TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The inner electrode is separated from the outer electrode by the separation component. The separation component serves as a diaphragm. The inner electrode and the outer electrode have an identical form. The form of the inner electrode and/or the outer electrode is a tubular or a spherical, or the inner electrode and/or the outer electrode is a hollow body with any cross section areas. The cross section area is a circular-, a quadratic-, a rectangular- or a neck shape. The inner electrode is the oxygen electrode. The separation component comprises at least an electrical conductive layer or at least one non-conductive structure on one of the inner or outer electrode facing side or on both sides. The openings or the perforation are holes. A further electrically conductive structure and gas-permeable structure are applied on the inner electrode. The further electrically conductive and the gas-permeable structures made of metal wool, wire meshes, expanded metal, carbon cloth and/or metal froth, or the further electrically conductive and the gas-permeable structures formed by surface modifications of catalytic coatings or catalytic activations or surface magnifications by mechanical-, chemical- or electronic and/or physical methods, are introduced into the surface of the inner electrode. The body of the inner electrode comprises a tubular, gas-permeable core made of an electrically non conductive material, preferably a porous ceramic or plastic, which exhibits the openings, holes or the perforation, where an electrical good conductive and gas-permeable structures are applied on the surface of the tubular, gas-permeable core, in the form of a metal wire fabric, a metal froth, a charcoal felt, a metal wool, an expanded metal, or a charcoal non-woven fabric. At least one rod-shaped electric conductor (6) with a favorable size of a cross section area is arranged at an inner side of the inner electrode, such that a very small electrical voltage drops arise along the conductor during an operation of the electrolyzer, and/or at least an outer electrical conductor (9) spaced from the rod-shaped electric conductor, is arranged around the outer electrode. The electric conductor is electrically connected with the outer side of the inner electrode. The outer portion of the inner electrode comprises a pliable, electrically good conductive and gas-permeable material e.g. a carbon non-woven fabric, the metal wool, a metallic or carbonaceous fabric, a composite material or the metal froth. The separation component comprises a micro- or a nonporous ceramic or a micro or a nonporous membrane. The inner electrode is coated with a material, which serves as a separation material between an anode and a cathode compartment of the electrolyzer and is insertable in an alkaline electrolyzer, which exhibits a chemical resistance against the used electrolytes and at the same time a good permeability for the electrolytes and/or the appropriate ions of the electrolytes, such that the portion of the ion resistance determined by the ion transport lies in a low value range and exhibits a very less permeability with respect to both product gases of oxygen and hydrogen, where the coating is applied by dipping-, spraying- or condensation methods and/or the material covering the inner electrode comprises an alkali resistance. The electric conductor inside the inner electrode and the outer electric conductor exhibit a low ohmic resistor, thus the electrical voltage drops remain below 50 mV, preferably below 20 mV, along the outer electrode and/or the inner electrode under conventional operation conditions of the electrolyzer. The electrolyzer comprises a pressure resistant housing and is operable with operating pressures of at least 30 bars.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The membrane comprises polypropylene, polytetrafluoroethylene, polysulfone, polyether sulfone or another alkali-stable material with pore sizes of 0.05-10 mu m. The material covering the inner electrode is a micro- or nano-porous polymer or a micro- or nonporous ceramic foil.