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Author: Subject: Glacial acetic acid...
evil_lurker
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[*] posted on 7-7-2005 at 15:41
Glacial acetic acid...


I'm working on a way to get as close to pure acetic acid without having to order it and pay those outrageous hazmat fees.

I know that you can reduce vinegar down to sodium acetate, and mix it with 98% sulfuric acid and get a finished product close to glacial.

However, that is another acid that is hard to come by in high purity, again without paying those ridiculous hazmat fees. I know I can get the stuff as drain opener, but most brands are only 93% and/or contain numerous buffers that would hinder the process.

I was thinking that I could take the sodium acetate and mix it with some store bought concentrated hydrochloric acid then filter out the salt.

I realize that the potential end product will be far from glacial, but mainly I want to know if the NaOAc will react with the HCI.

Is this doable?

[Edited on 7-7-2005 by evil_lurker]
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Twospoons
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[*] posted on 7-7-2005 at 16:10


In New Zealand glacial acetic is available OTC from pharmacies. Where are you?
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Magpie
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[*] posted on 7-7-2005 at 16:20


Yes, it is doable with HCl. I bought some muriatic acid specifically for that purpose. Did you search and read the postings? I believe this is also covered under Muspratt IIRC.



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Simon
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[*] posted on 7-7-2005 at 16:46


Some photographic shops sell acetic acid at, IIRC, ~900g/L as stop bath. (NB some shops also sell something called "odourless stop". Obviously this isn't concentrated acetic acid ;) )
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kclo4
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[*] posted on 7-7-2005 at 17:42


you could buy some NaHSO4 (sodium bisulfate) and add it to your sodium acetate and distill of the acetic acid. you can get NaHSO4 from Walmart as PH down in the pool supplies
i don't know how well it would work but because i have not ever tried it but i plan to in the future when i get a distiller. does any one know how good the yields would be?




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neutrino
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[*] posted on 7-7-2005 at 17:49


If you live near a pool store, you can probably get sodium bisulfate (NaHSO<sub>4</sub>;) cheaply. Reflux with sodium acetate and you get GAA:

NaHSO<sub>4</sub> + NaC<sub>2</sub>H<sub>3</sub>O<sub>2</sub> <--> Na<sub>2</sub>SO<sub>4</sub> + C<sub>2</sub>H<sub>4</sub>O<sub>2</sub>

This equilibrium is driven to the right by your acetic acid boiling off. This was described in another thread here somewhere.

edit: I posted at the same time as kclo4. These subscipts take too long...

[Edited on 8-7-2005 by neutrino]
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chromium
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[*] posted on 7-7-2005 at 22:07


I do not belive that 93% sulfuric does not give glacial acetic acid when sodium acetate is distilled with it. I think that buffers too cannot stop it doing so. You should at least try.

Another way is to make it from some vinegar by freesing. Does anyone know what temperature is needed to freese it out from 30% or 10% acetic acid? Is it possible at all? ( i have tried this @ -10C with no results )
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Magpie
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[*] posted on 8-7-2005 at 09:39


Check out the "Acetic acid/ sodium hydroxide" thread. Most of this has already been hashed out there. ;)



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jimwig
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[*] posted on 8-7-2005 at 12:51


this is so obvious but i had to say it

i went to a photo supply specialist and there on the shelf were $20 gallons of glacial acetic acid.

does New Zealand have these. it is a photo chemical used to make stop bath.

which is used in goth film and paper chemistry processing to stop the action of the alkaline developers.

try these places.

btw NZ is supposed one of the most beautiful places on Earth - z'that so?

jim
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16MillionEyes
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[*] posted on 20-5-2007 at 10:47


And where do you live? I'd like to know what store you can find this from.
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evil_lurker
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[*] posted on 20-5-2007 at 12:09


Well its been a long time since 2005 and I've significantly broadened my horizons.

That said, this is the place to get your glacial acetic acid:

www.hvchemical.com




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organometallic
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[*] posted on 22-7-2007 at 11:02


Is it not possible to fractionally distill or vacuum distill acetic acid from vinegar?



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Magpie
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[*] posted on 22-7-2007 at 13:04


Here's a long thread on the topic:

http://www.sciencemadness.org/talk/viewthread.php?tid=2194&a...




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evil_lurker
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[*] posted on 22-7-2007 at 13:06


No.

The acetic acid will form an azeotrope that is just about impossible to break.

The only practical means would be to neutralize the acid with a salt, boil off the water, and add to another acid such as sulfuric and distill.




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[*] posted on 22-7-2007 at 14:12


Isn't the azeotrope at like, 4%, but after that, the seperation between H2O and AcOH is really bad?

Tim




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chromium
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[*] posted on 22-7-2007 at 14:43


As far as i know there is no azeotrope with acetic acid and water, just evaporation rates are almost equal. It'is quite possible to make GAA by distillation but you need good hempel column and have to collect maybe only one drop of distillate per minute - or great part of acetic acid comes over along with H2O.

It is even possible to just boil out water from acetic acid but almost all acetic acid evaporates along with it. Long time ago i did some experiments with 30% acetic acid. I boiled it until volume decreased to about 1/10th of original volume. IIRC titration showed that residue was 58% AA.

Acetic acid is good example that rule of thumb which tells that remarakble differences in boiling points ensure easy separation, does not always hold.




