Conductivity, Transference Numbers, and the Diffusion Potential

In proceeding with the development, it is convenient to define the following quantities  

With the above definitions an expression for the current i carried by the mixture can be obtained 

Equation 2.4.26 shows that even when no current is carried by the mixture (i.e., i = 0), there exists a finite electrical potential 

Equation 2.4.28 can be written a little more compactly in terms of the transference numbers 

for pure diffusion as is encountered in processes such as ion exchange or extraction there is no current flowing through the mixture 

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