whodkins
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how to seperate Methonal from H2O
i was woundering if there is any way to seperate methanol from water?
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chromium
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Distillation. If you use column you can go to 100% with one time, otherwise you need several distillations. If no column is used one can get somewhat
better separation if lot of NaCl is added to initial mixture.
IIRC if mix of methanol and water is saturated with K2CO3 then methanol separates as upper layer.
[Edited on 28-7-2006 by chromium]
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not_important
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The trick of adding salt to the mix is useful when you have only a simple distillation rig, the alcohol rich layer will be on top while the water rich
brine forms the lower layer. This goes for most any salt, be it NaCl, K2CO3, or whatever. The brine may still have some alcohol in it, it is worth
distilling it until ~80 C is reach and adding the distillate to the next batch to be processed. The upper alcohol rich layer still needs to be
distilled, but it will have less water than the original mix.
Methanol does not form an azeotrope with water, so distillation can separate them. To get a clean separation you need some fractionation, with reflux
of distillate encountering the acending vapour. Or, as Chromium said, do a series of distillations. Adding salt to the distillation mix helps because
it makes the organic (MeOH) less associated with the water; I don't know to what degree it help with methanol/water but it is useful with the water
soluble fatty acids.
The last bit of water can be removed with anhydrous Na2SO4 or MgSO4. Don't use calcium chloride, it complexs with the alcohol.
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leu
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| Quote: | | Distillation. If you use column you can go to 100% with one time, otherwise you need several distillations. |
Actually, according to Riddick in Organic Solvents the usual level of purity of methanol achieved by fractionation in efficient columns is
99.99 %  Methanol will adsorb water from the air, and the formation of
formaldehyde occurs as well  Generally, the commercial synthetic product is about
99.85 %; if the methanol is produced by destructive distillation of wood, acetone is a major impurity 
Chemistry is our Covalent Bond
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Vitus_Verdegast
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If it's just to dry your methanol from small amounts of water, 3A molecular sieves do the job well.
0.18g H2O is taken up by every gram of sieves.
Of course, the sieves can be regenerated by heating them at 250°C for a couple of hours, followed by nuking them a short time in the microwave
[Edited on 31-7-2006 by Vitus_Verdegast]
Sic transit gloria mundi
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unionised
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Make sue to let the methanol evaporate first or you may put your oven in orbit.
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