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Author: Subject: Drying wet acetic acid.
Furch
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[*] posted on 8-10-2006 at 17:07
Drying wet acetic acid.


Greetings all,

I've got a bottle of presumably wet acetic acid, and I need glacial ditto... I assume it has a concentration of about 90% or higher (I haven't titrated it yet).

One way to go about the problem is to perform an azeotropic distillation, but I can't do that.

Now, if I would've had some Ac2O, I could've made AcO from the water in the solution... But I don't have any Ac2O, so I can't do that either.

What I do have, on the other hand, is SOCl2 (thionyl chloride). As we all know, SOCl2 reacts more or less violent with water, forming HCl and SO2, which are poisonous gases... That's not a problem for me however.

The above mentioned method would rid the solution from water, and leave more or less no trace behind, as the products of the reaction are gasses... However before I start to fuck the whole thing up, I would like someone elses thoughts on the subject. So what do you say? Is this a feasible method to rid water from water contaminated acetic acid? My worst fear is that the reaction is too violent, and that it can't be done for that reason...

Thanks in advance!


- Furch
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[*] posted on 8-10-2006 at 17:23


IIRC if you have 10% water contamination you can distill approx 20% of the volume off and get pure glacial... the azeotrope will come off first leaving pure glacial behind.

This only works with high concentrations of acid though.
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[*] posted on 8-10-2006 at 19:37


Furch...please do not waste SOCl2 on cleaning up acetic acid. If I had SOCl2 I'd probably be having an orgasm right now. You can always buy glacial at the photo shops.

Secondly, I'm sorry Evil Lurker, but there is no azeotrope. Gmehling's 50 odd citations say so. Please see thread "acetic acid/sodium hydroxide" by Hermes T.

Furch, also please see the above thread. I struggled like crazy just to get 92.5% acetic acid from 87% acetic acid using 2 fractional distillations. I did this just to see what was possible with my equipment.




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[*] posted on 8-10-2006 at 19:58


I heard the azeotrope was 96% H2O, and that it's certainly possible to get the AcOH out by distillation, but the boiling and vapor (analog of solidus and liquidus respectively) temperatures are so close that it's very impractical.

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[*] posted on 8-10-2006 at 23:13


Furch, why not just do it on a small scale and find out? If we tell you not to, that it will never work, will you believe us and never try it?

It is true that azeotropic distillation is used as a good way to get GAA, but the not-water part of the azeotrope is some added component, not acetic acid. There is no need to get into not-SOCl2 here, there are many acetic acid threads. I'm not sure how many exactly we need. It's all been gone over already, see? A Google search of two acetate addition compound patents that I was aware of brought up this thread. I suggest reading leu's patents at espacenet.
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[*] posted on 9-10-2006 at 02:17


I`m not certain, but I beleive the addition of P4O10, should lock up the excess water quite nicely.



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[*] posted on 9-10-2006 at 02:46


Just curious, would anhydrous CuSO4 or MgSO4 do the job?



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[*] posted on 9-10-2006 at 03:22


MgSO4.7H2O loses 6 water at roughly 150c the copper salt even lower temp.

so it could be tricky as Ethanoic acid has a BP of 118c.




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[*] posted on 9-10-2006 at 03:58


I really don't see why... You heat blue CuSO4.5H2O untill it's white, and then you add it to the glacial-to-be AA.

The salt absorbs the present watermolecules and you filter to remove the hydrate...




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[*] posted on 9-10-2006 at 04:30


Hello again, and thanks for all the replies.

The reason I asked was because I wasn't sure on how SOCl2 will react with water... Sure, it fumes when exposed to the humidity of air, but that doesn't say much about how it will react when the two liquids are mixed. I thought maybe you could provide me with that information.

Anyway, I will titrate my wet acetic acid and then perform the SOCl2 + H2O reaction and report the results back to you, partly for the sake of closing this thread (as there seem to be a lot of AA related threads).

Thanks again!


