Author Topic: Performing an A/B on alky pulls - Is it doable?  (Read 1618 times)

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ChemNewbie

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Performing an A/B on alky pulls - Is it doable?
« on: May 02, 2004, 02:56:00 PM »
This probably seems like a rather retarded question to those of the more chem savvy among us, but Swic's been out of the game for a little while, and doesn't remember that much of what little chemistry he did know.

Anyhow, Swic was wondering if it were possible to perform and A/B extraction on some pseudo saturated methanol pulls? He was thinking that if he were to add some dH20 to the alcohol, that it may prevent the alcohol from being miscible with the Xylene he wants to use for the extractions. (Damn where'd I put that miscibility chart?) He doesn't really know how much water he should add for somewhere around 200ml of alcohol, so any sugestions will be appreciated. Don't even ask why Swic wants to do this, just humor him please if you don't mind.

Thanks


kris_1108

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Solubilities
« Reply #1 on: May 02, 2004, 03:00:00 PM »
The problem is that freebase pseudo is soluble in alcohol. And, like you said, alc and xylene are miscible so thats also a problem.

You would have to evap the alky first for the pfed. Then you could dissolve it in water and perform and A/B.

geezmeister

  • Guest
Well... why not
« Reply #2 on: May 03, 2004, 09:17:00 AM »
Why not just boil the alcohol out of the other nonpolar solvent without basing it? You would precipitate the pseudo HCl out in the solvent, it can be filtered out of that solvent and dried, and if you still want to a/b it, you can do so without the alcohol being a problem.

You may also base an alcohol-pseudo-water solution, cover with solvent, and heat the whole thing up during the extraction to boil the alcohol off.

A little alcohol is not a a/b killer. The waterless a/b  uses alcohol or acetone, depending on the pills involved. The alcohol is deliberately limited in the process to keep it from being much of a problem.

I have based alcohol/water/pseudo solutions before and extracted into xylene. I do this sometimes when I clean beakers I have used in the pseudo extraction/recrystallization process, and have a little of this and that in any beaker, without knowing how clean all of them may be. I will base this alcohol, add some water, stir well, and extract with xylene. I dry the xylene before gassing it, but I often get some unexpected chunks of pseudo by this process that might otherwise be lost.


ning

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What would happen if he "recrystallized
« Reply #3 on: May 03, 2004, 09:25:00 PM »
What would happen if he "recrystallized"?

That is to say, if he had the alcohol full of HCl salt, he would add nonpolar, like xylene or ligroin; if he had base, he would add water (brine?)(saturated ammonia water?).

By diluting the dissolving solvent with something that was miscible with it but not with the pseudo, it would precipitate the pseudo, basically a crystallization.

Would this work, or would it bee to early in the game to do a recrystallization like this?


geezmeister

  • Guest
Recrystallizing now
« Reply #4 on: May 04, 2004, 08:58:00 AM »
You CAN do this at this point. The problem in my experience is that results have been inconsistent. SOMETIMES I have had good results, sometimes I have had no results, and sometimes I had bad results. The xylene clean pseudo precipitation technique was devised doing this sort of endeavor, looking for a way to avoid a certain gakk or two.

I suspect there are available avenues here, some of which have merit. Not many of them have been discussed or written up here. You are exploring an unmapped area, more or less.