Chloride transference numbers in steady-state migration tests

The present paper is part of a series to study the different basic aspects of migration experiments. In it, chloride transference numbers are used to find the optimal testing conditions. First, the evolution of transference number values of chlorides a steady-state experiment is studied. Then, the meaning of the maximum, which appears when the anodic chloride transport number is calculated, is interpreted. The experimental data from two series of experiments (NaCl and steel electrodes, using finite and infinite sources, and CuCl₂ and copper electrodes) with different Cl⁻ concentrations (0·05, 0·1, 0·2, 0·5 and 1 M) are fitted to a Gauss modified exponential equation, which has enabled us to obtain the coulombs corresponding to the mentioned maximum and to determine the better conditions to perform a steady-state migration test: it seems that they are 1 M NaCl as catholyte solution and steel electrodes. Also, some terms have been added to the nomenclature of transference numbers previously proposed by the authors.