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Sodium hydroxide


Key Points


  • Non flammable
  • Reacts with water in the air and attacks metals such as aluminium, tin, lead and zinc to form hydrogen gas
  • Generates heat on exposure to acids
  • Emits toxic fumes of carbonates, peroxides and sodium oxides when heated to decomposition. Reacts with metals to produce hydrogen gas causing a fire hazard
  • In the event of a fire involving sodium hydroxide, use fine water spray and liquid tight chemical protective clothing with breathing apparatus


  • Toxic by all routes of exposure
  • CHIP classification: corrosive
  • Inhalation causes irritation of the eyes and nose with sore throat, cough, chest tightness, headache and confusion
  • Ingestion will burn the mouth, throat and stomach 
  • Skin contact can result in severe burns
  • Eye contact causes pain, twitching of the eyelid, tearing, inflammation, sensitivity to light and severe burns
  • Sodium hydroxide is not considered to be carcinogenic


  • Avoid release into the environment
  • Inform the Environment Agency of substantial releases


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Compendium of Chemical Hazards