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.

WARNING!

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.


Contents

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).

Storage

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

References

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