Transport Number
The fraction of the total current carried by a particular ion in an electrolyte solution.
Formula / equation
t₊ = λ₊ / (λ₊ + λ₋)
Unit
Dimensionless
In depth
Cation and anion transport numbers sum to one and reflect the relative mobilities of the two ions. They are measured by the Hittorf method, which tracks concentration changes around the electrodes, or by the moving boundary method.
Examples in the real world
In HCl the proton carries about 82% of the current because of its exceptional mobility.