Caustic soda, also known as LYE, is a highly alkaline substance used in a variety of industrial and household applications. It is composed of sodium hydroxide, which is a white solid that dissolves easily in water. Caustic soda is often used to make soaps and detergents, as well as for cleaning and bleaching. It can also be used to unclog drains and remove grease and oil from surfaces. In addition, caustic soda is used in the production of paper, textiles, and aluminum.