[JMiller]

Hello Everyone. I'm trying to remove the ammonium hydroxide (BP 37.7) residues from some DCM (B.P. 40) that I have. The question is whether these two form an azeotrope - I've searched everywhere and found almost nothing on this - and whether there is some other process I should consider before going to the ol' vigreaux.

any help would be greatly appreciated!

cheers

Jeff

[tmartin]

Have you considered an aqueous extraction?  I'm guessing you also have some product in the methylene chloride along with the ammonium hydroxide you want to hang on to? 

[JMiller]

actually no, I've got no product in there, just want to clean up the DCM. 
I was told that a couple of washes, one with slightly acidic H20, and then a simple H20 one, followed by drying, would do the trick.  does this sound right to you?
thanks again

[tmartin]

That sounds to me that it should do the trick.  If you're trying to get the DCM super dry you could pass it through an alumina or silica column afterwords, or distill it (over CaH).

One question comes to mind, sorry if it seems silly...but why do you have ammonium hydroxide in the methylene chloride in the first place?  Could you not just get some more if it is a relatively small amount? 

[JMiller]

it's more of an excercise, trying to reuse as much as possible!
without trying to abuse of your helpfulness: I'm using a 10% HCl solution.  Should this be ok, or am I overdoing it?
thanks!

[cpncoop]

Hi,

If you are trying to develop something for solvent recycling, the best practice would probably be to filter the DCM through a strong acid exchange resin.  These are cheap, and are used at industrial scales.  If you are just doing it as a lab exercise, then an aqueous acid was will work, but DCM doesn't split as well from water at low pH's, and even with an optimum split will hold on to about 2% water. 

As you know, water azeotropes with DCM at 38 C in a 98:2 azeotrope.  If you do a full water wash with aq HCl, you may be trapping more H2O in your DCM, and then have to waste more DCM while azeotroping water.  I'd try hitting it with an acid resin (maybe a Dowex XW8 (H) resin washed w/ MeOH), and then distilling the liquid.

Hope this helps

[JMiller]

this is excellent, helps a lot.  thank you!