NOVELTY - Electrochemical cell for electrolysis of alkali solutions partitioned by an ion-exchange membrane into an anodic and a cathodic compartment, where anodic compartment comprises a liquid chamber delimited by an anodic wall and by the membrane, the anodic compartment containing an anode suitable for oxygen evolution and comprising unit for feeding and for discharging an alkaline electrolyte, the cathodic compartment consisting of a gas chamber delimited by a cathodic wall and by the membrane.    USE - The electrochemical cell is useful for electrolysis of alkali solutions (claimed) used for cathodic production of hydrogen and anodic production of oxygen.    ADVANTAGE - Electrolytic process is provided for production of hydrogen and oxygen overcoming the limitations of the prior art, coupling a high purity of products with the capability of operating at high current density on a large scale. The cathodic compartment is not involved in the circulation of liquid phase electrolyte. Circulating liquid electrolyte in one compartment only has the advantage of not requiring the remixing of a catholyte and an anolyte at the cell outlet in order to adjust pH, with important consequences on the purity of gaseous products, besides the apparent simplification of cell and system engineering. A further advantage is the possibility of accomplishing, as the overall electrolytic process, the electrolysis of water by coupling an alkaline electrolyte, not entailing any particular problem of corrosion, to a cation-exchange membrane, which resulted too complex from a system engineering standpoint with the cells of prior art having an electrolyte circulation in both compartments. The use of a cation-exchange membrane as separator, absolutely atypical in electrolysis of alkaline solutions, entails a further enhanced gas separation even at pressurized conditions, allowing operation with significant pressure differentials between one compartment to the other which contribute optimizing the overall efficiency.    DETAILED DESCRIPTION - Electrochemical cell for electrolysis of alkali solutions partitioned by an ion-exchange membrane into an anodic and a cathodic compartment, where anodic compartment comprises a liquid chamber delimited by an anodic wall and by the membrane, the anodic compartment containing an anode suitable for oxygen evolution and comprising unit for feeding and for discharging an alkaline electrolyte, the cathodic compartment consisting of a gas chamber delimited by a cathodic wall and by the membrane, the cathodic compartment containing a gas-diffusion cathode in intimate contact with the membrane through a catalytically-activated layer optionally containing platinum, the gas-diffusion cathode being suitable for the percolation of an electrolyte film coming from the anodic compartment. INDEPENDENT CLAIMS are included for:    (1) electrolyzer of alkali solutions consisting of a modular arrangement of cells , electrically connected through the anodic and cathodic walls according to a bipolar or monopolar configuration; and    (2) a process of electrolysis in cell involving simultaneous or sequential steps: feeding of an electrolyte consisting of an alkali metal hydroxide solution to the anodic compartment, with percolation of an electrolyte film inside the gas-diffusion cathode; connection of the cathodic compartment to the negative pole and of the anodic compartment to the positive pole of a power unit, with subsequent supply of direct electrical current; cathodic evolution of hydrogen within the electrolyte film and discharge of the hydrogen from the cathodic compartment; evolution of oxygen on the surface of the anode; and withdrawal of exhaust electrolyte containing dissolved oxygen from the anodic compartment.