Sodium hydroxide ( NaOH) , also known as lye and caustic soda, is a caustic metallic base. It is used in many industries, mostly as a strong chemical base in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents and as a drain cleaner. Pure sodium hydroxide is a white solid available in pellets, flakes, granules, and as a 50% saturated solution.