16MillionEyes
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Concentrating Vinegar
Yes, acetic acid is the most useful acid for a noob like me and unfortunately 5% won't cut it. I'm familiar with corrosiveness (and usefulness) of
concentrated acetic acid and I've in fact tried concetrating it before. Boiling it failed for the most part but I believe it got me up to 10% or so of
acetic acid (certaintly more concentrated than what I started with but without basic titration material I can't determine anything). I then looked up
in the internet and without much detail I got the solution by freezing it and then thawing. This certaintly proved to be a much better solution (I
even got an irritation by accidentaly smelling it) but again, I have no idea what concentration it was or if I'm getting all the avalible acid or not.
The general question is, is there an effective home-made plausible solution for concetrating vinegar with actual quantitive terms?
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Ramiel
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<html><a href="http://www.sciencemadness.org/talk/viewthread.php?tid=4122&page=1#pid46627">Glacial acetic acid</a> thread, some
useful information here if you can trawl through the entire thing.
<a href="http://www.sciencemadness.org/talk/viewthread.php?fid=5&tid=2194">A wealth of information</a> regarding acetic acid
purification.
<a href="http://www.sciencemadness.org/talk/viewthread.php?fid=11&tid=2533">Acetic acid salts</a> thread, especially note the last two
posts.
There are others, and I'm sure these aren't even the best  trust me, a lot of your
time will be best spent ferreting through references and past discussions.
Please use the friendly search engine.
- Ramiel
</html>
Caveat Orator
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16MillionEyes
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The friendly search engine didn't help but your links hopefully will.
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Mumbles
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If you have the equipment to distill, thing may be a lot faster and easier for you. Neutralization with NaHCO3 will yield a soln of Sodium Acetate,
which is then evaporated to yield solid sodium acetate. It is probably best for final purity, and concentration to dry the sodium acetate with
additional heat. Said sodium acetate is mixed with Conc H2SO4, and the product distilled to yield Acetic Acid. A second distillation of the acetic
acid, and an excess of H2SO4 may be neccesary to get a truely high concentration. I don't know if you could reach a "glacial" concentration by this
method. I do believe for the glacial classification it is around 99.8% pure.
I do advise reading through those threads, specifically the first one. They contain a lot of useful, and interesting information. More details of
the above possibility will be mentioned.
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phj
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Is it perhabs possible, to melt sodium acetate and bubble HCl through it?
Then you should get a sediment of NaCl, which only melts at much higher temperature.
Then you can filter and you should have glacial acetic acid.
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woelen
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The melting point of sodium acetate is quite high. The low-"melting" material is the hydrated salt, the anhydrous salt melts at higher temperature and
IIRC it decomposes, giving CH4 and other products. The "melting" of the hydrated salt is not real melting, it is simply dissolving of the salt in its
own water of crystallization.
Bubbling HCl through this will make CH3COOH, but for each molecule of CH3COOH you will have 3 molecules of water.
[Edited on 21-5-07 by woelen]
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Nerro
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Do all acetates form acetone upon heating or is Ca(OAc)2 somehow an exception to this "rule"?
#261501 +(11351)- [X]
the \"bishop\" came to our church today
he was a fucken impostor
never once moved diagonally
courtesy of bash
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Pyridinium
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A common drawback to using H2SO4 + NaOAc is that people forget conc. H2SO4 is an oxidizer when hot. There's also a misconception that a carboxylate /
carboxylic acid is already as oxidized as it's going to get. Guess what, it's not. There's still CO2 left in the progression. Hot, conc. sulfuric
is just the material to do it.
As a result, some of your carboxylate turns to CO2 and charred matter (a bunch of C plus who knows what else) before it can escape the reaction
vessel. Distilling HOAc out of sulfuric acid + acetate requires the mixture to be kept cool during addition, then preferably heated on a bath whose
max. temp. is just above the b.p. of acetic. Even though the HOAc boils off at 118 C, the H2SO4 mixture can get hotter than that, especially where
there's undissolved solid against the glass. This explains why a lot of people are getting charring.
Fractional distillation of dilute HOAc is indeed possible. You need a pretty efficient or tall column. I don't recall offhand how many theoretical
plates it requires-- this also depends on reflux ratio and boilup rate-- but I'm pretty sure 90-97% HOAc is within reach. I think someone else on
here was using a 6-ft-tall packed column with decent results.
A lot of experiments call for 28-30% acetic acid or thereabouts, that should be easy to do with even a stubby fractionating column.
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garage chemist
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If acetic acid of about 25% concentration is available (OTC as Spirit of Vinegar), can it be concentrated by extraction of the acid with e.g. Ether,
followed by drying of the extract with CaCl2 or similar and distillation?
That would be the kind of method I would think of when trying to isolate a watersoluble organic compound.
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Pyridinium
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| Quote: | Originally posted by garage chemist
If acetic acid of about 25% concentration is available (OTC as Spirit of Vinegar), can it be concentrated by extraction of the acid with e.g. Ether,
followed by drying of the extract with CaCl2 or similar and distillation?
That would be the kind of method I would think of when trying to isolate a watersoluble organic compound. |
I have a reference here that gives the Kd of acetic acid in an ether-water extraction system as 0.63. So the ether layer would hold 0.63 times as
much HOAc as the water layer. I presume this value changes depending on concentration and other factors, but it's a good start.
