Kohlrausch’s Law

Kohlrausch determined the molar conductivity at infinite dilution for a large number of strong electrolytes. On the basis of his observations he concluded that at infinite dilution,
each ion makes a definite contribution to the total molar conductivity of an electrolyte. This individual contribution is called molar ionic conductivity.

At infinite dilution each ion of the electrolyte makes a definite contribution towards conductivity of the electrolyte and it is independent of the presence of other ions of the electrolyte. This is called Kohlrausch’s Law of independent migration of ions.

For a salt like KCl, molar conductivity at infinite dilution can be written as:

λ_m^∞ KCl = λ_m^∞ K⁺ + λ_m^∞ Cl^-

In general for a salt of formula A_xB_y the molar conductivity at infinite dilution is written as:

λ_m^∞ A_xB_y = xλ_m^∞ A^y+ + yλ_m^∞ B^x-