- Furch
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[*] posted on 9-10-2006 at 04:52


use molecular sieve
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[*] posted on 9-10-2006 at 05:01


but isn`t copper sulphate somewhat soluble in AA? I know it is a little in EtOH.
it`s something like the second step in TACC synthing IIRC.




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[*] posted on 9-10-2006 at 07:11


Acetic Acid and Water do not form an azeotrope.

The reason why industrially "Azeotropic Distillation " (with Benzene as an entrainer) is used to separate them is their "relative volatility" is very low. Which means to make glacial AA you would need large number of contacting stages - i.e. very tall column and very high reflux ratio -i.e. very high energy input. Hence when an entrainer like benzene is used eventhough it means 2 distillation columns the over-all fixed as well as operating cost is significantly lower.

gsd

[Edited on 9-10-2006 by gsd]
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[*] posted on 9-10-2006 at 07:52


Using SOCl2 to dry acetic acid is not only pretty stupid considering how precious SOCl2 is, but is also very difficult. You would first have to measure the H2O concentration to calculate how much SOCl2 you need. If you add too much you will form acetic anhydride as well. Next, you would have to remove SO2 and HCl from the so dried acetic acid, which is nearly impossible by easy means. SO2 may be removed to some extent by vacuum, but HCl will stay in solution. One way would be to use anhydrous AcONa and then distill, but what a waste of time and precious chemicals just to get something so cheap like acetic acid!

Edit:
And consider that you would need almost 700g of SOCl2 to dry just one liter of 90% acetic acid!

[Edited on 9-10-2006 by Nicodem]




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[*] posted on 9-10-2006 at 10:27


What?
Nobody mentioned freezing out the bulk of the acid, pouring off the water/ acid mix then re melting the purified acid. (Of course, you can always distill the wet acid that you pour off).

I'm pretty sure that someone here would gladly swap a litre of GAA for 700 ml of SOCl2.
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[*] posted on 9-10-2006 at 10:33


ok, I`ll bite *sigh* What is so special about this SOCl2?



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[*] posted on 9-10-2006 at 11:31


To me SOCl2 isn't that exotic... You see, what I _need_ is GAA, not SOCl2, hence I'm not stupid for that reason. I would've been stupid if I needed AcOH and somehow spent it to acquire SOCl2, which I don't need. Makes sense, eh?

Moving on: I titrated my presumably wet acetic acid, and came to the conclusion that it's still of high enough concentration (18.5 mol/L) to be used for my purposes.

Anyway, thanks for the replies folks... You were great.


- Furch
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[*] posted on 9-10-2006 at 16:00


Quote:
Originally posted by Furch
To me SOCl2 isn't that exotic... You see, what I _need_ is GAA, not SOCl2, hence I'm not stupid for that reason. I would've been stupid if I needed AcOH and somehow spent it to acquire SOCl2, which I don't need. Makes sense, eh?


Anyone who can obtain thionyl chloride can also get glacial acetic acid, it's strange that you can't, which raises the question how the hell you got your hands on SOCl2 in the first place. One who thinks that this is a good idea shouldn't mess around with large quantities of chemicals as dangerous and nasty as thionyl chloride, esp since operations with it easily get out of control.

Quote:
One way to go about the problem is to perform an azeotropic distillation, but I can't do that.

As we all know, SOCl2 reacts more or less violent with water, forming HCl and SO2, which are poisonous gases... That's not a problem for me however.



Let us hope that you won't hurt any innocent people...

[Edited on 10-10-2006 by Sandmeyer]

[Edited on 10-10-2006 by Sandmeyer]
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[*] posted on 9-10-2006 at 16:57


Hello Sandmeyer.

I got rather offended by your post. Usually I don't bother answering people who actually make an effort trying to insult me (I know, I know, you're going to claim that it wasn't your intent etc.), however this time I will.

First of all... In case you didn't notice, I brought this topic up for discussion before even considering starting to experiment with it. So I have no clue as to where you got the idea that I thought of it as a "good idea".

