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Drying acetic acid

Alastair - 10-11-2011 at 09:49

So i have some 70 per cent acetic acid and i was hoping to dry it (now what i really dont get and even wikipedia didnt help my dumb brain on this is acetic anhydride. It is crystals right? and anhydrous acid is? just staggers me...and why the hell use AcOH as a name? :mad:

)

Anyway, i was making some apple pie and on that occasion dried some MgSO4 in oven (not sure about perfectly anhydrous but it became white and i covered immediately after removing from heat).

I tried absorbing water with the powder but it didnt go well, i got a white solution.
Adding it to AcOH did nothing obvious.

What i did later was disolve it in some water (some crystals did absorb H2O but it was mainly a whitish somewhat oversaturated solution). Then i added it to 70% AcOH. This was done on very small scale but in a matter of minutes i noticed some ''glaciers'' floating on top of solution, while white residue was on the bottom. I think if done on larger scale it may become an easy and very ghetto method for glacial acetic acid.

By the way, if i add minor quantities or water to disolve the floating crystals it wont be anhydrous acetic acid, right? im having real problems with its concept

[Edited on 10-11-2011 by Alastair] Typos.

[Edited on 10-11-2011 by Alastair]

Adas - 10-11-2011 at 09:57

AFAIK, glacial acetic acid freezes around 17°C. Maybe you haven't dried your MgSO4 very well. Try to heat it over 150°C.

Neil - 10-11-2011 at 10:05

http://www.sciencemadness.org/talk/viewthread.php?tid=9

ScienceSquirrel - 10-11-2011 at 10:08

Drying 70% acetic acid is going to be really hard as there is so much water in it. Most drying agents and methods are meant to deal with a few per cent of water at most. 70% acetic acid contains just over sixteen and a half moles of water per litre, in molar terms it is more water than acid!
I would suggest something drastic like distilling it from concentrated sulphuric acid which is cheap and readily available and loves water.

Chemistry Alchemist - 10-11-2011 at 10:11

On my blog page ive got a list of chemicals and there drying agent, you can check it out... pretty sure acetic acid is one of those chemicals

toothpick93.blogspot.com

bahamuth - 10-11-2011 at 11:03

Anhydrous copper sulfate is a excellent drying agent for acetic acid, though with the amounts of water you have you would need alot of it, and the copper sulfate is really hard to dehydrate, loosing the last water molecule at around 200 degrees Celsius, though in my own experience the copper sulfate does not turn completly white/grey white (indicating anhydrous state) before around 300 degrees C. and several hours at those temps.

Bot0nist - 10-11-2011 at 12:14

I agree about the copper sulfate. It is kinda a bitch to dry.

Sedit - 10-11-2011 at 16:21

Dilute with DCM and add MgSO4, Filter, after that distill off the DCM to recover crystals of Glacial Acetic acid.

DJF90 - 11-11-2011 at 03:35

You wont have crystals of GAA unless the temperature is low enough. More likely, the GAA will be a liquid after distillation of the DCM. You might want to fractionally distil your product to ensure purity...

bahamuth - 11-11-2011 at 11:47

I propose that instead of using multi-solvent approaches, dry it with a high water capacity drying agent like anhydrous MgSO4 (might even work with silica gel), distill it and dry it with anhydrous copper sulfate, giving less than 0.01% water IIRC if done properly. All substances are reusable ensuring cheapest route. If DCM or any other solvent is used one might just buy GAA analytical grade as it is dirt cheap, or even industrial grade/food grade in 25L plastic drums, which even here in Norway is as cheap as 175-200 USD and no restrictions on.

Alastair - 11-11-2011 at 12:06

Well im not in US or Norway sadly. Thank you all for great support and help! But what could the crystals have been then? Im sure there was only dH2O and acetic acid with pure MgSo4. Oh, maybe because i did it in a metal container (not aluminium but idk what metal)?

bahamuth - 11-11-2011 at 20:11

As I see it, but can not be certain, your solution of MgSO4 in water, added to your 70 % acetic acid did precipitate MgSO4 upon mixing the two solutions leaving you with "glaciers" and white precipitate in the bottom of your tube.

