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entropy51
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| Quote: | | Sounds so good in theory don't it? But reality does not always run according to theory. Never once was I able to achieve glacial statues on the first
run |
I have to agree with Sedit on this one. I've done this dozens of times. At the temperatures required for the distillation the H2SO4 decomposes the
acetate and the distillate does indeed contain 2 - 5% H2O. This is the reason that all the published methods for this prep say to fractionate the
distillate through a column.
I say this based on titrating the distillate, not on your CaCO3 test, though it sounds reasonable.
I just tried your CaCO3 test on some 96% that had not been redistilled. No bubbles. It required more than a drop or two of H2O added to produce
bubbling. AcOH is a weak acid, not highly dissociated in concentrated solution.
I'll stand by a titration any day.
[Edited on 5-11-2009 by entropy51]
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S.C. Wack
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As has been said before here in the relevant thread, vinegar is full of not-acetic-acid-or-water. Purification of either calcium or sodium acetate
made in this way from the concentrated organic crap requires some wasteful recrystallizations. You need good stirring to avoid hot spots on addition
of acid, and the best way to make this easier is to use a diluent such as...acetic acid...acid-washed oil, whatever.
[Edited on 6-11-2009 by S.C. Wack]
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Sedit
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Point made S.C thank you.
For anyone looking for only a few ml of AcOH then just do as a freind told me as it works quite well. Put the stove on a low heat with your Vineger
and add salt until no more will dissolve. Its at this point you add IpOH. The isopropyl alcohol will seperate itself as the upper layer and yeild a
mixture of acetic acid and IpOH.
the IpOH forms an azeotrop with water and careful distillation will take out the remaining trace amounts of water and the AcOH dimmer can be distilled
at a later time.
If all else fails at this point just add some dry MgSO4 to make damn sure its dry before you distill and you have a "cheap" way to about 100ml of GAA
albeit with a messload of bulk associated with it.
[Edited on 6-11-2009 by Sedit]
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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Panache
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Apologies for my simplifications, they were not intended to cause confusion.
Firstly i should have said 'just buy dilute acetic acid solution'. In australia this manifests itself as 'no name' or home brand white vinegar. It is
not a fermented product its just acetic acid in water.
Titrations are better than my quickie CaCO3 suggestion of course, there's no question of that.
As for this not working very well the first few times you try it or 'never at all' unfortunately i would have to say generally things get better as
you do them. I don't believe you think glacial acetic acid cannot be produced by anyone anywhere with only H2SO4, sodium acetate and sodium hydrogen
sulphate. If you are i would have disagree with you.
People must appreciate the patent literature for what its for. Its not peer reviewed, it has a completely different set objectives to that of journal
articles. It aims to exaggerate how difficult life is without this new bell and how well and good life could be if only everyone had one of these
bells. It generally also concerns itself with how one would go about making 500,000 of these bells. I appreciate 'hotspots' would be a real concern if
doing these things on a multi tonne scale but in a sedate 1L flask i think it's manageable.
Sure fractionating it would be more ideal, but really i can't see the problem.
And yes i have done it, both with acetic and propionic acids, however the latter is less problematic to get dry.
Lastly adding MgSO4 doesn't remove any water, merely binds it reversibly to another site. Works great for somethings but not very well for the last
bits of solvation water from this system. The acetate does not decompose below 150, so use an oil bath for the distillation if you're having trouble
regulating temperature and never let it go past 150.
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Sedit
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"Lastly adding MgSO4 doesn't remove any water, merely binds it reversibly to another site. Works great for somethings but not very well for the last
bits of solvation water from this system"
Try it. Its about the only way to get decent yeilds out of H2SO4 of Bisulfate methods. Everything else is just spinning your wheels and waiting for
your heating mantal to reach that high temperature.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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JohnWW
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What sort of impurities does naturally-brewed vinegar contain, i.e. other than acetic acid and water? I would think that propionic acid,
propionaldehyde, acetaldehyde, ethanol, n-propanol, and sodium and potassium acetate, would be most likely. There could be traces of butyric acid,
butyraldehyde, n-butanol, formic acid, formaldehyde, and methanol, the last three being toxic in larger amounts.
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entropy51
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| Quote: | | I don't believe you think glacial acetic acid cannot be produced by anyone anywhere with only H2SO4, sodium acetate and sodium hydrogen sulphate. If
you are i would have disagree with you. |
I would appreciate it if you would post your procedure in detail
then. I will quickly become a convert to your point of view if it works as well as you imply!
My opinions are not based on patent literature, but on dozens of experiments I have tried over several years.
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Panache
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I would appreciate it if you would post your procedure in detail then. I will quickly become a convert to your point of view if it works as well as
you imply!
