The effect of uniform constant magnetic fields on free-convective ion transport in magnetoelectrolytic cells employing parallel vertical plate electrodes has been investigated in experiments with CuSO4/H2SO4 and K3Fe(CN)(6)/K4Fe(CN)(6)/KOH electrolytes. A modified free-convective diffusion model, developed from fundamental principles of magnetohydrodynamics and classical convective diffusion theory, offers a reasonable approximation to experimentally observed transport rates in horizontal magnetic fields.