Acetic acid is way to miscible with water to be able to salt anhydrous(100%)/glacial(97-100%) acetic acid out of the water with MgSO4 or any salt that I know of...

As per your questions about the state the compounds, glacial acetic acid and acetic anhydride. Glacial acetic acid freezes around 16-17 degrees Celsius, giving rise to the name "glacial" acetic acid. Acetic anhydride freezes at -73 degrees Celsius. Those are two different compounds if there was any doubt. AcOH is not a name for acetic acid, it's an abbreviation. The common abbreviation for acetic anhydride is Ac2O.

Hope this helps.

Damn, had to edit spelling twice, to late need to sleep..

[Edited on 12-11-2011 by bahamuth]

[Edited on 12-11-2011 by bahamuth]

White Yeti - 13-11-2011 at 13:27

I agree with bahamuth, acetic anhydride and glacial acetic acid are NOT the same thing. One is used to make esters and the other is a highly regulated chemical used to make heroin O.o

Acids exists as "anhydrides", but be careful because following this logic, SO3 is the "anhydride" of sulfuric acid, CO2 is the anhydride of carbonic acid and NO2 is the anhydride of nitric acid etc....

Acetic anhydride is the anhydride of acetic acid because it can be hydrolysed into acetic acid.

Hope this helped.

Lambda-Eyde - 13-11-2011 at 14:57

Quote: Originally posted by White Yeti

I agree with bahamuth, acetic anhydride and glacial acetic acid are NOT the same thing. One is used to make esters and the other is a highly regulated chemical used to make heroin O.o

Both are used for making esters, it's just that acetic anhydride does the job much better in most cases. That's why it's used in production of heroin (diacetylmorphine).

Quote: Originally posted by White Yeti

Acids exists as "anhydrides", but be careful because following this logic, SO3 is the "anhydride" of sulfuric acid, CO2 is the anhydride of carbonic acid and NO2 is the anhydride of nitric acid etc....

No, dinitrogen pentoxide, N<sub>2</sub>O<sub>5</sub>, is the anhydride of nitric acid.

White Yeti - 13-11-2011 at 15:22

I apologise for mixing up a few facts, I was trying to make a point, not to supply the OP with all the information about acids and their anhydrides.

Acetic acid is used for many different things, making esters is the only one that came to mind at the time.

Sedit - 13-11-2011 at 20:41

Glacial acetic acid is a dimmer not an anhydride.

I have found the DCM method the only way to get glacial acetic acid because MgSO4 starts to loose water when you heat it and that comes over when you distill. Dilute with DCM and it becomes a walk in the park and ensures you don't lose much AcOH when adding the drying agent.

bahamuth - 13-11-2011 at 23:16

Well one way to avoid that the magnesium sulfate loses water on heating is to remove it before heating by filtering/decanting etc. This is what i commonly do, and if I want to distill a dried solvent over a desiccant of sorts, I make sure that it will keep its water at distilling temp. One way is to add as much desiccating salt that only the first water of hydration is allowed to exist, thus preventing loss of it on heating to distilling temps.

Copper sulfate loses its last water of hydration at atleast 200 degrees Celsius, way more than enough to distill acetic acid.

Think stoichiometry is the key to sucess.

Alastair - 14-11-2011 at 06:40

Quote: Originally posted by bahamuth

AcOH is not a name for acetic acid, it's an abbreviation. The common abbreviation for acetic anhydride is Ac2O.

Hope this helps.

This explained everything thank you.

Information given is awesome (and im not making heroin, get real). Do you guys know about the azeotrope of water and AcOH?

Sedit - 14-11-2011 at 09:43

Quote: Originally posted by bahamuth

Well one way to avoid that the magnesium sulfate loses water on heating is to remove it before heating by filtering/decanting etc.

The fact that he's starting with 70% AcOH means a relatively large amount of MgSO4 will need to be used and much loss will be had hence the reason why I suggested diluting with DCM. It distills quickly and cleanly. Also as an added bonus he should have two layers at the start so he will know that the drying agent is having effect as the water water later goes away.

bahamuth - 14-11-2011 at 10:43

Don't they have search engines in Bat Country?

