Sciencemadness Discussion Board

Purifying Contaminated Ammonium Hydroxide idea

smaerd - 20-7-2010 at 12:12

This is a pretty well debated on subject on some forums, and I've seen a lot mention of it here. I would post this in the other thread, I probably should, but this is about using tainted ammonium solution with "surfacant", instead of just concentrating an ammonium hydroxide solution.

So now your probably going to say just go buy untainted ammonium hydroxide solution, one without surfacant. But that's kind of part of the fun :). I'm a hobbyist novice chemist, and this sounded like sort of a fun project. So far I've done some preliminary test's on the product/solution which is "Red Max Clear Ammonia".

It contains supposedly only water, ammonia(ammonium hydroxide while in soln.), and "surfacant".

Some observations:
On shaking the solution I noticed it bubbled exactly like how shampoo and water bubbles. I presumed that as a "surfacant/emulsifier" it could possibly be Sodium Stearate. No MSDS was available nor a company website. It could also have been a number of many other compounds so I decided to do some simple tests.

I added 4 grams of non-iodized table salt(NaCl) to 30mL of the solution and stirred well. As soon as the NaCl started to dissociate there was a white precipitate. I filtered this through a funnel filter(grav. filtration). No conclusive information on what the ppt was, could have been some kind of glycerol or something, I'm not that educated nor well equipped to find out.

The solution clearly still wreaked of ammonia(as presumed), but now I was left with NaCl in soln. and I realized I just wasn't going to have that. So removing the surfacant is a pretty stupid idea, it's going to contaminate the product with something else... But it was good to make note of maybe.

So it was back to the drawing board again. I used google books and checked out a book called "Purification of Labratory Chemicals" for the part on aq. soln.'s of ammonia. They said leave two trays, one with water and one with the contaminated ammonia soln. in a dessicator for a few days and the ammonia will make it's way to the other dish. It's a form of distillation I forget the specific kind(isothermal I think?).

So I started doing some thinking, reading the bottle again. It said on the bottle "Do not leave in an aluminum dish". So I thought to myself, well, why not? So I soon realized Al3(s) + 3NH4OH(g) + H2O(l) -> Al(OH)3(s) + 3NH3(g) + H2O(l) . I wanted to check this and found a cool old article mentioning it(http://blog.modernmechanix.com/2007/11/10/weird-stunts-with-...) .

I'm not sure if that equation is completely correct. A hydrogen slips away when Ammonium cations leave the hydroxide anions to become ammonia gas(that's what would happen right? maybe haha)?

So I prepared a small test. I added a few strips of Aluminum foil to 20mL's of the ammonia solution. It began to bubble and fizz gently for several hours. I ceased the reaction, or perhaps it was done, either way I wanted to go to sleep. The Aluminum definitely changed in appearance and texture. So it was obvious there was a rxn going on with the aluminum foil strips(good news).

I decided to combine all three methods so here is my procedure leaving out stoichiometric figures as I haven't had time to figure them out yet.

Before I go off and calculate all this, thinking the steps through again, will someone make sure I'm not gonna like end up blowing something up or something. Thank you very much!

1. Mix ammonia solution with NaCl to remove some of the surfacant. Filter and remove ppt.

- this step may prove to be worthless because I don't think ammonia vapor has a hard time permeating soap bubbles that may form from the aluminum reaction.

2. Weigh appropriate amount of aluminum foil approximated by the % concentration of ammonium ions in the solution.

3. Place two wide-mouth glass dishes in a plastic bin(HDPE 5) with a good seal on the lid. Have double distilled water in the one dish and the aluminum+nacl+ammonia solution in the other. Let that sit for a few days(the aluminum should help evolve the gas quickly?)

4. Titrate the distilled water(now ammonium) solution to figure out the concentration. Label and store ammonia solution :P.

Thank you for your time, I don't have too many references I know but I really am looking and thinking this all out as good as I know how too right now.

[Edited on 20-7-2010 by smaerd]

gardenvariety - 20-7-2010 at 12:23

*facepalm*

Add acid to neutral. Dry. Recrystallize to remove surfactant. Dissolve and basify.

smaerd - 20-7-2010 at 12:36

Wouldn't that leave me with an acid contaminant? Or are you saying do that instead of the NaCl and Aluminum silliness?

