Abstract: The device comprises a tank filled with electrolyte, flat electrodes which are stacked horizontally so as to rest upon one another under the action of gravity and at least a certain number of which are consumable. Two successive electrodes are separated by spacer elements having the same thickness and formed of material which is inert to electrolysis. The contact surfaces between the spacer elements and the electrodes therefore permit substantially uniform erosion of the consumable electrodes over their entire surface and the spacing between two consecutive electrodes thus remains constant.