Abstract: An electrolytic cell comprises two vertically extending, adjacent electrodes. The space between the electrodes is an electrolysis zone. The electrolysis zone has upper, middle and lower portions. The cell further comprises upper and lower plenum chambers above and below the upper and lower portions of the electrolysis zone, respectively. The cell has a channel which at least partially defines a passageway. The channel may be in an electrode, a cell wall, or in both. The passageway extends between the upper and lower plenum chambers but is inaccessible from the middle portion of the electrolysis zone. The cell may have a plurality of passageways. The improved design is particularly applicable to electrolytic processes in which gases are evolved at either or both of the electrodes, and in which the electrolytes and gaseous products are separated by a diaphragm or ion exchange membrane.