I don't know where you are situated, but in my country thionyl chloride is a lot less restricted than glacial acetic acid. Trust me, I know. You want to know where I got my SOCl2? I bought it from a chemical supplier. The very same chemical supplier that denied me to purchase glacial acetic acid, on the grounds that it is restricted for individuals to posess it without a special permit from the authorities.

Stop being an ass just because you haven't got your facts straight, Sandmeyer.

Also, stop hurting innocent people.


- Furch
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[*] posted on 9-10-2006 at 17:17


Sorry if I insulted you, I'm in a pretty bad mood today due to some personal stuff. I just can't belive that you can buy SOCl2 and not acetic acid, it sounds too absurd to be true. If you're gonna work with SOCl2 in appartmant and simillar (not reccomended), be prepared that nearby metal objects can and will rust - it seems inevitable, but trap must be used to prevent this somewhat. Only an asshole will lead these reaction fumes outside - neighbours will definitly notice. It is enough to simply open the flask briefly to stink up the whole room, doing reaction with such amounts is something to avoid, and trap is a must.

[Edited on 10-10-2006 by Sandmeyer]

[Edited on 10-10-2006 by Sandmeyer]
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Furch
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[*] posted on 9-10-2006 at 17:47


Thanks for the tips, Sandmeyer!

Indeed it is quite odd... I was amazed myself to find AcOH not being OTC here. It's got the same restriction as concentrated sulphuric- and nitric acid...

I work in a more or less well equipped lab with great ventilation... However that's a good point you're making, about the smell and health hazard concerning my neighbours.

Anyway, I've got my GAA now, and I didn't have to use SOCl2 on it, fortunately... Though I might give it a try in the future just for the science of it, on a microscale of course.

You've got my respect, Sandmeyer!


- Furch
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[*] posted on 9-10-2006 at 19:15


..........One way would be to use anhydrous AcONa and then distill,..............

I can attest to this , however your flask will be severily damaged. Found this out the hard way!


............. but what a waste of time and precious chemicals just to get something so cheap like acetic acid!..............

Last I checked was $5.40/liter by the jug for the RA, ACS, Glacial Acid.

.................. in my country thionyl chloride is a lot less restricted than glacial acetic acid. Trust me, I know..............

Strange laws, I quess, in some countries these days!

................... you can buy SOCl2 and not acetic acid, it sounds too absurd to be true....................

Yes, it does. Even high purity CH3COOH is like water availability in the chemical industry.
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[*] posted on 9-10-2006 at 19:54


HI all,

I once left a glass of vinegar in a hot room for 2 months. After that time i got some crystals at the bottom.
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[*] posted on 9-10-2006 at 22:31


Quote:
Originally posted by scientistfromdarkness
use molecular sieve


:o

What Molecular sieve will seperate Acetic acid and water?

[Edited on 10-10-2006 by KingKarloff]

[Edited on 10-10-2006 by KingKarloff]
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[*] posted on 9-10-2006 at 23:01


Quote:
Originally posted by bio2


............. but what a waste of time and precious chemicals just to get something so cheap like acetic acid!..............

Last I checked was $5.40/liter by the jug for the RA, ACS, Glacial Acid.

.................. in my country thionyl chloride is a lot less restricted than glacial acetic acid. Trust me, I know..............

Strange laws, I quess, in some countries these days!

................... you can buy SOCl2 and not acetic acid, it sounds too absurd to be true....................

Yes, it does. Even high purity CH3COOH is like water availability in the chemical industry.


Note that in Forensic Investigation of Clandestine Laboratories (Donnell R. Christian) acetic acid is tagged with "No legitimate home or hobby use". Given recent changes in laws in the US, and Iraq becoming a double plus ungood War to win voters with, expect the WoD to heat up and do not be surprised if possesing or attempting to obtain chemicals so flagged will win you a trip to places you'd rather not go.
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