No need for a facepalm brother, this is beginning's.

UKnowNotWatUDo - 20-7-2010 at 12:45

Sorry man but the adding of aluminum foil isn't going to somehow turn your ammonium hydroxide into ammonia when it's still in solution anyways. The bubbles you're seeing are bubbles of hydrogen gas. When you add the aluminum foil to the ammonia solution the hydroxide ions presents react with the thin layer of aluminum oxide on the surface of the metal. This forms a complex and dissolves the metal oxide layer, exposing more aluminum which is reactive enough to produce hydrogen and more aluminum hydroxide on contact with water. This process continues slowly (because of the low concentration of your solution) until all the aluminum is gone, and you've just made a bunch of hydrogen. So PLEASE be careful and find another way to do this because if you keep throwing these things together you just MIGHT blow yourself up. Gardenvariety had a good idea, think about that process.

smaerd - 20-7-2010 at 13:02

See I was wondering where that loose hydrogen went haha. Bummer though about the ammonia gas not evolving from the water. Is that because it trades ions with the self-ionization of water reaction? I need to do more research on gasses and review some gas laws.

I will try looking into garden varieties methodology, I'll just need to figure out what a good salt and solvent system would be for re-crystalization I guess.

Thanks UKnowNotWatUDo for the warning, hydrogen gas is pretty damn flammable haha.

Thanks GardenVariety for the helpful suggestion :).

UKnowNotWatUDo - 20-7-2010 at 13:16

You are partially correct, yes. Aluminum metal reduces hydrogen ions into elemental hydrogen gas. Because, as you said, water self ionizes (H20 <==> H+ + OH-) it produces hydrogen ions to react with the aluminum (2Al + 6H2O ==> 2Al(OH)3 + 3H2) to make hydrogen gas. However since you also have ammonium ions in solution which also dissociate into hydrogen ions (NH4+ <==> NH3 + H+) you will produce some free ammonia in theory. Again IN THEORY. But I encourage you to look up the equilibrium constant of ammonia with water (NH3 + H2O <==> NH4+ + OH-) because as your ammonia is still in solution with water, it will quickly reestablish it's equilibrium as ammonium hydroxide again. Hope this helps you understand, good luck.

Sedit - 20-7-2010 at 13:59

I know it seems like a no brainer but... why not just distill the solution? Titrate the distillate and determine concentration. If you raise the PH of the solution prior to distillation you should in theory be able to have a higher concentration of Ammonia solution in your recovery flask.

On a side note you could always take Ammoniasulfate or ammonium chloride and mix this with NaOH and capture the off gassed NH3 in H2O.

smaerd - 20-7-2010 at 14:14

I considered distillation I just wasn't sure if it was safe or if the ammonia would indeed carry to the other side. I don't have a fractional distillation set-up. Just a boiling flask, a still head adapter, a liebig, a vacuum outlet and a receiving flask.

I was definitely considering the Amonium Chloride and NaOH, but I am lacking in proper gas handling equipment. I was thinking about using just polyethylene tubing and some rubber stoppered flasks, with the one end of the tubing submerged in water. I'm not sure what gas equipment is even called to be honest. Oh well I can't buy anymore glass for a few months anyways(just blew a hundred dollars last week on more necessities) haha.

psychokinetic - 20-7-2010 at 19:49

Does the surfactant make it smell any more.... friendly?

smaerd - 20-7-2010 at 20:07

no there's no scent's just suds. Wreaks of straight ammonia with two wafts.

unionised - 21-7-2010 at 02:56

Don't bother with the aluminium or salt, Just place the contaminated ammonia and some clean water in separate dishes in a closed container. The ammonia will diffuse into the water until the concentration of ammonia is (very nearly) the same in both liquids.

An important point to grasp is that ammonium hydroxide practically doesn't exist.
Ammonia dissolves in water; only a very little of it is ionised. The stuff that isn't ionised is free to evaporate- that's why it stinks.

A straight distillation doesn't work.
As you heat the solution ammonia comes off first together with a little water. when you cool that mixture in the condenser, the water condenses, but there's not nearly enough to dissolve all the ammonia so most of that escapes, filling the room with toxic fumes.

Sedit - 21-7-2010 at 06:08

The reciever should be filled with ice if you wish to capture it and I never had much of an issue with a large amount of fumes that way.

