Transference and transference Numbers :

Transference and transference Numbers :
Although current I is transported through a solution by migration of positive and negative ions, the fraction of the total current carried by each is not necessary the same.
For example :
In dilute solution of & :
Mg+2 carries about 0.38 of the total current,
SO4-2 carries about 0.62 of the total current.
While,
carries about 0.16 of the total current,
H+ carries about 0.84 of the total current .
The H+ and ions transport the greater fraction of the total current, because in their respective solutions they move faster than the other ions present.
If both ions in a solution moved with the same speed, each would transfer past any fixed plane in the solution the same quantity of electricity in any given time.
When the speeds of two ions are not the same, in any given period of time the faster ion will carry past any plane a greater fraction of the current, and hence will perform a greater percentage of the total work involved in current transfer.
The quantitative relation between the fraction of the carried by an ion and its speed can be established as follows :