Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with formula . Solid sodium hydroxide is most commonly sold as flakes, prills, and cast blocks. Sodium hydroxide is a popular strong base used in industry. Around 56% of sodium hydroxide produced is used by industry, 25% of which is used in the paper industry. Sodium hydroxide is also used in the manufacture of sodium salts and detergents, pH regulation, and organic synthesis.