Sciencemadness Discussion Board

distilling vinegar

pneumatician - 25-4-2021 at 10:10

Hi, how can I obtain acetic acid at maximum strength starting from vinegar?

No, I don't want to freeze vinegar in bottles again and again... anyway, how strong is the end acid using this method???

So, I make a low heat distil, separating the water, until it tastes sour and I get a yellow-orange acid...

now, a rectification colunm and like alcohol I get more strong acid??

Glacial AA is possible with normal hobby labware??

the process:

https://www.youtube.com/watch?v=eV7Rdge_VTQ

TIA.

njl - 25-4-2021 at 10:22

This has been discussed before on the forum and elsewhere. While acetic acid and water do not formally have an azeotrope, it is extremely difficult to achieve good separation by distillation without a long packed column. Glacial acetic acid is not practically obtainable this way. Starting from 10 percent vinegar (already more concentrated than the 5 percent in most brands) you would need several distillations just to get up to 25 percent, and the return on each distillation drops as the concentration increases. This is why most GAA is made from acetate and an acid (usually sulfuric or phosphoric).

Triflic Acid - 25-4-2021 at 10:34

If I were you, I would dump some eggshells in the vinegar, then boil off the water to get Calcium acetate. Add something like conc. sulfuric or phosphoric and get a Calcium precipitate and GAA. Much simpler and cheaper than distilling. If you need really good acid, distill the filtered product.

Fluorite - 25-4-2021 at 12:07

Best way i think is to add sulfuric acid to hold the water and boil the acetic acid, or a drying agent for acetic acid like magnesium nitrate for nitric acid

S.C. Wack - 25-4-2021 at 12:40

Quote: Originally posted by Fluorite  
or a drying agent


Although it fails in some cases (dehydrating an alcohol-sulfuric acid mixture) vinegar will be much more giving, in due time. No organic chemistry will be taking place.

[Edited on 25-4-2021 by S.C. Wack]

Panache - 25-4-2021 at 17:50

Adding a drying agent to remove the 96% of the mass that is the water is certainly not spoken about in Vogel.
Sodium Hydroxide, boil off water, heat the acetate to 150C in an oven, cautious addition of sulphuric, some charring occurs, acetic acid is distilled off, ideally under vacuum. I have done this, it absolutely works and is a fucking pain in the arse.


[Edited on 26-4-2021 by Panache]

S.C. Wack - 25-4-2021 at 21:19

Vogel surprisingly does not use vinegar or other items from the grocery...it's as though he's uninterested in obtaining chemicals through such channels. Complete dehydration of less than 4% solutions of certain organics in water (with 100% recovery) doesn't have to be the slightest pain anywhere, and can in fact be most simple and convenient. The real issue here is how does one get yellow orange distillate from "low heat", and was the still temperature actually measured?

draculic acid69 - 26-4-2021 at 02:29

Quote: Originally posted by Panache  
Adding a drying agent to remove the 96% of the mass that is the water is certainly not spoken about in Vogel.
Sodium Hydroxide, boil off water, heat the acetate to 150C in an oven, cautious addition of sulphuric, some charring occurs, acetic acid is distilled off, ideally under vacuum. I have done this, it absolutely works and is a fucking pain in the arse.


[Edited on 26-4-2021 by Panache]


How much of a pain in the ass is this.sounds simple.
Also I'm curious because I have some Ca propionate and h2so4
but have been putting it off because I don't want to have to deal with
CaSO4. Usually I would just filter with a t-shirt but the mixing of
H2so4 +t-shirt is a no go

Swinfi2 - 26-4-2021 at 05:21

I did a similar process, took a bunch of pickling vinegar. Filtered out the herbs, distilled it to remove non volatile components. Dumped in a bunch of impure CaCO3. Heated to speed up the process and drive out CO2. Filtered again to remove excess. And dried out the Ca(OAc)2. This is how it is now mostly white needles with some yellowing from an impurity. At any time I can add a non-volatile acid and filter out the Acetic acid.

My first attempt I did convert to the acid form and skipped the first distillation. Product went orange on standing. Not sure if the metal lid is the cause, it's plastic liner seemed intact? Or if it can be decomposed to acetone and the acidity causes aldol condensation (orange tar)?

Praxichys - 26-4-2021 at 05:36

The boiling down part is a pain. It is an all-day project; prepare for a steamy kitchen that reeks of vinegar. Near the end it requires constant temperature supervision because the melting point and the point where it burns is quite close.

Even with H2SO4 mine never comes out quite glacial. The only "glacial" I've ever made was after using a bit of acetic anhydride from my ketene lamp to soak up that little percentage of water. For the most part, >98% is fine for the majority of applications anyway.

Regardless, it is much easier to start with a commercially available acetate salt. Owing to the popularity of that supersaturation "hot ice" demo, it has become widely available and inexpensive on eBay in particular.

pneumatician - 26-4-2021 at 12:06

Well, i thing many of people distilling vinegar is because can't buy it from a store, no? at 8-20 €/L...

symboom - 26-4-2021 at 14:26


I see what you All were talking about how the ketene process is dangerous here is a guy doing the synthesis at 5ppm it's deadly compared to hydrogen cyinide at 50 ppm.

https://youtu.be/g9sPlMkYEIw

Acetic anhydride using acetyl iodide
https://youtu.be/SGQ35JWq0eg

Acetic anhydride by nitrogen dioxide
https://youtu.be/gsVDuPjE9zY

Acetic anhydride by acetic acid and phosphorus pentoxide in DCM
https://youtu.be/Spd1RnRZbvk

[Edited on 26-4-2021 by symboom]

Runic7 - 26-4-2021 at 16:34

As most have said here before, distillation is impractical. If you really want to make glacial acetic acid at home, you typically start Ethyl Acetate + NaOH = Sodium Acetate + 80% H2SO4 = Acetic Acid.