Abstract: An apparatus is provided for decomposing water and producing detonating gas by electrolysis. The apparatus includes a plurality of annular carbon electrodes which are concentrically arranged about a common vertical axis. The annular electrodes are perforated and have upper and lower ends, the lower ends being positioned adjacent to sealing and insulating elements in order to form a plurality of concentrically-arranged cells for containing electrolyte, e.g., water. A solid carbon electrode, preferably cylindrical, is positioned within the smallest concentric electrode and along the common axis. Apparatus is provided for supplying water to the cells, and for applying a direct current across the electrodes in order to evolve the detonating gas from the electrolyte in the cells by electrolysis.