In the electrolysis apparatus for the production of chlorine, sodium hydroxide solution and hydrogen from aqueous alkali-metal halide solutions, which electrolysis apparatus comprises at least one electrolysis cell, anode and cathode, which are separated from one another by a partition, are disposed in a housing composed of two half-shells electrically separated by an insulating seal. The housing is provided with devices for supplying the electrolysis starting substances and for removing the electrolysis products, the latter comprising at least one discharge pipe which extends in the vertical direction in the interior of the half-shells, passes through the half-shell in the vicinity of the lower edge and extends up to the upper edge. The discharge pipe (9, 10) terminates in a separating chamber (14, 15) which is disposed in a stilling zone. The stilling zone is formed by a plate (11, 12) attached to the electrode (4, 5) and to the associated half-shell (1, 2).