mycotheologist
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Liquid liquid extractions of polar solvents from non polar solvents
I bought a big 5L container of paint stripper from the hardware shop which contains toluene, xylene and methanol. The percentage of methanol is 40%. I
want to separate the methanol from the other 2 but I'd prefer not to have to distill. I know that water is immiscible with tolly/xylene so I was
wondering what would happen if I added water to the solution. Will two layers form or will the methanol make the water miscible. If its the latter,
would it depend on how much water is added. For example, if I have 100mL of the paint stripper then add 100mL of water, surely the toluene/xylene
couldn't mix with that much water and 2 layers would form. Once those 2 layers formed, then most of the methanol would go into the aqueous phase since
its pretty polar. Is my thinking correct?
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watson.fawkes
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Do you own a test tube? It would only
take a minute or two to answer your question with an experiment.
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Amy Winehouse
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Xylene is about as nonpolar as you can get, but toluene is a little more polar (still considered nonpolar) and mixes with water a little bit. Maybe if
you saturated the water with NaCl (the kind WITHOUT calcium silicate) the ions would rush to the bosom of the methanol and they would all have a nice
no-nonpolar bonds allowed party and yeah the organic layer would probably float up
"I'm too drunk to taste this chicken"
-Colonel Sanders
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fledarmus
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Toluene is almost totally insoluble in water - about 0.47 g/L (wikipedia). You shouldn't have any trouble separating the methanol from the
toluene/xylene mix by liquid/liquid extraction. If you make your final wash using a saturated salt solution, you will remove almost all of the water
that might still be absorbed in the toluene/xylene layer.
This dissertation shows the mole fraction of toluene in water to be on the order of 10-4, and the mole fraction of water in toluene on the
order of 5x10-3
[Edited on 26-4-2012 by fledarmus]
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mycotheologist
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I added about 10mL of water to around 20mL of the paint stripper and it rapidly separated into 2 phases but the aqueous phase at the bottom was quite
cloudy for some reason. Maybe thats some toluene suspended in the aqueous phase so I'll try adding NaCl next time. I think I'm gonna use this method
to separate the methanol from the xylene/toluene because it'll be much faster and easier than distillation.
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DDTea
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Yes, adding a few mL's of saturated sodium chloride should aid your separation. To ensure everything is properly partitioned, try shaking and giving
the layers time to resolve.
Once you've finished the initial separation and discarded the aqueous phase, you should dry your xylene/toluene with sodium sulfate (that has been
baked at 100 * C to drive off moisture). Pour the sodium sulfate into your solvents and stir until you get a "snow globe" effect. The sodium sulfate
is easily filtered afterward.
[Edited on 4-27-12 by DDTea]
"In the end the proud scientist or philosopher who cannot be bothered to make his thought accessible has no choice but to retire to the heights in
which dwell the Great Misunderstood and the Great Ignored, there to rail in Olympic superiority at the folly of mankind." - Reginald Kapp.
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