Depanding variable of migration current:

A migration current depends on the transference number of the reducible or oxidizable ion in the solution and the total limiting current.

i_m = T_i i₁                                                                                                        

Table 8.1 Limiting Current in solutions containing various concentrations of supporting electrolytes

(0.05 mM lead nitrate in potassium nitrate supporting electrolyte and 0.0004% sodium methyl red maximum suppressor)

Table 8.1 clearly demonstrates actually that the transference number of an ion decreased practically to zero within the presence of 100 fold excess of a supporting electrolyte.  Within such solutions almost all the current is carried through the cell through the potassium and nitrate ions. Therefore, these are not decreased before the evolution of hydrogen and so the reduction of lead ions remains the just process through that electrons could be transferred across the interface among the electrode and the solution.  Within this way the migration current is practically eliminated through keeping the supporting electrolyte 50 to 100 times the concentration of reducible ion.