I already did in a post in this thread on the previous page. Some finer detail though. Do grind the acetate and sodium hydrogen sulphate together in
stoiciometric ratios until you have a very fine intimately mixed powder that has begun to smell of acetic acid and is beginning to appear damp. The
sulphuric acid is really just to act as a solvent of sorts and as a heat transfer agent. I find it doesn't heat up the powders very much when added. I
just cover the powder with enough.
Additionally i use a vacuum, this helps enormously but it is not important whatsoever as i used to never use a vacuum. It speeds things up. i use a
stillhead vertical setup for this one. I intially have the conc sulphuric in the stilhead resovoir. that way everything can be assembled and the
sulphuric run in and the system run under reflux for a time before taking a your acetic acid. The vacuum negates the need for a drying tube however if
not running under vacuum do use a drying tube.
Is that enough detail, i only did this over the weekend so i have it fresh in my memory, previous to that i hadn't done it for some 18months.
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entropy51
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Thank you, Panache. Could you give your mass ratios, please? They might be critical for getting honest to goodness glacial AcOH? I've found this
prep to be fairly tricky! Thanks again!
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Sedit
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I was running pretty much the same exact thing Panache and it always worked fine on smaller runs but when I tried to scale up to get larger amounts it
was just one problem after another and I later just went to mixing them "wet" as a paste and distilling. I would then allow the distillate to clear up
because it would always be cloudy yet after a day or so a scum would form on the surface leaving a clear distillate.
Addition of MgSO4 in liberal amounts and left over night would suck up the last of the H2O and a quick filtering and redistilling over fresh MgSO4
would produce clear dry acid.
I always found the main issue to be heat transfer and over heating more then the reaction itself. Thats the reason I started looking into ways of
recovering AcOH from aq solutions.
This is one of the few things I did keep pretty detailed notes of and if I manage to fine the notes as Im attempting to recover all my files from a
failed hard drive I will post some better details.
Entropy getting NaOAc fully dry is a bitch so there is a good possibility that is where the water was comming into the equation. Whatever the cause I
suggest for anyone to just pass the distillate over dry MgSO4 and not mess with the fuss of trying to get GAA in one pass. It produces a cleaner
product that never has the harse sulfur oder that dry distilling produces.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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Panache
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my supermarket now sells molecular sieves, i guess these should do a pretty dandy job also.
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entropy51
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| Quote: | | Entropy getting NaOAc fully dry is a bitch so there is a good possibility that is where the water was comming into the equation. Whatever the cause I
suggest for anyone to just pass the distillate over dry MgSO4 |
Sedit, drying NaOAc is not that difficult,
just not any fun! Drying in a vacuum dessicator over silica gel removes about 2 molecules of H2O by weight. Melting carefully with constant stirring
removes another molecule; it seems to be nearly anhydrous based on H2O loss. I also have the real stuff that I can use for check runs and I see no
difference in H2O content of the AcOH that distills.
My experience is that attempting to dry wet AcOH on MgSO4 doesn't dry it significantly, based on titrating the AcOH before and after. But I'm glad
that it works for you.
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Sedit
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I have enough NaOAc to attempt another run to document to show my process but it may be a while since I have alot going on at the moment and my camera
is missing as well but first chance I get I would like to go indepth with both methods as a means to compair yeilds. I want to do the extraction from
an aq solution using DCM and I will rerun another Sodium Bisulfate and NaOAc. From the initial test I think that the aq extraction is going to prove
higher yeilding and cleaner then when using acid on NaOAc.
PS: The MgSO4 works best if you let it sit there for some time possibly two days in a closed container. At that point you will see the MgSO4 not only
clumped up but some will be in needle like crystals precipitating out showing that it absorbed ALOT of the water now completly locked away as the
hydrate.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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Sedit
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Materials
300ml 5% AcOH Saturated with NaCl.
70ml of 70% IPA saturated with NaCl.
Procedure
Mixing of the two solutions showed no seperation of layers and after extra NaCl was added it still showed only slight signs of seperation.
MgSO4·7H2O was employed to further saturate the solution some more to aid in seperation. Obviously Anhydrous MgSO4 is more desirable but I used it
all up and have not made more yet.
This proved effective and approximately 20ml of IPA/AcOH seperated out of the 370ml mother liquor.
Mild tragedy strikes as 1 single drop of water fell into the 20ml after washing the other glassware and having a single drop fall into the solution.
Should not be to much of an issue though considering that it should form an azeotrop with the IPA and leave as im burning it off.[note 1]
I ignited the 20ml in a Stainless Steel container nestled in an icebath and allowed it to burn out(I feel a bit premature due to the wind)to yeild
7.5ml of slightly yellow liquid with faint hint of IPA.
This was placed in the freezer till chilled to no avail so it was once again taken outside and ignited.
This left me with a mixture that would no longer ignite at about 4ml of now much darker colored liquid.
Placing this in the freezer for only a couple minutes it was obviously much thicker consistancy then before and was simular to thin cough medicine or
a thick sugar solution clinging to the sides of the test tube.