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16MillionEyes
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[*] posted on 25-7-2007 at 08:36


I don't remember well where I read this from but you can heat sodium acetate to decomposition giving off acetic acid. Never tried it nor I know if it works for sure. I don't know how this reaction actually works or what byproducts it gives.
The following section from an MSDS also seems to suggest this reaction does occur:
"Unusual Fire or Explosion Hazard:
THERMAL DECOMPOSITION MAY PRODUCE ACRID SMOKE AND IRRITATING FUMES." (http://www.sefsc.noaa.gov/HTMLdocs/SodiumAcetate.htm)
Also, in this other MSDS clearly states the production of the acetic acid (http://www.ambion.com/techlib/msds/msds_9740.pdf)

Perhaps the reaction goes as follows:
2NaCH3COO ---> CH3COOH + H2O + 2C + Na2O
Any ideas?

[Edited on 25-7-2007 by __________]

[Edited on 25-7-2007 by __________]
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chromium
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[*] posted on 25-7-2007 at 12:32


Quote:
Originally posted by __________
I don't remember well where I read this from but you can heat sodium acetate to decomposition giving off acetic acid. Never tried it nor I know if it works for sure. I don't know how this reaction actually works or what byproducts it gives.
The following section from an MSDS also seems to suggest this reaction does occur:
"Unusual Fire or Explosion Hazard:
THERMAL DECOMPOSITION MAY PRODUCE ACRID SMOKE AND IRRITATING FUMES." (http://www.sefsc.noaa.gov/HTMLdocs/SodiumAcetate.htm)
Also, in this other MSDS clearly states the production of the acetic acid (http://www.ambion.com/techlib/msds/msds_9740.pdf)

Perhaps the reaction goes as follows:
2NaCH3COO ---> CH3COOH + H2O + 2C + Na2O
Any ideas?

[Edited on 25-7-2007 by __________]

[Edited on 25-7-2007 by __________]


This does not work. Acetates yield acetone on pyrolysis but if i recall correctly sodium acetate complexes with acetic acid and it is somehaw possible to precipitate this complex. It decomposes on mild heating giving some acetic acid.




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chemrox
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[*] posted on 25-7-2007 at 14:31


I just posted this in another thread. I shan't retype the citation. For homebake I'd go the benzene/butyl acetate route or maybe try CuSO4 by itself.

[Edited on 25-7-2007 by chemrox]

acetic.jpg - 123kB
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[*] posted on 25-7-2007 at 19:04


So how would the chemical equation for that reaction go? Besides, why would the last MSDS list "acetic acid" as one of the decomposition products if it supposedly doesn't do it?
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[*] posted on 25-7-2007 at 20:16


Thermal decomposition of acetates tends to be messy, especially if it is a hydrated salt.

Sodium acetate gives a mixture of stuff, including some acetic acid, methane, acetone, diacetyl, and others. Calcium acetate gives mostly acetone, but other products as well. Some of the heavy metal acetates will yield a fair amount of acetic acid or (apparently, haven't tried) acetic anhydride.

Just being listed as a decomposition product doesn't mean you'll get a decent yield, or that the products will be easy to separate in pure form.
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[*] posted on 26-7-2007 at 18:26


Never said they would but saying it will be a low yield is different to "it does not work".
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[*] posted on 27-3-2008 at 06:04


Here is a method if you have access to Sulphuric Acid.

NH4Cl + NaOH -> NaCl + NH3 + H2O

You have your salt if you boil away the water.

H2SO4 + NaCl -> Na2SO4 + HCl

Mix the HCl gas with water. Put it aside, you can use it later.

CH3COOH + NaHCO3 -> CO2 + H2O + CH3COONa

Add an slight excess of Vinegar. Boil to but not beyond 320oC. The Sodium Acetate will decompose. The remaining solution if using Tesco's Value Vinegar is a guey mess (Ammonia Caramel) and a white powder. Cook in an oven at 103oC, chop and grind the powder.

HCl + CH3COONa -> CH3COOH + NaCl + H2O

Use an excess of Sodium Acetate, filter and dry distill.

I haven't tried the last step, I still have Sodium Acetate sitting in my room. I haven't had any time to make any new Sulphuric acid.
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[*] posted on 27-3-2008 at 07:51


I have some excess sodium acetate so I'm going to get some bisulfate today and try that method. Many pictures will hopefully insue. Will this thread be the right place to post a "write-up"?

Also, in my area, 90% of the photographers and photographic stores that I called just straight up said "No!" when I asked for GAA. The other ones gave an explanation of why I shouldn't use it and/or referred me to a place that had 28% acetic acid for an outrageous price.

"You want what!??", "You don't want to use that, it stinks up the whole place and it burns your skin and nostrils.", "Nobody uses that anymore".

A couple didn't even know what it was.

This chemophobic society is truly pathetic.




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[*] posted on 27-3-2008 at 08:10


Ive tried this, its not really worthwhile because

1) vinegar contains very little CH3COOH, theres a lot of water to be boiled
2) It contains other rubbish such as sugar, which yield acrolein and other unpleasant stuff which foul when you distill the acetic off H2SO4. The sugar i very hard to be rid off

Using HCl instead of H2SO4 will lead to a huge Cl- content

Using NaHSO4 will lead to excessive decompoition of the acetate and other products

Haloform with acetone is far more economical
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