Caustic soda is one of the common names for sodium hydroxide, also known as lye, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations Na⁺ and hydroxideanions OH⁻. Its common name derives from its chemical identity as a sodium hydrate and because it is caustic or corrosive. In pure form, caustic soda is a waxy, white solid. It readily absorbs water and forms aqueous solutions. Commercially available caustic soda or sodium hydroxide is usually sodium hydroxide monohydrate, NaOH·H2O.

Caustic soda is one of the common names for sodium hydroxide, also known as lye, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations Na⁺ and hydroxideanions OH⁻. Its common name derives from its chemical identity as a sodium hydrate and because it is caustic or corrosive. In pure form, caustic soda is a waxy, white solid. It readily absorbs water and forms aqueous solutions. Commercially available caustic soda or sodium hydroxide is usually sodium hydroxide monohydrate, NaOH·H2O.