Ionic constituents, transference number

The equation necessary for their interpretation is 5.8.7. At concentrations well below the conductance minimum, where the presence of ionic triplets may be disregarded, the cation-constituent transference number (with LiBr as the example) becomes ... 

Combined with densities, molecular weights, and transference numbers (fractions of the current carried by the various ionic constituents), the conductivity yields the relative velocities of the ionic constituents under the influence of an electric field. The mobilities (velocity per unit electric field, cm2 s-1 V-1) depend on the size and charge of the ion, the ionic concentration, temperature, and solvent medium. In dilute aqueous solutions of dissociated electrolytes, ionic mobilities decrease slightly as the concentration increases. The equivalent conductance extrapolated to zero electrolyte concentration may be expressed as the sum of independent equivalent conductances of the constituent ions... 

The transference number ti of an ion Xt is equal to the net number of faradays carried by this ion, free ion, or constituent of an ionic species, across a reference plane that is fixed with respect to the solvent, when one faraday collectively passes (total electric current I partial electric currents /+ and / [see Eqs. (5)] ... 

Equations (20.1.2-2) and (20.2.1-7) relate the diffusion potential to mass-transport within the electrolyte and to transference numbers, respectively. If both the transference numbers are equal to one-half in the latter equation, then the diffnsion potentials in solution arising from contact of solutions with differing concentrations will be eliminated. The limiting values of the ionic diffusion coefficient are related to their mobility by the Einstein law, equation (20.2.1-10), which provides justification for the argument that balancing the mobilities of the electrolyte s constituent ions wiU nullify any diffusion potential. This approach to eliminating diffusion potentials clearly suffers from the severe restriction that... 

---