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Author: Subject: Your favourite ethanol cleanup?
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[*] posted on 28-1-2022 at 04:21

Quote: Originally posted by Tsjerk  
I wouldn't use brand new glassware when boiling hydroxide in ethanol, it will etch the glass a bit, making it look dull.

I don't how NaOH or KOH would dry ethanol as it dissolves, maybe it breaks the azeotrope? I would use something like MgSO4 or CaO. Na2SO4 can be used but then filter before distilling, as it loses water at low temperature already.

Maybe neutralize the hydroxide/ethoxide into a non volatile salt (sulfate?) first before distillation?

It seems CaCl2 (reputedly not suitable for drying lower alcohols) can break the ethanol-water azeotrope (Nishi 1975) ... I might try this, but only after I purify my ethanol. I have no use for absolute ethanol, yet, and I have no way of measuring the last few percentage of water in ethanol.

I have CaSO4, MgSO4, 3A MS, ...

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[*] posted on 3-2-2022 at 13:49

Quote: Originally posted by Chemgineer  
DocX, have you tried Tomato Paste Wash?

Um, no? But thanks!
Like I wrote, the spirit is already distilled and concentrated, using classic turbo yeast and sugar. And also, like I written multiple times, the object is NOT TO MAKE DRINKABLE BOOZE. I want to make a pure reagent. 100% ethanol, no lower or higher or secondary alcohols. So I just want to clean the stuff.

But can this tomato soup wash produce pure ethanol? Its not a lot of info in the link, just recipe. What exactly will the tomato paste achieve?

[Edited on 20222222/2/3 by DocX]
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[*] posted on 4-2-2022 at 09:43

Tomatoes or tomato paste is a pretty common source of nutrients for the yeast, and I think it came out of the homebrewing community. They treat ethanol distillation like more of an art or alchemy than a science. While it may prove effective in getting a high yield of ethanol I doubt it's the best or purest among nutrient-rich plant matter. But it does underscore the importance of adding something to your ferment that mimics what the yeast are actually looking to feed on in nature.
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[*] posted on 4-2-2022 at 11:51

A previous thread on this subject included posts from Happyfooddance recommending that the mash should be rapidly distilled with no column before rectification to limit breakdown of materials and chemicals in the mash into volatile impurities which can pass over with the ethanol.

This worked well for me, but I was only doing it because I didn't have a large volume still that would take a rectifying column. Didn't know about the theory behind it till I read that post.

A falling film distillation apparatus might be Ideal here, but probably not worth the considerable price tag. Still, they are truly amazing at distilling a sample without subjecting it to prolonged heating.

Potassium carbonate draws water out of ethanol well enough that you get two layers and can separate the lower water/carbonate layer in a sep funnel. There are threads about this on here somewhere.
It doesn't give you anhydrous, but does give better than 95%.
This can be a real time saver if you're just working with a Vigreaux column 400mm long and a non refluxing distillation head, which is marginal for getting azeotropic distillate.

A Hempel with glass rings or helices or stainless steel SPP (spiral prismatic packing) gives a BIG reduction in theoretical plate height and makes it easy to get azeotropic ethanol in one go if you use a partial take-off head.
(There are even better manufactured packings from guys like Cannon industries, but they cost an awful lot)

One thing about trying to get very dry ethanol by distilling from CaO, or other drying agents: remember to dry that glassware! Dry it like you're setting up to make a grignard reagent.
Seemingly dry glass still holds a lot of water unless baked or torched, and your dry distillate may pick up water again from an insufficiently dried receiver flask.

Aw crap, I almost forgot to mention copper column packing. I haven't used this but a lot of distillers swear by it for neutralizing various impurities during distillation.
Maybe somebody who distills moonshine can chime in on this.
I know you're not distilling to drink, but moonshiners have a lot of tricks to deal with volatile impurities because they really screw up the flavor.

Edit: Most columns with discrete plates (Oldershaw, etc) are also great for distilling ethanol. Low plate high and high throughput potential.
But these are more expensive than jacketed Hempels and good packing, at least on the used glassware market.
Also, they aren't as widely applicable for distillation in general as most don't work under vacuum.

[Edited on 5-2-2022 by SWIM]

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