two end plates 6 and 8 are clamped to one another via tie rods which are not represented in the drawing a certain pressing force which is necessary for a high efficiency of the electrolysis taking place in the electrolysis cell 4 is exerted onto the electrolysis cell 4 by way of this if a high gas pressure which is mainly due to the hydrogen occurring with the electrolysis prevails in the electrolyzer 2 then the pressing force exerted by the end plates 6 and 8 onto the electrolysis cell 4 is no longer sufficient for an electrolysis which takes place with an adequate efficiency for this reason an additional pressing force must be exerted onto the electrolysis cell 4 the constructional measures which are selected for this are described hereinafter a recess 28 which tapers in the direction away from the plate 20 amid the formation of a shoulder 30 is formed on the flat side of the end plate 6 which faces the plate 20 the shoulder 30 extends around the complete periphery of the recess 28 and serves for receiving a seal 34 which seals the end plate 6 with respect to the plate 20 in a fluid tight manner a bore 36 which runs out in the recess 28 extends through the end plate 6 the bore 36 thus forms an access to the chamber which is formed by the recess 28 and the pressing body 32 a conduit branching 38 is formed on the conduit.