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Author Topic: How to purify a Sodium Hydroxide Solution?  (Read 4589 times)

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blink182chase13

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How to purify a Sodium Hydroxide Solution?
« on: July 19, 2010, 10:08:27 PM »

I performed an electrolysis of Saturated NaCl water.  The two NaCl solutions were in separate beakers with a salt bridge connecting both. The ionic equation for this is: 2Na+ +2Cl- + 2H2O + 2e− → H2 + 2Cl- + 2Na+ 2OH−
The question is, after the electrolysis is completed, I have a solution of NaCl and NaOH. How to I seperate these so I just have NaOH? Possibly by recrystallization? The uses I will use this sodium hydroxide for are in a Desiccator bag and as a common solvent.  Thanks for your time.
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blink182chase13

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Re: How to purify a Sodium Hydroxide Solution?
« Reply #1 on: July 21, 2010, 07:45:04 PM »

39 views and no posts. Anyone having any advice? I was possibly thinking a distillation would work, but a hot solution of caustic sodium hydroxide in a glass container spells stupidity. 
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nj_bartel

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Re: How to purify a Sodium Hydroxide Solution?
« Reply #2 on: July 21, 2010, 08:42:39 PM »

Doesn't need to be pure at all to be a dessicant - can just let it evaporate down then heat of the renaming water.  As for solvent, I assume you mean to add to your solvent? NaCl is pretty unreactive. Depending on the rxn, you might be able to get by with the impurity.
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blink182chase13

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Re: How to purify a Sodium Hydroxide Solution?
« Reply #3 on: July 22, 2010, 09:56:17 PM »

Appreciate the reply a lot. Yes I can evap off but I'm still left with NaCl and NaOH crystalls. I don't know how concentrated the NaOH is in the solution so I would like to separate it to be able to have a fair concentration of relatively pure sodium hydroxide. The solvent part I just meant in general, it would be nice to make because it is so hard to find in stores now.
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nj_bartel

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Re: How to purify a Sodium Hydroxide Solution?
« Reply #4 on: July 23, 2010, 07:39:29 AM »

Fwiw, it's available in kg quantities for cheap on eBay. I know that doesn't answer your question - just an alternative to purifying.
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blink182chase13

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Re: How to purify a Sodium Hydroxide Solution?
« Reply #5 on: July 23, 2010, 12:41:00 PM »

Yes I know I can. I was just interested in maing my own :). Thanks anyways though.
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blink182chase13

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Re: How to purify a Sodium Hydroxide Solution?
« Reply #6 on: July 23, 2010, 10:11:20 PM »

Another thought to anyone that could help, NaOH is not soluble in ether so I could use that as an extraction?  But only if the NaCl is soluble in it? So if not that, I need a substance that NaOH is soluble or insoluble in as well as one that makes NaCl the opposite of NaOH in order to decant one or the other.  If not that, anyone else have an idea?
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nj_bartel

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Re: How to purify a Sodium Hydroxide Solution?
« Reply #7 on: July 24, 2010, 09:50:32 AM »

NaCl is also insoluble in ether.  The problem is that they're very similar salts.  You could get at least some of the NaCl out by chilling the soln after concentrating it.
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blink182chase13

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Re: How to purify a Sodium Hydroxide Solution?
« Reply #8 on: July 25, 2010, 11:24:10 PM »

That is true.  I found this http://www.patentstorm.us/patents/6113657/description.HTML It mentioned using ammonia to to extract some of the NaCl.  Another one was to make the Noah into sodium hydroxide dehydrate Noah.2H2O, which I have not the faintest idea how to do, and cool it. Then to pass a gas through the cooled slurry which makes the NaCl float to the top where they are I would guess scooped off.  The document also contains one other method if anyone is interested.
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