Sodium hydroxide

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Sodium hydroxide, also called lye or caustic soda, is a strongly caustic chemical and corrosive for several metals like aluminum or tin. Molecular weight is 39.997 g/mol. Melting point 323 °C (605 °F), boiling point 1388 °C (2534 °F). CAS number : 1310-73-2.


Sodium hydroxide reacts with lipids and proteins so it dissolves flesh. This makes it a really dangerous chemical to handle. Precautions has to be taken when using sodium hydroxide. Chemical gloves and a splash screen is a good protection.


Dissolving in water

At 25 °C a saturated sodium hydroxide solution contains 111g NaOH per 100g H2O and is a viscous white liquid.

wt/wt % pH g/l Mol/l
0.05 % 12 0.5 0.0125
0.5 % 13 5 0.125
4 % 13.9 40 1
5 % 14 50 1.25

Some reactions

  • Solid NaOH and concentrated solutions absorbs CO2 from the atmosphere forming sodium carbonate.
  • Sodium hydroxide turns silver nitrate into sodium nitrate and silver oxide.
  • May steam and spatter and generate a lot of heat when dissolved in water (hydrolysis).


Keep sodium hydroxide in an air tight container to avoid turning it into sodium carbonate and absorbing moisture from the air.


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