Ionic cloud electrophoretic effect

As the dependency does not include any specific property of the ion (in particular its chemical identity) but only its charge the explanation of this dependency invokes properties of the ionic cloud around the ion. In a similar approach the Debye-Huckel-Onsager theory attempts to explain the observed relationship of the conductivity on c1/2. It takes into account the - electrophoretic effect (interactions between ionic clouds of the oppositely moving ions) and the relaxation effect (the displacement of the central ion with respect to the center of the ionic cloud because of the slightly faster field-induced movement of the central ion, - Debye-Falkenhagen effect). The obtained equation gives the Kohlrausch constant ... 

Electrophoretic effect — A moving ion driven by an electric field in a viscous medium (e.g., an electrolyte solution) is influenced in its movement by the - relaxation effect and the electrophoretic effect. The latter effect is caused by the countermovement of ions of opposite charge and their solvation clouds. Thus an ion is not moving through a stagnant medium but through a medium which is moving opposite to its own direction. This slows down ionic movement. See also -> Debye-... 

A Second Braking Effect of the Ionic Cloud on the Central Ion The Electrophoretic Effect... 

The interesting point is that when the ionic cloud moves, it tries to carry along its entire baggage the ions and the solvent molecules constituting the cloud plus the central ion. Thus, not only does the moving central ion attract and try to keep its cloud (the relaxation effect), but the moving cloud also attracts and tries to k p its central ion by means of a force which is then termed the electrophoretic force F. ... 

At infinite dilution, neither relaxation nor electrophoretic effects are operative on the drift of ions both these effects depend for their existence on a finite-sized ionic cloud. Under these special conditions, the infinite-dilution mobility can be considered to be given by the Stokes mobility... 

In solution, not only the central cation but also the surrounding ionic cloud moves, however, with its opposite excess charge in the opposite direction (Figure 1.7b). Therefore, the central cation feels a larger velocity relative to its local environment and thus is exposed to higher friction forces. In consequence, this ion is slowed down relative to the laboratory system in comparison with a situation with a missing ionic cloud. This is the electrophoretic effect expressed by Equation 1.29, where qy is the viscosity of the electrolyte. 

The other physical phenomenon responsible for the reduction of the ionic mobility in the bulk electrolyte solution is the electrophoretic effect, which arises from the motion of an ion in a medium (solvent) not at rest. This electrophoretic correction to the mobility of the ions in the bulk concentrated electrolyte solutions can be calculated by the following arguments. In the steady state of the ionic transport the electrophoretic velocity is the result of the equilibrium between the electric force driving the ionic cloud and the viscous force... 

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