الفهرس 
CHAPTER 1Only 14 pages are availabe for public view
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Abstract
Random thermal motion of ions in solutions of strong electrolytes constantly brings anions and cations into proximity. Electrostatic attraction then alters the ionic motions so as to bring the ions closer together, occasionally to contact or near contact distances. Such pairs remain together until sufficiently large thermal fluctuations again send the ions apart. The tendency of the ions to associate in this way depends upon the balance between the interionic coulomb forces and thermal energy – thus upon the ion valancies, the dielectric constant and the temperature. It depends also on the solvation energy of the ions. Since the heat of solutions is small, dissolution of soluble salt as free ions requires sufficient solvation energy almost completely offset the lattice energy. Dissolution as ion-pairs requires solvation energy only approximately equivalent to the sublimation energy. Thus poor solvation promotes ion association 1 The effect of a solvent on the equilibrium constant of ionic association (KA) is of major interest for the theory of electrolytic solutions.2 many investigations have established a relation between KA and the micro- and macroproperties of the electrolytic system, starting from the Bronsted equation 3 to the most general Izmallov equation.4 The crystallographic or effective ionic radii, ion-ion and ion-dipole interaction energies belong to the former, the latter are crystalline lattice energy and solvent permittivity (ε).
For symmetrical electrolytes, where co-spheres of a pair of ions Mn+ and Xn- overlop, the net charge is equal to zero and thus taken no part in charge transport. On the other hand, in case of asymmetrical electrolytes the formed ion-pair has a charge and contribute in conducting process but less than that of the free ion.
The term ion association is frequently employed and was firstly introduced by Bjerrum 5 that defined, for dilute solutions, the probability (Pr) of finding an ion of charge (z-eo) in dr thickness spherical shell of radius r around a reference ion of charge (z+eo) by the equation.