Sciencemadness Discussion Board - Concentration of NH4OH

Concentration of NH4OH

AirCowPeaCock - 10-1-2012 at 11:19

I'm attempting to concentrate NH4OH from household ammonium by heating the solution to 95 C and bubbling the gas (mostly NH3) through distilled water in an ice-bath. It works and I get about 20% concentration. The problem is when all is said and done more than half the original volume I put into the collection flasks (I have them chain linked) is gone. In fact the more volume I use the more % loss. And the flasks further down the line have more and more water loss--so its not heat dependent.

Advise?

Hexavalent - 10-1-2012 at 11:34

Learn how to spell and then come back to the ammonia.

neptunium - 10-1-2012 at 11:39

he clearly meant ammonia NH3 not a big deal....

Hexavalent - 10-1-2012 at 11:50

Yes, there's that, but there's also the 'advise'. Clearly it should be 'advice'.

Also, I don't think that this is the best route to more concentrated ammonia, as NH3 is still very soluble in water at 95C.

AirCowPeaCock - 10-1-2012 at 12:14

It difficult to get it past 95C, the ammonia solution has a surfactant(?) in it so it boils over even if I put 25 ml in my 250 ml round bottom. I'm going to toss that though I think. I don't know what I was thinking, not checking the label--obviously I wasn't. I'm also going to scale it up a bit, move to my 1 L flask, hopefully I can get it to 100 C this time.

..someones a little :mad:

<--

[Edited on 1-10-2012 by AirCowPeaCock]

Hexavalent - 10-1-2012 at 12:22

Even at 100C, ammonia is still very soluble in water. Its solubility equilibrium is not like a vast majority of other gasses.

And what did you mean, AirCowPeaCock, by your comment 'I don't think he needs these ideas..literally--obviously he has them all on his own!' on the thread about t-butyl lithium?

AirCowPeaCock - 10-1-2012 at 12:27

Quote: Originally posted by Hexavalent

Even at 100C, ammonia is still very soluble in water. Its solubility equilibrium is not like a vast majority of other gasses.

And what did you mean, AirCowPeaCock, by your comment 'I don't think he needs these ideas..literally--obviously he has them all on his own!' on the thread about t-butyl lithium?

I mean you don't need to be told what potentially dangerous reagents to "play" with

AirCowPeaCock - 10-1-2012 at 12:32

What about synthesizing ammonium gas through NH4Cl and CaO. My issue is although I have plenty of CaCO3, I don't have a container I can heat it in to 1300 some degrees to decompose it into CaO.

unionised - 10-1-2012 at 12:34

"Even at 100C, ammonia is still very soluble in water. Its solubility equilibrium is not like a vast majority of other gasses."
What would your second guess be?

Oh, BTW, the word is gases, I think that's an example of someone's "law".

Hexavalent - 10-1-2012 at 12:38

No, the word can be spelt either way;

http://www.thefreedictionary.com/gasses

neptunium - 10-1-2012 at 12:38

how about NaOH? dry with NH4Cl (if you have some)
NH4Cl+NaOH=NaCl+NH3+H2O
it does need to be heated a little but as soon as the mix is completed you'll smell ammonia!

AirCowPeaCock - 10-1-2012 at 12:43

I have plenty of both. Should I bubble it through water, or because of the water content should I just run it through a condenser? Although my condenser is kinds short, 6 inch liebig. Thank you! How much heat? I think ill add a little water, I don't need 50% solution?

[Edited on 1-10-2012 by AirCowPeaCock]

Hexavalent - 10-1-2012 at 12:58

Why not try both on a small scale, titrate and then compare results? That would be more exciting than just having someone spoon-feed you instructions!

Pulverulescent - 10-1-2012 at 13:01

Quote:

Clearly it should be 'advice'.

Even more clearly, you've been wrongly advised!

[edit] Because NH<sub>4</sub>OH is less dense than water, and ammonia having high solubility, the 'funnel trick' is required with circulation (mag stirrer)!

P

[Edited on 10-1-2012 by Pulverulescent]

AirCowPeaCock - 10-1-2012 at 13:07

I would, but I'm low on time..I'm already a few days behind because ammonia hates me! This is part of a school project. Ive decided Ill add enough water assuming 100% collection to produce 30% w./w. That way even with decreased efficiency it'll produce at-least 20%, which is sufficient--although not ideal.

AirCowPeaCock - 10-1-2012 at 13:36

Unfortunetly I don't have a mag stirrer, but NH4Cl + NaOH should work just fine, 300 C is easy. Thanks for the help guys!

Hexavalent - 10-1-2012 at 14:01

Quote: Originally posted by Pulverulescent

Quote:

Clearly it should be 'advice'.

Even more clearly, you've been wrongly advised!

I'd have thought when he said 'bubble' he knew to use a funnel . . .I did that once (omitted the funnel) when I was trying to prepare hydrochloric acid. . .the cold liquid on hot glass broke my reaction vessel!

AirCowPeaCock - 10-1-2012 at 14:03

Quote: Originally posted by Hexavalent

Quote: Originally posted by Pulverulescent

Quote:

Clearly it should be 'advice'.

Even more clearly, you've been wrongly advised!

Weren't you using borosilicate?

Hexavalent - 10-1-2012 at 14:16

Yes, but it was very old and probably was damaged inconspicuously.

