Application of chronopotentiometry to study the diffusion layer thickness adjacent to an ion-exchange membrane under natural convection

It is found that the DBL near an ionexchange membrane is formed quasi-instantly under natural convection and follows the variation in solution concentration drop through the DBL (Dc): d ~ (Dc)–0.2. The fact that the value of power differs from the value predicted by Levich (–0.25) is explained by the microscopic chaotic convection motion described recently by Amatore et al. The use of the latter relation for d in the numerical solution of Kedem– Katchalsky equations results in an excellent agreement between calculated and measured chronopotentiometric curves at underlimiting current densities.