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Author: Subject: How to concentrate an ammonia solution via distillation?
thrival
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[*] posted on 12-3-2013 at 14:32
How to concentrate an ammonia solution via distillation?


Is it possible to concentrate ammonia via simple distillation? If yes, which fractions (the beginning or end) should I throw away? I simply want to get rid of unnecessary water. Please don't suggest I buy more concentrated solution, this is about DIY; Thanks!

[Edited on 12-3-2013 by thrival]
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GammaFunction
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[*] posted on 12-3-2013 at 14:51


Drive out ammonia using heat (not boiling), and redissolve in small amount of cold water. Problem is that at 100C water still holds 7% ammonia, which is more than household ammonia (but janitorial ammonia is 10%).

With a big-container-hot-side / small-container-cold-side apparatus, an equilibrium should be established with more concentrated ammonia in the cold side.

Maybe one could consume the water in the hot side with a desiccant?
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[*] posted on 12-3-2013 at 14:54


There are a number of threads on the forum on the subject of concentrating ammonia. You should read them first before posting a new one...

[Edited on 12-3-2013 by sbbspartan]




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thrival
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[*] posted on 12-3-2013 at 15:03


So I need to have a cold side and the ammoniated gas will move in that direction?
How do I know when the reaction is done or the most possible ammonia has been transferred? ...or how much cold water to start with?

Yes I've seen other threads about concentrating ammonia but they were not useful to me. My specific request was for methods using distillation, not others.
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Mailinmypocket
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[*] posted on 12-3-2013 at 15:20


Check this page here, unless you already have of course:

http://woelen.homescience.net/science/chem/exps/concentratin...
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thrival
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[*] posted on 12-3-2013 at 15:24


Thank you, the last link was very useful. But again, how do I know what amount of ammonia I have to begin with (unknown sample) or when the concentration has gone as far as possible?
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[*] posted on 12-3-2013 at 18:35


You can find out the original concentration of the ammonia by titrating it with HCl. I've never done it, but it should be farely easy. I think you would use methyl orange as an indicator.

I think you can tell when you get as much ammonia out of the original solution as you can (or when the % is as high as it goes in the new solution), when it stops being absorbed into the water as well as it does originally. When bubbling pure ammonia into the water, barely any bubbles will reach the surface, it gets absorbed into the water so well, whereas after driving the majority of the ammonia out of the water, water vapor will start to come over and will not get absorbed as well.

This is my understanding at least, I may be wrong. I hope that is not very confusing... :)




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[*] posted on 13-3-2013 at 05:32


wouldnt it be possible to lead ammonia gas through an solution already containing ammonia to get higher concentrations faster?



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[*] posted on 13-3-2013 at 08:18


Yes, that is possible. If you have very pure household ammonia, then you can start with that instead of distilled water. In my experiment I did not do that, because I wanted the ammonia to be pure and I do not know what kind of crap there may be in the household ammonia. Household ammonia looks clear and colorless, but it may contain all kinds of dissolved salts.



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[*] posted on 13-3-2013 at 16:49


I've taken dilute clear ammonia and distilled it straight. A rough titration put it at 37% IIRC(while still very cold). As it warms to RT, it's happy to release ammonia and wreak havoc with the mucous membranes and eyes so be careful.

If you pump too much heat into the boiling flask, it tends to bubble/foam up the condenser. Even 'clear' ammonia seems to contain surfactant. I don't remember the reason I used a flood light for heat source. I used boiling chips and a TALL column composed of a liebig + graham IIRC. Cool water through the condenser and receiving flask immersed in ice. Takes a while and volume yield is low but the product is obviously concentrated and free from surfactants, salts and so forth. The storage container builds up a fair bit of pressure unless you live in Antarctica or store it in the freezer (don't).

It's interesting watching the bubbles in the boiling flask 'grow' at the bottom then become partially reabsorbed as they work their way up. This is about how much heat you should aim for. Less and you'll get slow or no distillate. More and you'll have the foam and more water in the distillate.

Tank




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[*] posted on 28-5-2013 at 03:47


Back to original question: In distilling/concentrating ammonia, which part, the beginning fraction, or end(?) ...should be tossed ...to get highest concentration. I've got about 20 gallons of dilute solution to go through. (Not using a bubbler or cold-water receiver.)
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[*] posted on 28-5-2013 at 09:36


the ammonia comes off first. however, i've tried to do this with simple kitchen equipment and had problems. dont allow the vapours anywhere near your skin as they are very corrosive. my cuticles cracked and bled right away. you will want to cool your receiving vessel and keep it at below zero celsius.

if you want industrial scale, check here
http://chemistry.stackexchange.com/questions/174/why-is-dist...

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[*] posted on 30-5-2013 at 05:21


You would be better served doing what Woelen did, but using a basic chemical to drive ammonia from its salts - NaOH/KOH, will drive ammonia from its salts and gaseous ammonia, will be driven off. It will be hot, so put it through a condenser on the way to the wash bottle.



