Sodium Hypochlorite: its Application and Stability in Bleaching

Abstract One of the end uses of chlorine and sodium hydroxide, both produced by the electrolysis of aqueous sodium chloride, is in the manufacture of sodium hypochlorite, commonly called liquid “bleach.” This article outlines the methods of manufacturing liquid bleach, including the factors involved in the selection of materials of construction for handling chlorine, sodium hydroxide and sodium hypochlorite. Experimental results were presented addressing the stability of sodium hypochlorite as influenced by temperature and pH, and by anionic impurities such as Cl−, ClO3−, CO3− and SO4−, and cationic impurities which include Ca++, Mg++, Cu++, Ni++ and Fe++. Various techniques were also outlined to minimize the formation of chlorates during storage and bleaching and to improve the quality and stability of sodium hypochlorite.