A study of the utilization of aqueous decomposition of sodium amalgam for the production of deuterium-depleted water is presented. In the framework of this work the correlation between the deuterium content of the hydrogen gas and the concentration of the aqueous alkali, both formed in the reaction of sodium amalgam with water, is established. The sodium amalgam is prepared via sodium chloride electrolysis. In addition to the formation of an industrial alkaline solution containing 50% w/w sodium hydroxide, hydrogen gas with a deuterium concentration of 50 ppm is obtained. This hydrogen gas is suitable (e.g., via combustion) for the preparation of deuterium-depleted water used, e.g., in cancer therapy.