Sodium hydroxide

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Sodium hydroxide, (molecular formula: NaOH) is a white, crystalline, odorless solid that absorbs moisture from the air. It is a manufactured substance. When dissolved in water or neutralized with acid it liberates substantial heat, which may be sufficient to ignite combustible materials. Sodium hydroxide is a strong base and is very corrosive. It is generally used as a solid or a 50% solution.
Sodium hydroxide is used to manufacture soaps, rayon, paper, explosives, dyes, and petroleum products. It is also used in processing cotton fabric, laundering and bleaching, metal cleaning and processing, oxide coating, electroplating, and electrolytic extracting. It is commonly present in commercial drain and oven cleaners.[1]


Synonyms: caustic soda, soda lye, lye, white caustic, aetznatron, ascarite, Collo-Grillrein, Collo-Tapetta, sodium hydrate, fotofoil etchant, NAOH, STCC 4935235, sodium hydroxide pellets, Lewis Red Devil Lye®

Physical data

Appearance: odourless white solid (often sold as pellets)
Melting point: 318 C
Boiling point: 1390 C
Vapour pressure: 1 mm Hg at 739 C
Specific gravity: 2.12
Water solubility: High (Note: dissolution in water is highly exothermic, gives off a great deal of heat)


Incompatible with a wide variety of materials including many metals, ammonium compounds, cyanides, acids, nitro compounds, phenols, combustible organics. Hygroscopic. Heat of solution is very high and may lead to a dangerously hot solution if small amounts of water are used. Absorbs carbon dioxide from the air.


Very corrosive. Causes severe burns. May cause serious permanent eye damage. Very harmful by ingestion. Harmful by skin contact or by inhalation of dust.
Toxicity data
LD50 40 mg/kg; (which is the lethal dose for 50% of the test subjects.)[2]