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Author: Subject: Weird EtOH distillation
DP
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[*] posted on 20-8-2005 at 05:54
Weird EtOH distillation


They don't sell Everclear or Golden Grain where I live and I am in need of 95% ethanol so I purchased a 1/2 gallon of the cheapest 80 proof vodka I could find and proceeded with a fractional distillation. Actually, I am still performing it. About an hour after the temp rose to 78.5C all of a sudden it dropped to ~65C for about 20min and something was coming over. I don't understand... why am I getting a fraction at that temp? Also, the ethanol/water in the distillation flask seems to go through cycles... it boils a lot for a while and then settles down. Is that normal? After that drop to 65C the temp has been rather steady at 78.5C. Since I'm using a Vigreux and distilling so slow do you think one distillation will be enough to get 95% ethanol?
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[*] posted on 20-8-2005 at 06:28


Quote:

Also, the ethanol/water in the distillation flask seems to go through cycles... it boils a lot for a while and then settles down. Is that normal?

Very normal if you forget to add some boiling chips, but otherwise no.




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[*] posted on 20-8-2005 at 14:29


It should be at least 90%+ depending on column size and how carefully you conducted the distillation. From there, you can upgrade it to about 96.5% by adding a large amount of salt and redistilling. I suggest you buy some molecular sieve if you want to make it near anhydrous.
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[*] posted on 20-8-2005 at 16:47


Could one perhaps add lots of anhydrous magnesium sulfate to absorb.
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[*] posted on 20-8-2005 at 22:57


Oh yeah, I forgot the boiling chips... duh. This distillation is taken forever. It's still distilling... it's almost been 24 hours already. :o Is that normal for distilling this amount of alcohol? The column is 300mm. 90% should be ok though. I guess I'll have someone send me Everclear from now on. I wonder if that was methanol coming over when it dropped to 65C. This is a very cheap brand, but do you think the quality control is so bad that they let small amounts of methanol get through? :o :o It wasn't measured, but it looked like ~10ml.

[Edited on 21-8-2005 by DP]
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[*] posted on 20-8-2005 at 23:20


Methanol can be toxic (as of course Im sure you knew), but 10ml in 1/2 a gallon... I dont know, I think it would be pushing it. I know SOME gets through, but it shouldnt be much... I remember learning a bit about heads and tails (beginnig and ending distillate fractions) from my ethanol adventures... Basically they always suggest disguarding the first 10-50ml to get out all the methanol...

But thats home-brewed kind, I dont know about commerical.




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[*] posted on 20-8-2005 at 23:46


Quote:

This distillation is taken forever. It's still distilling... it's almost been 24 hours already. Is that normal for distilling this amount of alcohol?

Very normal if you use a heating source with 300W or less of output, but otherwise no.
You need at least 1kW of output for distilling 1.9L of ethanol/water in an efficient (use SI units please). In such case the distillation would be over in couple of hours.




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[*] posted on 21-8-2005 at 01:01


This stirring hotplate is 1440W so I must have done something very wrong then. I wrapped the column in fiberglass pipe wrapping, but it's on somewhat loose. I see some of the distillate refluxing to a certain degree. Would that make it take this long? If not, what else could it be?
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[*] posted on 21-8-2005 at 01:36


Then I don't know what the problem is.
I suppose your hotplate has a power regulation, so is your heating really adjusted to the max?
What do you use to transfer the heat?




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[*] posted on 21-8-2005 at 05:51


You can adjust the temp in 5C increments from 5-400C, but that's all you do to regulate it. The ethanol didn't start coming over until I turned it up to 195C. I was using a 4000ml flat bottom flask directly on the plate and I didn't think there would be such a big difference between the surface and internal flask temp. I thought there would be less difference than using an oil bath. Well, the distillation is done and I drank a small amount of the liquid in the distillation flask and it was almost like water so that's good.

[Edited on 21-8-2005 by DP]
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[*] posted on 21-8-2005 at 10:01


When I got my hotplate, mine was stated as being good for 1000ml or less. I cannot remember the wattage exactly but if I keep everything 800 or 900ml it boils it short time and I am sure it would distill these volumes in a few hours max.

P.S. I just looked and mine is 650 watts. Nice unit but small I guess. Since I was looking at it I decided to clean it. It is obvious how much I love the thing, cupric salts on the light up display panel, ferrous/ferric salts on the heating surface with ammonium sukfate for flavor. I have had it since I bought it used on ebay in 2003 and I use it almost daily.

[Edited on 8/21/2005 by chloric1]




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[*] posted on 21-8-2005 at 12:17


If it was methanol it would have come off first.
Since the temperature reached the bp of ethanol then fell it looks like poor temperature/ power control. Is there an over-temperature cutout that tripped and switched off the power for a while (until it cooled and reset) or something ?
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[*] posted on 22-8-2005 at 11:59


Nope... it was on the whole time. The problem definitely must have been with the column wrapping... next time I'll wrap it much better. Thanks for all the info.
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