This is such a common problem that using goggle will give you a couple good hits on "acetic acid water azeotrope" or the similar.

Me, I found azeotrope data on wiki, and discovered there is no azeotrope between the two compounds in question, but rather a zeotrope. Wiki Link

And since "we" now know about the azeotropic nature of acetic acid:water, what did you really want to know, specificity is the key to proper spoonfeeding

PS. If you are going to quote keep it proper, as half your quote in your last post is mine and half is your own post.

PSS.

Quote: Originally posted by Sedit

Quote: Originally posted by bahamuth

Well one way to avoid that the magnesium sulfate loses water on heating is to remove it before heating by filtering/decanting etc.

I've never tried the DCM route, though I agree it sounds quite easy if you have small amounts of acid to dry (separating funnel size depending..?). But for someone that isn't able find in the litterature the drying agents and reasoning which ones he could/should use might not have DCM at hand.

Me myself has always used textbook drying agents and they usually work quite well.

Guess that the total volume of the 70 % acetic acid:water solution he wants to purify is something to consider when he decides on the approach.

Alastair - 15-11-2011 at 03:39

Hey bahamuth, thanks for being a buttock, i hope it feels good to have been born knowing every goddamn thing on earth and being so much smarter than everybody. If i am offended by a question i dont answer it. Unless it makes you happy to speculate how smart somebody is and dramatize over spoonfeeding, just ignore my posts, thank you.

Panache - 16-11-2011 at 09:27

dcm by itself azeotropes about one percent water with it. I think that's why sedits solution is so effective. By itself the mag sulphate is not known to effectively dry AA, however by diluting into dcm removing most of the water with mgso4, then distilling the dcm this removes the final portion of water leaving you with dry enough AA to crystallise readily in a cool place.
Having produced dry AA from vinegar by going down the acetate route I known how difficult aa is to dry. I would listen to sedit, dcm is generally widely available, easily distillable from a warm water bath using any old polyolefin vessel (read plastic bucket with snap on lid) and non flammable.

kmno4 - 16-11-2011 at 09:48

I am going to try this "DCM methode", because it looks very unusually - I do not think if it works at all.
But experiment is king.
First - I have to prepare 70% sol. from my pure acetic acid....
We will see

Panache - 19-11-2011 at 08:10

Quote: Originally posted by kmno4

I am going to try this "DCM methode", because it looks very unusually - I do not think if it works at all.
But experiment is king.
First - I have to prepare 70% sol. from my pure acetic acid....
We will see

Me too!

Sedit - 19-11-2011 at 11:23

Why does it seem odd?

The DCM is just a low boiling point solvent to minimize loss when adding the bulky drying agent. Im sure other solvents can be used as well but DCM is ideal for its rapid removal.

[Edit]

Water does not mix with DCM and yet AcOH does... Look at the other thread for salting out AcOH where I performed many experiments on the synthesis and extraction of AcOH. Its easy.

[Edited on 20-11-2011 by Sedit]

kmno4 - 21-11-2011 at 09:17

I have just made simple experiment with extraction of acetic acid with DCM + MgSO4.
Titration of evaporated extract gave 95% of AcOH. Not large amount of MgSO4 was added, just to see that it works at all.
Amazing, but it really works....

Sedit - 21-11-2011 at 11:11

Seems like you need more MgSO4 and a trip to the freezer afterwards to get the full glory of Glacial acetic acid crystals

70% AcOH I assume you started with correct?

And for my next trick I will be adding 800 plus some odd grams of NaOAc hydrate to Sodium Bisulfate and slowly allowing it to cool so that the Sodium sulfate can form the decahydrate. Then I will filter and wash the precipitate with DCM and add this to the resulting solution for further drying.

Quick cheep high yielding. It go so typical hence the reason I started to look into ways to quickly oxidize EtOH to AcOH and got great results there as well meaning soon that cheep gallon of EtOH in the store will be a cheep gallon of GAA with only a small investment in semi-reusable reagent.

