Movement of ions in solution diffusion and migration

In the presence of an applied electric field of strength E = dcfr/dx, 

The combination of the attraction of the electric field and the retarding effects leads to a maximum velocity for each ion. Measurement of these velocities gives information about the structure of the solution. Different cation and anion velocities give rise to a potential difference this is the liquid junction potential. It is interesting to know the magnitude of this potential, as it affects the measured potential of the whole electrochemical cell in other words, ion conductivities need to be measured. 

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