice energies of the solids and other factors including differences in solvation energy of the chiral molecules in the presence of other dissolved chiral species and, in electrolytes, differences in interionic forces. Interfaces with soluble solids will be considered here and those with insoluble solids in Section 1.6. 

The large ionic interaction often renders the Onsager equation useless (it is still presumably correct) for the extrapolation to obtain A . The solutions for which the Onsager relation is valid are so dilute that it is not possible to obtain reliable measurements of their conductivity. In these cases, special methods of obtaining A are used. If the electrolyte is weakly dissociated, then the A can be obtained by application of the Ostwald dilution law, modifying it in precise work to correct for the interionic forces. 

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