[Edited on 21-11-2011 by Sedit]

kmno4 - 21-11-2011 at 14:06

Yes, it was 70% solution.
Fortunately I do not have to play with preparing of acetic acid.
In my country it is inexpensive and available without problems (including "glacial" version of course).
I was doubting that it is extractable with DCM, but indeed it is

Sedit - 21-11-2011 at 22:04

Yup, I have references in another thread around here that details that Acetic acid can be directly salted out of highly aq solutions using various salts and liquid/liquid extraction. This is sort of a variation of that but the MgSO4 just down right drys the AcOH. Potassium Sulfate IIRC has the highest potential in the reference to force AcOH out of the (aq) phase into the organic phase.

Its rather neat chemistry when you get down to it but if you already have concentrated AcOH like 70% then no need for all that as its best to just dilute it with a Nonpolar solvent as you have seen and dry the mixture. It can be done neat without the DCM but the overall bulk of the MgSO4 gives to much loss.

Glad to see my results where repeated with ease, I would have hated for this to turn into another one of the Nickle separation threads where everyone had trouble duplicating my results

Alastair - 22-11-2011 at 07:37

Now thats something

You guys really diluted GAA just to try this? Seems like a human sacrifice to me

I will surely try to get DCM but imo my country is not familiar with it (never seen it anywhere for any use, maybe only small amounts for dentistry)

Bot0nist - 22-11-2011 at 08:30

DCM is easily distilled from many common paint strippers. Look for the non-flammable kind that have a good fraction of methylene chloride in them. Methylene chloride = dichloromethane = DCM of course.

Sedit - 20-12-2011 at 20:06

I lost my scale so I made a quick attempt just to show its possible to get GAA without distillation I might add. I could have distilled but I did this because I have been observing it through the various steps.

Best to just add the MgSO4, mix with DCM and heat so that the DCM and AcOH mixture comes to the top where it can be separated with ease. Distill off the DCM and toss the remains in the freezer. The impurities will separate out. Thawing and refreezing will yield an increasingly pure product. Its not needed as a simple distillation would be simpler but like I said I was observing and playing around as I went along. It killed any good yields but gave me the information I needed to share so its an even trade.

You can see due to the discoloration from my H2SO4 used in the process that the AcOH moved to the DCM after the MgSO4 was added. I filtered, distilled off the DCM, and froze the remainders where the impurities could be filtered off which you see in the third and forth pictures. It is by far the simplest method for drying Acetic acid I have found. Trying to do it neat with a drying agent always caused to much loss. That is no longer and issue and neither is the water that comes when MgSO4 hydrate is heated.

I got more photos but Im still playing with the product at the moment trying to see where I can get before I distill the AcOH so when im all done I will post a picture of the purest GAA I can get.

Alastair - 21-12-2011 at 13:20

I finally travelled a little and bought pure GAA :cool:

I still cant find much DCM used anywhere, i guess this way is off limits for me.

Sedit, i think you should make a new thread with your method as it deserves it for simplicity. Im still missing something. If H2SO4 was in the mixture, how did you remove it?

Sedit - 21-12-2011 at 16:31

There might have been a little H2SO4 in the mix but I doubt it. I quickly prepared the Acetic acid using Sodium Bisulfate and NaOAc with a little H2SO4 to get the reaction started. This was allowed to settle and then the fluids where filtered from the remaining Sodium sulfate hydrate. This was just done to quickly prepare some (aq)AcOH and if I had my scale would have been a more complete writeup.

Any organic solvent would do as long as you have a means of separation, I use DCM due to its relatively low BP and ease of acquisition. I suspect you are not looking hard enough for Methylene Chloride.

If one had 70% AcOH is would be very simple to Dilute it with DCM, Add MgSO4 or another drying agent until its dry and filter. Removing the DCM will give you GAA.

Im working on the oxidation of EtOH using Nitric acid so a viable route to separation needed to be found. It will make GAA cost around 30$ a gallon or so and cheeper following reactions.

[Edited on 22-12-2011 by Sedit]

MagicJigPipe - 21-12-2011 at 19:46

Quote:

to show its possible to get GAA without distillation I might add.

Quote:

Distill off the DCM

?

Also, Sedit, where do you live again? Why can't you get better H2SO4?

