BeerChloride
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NaI from I2. (help?)
I was hoping someone could help. I'm trying to get the KI/NaI from tincture without wasting the elemental iodine (i.e. I could just boil it away).
Thus, I have searched for a simple procedure for converting I2 to NaI. (Converting back to elemental is easy enough if I need to).
I believe that sodium hydroxide disproportionates I2 into NaI and NaIO. I'm just not seeing any simple way to do it. Is there a way to reduce the NaIO
back down to NaI maybe?
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unionised
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Reaction with iron filings followed by addition of NaOH to ppt Fe(OH)2 should work.
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BeerChloride
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Hmm... It works - I just tried it. Thanks! Many metals would work, too. The only thing is it requires exact stochiometric balance, else I get ferrous
iodide or sodium hydroxide contaminant. Hmm.. I'm thinking about acetone which NaI is quite soluble in, or maybe the best aqueous recrystallization
scheme. Actually, I don't think I could titrate it to a certain pH because I don't know the exact concentrations involved. Hmm..
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not_important
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You can use excess NaOH, then CO2 (dry ice) or sodium bicarbonate (in excess) to convert excess hydroxide to carbonate (or bicarb if you really use a
lot of CO2). Then do the acetone or anyhydrous alcohol (MeOH or EtOH) extraction to remove NaI from the carbonate/bicarbonate.
Alternatively is to use thiosulfate and hydroxide, to get sodium sulfate and iodide. Argh - don't remember the full set of reactions, shouldn't be
hard to find but I'll dig them out tomorrow. Anyway, same idea. The thio/NaOH solution is made up in the proper ration, titrate until I2 color is
gone, then evaporate, extract NaI from the sulfate.
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BeerChloride
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Ahh, interesting idea. I don't know the solubilities in acetone, but carbonate is less soluble than the hydroxide, then?
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not_important
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Sodium or potasium hydroxide dissolve fairly well in the lower alcohols, and cause condensation problems with ketones. Sodium carbonate, bicarbonate,
and sulfate all have much lower solubilities that NaI in alcohol and acetone.
One other possibility is to add a small amount of ammonium sulfate to turn excess NaOH into the sulfate, the ammonia released will depart when the
water is evaporated. Ammonium sulfate doesn't dissolve in the organic solvent either; there is a small chance of getting some NH4I going into solution
with the NaI, but it didn't seem to happen the time I tried it. Be fairly easy to test for, just run a few grams and treat the final NaI with NaOH and
sniff for ammonia.
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