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[*] posted on 30-5-2013 at 14:06


If you really want to concentrate it you can condense it straight by cooling the receiver with dry ice and acetone. If you have a means to contain it you can achieve anhydrous ammonia in this fashion.
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[*] posted on 4-8-2013 at 14:52


OK I've gathered from the above that simple distillation will work and if I just throw away the last
half by volume I will at least have doubled the concentration from what I started with. I'm using
simple cooling coil (nylon pneumatic hose sold at truck stops, HarborFreight, etc.) that cools to
ambient. I think this way is a lot cheaper, easier and less heroic than some of those mentioned
above.
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[*] posted on 5-8-2013 at 02:32


Get some urea and calcium hydroxide and make water solution and distill it with steel vessel and bubble to water to get good ammonia. Household ammonia is PITA and strongest I can find in my totalitarian country is something like 3-5%.
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[*] posted on 5-8-2013 at 03:08


Wow that's easy and available. Fertilizer and pickling lime.
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[*] posted on 21-4-2014 at 17:33


Quote: Originally posted by m1tanker78  
I've taken dilute clear ammonia and distilled it straight. A rough titration put it at 37% IIRC(while still very cold). As it warms to RT, it's happy to release ammonia and wreak havoc with the mucous membranes and eyes so be careful.

If you pump too much heat into the boiling flask, it tends to bubble/foam up the condenser. Even 'clear' ammonia seems to contain surfactant. I don't remember the reason I used a flood light for heat source. I used boiling chips and a TALL column composed of a liebig + graham IIRC. Cool water through the condenser and receiving flask immersed in ice. Takes a while and volume yield is low but the product is obviously concentrated and free from surfactants, salts and so forth. The storage container builds up a fair bit of pressure unless you live in Antarctica or store it in the freezer (don't).

It's interesting watching the bubbles in the boiling flask 'grow' at the bottom then become partially reabsorbed as they work their way up. This is about how much heat you should aim for. Less and you'll get slow or no distillate. More and you'll have the foam and more water in the distillate.

Tank

Can someone explain how this works? 37%? From household ammonia? That is very concentrated, at 100°C water dissolves only 7% NH3, so I guess the NH3 gasses off while very little water evaporates and re-dissolves as it's cooled. Can someone confirm this?

If water dissolves 7% at 100°C, why would 5% solution off gas NH3 at <100°?

[Edited on 22-4-2014 by Zyklonb]




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[*] posted on 21-4-2014 at 18:58


Quote: Originally posted by Zyklonb  

Can someone explain how this works? 37%? From household ammonia? That is very concentrated, at 100°C water dissolves only 7% NH3, so I guess the NH3 gasses off while very little water evaporates and re-dissolves as it's cooled. Can someone confirm this?

If water dissolves 7% at 100°C, why would 5% solution off gas NH3 at <100°?

[Edited on 22-4-2014 by Zyklonb]

The physical act of the water vapor moving through the solution
picks up ammonia and concentrating it, would be my first guess.
Argon gas bubbled through dissolved gas solutions tends to
entrain the gas from the solution, I am assuming the same thing
happens with water vapor.

calcium chloride or magnesium sulfate in the vapor path
will also preferentially absorb water over ammonia. You should
use the minimum possible to absorb the water as they will
also complex with ammonia.
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Zyklon-A
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[*] posted on 21-4-2014 at 19:03


Ok thanks, I'll try this tomorrow and report my progress.




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[*] posted on 22-4-2014 at 00:59


Boil your solution with reflux condenser and disolve gas from condenser in water!
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[*] posted on 22-4-2014 at 04:44


Quote: Originally posted by testimento  
Get some urea and calcium hydroxide and make water solution and distill it with steel vessel and bubble to water to get good ammonia. Household ammonia is PITA and strongest I can find in my totalitarian country is something like 3-5%.


A concentrated solution of ammonium sulfate fertilizer onto NaOH, KOH, or Ca(OH)2 works as well, no external heating required... This method is a bit more compact and the ammonia is less wet and can be dried with a reasonably sized drying tube, if you are trying to condense it for instance. It is also easily built with aquarium tubing and soft drink bottles, in the event that there are budget constraints.

I gave up distilling "household ammonia" years ago. The foaming is unmanageable. Maybe if you had some silicone oil as a defoamer?





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[*] posted on 22-4-2014 at 05:27


Ok, I don't have a reflux, only a Liebig. I have some "drain cleaner", which contains 30-60% NaOH, 30-60% NaNO3 and about 5% aluminum ( the rest is coloring I guess.) If I mix this stuff with more aluminum shavings, and add some water, it gives off crazy amounts of ammonia gas. I once made the mistake of using aluminum powder, the reaction was way too fast, my garage was completely fumigated with ammonia... Anyway, this will be the key to concentrated ammonia solution, I'll just bubble the gas through cold water, or maybe distill it - which would be better?

[Edited on 22-4-2014 by Zyklonb]




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[*] posted on 24-4-2014 at 15:51


Quote: Originally posted by Praxichys  

I gave up distilling "household ammonia" years ago. The foaming is unmanageable. Maybe if you had some silicone oil as a defoamer?



I agree with you on that… a few weeks ago I tried distilling some cheap 'clear' ammonia that I bought at the hardware store (first thing I tried in my new apparatus), and the bubbles were extremely out of control and just carried right over into the condenser along with the ammonia. The silicone oil is an interesting idea though. I think I'll try that. It would be nice to be able to purify that ammonia without having all those surfactants carry over.
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[*] posted on 24-4-2014 at 22:39


use liebig as reflux, some NaOH
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