Sedit - 22-12-2011 at 00:49

I can get better H2SO4, but at walmart is is about 10$ or so for a jug of it where the 97% clean H2SO4 I get at my local supplier is about twice that if not more, much more then Im willing to spend when cheep H2SO4 or ultra cheep Sodium Bi-sulfate are able to do the job just as well.

I was inspired by you matter of fact, in an old thread where you and if my memory does not fail me, Madscientist discussed the financial factors that come into play when synthing Glacial acetic acid. I have found it not only cheep but easy this way. Performing the acidic oxidation of EtOH with some skill may yield me much closer to my ultra cheep goal then acid + NaOAc routes.

Make the (aq)AcOH using cheep acids and cold filtering and dry using DCM and MgSO4 or dehydrated Sodium Sulfate if your cheep as shit.

MJP, Yes my statements seem contridictory but understand I never distilled the AcOH, only recovered my DCM which would have been just the same as evaporating on an open tray if one wanted to waste. I do not have the desire to waste DCM even if it is easy for me to get. It goes against my monetary aspects of the synthesis.

[Edited on 22-12-2011 by Sedit]

entropy51 - 22-12-2011 at 18:53

If Sedit's dichloromethane extraction and MgSO4 drying method does work, it would probably be efficient to start with photographic stop bath which is about 88% acetic acid. The stuff I buy is shipped as a consumer commodity without any hazardous material charges. It contains bromothymol blue indicator, but this is easily removed by a quick distillation.

I would like to try Sedit's method on this material sometime soon myself.

Sedit - 22-12-2011 at 19:36

Entropy that's great to hear, its rather straight forward and works just as one would expect. The MgSO4 drys it, it just takes a lot more of it then one normally uses to dry things. If needed you could calculate a good estimate of how much MgSO4 would be needed with ease. I'm also sure further drying could be done using anhydrous CuSO4 if needed.

I'm going to try using a solid bed of Anhydrous MgSO4 next time so that separation is a snap.

It works as advertised I mean hell, I tossed together that Shitty AcOH and dried it to crystalline glacial acetic acid in no time. It stayed crystalline in 60 degree weather and never thawed. That brings me to my next point, why the hell is it 60 degrees outside a couple days before Christmas that's just messed up.

Bot0nist - 22-12-2011 at 19:50

"why the hell is it 60 degrees outside a couple days before Christmas that's just messed up." -sedit

Agree, 58F as a low here tonight. Not seasonal at all. My papavers are loving it though. Love the workup, BTW. Entropy, could you post or u2u me ur source to 88% ORM acetic acid?

[Edited on 23-12-2011 by Bot0nist]

Sedit - 22-12-2011 at 20:05

Rereading my post I want to make sure everyone knows what they are seeing in those pictures so there's no confusion down the line.

1: bottom layer is (aq)AcOH saturated with Sodium Sulfate, top layer is DCM.

2: Bottom layer is MgSO4, top is DCM/AcOH.

3: In the upside down flask is frozen GAA and in the bottom jar is the contaminates that was separated by what is basically cold filtering.

4:Glacial acetic acid in a filter.

Good luck, you probably will not need it as its simple but best of luck anyway. I would hate to have to end up trying to figure out how the hell something I have been doing works again just to prove it

Acetic anhydride or what???

Sedit - 27-12-2011 at 14:35

Um... Guys can someone help a bit and give me an explination to what I'm seeing here...

I left some Acetic acid/DCM mix over CaCl2 to dry for a couple days. When I distilled it what remained in the flask smelled a little funny. Its highly contaminated AcOH left over after removing the DCM but this smell was odd. Almost like burnt Acetic acid if I had to describe it.

So I placed a couple small drops onto a watch glass and ignited it. It slightly burned with a faint greenish flame at the bottom. When dripped into cold water it sank to the bottom yet created an emulsion look of sorts.

If there is any DCM left it is surely not enough to cause it to sink like this and only trace DCM at best. DCM is also not flammable.

What the hell is going on?

I'm freezing it right now and going to cold filter it as before and test the liquid portion I normally toss back into the stuff to be processed.

