The enhancing effect of magnetic fields on ionic mass transport has been amply documented in the literature, nevertheless, very little quantitative information is available on this effect in certain electrode-cell-magnetic field configurations. Electrolysis in annulus flow between two electrodes, and with a large aspect ratio (cell length/cell equivalent diameter) is one such example and the purpose of this communication is to present experimental data for this system, obtained in uniform solenoidal magnetic fields. The experimental apparatus is sketched in Fig. 1. The outer copper cylinder (R, = 1.92cm) serves as cathode, and the inner lead rod (R, = 0.5 cm) as (indifferent) anode; the active electrode length is 55.5 cm, thus, 0, = 2.8Scm and A, = 10.86cm2. Electrolysis was carried out by means of a conventional regulated dc power-supply and the electrolyte flow was maintained by circulation between a head tank and a collector tank. The circulation line was equipped with a calibrated rotameter. The electrolytic cell was placed in the air-core ofa solenoid wound on a Plexiglass-acrylic support, -FLOW OUT COPPER CATHODE LAYERS OF I8 A.w.G.