Still the closed container idea would be much simpler for someone that needs to ask this question so I would say add some NaOH to the main container because it will lower the solubility of NH3 and push a greater amount into the new one. And add it slowly please.

unionised - 21-7-2010 at 08:11

I guess it depends on how concentrated the ammonia is in the source material.
Adding NaOH will slightly increase the yield but ammonia solution is cheap and the exothermic dissolution of NaOH in NH3 soln will make your eyes water at best.

smaerd - 21-7-2010 at 15:09

I really appreciate all of the advice here folks. It means a lot.

Add NaOH do the isothermal distillation, makes more sense. I was just over-complicating things, next time what the book says I'll just do haha.

Thanks again! :)

smaerd - 28-7-2010 at 16:14

Hate to bump an old thread, but I just wanted to leave a post saying that the iso-thermal distillation with naoh worked great. I have a 120 ml boston round with an unknown concentration of ammonium hydroxide aq. solution. Cool stuff thanks for the help again!

The WiZard is In - 28-7-2010 at 18:41

Quote: Originally posted by smaerd  
This is a pretty well debated on subject on some forums, and I've seen a lot mention of it here. I would post this in the other thread, I probably should, but this is about using tainted ammonium solution with "surfacant", instead of just concentrating an ammonium hydroxide solution.




If you heat ammonia water da ammonia comes off, it do be
tremendously soluble in water..... all you need is a rubber
stopper, a little tubing and some fresh water. You can, however,
create strong ammonia water.

By da ammonium hydroxide does not exist.

Sedit - 28-7-2010 at 20:06

Don't exist?

Quote:
Basicity of Ammonia in Water
In aqueous solution, ammonia deprotonates a small fraction of the water to give ammonium and hydroxide according to the following equilibrium:

NH3 + H2O NH4+ + OH−.
In a 1M ammonia solution, about 0.42% of the ammonia is converted to ammonium, equivalent to a pH of 11.63. The base ionization constant is

Kb = [NH4+][OH-]/[NH3] = 1.8×10−5


from everyones favorite reference source WIKI:D However If I felt like putting in the time I could have found a better one. The species does exist but its practicality and formation falls rapidly when outside of a solution.

psychokinetic - 28-7-2010 at 21:11

There is a reason and logic behind it not existing, but I can't remember what it is.

Edit: It doesn't saltificate, and is unisolatable.

[Edited on 29-7-2010 by psychokinetic]

unionised - 29-7-2010 at 11:08

Sedit,
A solution of ammonia as you say is about 99.58% not anything like ammonium hydroxide.
There is a little of each of the two ions (ammonium and hydroxide) present but, until you show me the raman spectrum of ammonium hydroxide I will still say that, as a compound, it doesn't exist.

Smaerd,
glad it worked and I don't think there's anything wrong with bumping an old thread to report a result of an experiment.

[Edited on 29-7-10 by unionised]

Sedit - 29-7-2010 at 11:45

Fair enough,

So what about H2O dissolved in a large excess of liquid NH3. Would the water remain mostly undisassociated?

MagicJigPipe - 29-7-2010 at 12:26

Ammonium hydroxide does not exist. It's just an easy way of talking about a solution of NH3 in water.

Why not heat the original solution in a bottle with a rubber stopper and a hose coming out. Then, attach an inverted funnel to the other end of the hose and place that on the surface of some DH2O in another container? This way, you could even make your "ammonium hydroxide" more concentrated.

This, in my opinion, should be the easiest way. You won't even have to boil the orginal solution.

Above question:

The water would be completely dissociated at any time due to the reaction between NH3, NH4+ and water. You would have to have a LARGE excess though that would be determined by the dissociation constant of the ammonia/ammonium.

Let me know if I'm wrong. Thanks.

[Edited on 7-29-2010 by MagicJigPipe]

smaerd - 29-7-2010 at 16:55

hmmm I need to invest in one of those rubber stopper borrer(spelling?) sets, unless a power drill will work? haha I doubt that the material feels to weird. it would be cool to see via titration which method gets the most and how I can improve upon the process.

I do have some spare PE tubing I'll just need to check compatibility maybe that will be the next experiment :P.

[Edited on 30-7-2010 by smaerd]