this tube 10 which is welded to the base 2 extends along the axis of the tubular container 1 and ends just below the outlet aperture of the elbowed pipe 8 leading into the container as can be seen in the drawings at that point it carries a circular horizontal deflector plate 11 screwed on in such a manner that it can easily be removed in the upward direction once the cylindrical part 3 of the container 1 has been removed as indicated by the arrows in solid lines which show the path of the electrolytic liquid the liquid entering at 7 falls onto the horizontal deflector 11 flows towards the edges of the latter and then continues its journey downwards inside the container 1 following the path which will be described later on the containr 1 is filled with liquid the mean level of which is situated at 12 between the deflector plate 11 and the pile of compartments 13 which will be described later on the level 12 corresponds to the maximum level of liquid in the electrolysis plant so that in accordance with one very interesting aspect of the invention the container 1 also serves as expansion vessel for the plant since the container is tubular and vertical the variations of the level 12 are relatively considerable in dependence on the variations of pressure so that it is easy if desired to effect a regulation of pressure with the aid of a detection device not shown detecting the level 12 referring now also to fig2 and 3 the container holds below the minimum position of the level 12 a stack 13 of identical annular plates 14 forming a series of superposed degasification.