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Author: Subject: Purification of 70% Ethyl Rubbing Alcohol
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[*] posted on 16-8-2015 at 16:56
Purification of 70% Ethyl Rubbing Alcohol


There is a detailed writeup of this experiment in the Prepublication section with lots of pictures: http://www.sciencemadness.org/talk/viewthread.php?tid=63320

Here is the abridged version.
1 L of 94% Ethanol was obtained from 1892 mL of 70% ethyl rubbing alcohol from the pharmacy ($4) in a 66% yield (a cost of $16 per kg of Ethanol).

The purification process went as follows:
Step 1: Simple distillation to concentrate the ethanol to ~85%. This distillation also carries over the acetone.
Step 2: Drying the ethanol (in this case with magnesium sulfate).
Step 3: Fractional distillation to remove the acetone.
Step 4: Distillation to separate the ethanol from any MgSO4 that may have dissolved (this step is not necessary if you use molecular sieves.

NOTE* Drying with MgSO4 should have yielded ethanol with a concentration of at least 98%. However, I waited several days to distill the ethanol after drying, so this allowed time for the ethanol to absorb water from the air. If you distill right after drying, you probably could acheive >98% pure.

I will be making a post in the future on drying ethanol completely using magnesium.




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ave369
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[*] posted on 19-8-2015 at 14:15


From my moonshining practice, the best way to remove acetone contamination is diluting the alcohol to 20% and then distilling it slowly. The acetone concentrates in the first millilitres, or the "foreshots". This applies to food grade ethanol, but I see no reason why it won't work with chemical grade.



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aga
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[*] posted on 19-8-2015 at 15:23


ave369's suggestion will work, mostly, however there is simply no point.

Just brew some ethanol with no acetone contamination and distill it.

Maybe use a Thumper to get to around 80% :o

Edit :

Ok, so Less Acetone. Blegh.

[Edited on 19-8-2015 by aga]




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