Kohlrausch's law states that the limiting molar conductivity of an electrolyte is equal to the sum of the individual limiting molar conductivities of its constituent ions. It is used to determine the limiting molar conductivity of electrolytes, especially weak electrolytes, by calculating the independent contributions of the ions based on their individual conductivities. The law also allows calculation of properties like the dissociation constant of a weak electrolyte from its molar conductivity and limiting molar conductivity at a given concentration.