The same book also says acetone can be used to extract HOAc if the aqueous phase has a high enough salt concentration to give phase separation. The
table shows a fairly high Kd value, 1.20.
Not sure how well this works in practice, but it might make a nice experiment. I have been eyeing up the separation of HOAc for a while now, because
it makes a nice instructional showcase of chem principles.
EDIT: forgot, the book is called Handbook of Solvent Extraction. Unfortunately when you can find one for sale it usually costs over $100.
[Edited on 21-5-2007 by Pyridinium]
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not_important
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You could fuse the hydrated salt to drive of the water, then quickly crush it and pass HCl gas over it. You'll still get NaCl and acetic acid, the
reaction will be slow at first, then speed up some as enough acetic acid is formed to function as a solvent.
If you just dumped fused NaOAc into hardware store grade concentrated hydrochloric acid, enough acetate to be in slight excess, stirred for awhile,
and filtered off the NaCl, you'd have roughly 50-60 percent by weight acetic acid. You'd still want to distill it to remove the last of the NaCl,
iron and on from the HCl, and whatever.
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jimmyboy
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Using acids will almost always oxidize acetic - it is a pretty fragile compound that will easily turn into carbon gunk and
CO2 -- if you really want a proven way try dry distilling copper acetate - it should not form acetone like calcium and lead acetates -- this is how it
was made early on
mix copper chloride with sodium hydroxide for your copper hydroxide to start off with ...
[Edited on 21-5-2007 by jimmyboy]
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neilson80
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Acetic Acid From H3PO4
I've tried the H2S04 method for HOAc from NaOAc and experienced the same charring that everyone is talking about;however, when I mixed some NaOAc with
85% H3PO4,
it warmed only slightly with no charring as a pungent acetic smell evolved. I believe this is strong 70%+ acetic acid in sodium phosphate. H3PO4 is,
at least in my part of the world, easier to obtain than H2SO4. I purchased 40L food grade H3PO4 for 75$ from a hydroponics store with no scrutiny
unlike sulfuric acid which can be used for Meth production.
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Aqua_Fortis_100%
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"Using acids will almost always oxidize acetic"
so, why not use the old and good NaHSO4 (from swimming pool pH lowering..or caught in the form of a white yellowish cake in the distill flask when you
distill nitric acid from xNO3 and H2SO4 or any other method of acid production using H2SO4 and the salt of the desired acid(so some acetic acid can be
made just reacting with H2SO4 and distill and then the NaHSO4 caught and just feed in another distill apparatus with more acetate)..(washing further
and drying after) ) ¿¿¿
this theoretically would produce only acetic acid and Na2SO4, right ¿
[Edited on 22-6-2007 by Aqua_Fortis_100%]
"The secret of freedom lies in educating people, whereas the secret of tyranny is in keeping them ignorant."
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Chemistry Alchemist
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Could I buy the spirits of vinegar and then either freeze out the acid or leave to evaporate till 50-75 % of the water is gone..
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ScienceHideout
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Doesn't CH3COOH form an azeotrope with H2O? Would be aweful hard to distill- try refluxing! The water will eventually boil off leaving you with
boiling acetic acid (acetic acid boild 18 degrees higher than water)!
hey, if you are reading this, I can't U2U, but you are always welcome to send me an email!
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bbartlog
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Quote: Originally posted by ScienceHideout  | | Doesn't CH3COOH form an azeotrope with H2O? Would be aweful hard to distill- try refluxing! The water will eventually boil off leaving you with
boiling acetic acid (acetic acid boild 18 degrees higher than water)! |
You don't know what you're talking about. If it *did* form an azeotrope (which it doesn't), then refluxing would not help you. But in any case, reflux
means all the liquid is coming back down the column, i.e. you're not separating anything. Partial reflux, where some drips back down and some passes
over, is the usual state of distillation. But to have much of a shot at separating water and acetic acid you would need a fractionating column with a
lot of effective plates (I estimate ~20 based on my own attempt at this). It's not an azeotrope, but even in cases where the vapor-liquid curves for
the two compounds don't cross, it seems they can get really close.
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Chemistry Alchemist
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Is it safe to boil off all the water in Vinegar to obtain the Stronger acid?
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Wizzard
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I think that will smell far more than it will concentrate 
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Chemistry Alchemist
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say u were to do it out side, out it be safe to boil down all the way?
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Magpie
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| Quote: Originally posted by bbartlog |
...But to have much of a shot at separating water and acetic acid you would need a fractionating column with a lot of effective plates (I estimate ~20
based on my own attempt at this). It's not an azeotrope, but even in cases where the vapor-liquid curves for the two compounds don't cross, it seems
they can get really close. |
Also see:
http://www.sciencemadness.org/talk/viewthread.php?tid=2194
So, you need a sophisticated set-up to have a chance at this. And, unless this is just an academic exercise or you enjoy a stiff challenge, you would
just buy glacial acetic acid. It's cheap and readily available. But everyone has the right to give it their best shot. 
The single most important condition for a successful synthesis is good mixing - Nicodem
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