AirCowPeaCock - 10-1-2012 at 14:18

Must have been...or just some freak occurrence...

entropy51 - 10-1-2012 at 15:58

Quote: Originally posted by Hexavalent

Even at 100C, ammonia is still very soluble in water.

Without looking up the data, I don't think that is true. If you heat a strong ammonia solution I think most of the NH3 will enter the gas phase before you reach 100 C.

I know for a fact that if you let the water in the absorber vessel become warm (and it does without cooling) that not much ammonia will be absorbed in the water.

Concentration of ammonia solutions is easier if you start with Janitorial Strength Ammonia from the hardware store. The stuff I get is 15% and contains no surfactacts.

Edit: According to the Merck Index, water at 15 C holds 38% NH3 and water at 50 C holds only 18%. If you extrapolate up to 100 C you will have very little NH3 left in solution, a fact that is easily demonstrated if you know how to titrate.

[Edited on 11-1-2012 by entropy51]

AirCowPeaCock - 10-1-2012 at 18:37

Thanks entropy51! Im alreading trying the sal ammoniac method..I think it will work looking at it now, but if it doesnt work ill go buy some janatorial if i can find it!(:

entropy51 - 10-1-2012 at 19:15

It is possible to concentrate weak NH4OH by distilling something like 1/4 the volume into a chilled receiver which in turn is trapped into a chilled trap containing some of the stuff you're distilling. I played around with it once, titrating the different solutions, just to see what was possible. Using the weak household NH4OH I was able to concentrate it by a factor of two to four, according to my notes.

The best method I've found is to make NH3 gas using ammonium sulfate fertilizer and NaOH dissolved in the minimum amount of water and to absorb that in the janitorial ammonia, chilled quite cold and magnetically stirred so that the less dense concentrated NH4OH doesn't sit on top of the weaker solution. Once you get the hang of it you can make quite strong NH4OH this way.

Before you buy NH4OH in the store, carefully give the bottle a shake to see if it foams, which indicates the presence of undesirable surfactants.

AirCowPeaCock - 10-1-2012 at 19:22

Thanks for your help, I think this is going to work just fine though. A little NH4Cl impurities, but I can easily remove thoughs through distilation--the probably wont be of concern for methyl ethyl ketazine synthesis anyways

AirCowPeaCock - 10-1-2012 at 19:26

Sorry for the spelling grammer errors. I am in the lab, im trying to type as fast as possible to keep my attention on the reaction. Its going real slow though, i need a mag stirrer/hot plate!

Bot0nist - 10-1-2012 at 19:44

Quote: Originally posted by AirCowPeaCock

Im alreading trying the sal ammoniac method..(:

Here is a great work up of a fun method by smuv with some good pictures too. In your set up though, you wouldn't even need the nice drying tube since you'll be bubbling onto an ice cold, ammonia solution in distilled water.

http://www.sciencemadness.org/talk/viewthread.php?tid=16061#...

Obviously look up the dangers of NH<sub>3</sub>(g), be careful, blah, blah, fume hood or outdoors, etc, etc.

Oh, and to help with the spelling police. Try and download Mozilla Firefox as your browser. It's got a build in spell check. Or you could always draft them in a word processor and the copy pasta them here after spell check. I do that for really long posts, or if I want a writeup to look more structured and neat.

[Edited on 11-1-2012 by Bot0nist]

AirCowPeaCock - 10-1-2012 at 20:53

It worked great! I got 125 mls of 30% solution, just what I was looking for, it took 2 hrs though! If I need more ill try the sulfate method if I need more--NH4Cl(s) + H2SO4(l) => (NH4)SO4(s) + HCl(g)? I have 95% sulfuric acid at my diposal. So only a small fraction of the HCl produced would disolve into the water. Could be boiled off afterwords. Don't worry, I have a fume hood with a face volocity exceeding that of 30 m/min

Bot0nist - 10-1-2012 at 21:21

Quote: Originally posted by AirCowPeaCock

So only a small fraction of the HCl produced would disolve into the water. Could be boiled off afterwords. Don't worry, I have a fume hood with a face volocity exceeding that of 30 m/min

Or you could pipe it into a train of neutralizing baths in wash bottles and trap most all of it as (useful) HCl salts. Even fish-tank tubing and 20oz soda bottles work for this in my experience (Though they do get milky white and brittle with time). If your seals are decent it works wonder. Account for suckback! Still, do it in the fume hood, of course.

[Edited on 11-1-2012 by Bot0nist]

[Edited on 11-1-2012 by Bot0nist]

entropy51 - 11-1-2012 at 07:12

Quote: Originally posted by AirCowPeaCock

I need more ill try the sulfate method if I need more--NH4Cl(s) + H2SO4(l) => (NH4)SO4(s) + HCl(g)? I have 95% sulfuric acid at my diposal. So only a small fraction of the HCl produced would disolve into the water. Could be boiled off afterwords. Don't worry, I have a fume hood with a face volocity exceeding that of 30 m/min

If you have NH4Cl that will work fine. I use the sulfate only because it is cheap and available. There is no need to convert one to the other. Perhaps you should spend some time reading a chemistry book.

AirCowPeaCock - 11-1-2012 at 07:31

NH4Cl did work fine--next time ill remember to add an excess of sodium hydroxide to be sure to neutralize all the HCl. I've been through a few chem texts, or at-least through the inorganic section, and a little into organics. No need to neutralize the HCl, I can just collect it in water--you can never have enough muriatic(?) acid.