Sciencemadness Discussion Board

NaOH extraction

NaturalOne - 20-3-2011 at 23:12

How is sodium hydroxide extracted from sea salt?

Bot0nist - 21-3-2011 at 04:53

Sea salt is composed mainly of the following ions:

Chloride (Cl-) 55.03%
Sodium (Na+) 30.59%
Sulfate (SO42-) 7.68%
Magnesium (Mg2+) 3.68%
Calcium (Ca2+) 1.18%
Potassium (K+) 1.11%
Bicarbonate (HCO3-) 0.41%
Bromide (Br-) 0.19%
Borate (BO33-) 0.08%
Strontium (Sr2+) 0.04%

Since it's mostly NaCl we will look at it first.

Solubility of NaCl in water at 25c =359g per liter
Solubility of NaOH in water at 20c =1110g per liter

So in theory you could fractionally recrystallize some of the NaOH out since it is way more soluble. The other ions will likely cause grievous problems for you though.

Why not just synthesize some? Its pretty trivial. Or, just buy some it's cheap and commonly available almost everywhere.

[Edited on 21-3-2011 by Bot0nist]

White Yeti - 4-8-2011 at 07:14

There is no sodium hydroxide in sea water.

DJF90 - 4-8-2011 at 08:53

Look into the chloralkali process - its industrial so I have a hard time believing you looked very hard for the answer to this one!