[Edited on 27-12-2011 by Sedit]

Sedit - 29-12-2011 at 14:27

I have ruled out the possibility that the oily liquid is just trace DCM left over. The density of the liquid is denser the distilled H2O yet appears less dense the a saturated Sodium sulfate/MgSO4 floating on top of the solution. I personally am at a loss as to what it can be because it does not react with H2O the way i would expect it to. I am going to remove the acetic acid and then reflux it with a few drops of water to see if more AcOH forms. It appears that this post is not getting any attention so i may move it to the AA preparation thread to try and get more answers.

entropy51 - 29-12-2011 at 18:47

Well Sedit, if you think it's Ac2O, measure a boiling point. Ac2O clocks in at about 140 C.

Sedit - 29-12-2011 at 19:25

Im going to soon maybe even tonight. Im only getting small amounts of it off of each extractions and until the other day I never thought much of it to be honest. I just thought it was tar but the materials I used to make the AcOH should not produce this amount of crap. It was NaOAc from instant hot packs and Sodium Bisulfate with only a small amount of H2SO4 added to get the reaction started. It was never really heated either so there is no real reason there should be this amount of left over organic material.

I highly doubt its Acetic anhydride but honestly im at a loss as to what it might be. I always figured it was just trace amounts of DCM left over that was being removed when I froze the GAA and let the impurity run off. It wasn't until I set it on fire that got my mind really wondering what it could be. I know Sodium Sulfate is a powerful dehydrating agent when cold but I just can't see it being strong enough to dehydrate AcOH. Could there be a possibility that the DCM is aiding this some how?

When the kids go to sleep I will try to get an accurate measurement of the BP to give me a better idea what it may be.

Sedit - 29-12-2011 at 21:39

Boiling point has so far topped out at 60 degrees C, well below Acetic anhydride.

However, Due to the way it is boiling, the bumping and other factors that I have taken note of though the years I am sure that a lower Boiling point material is being released right now and there is a higher boiling point material waiting in the midst. Since I currently have nothing small enough to distill this minute quantity of material I will have to put on my engineers hat and get cracking on a micro distillation setup for my test tubes.

I already have something in mind and it should only take me an hour or so to rig it up so ill keep you updated.

Can DCM react with H2SO4 or Sodium Bisulfate creating some sort of substituted methane? Just curious.

UnintentionalChaos - 30-12-2011 at 12:34

Is your DCM pure or was it distilled from paint stripper containing methanol? If the latter, perhaps chloromethyl methyl ether is something to look into.

Sedit - 30-12-2011 at 12:59

Its distilled from paint thinner containing Toluene, MeOH, DCM and some waxes. I capture the DCM in water and wash it a couple times before drying it and redistilling it so I doubt there is any Methanol left in the mix. Once upon a time I had trouble with Toluene coming over as well but I have found a nice slow distillation at the end to remove the toluene from the Methylene Chloride.

I'll look into the properties of the ether because that is something that struck me about it in that it did have an almost etheral smell to it but not quite so. Im going to distill it later and see if there is any other fractions hiding down there.

Adas - 30-12-2011 at 13:13

AFAIK, DCM is flammable. And I think this may describe the greenish colour of the flame, but I am not certainly sure.

DJF90 - 30-12-2011 at 13:20

You best hope that its not chloromethyl methyl ether - its a potent carcinogen!! I'm a little confused as up there you say you was using CaCl2, then you mention sodium sulfate?

Quote:

I left some Acetic acid/DCM mix over CaCl2 to dry for a couple days.
...
I know Sodium Sulfate is a powerful dehydrating agent when cold but I just can't see it being strong enough to dehydrate AcOH.

I know that CaCl2 can be used to form acetyl chloride from acetic anhydride, but yields are terrible and long reaction times are required. I don't believe CaCl2 can effect the transformation of acetic acid to acetic anhydride.

Bear in mind ethyl chloride burns with a green flame. maybe DCM does too, albeit reluctantly.

[Edited on 30-12-2011 by DJF90]

Sedit - 30-12-2011 at 13:27

Iv ruled out DCM all together, it has been exposed to prolong heating long enough that any DCM left is gone. The flame isn't completely green its just at the base of it that it shows green.

Im just going to have to distill the mixture and test it again. Its an anomaly nothing more at this point. Im just curious as to what it might be.

