THE ALTERNATING CURRENT ELECTROLYSIS OF WATER

Abstract

An examination of commercial hot water heaters and steam generators of the electric water resistor type operating on alternating current shows that hydrogen and oxygen are generated within the electrode chamber. Current density is found to be the primary factor in the A.C. electrolysis of water at low voltages. At high voltages, arcing on the electrodes also results in the decomposition of the water. A critical current density exists for metallic electrodes below which electrolytic gases are not produced but above which all the current is utilized in decomposing the water into hydrogen and oxygen in accordance with Faraday's Law for continuous current. This critical current density varies with the nature of the electrode material, the temperature of the electrolyte and the frequency of the alternations: the higher the frequency the higher the critical current density. The storage capacity of the electrode for hydrogen and oxygen known as the "electrolytic capacity" is constant for copper but varies with the quarter-wave area for platinum and silver. At constant quarter-wave area the electrolytic capacity decreases to a minimum with increasing frequency. A difference in the phase for current and voltage is observed, the current leading the voltage. Wave distortion occurs in the case of platinum and copper electrodes. High voltage arcing by an alternating current produces a thermal decomposition of the water quite independent of A.C. electrolysis. The rate of decomposition by arcing is primarily dependent upon the rate of consumption of electrical energy. Hydrostatic pressure in the electrode chamber inhibits arcing. The application of the results to the design and operation of electric steam generators and domestic heaters is discussed, and the explosion hazard connected with the generation of electrolytic gas is also commented upon, a means being suggested for reducing the danger.