JJay
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Removing Ammonium Hydroxide from Ethanol
I have contaminated some ethanol with ammonia. I think the easiest way to remove it would be to react it with some acid and distill, but if there is
an easier way, I'd like to give it a try. Can anyone think of an easier way to remove it than to just stir in a little vinegar and distill?
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Big Boss
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Reflux the mixture, the ammonia is insoluble in warm solutions
Kept you waiting, huh?
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macckone
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Phosphoric acid would probably work best.
No chance of breakdown products like acetic.
No ether by products like sulfuric.
And no water like hydrochloric.
Although I guess hydrogen chloride gas might work
But then you have hydrogen chloride contamination.
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JJay
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Quote: Originally posted by macckone  | Phosphoric acid would probably work best.
No chance of breakdown products like acetic.
No ether by products like sulfuric.
And no water like hydrochloric.
Although I guess hydrogen chloride gas might work
But then you have hydrogen chloride contamination. |
I was strongly considering phosphoric acid too; I just don't happen to have any. I've seen phosphoric acid in several OTC products, and I know it's
useful, but usually I use other acids.
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JJay
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I'm obviously not going to waste expensive organic acids on this project, but I wonder if citric acid would work well.
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Oscilllator
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| Quote: Originally posted by JJay | | I'm obviously not going to waste expensive organic acids on this project, but I wonder if citric acid would work well. |
You can buy this stuff at the supermarket where I live, along with tartaric acid. Pretty cheap.
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JJay
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The supermarket here doesn't have tartaric acid, but it does have potassium bitartrate. (My tartaric acid was too costly.) I should probably pick up
some citric and ascorbic acids....
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JJay
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Say... violet sin mentioned a reaction in another thread that could work:
| Quote: Originally posted by violet sin | epsom salt MgSO4 + janitorial ammonia NH4OH / NH3 / H2O => Mg(OH)2 ppt +
(NH402SO4
filter off the Mg hydroxide to attack with HCl later, water the lawn with the ammonium sulfate |
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ave369
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Filter off the Mg hydroxide? Sounds like pain... This hydroxide precipitates as a gel and clogs all known filters.
Smells like ammonia....
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Amos
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Just toss in a concentrated solution of a metal salt with an insoluble hydroxide, or any acid at all really, and then re-distill the ethanol off. You
don't have to come up with some genius-sounding plan; the solution is simple.
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AJKOER
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I think the answer depends on what are your plans for the ethanol?
My concern is upon trying to boil off the ammonia in air. In the current case of ammonia plus ethanol, the product of the reaction has a better
leaving group (NH3, conjugate base of NH4+, which has a pKa of +9.75) than the OH− leaving group in the reactant, so the reaction equilibrium will
strongly favor the reactants.
CH3CH2OH + NH3 = CH3CH2NH3(+) + OH− Ka<<1
but, still to a very small extent, there could be residual ammonia or an ethylamine presence. If either of these is an issue in your intended use of
the ethanol, throw it out and buy more.
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JJay
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We're talking about parts per trillion... I think it will be ok.
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DraconicAcid
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| Quote: Originally posted by AJKOER | I think the answer depends on what are your plans for the ethanol?
CH3CH2OH + NH3 = CH3CH2NH3(+) + OH− Ka<<1
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Not a chance.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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AJKOER
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Yes, not likely one would hope. But this is nasty stuff, here is one sample depiction:
"Ethylamine vapor is a primary irritant to mucous membranes, eyes, and skin. Exposure to 8000 ppm for 4 h was lethal to rats. Rabbits survived
exposures to 50 ppm daily for 6 weeks but showed pulmonary irritation and some myocardial degeneration; corneal damage was observed after 2 weeks of
exposure. In the rabbit eye, 1 drop of a 70% solution of ethylamine caused immediate, severe irritation. Eye irritation and corneal edema in humans
have been reported from industrial exposure. A 70% solution of the base dropped on the skin of guinea pigs caused prompt skin burns leading to
necrosis; when held in contact with guinea pig skin for 24 h there was severe skin irritation with extensive necrosis and deep scarring"
Source: https://www.osha.gov/dts/sltc/methods/organic/org036/org036....
Combine the above with anything that could introduce a hydroxyl radical (sunlight exposure, heating in a microwave, electrolysis, the presence of
oxygen in tap water in the making of the ethanol rich in transition metals like Cu,..), and the reactions:
NH3 + .OH --) .NH2 + H2O
.CH3 + .NH2 --) CH3NH2
And I would not want to drink that alcohol.
[Edited on 25-11-2015 by AJKOER]
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JJay
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I'm not planning on drinking it; it will be used either as a solvent and/or as a reactant. 8000 ppm in air is a ridiculously strong concentration that
no human would tolerate if conscious. 50 ppm ethylamine is a million times stronger than what might possibly be in the ethanol if saturated with
ammonium hydroxide, and a human would consider such a concentration unpleasant enough to avoid. Plus we're talking about what is in the ethanol, not
what's in the air around it.
...also, isn't that methanol/methylamine depicted in your reaction? I wouldn't want to drink that either.
[Edited on 25-11-2015 by JJay]
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AJKOER
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Some may think my answer is a little extreme, and it may be, but ethanol is relatively cheap.
Interestingly, even water left in plastic bottles after a few days of exposure to sunlight and warming in a car, for example, will develop a sweet
taste, especially if already opened (adding more oxygen). The latter is a product of photolysis induced hydroxyl radicals attacking the plastic, and
not insignificant if you can taste it.
Now that with pure water, with ammoniated ethanol under catalytic conditions, just throw it out.
[Edited on 25-11-2015 by AJKOER]
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aga
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Lob in some dry K3PO4
The ethanol will quickly separate from whatever water you have in there and the majority of the ammonia will probably boil off before that happens.
Dry the tripotassium phosphate to re-use.
Do you have any estimates as to the w% of the ethanol before contamination and how much ammonia got in there ? Also voloume of ethanol.
Sounds an easily do-able experiment, so would like to try it.
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unionised
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Lemon juice anyone?
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JJay
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I really don't know how exactly much ammonia was in it (it was about 250 mL of ethanol), but I ended up just mixing it with some other ethanol that
was contaminated with acetic acid. I'll distill it when I get a chance.
[Edited on 26-11-2015 by JJay]
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