Sedit - 2-1-2012 at 21:02

Well I told you I would figure something out to distill this stuff and indeed I did. I was kind of surprised by what resulted. There are at lest three fractions with distinct BPs. One was the initial BP I already mentioned, there was a 72 degree C fraction that came over as a milky oil that showed the flammability traits I was seeing, there was a second fraction that was also flammable but this could just be due to carryover from the first fraction which boiled at 97 degree C and what remains in the test tube right now boils at 120 degrees Celsius. What is striking me as odd is the smell of mainly the first fraction. It smelled exactly like DMSO. The last fraction smelled similar but more like acetic acid and the DMSO smell is more then likely just due to the crude distillation attempt and small scale causing carryover of the various fractions.

What the hell could be the DMSO smelling stuff. I honestly feel somehow the Dichloromethane underwent some sort of minor chemical reaction yielding these contaminates. I do not know what the hell they are so I am a bit leary about reporting anymore smells and what not about them.

I highly doubt its acetic anhydride in any amount so quite honestly im more then likely just going to toss the stuff before it becomes a nuisance. I already feel like its decreasing my yields so Im not at all happy that its there because I have to not only clean it from my GAA but It more then likely also decreases the solubility of my AcOH in the DCM making it an even greater pain in my ass.

I must not allow curiosity to side track me this time even though I do want to know what the hell this smelly contaminate is.

Neil - 3-1-2012 at 06:07

Pictures? While I have no insight into what is going on, I am finding your ordeal intensely interesting.

Sedit - 3-1-2012 at 06:42

I was going to take pictures but theres nothing really interesting about it, just some vials of clear liquids(the first fraction was mlilky but you get the point). The other pictures I already uploaded show the material I am distilling. The brown stuff being caught in the jar in the third picture is the stuff I'm now distilling. I always assumed it was trace DCM or wet Acetic acid so I would toss it back in for the next pull not realizing it was something else all together.

I find it interesting as well but I also don't really see any ideas as to what it may be and as such I could find myself wasting alot of time trying to figure out what it is. I have seen it in the past as well so its not something unusual to this run. When all is said and done I suppose I could combine all the gunk and see about identification. If I can gather more material I could perform better test in an effort to identify it.

Athiril - 19-1-2012 at 23:40

With simple distillation to get to higher percentages, you could just use ethyl acetate to lower the water boiling point drastically, then just drive that off, then use a small amount of drying agent.

In any case, with the copper sulphate drying, how are you going to filter that? Shouldn't dissolve a fair bit of the paper filter into cellulose acetate?

Sedit - 20-1-2012 at 11:42

Use fritted glass. I find it to filter better anyway since it does not seem to stick to polar solvents like paper does. I normally just stuff fiber glass into the stem of funnels anymore as i like the way it filters over paper.

Fantasma4500 - 17-4-2022 at 08:56

okay- old thread
but a returning issue
i see DCM mentioned here, thats rather difficult to get to in europe nowadays
so i came across a study mentioning using other solvents
i went ahead and tried it with my hexane-heptane gasoline fraction. it was difficult getting data on density since acetic acid is quite damn similar
i used 32%
unfortunately it gave me basically nothing, i shaked it quite vigorously and used seperatory funnel, then i distilled off the solvent- in this picture it does describe quite low concentrations, i didnt bother with higher boiling fractions since theyre just an pain in the ass- however if they can extract it, acetic acid would distill off first? must have extremely low solubility if this didnt work
https://gyazo.com/66e97a7b79f832855b17a733a859988e

i guess the only feasible method is to use H2SO4 to dry out high concentration acetic acid- or conc H2SO4 (or NaHSO4 with sodium acetate, silly me)
if HAc is used from start, the H2SO4 is merely gonna hold the water and it should be doable to evaporate out the water and a bit of SO3 +70% inside of a flask, with a hose attachment leading into a bucket of CaCO3 rocks or similarily a funnel-gas trap to prevent suckback

i used 150mL of organic solvent for about .. 87mL of 32% HAc, only minor hint of HAc in the solvent, so little bubbles forming with Na2CO3 that im not even sure that they did form from a chemical reaction.