DP
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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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Nicodem
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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?
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Very normal if you forget to add some boiling chips, but otherwise no.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Fleaker
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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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ADP
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Could one perhaps add lots of anhydrous magnesium sulfate to absorb.
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DP
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Oh yeah, I forgot the boiling chips... duh. 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? 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? It
wasn't measured, but it looked like ~10ml.
[Edited on 21-8-2005 by DP]
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Duster
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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.
Duster
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Nicodem
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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?
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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.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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DP
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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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Nicodem
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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?
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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DP
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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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chloric1
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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]
Fellow molecular manipulator
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unionised
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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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DP
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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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