It still failed to crystalize on refridgeration.[note 2]
Notes
1: This is obviously not the best way to go and distillation is the prefered methods but Im just running a fun small test and did not feel like
getting that involved. Plus it proves a point in that it will cease to ignite once the IPA leaves the system.
2: I would thing it be prudent to add anhydrous MgSO4 and filter prior to distillation.
Discussion:
Well it all pretty much came out of a fit of bordem since I was off work and had the house to myself for a change which left me with an itching desire
to do something but since I live in bumblefuck without a store to even go to for a few miles I decided to see what I could play with. I wanted to see
if it can be done and to what effect could be yeilded from such a dilute solution. 4ml of not quite anhydrous, or more probable tainted with IPA,
Acetic acid sounds pretty bad but basing it more on the idea of how much a given amount of IPA will extract for a given volume does not work out
extremely bad given the extreme dilution of the starting solution. Also since only a single extraction instead of the prefered two maybe three shown
from previous experients means yeilds could atlest double if not more. I will more then likely not partake in another attempt to extract such a dilute
solution again but I do feel confident from the experiment and those prior that a bottle of IPA and a gallon of 5% could yeild about 150ml of Glacial
acetic acid if one where determined enough. I perhaps will attempt this one day just for shits and giggles but more then likely not for a while since
I want to focus more on concentrated solutions.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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Panache
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Ok i tried this today using ~600g of calcium acetate and i now understand what sedit and entropy were talking about, nothing happens, well that how it
seems it goes so painfully slowly. In all the damm thing took 10hrs to distill over the ~450mL (and no i have as yet not titrated it). Made me think
this would go so much better with a carrier gas instead of vacuum but you have all those issues of ensuring you manage to condense it out. Anyway at
about the 7hr mark i suddenly realise this would go infinitely faster on the roto vap, every if i allow for the tedious drying of it. Anyway i have
now replaced the 500ml bottle of glacial acetic i dropped earlier in the year, it can sit with my other stuff until i manage to drop it again in a few
years.
IMO using NaAcetate is better than the calcium, albeit the calcium is reportedly easier to dry, i find both salts dry wonderfully well in a convential
microwave, they don't appear to have much of a cross-section for the adsorption of the frequencies used in conventional ones, which i believe are
tunned to water (and thats why feathers don't heat up in the microwave, unless they are wet). Once the water has left you can run the microwave
forever and the only thing that happens to the salts is they cool down, even through 'heating'. During drying i tend to open the door every thrity
seconds and blast it with compressed air to remove the after vapour as the fans in microwave are pathetic. In all it took some 15minutes to dry the
600g of Ca acetate i used, which beats the shit out of oven drying. I acertained the dryness by placing some in a dry cold testtube and heating until
redness. if there is hydration water remaining you can clearly see it as a condensate at some point on the testtube, proved one only heats the bottom
of the tube.
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entropy51
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Panache, thanks for that tip on microwave drying NaOAc. I will definitely have to try that.
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Magpie
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I second that. This could be a good way to prepare anhydrous NaOAc for use in making Ac2O.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Sedit
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Third .
Panache, Did you use Bisulfate to "dry" distill the AcOH out or did you use H2SO4? If you used Bisulfate I suggest adding some H2SO4 and stir it to a
slush first to aid in heat transfer or else you will have many many problems. The time issue you see is why im starting to resort to aq extraction of
the AcOH instead. I have gotten it now to the point where it is not as messy as when I first started experimenting but it still requires a few steps.
The best part about the aq extraction though is that you can add drying agent while its still in the non polar with ease to make sure its dry before
you distill it.
I would like to heat a report of it passing the Glacial test because I have a very hard time getting it to do this on the first run and resort to
adding MgSO4 to the AcOH and slowly redistilling just above the temperature of AcOH to not release the water trapped in the MgSO4. After this you
should be able to get it to crystalize to its dimmer with relative ease.
Congrates on the Synthesis though. No matter how long it takes or how annnoying it may be i still feels like a good accomplishment when completed.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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blogfast25
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Merry Xmas (to those that way inclined)!
Very interesting thread. With this bad weather my attention was drawn also to isopropyl alcohol (propane-2-ol or IPA) as a major component of screen
wash. I thought perhaps of esterification with acetic acid to isopropyl acetate. Of course that requires both reagents to be relatively water free:
glacial acetic acid and relatively pure IPA.
My 'Tesco brand' screen wash doesn't mention composition of course. I measured the boiling point of the liquid using reflux and a calibrated digital
thermometer to be 94 - 95 Celsius. IPA's boiling point is 82.4 Celsius, so the screen wash must contain considerable amounts of water (and perhaps
also glycol?), perhaps as much as 50 w%?
A better idea of IPA content could be obtained by oxidising the secondary alcohol to acetone with a known quantity of potassium dichromate and back
titrating the excess dichromate.
Rectifying the screen wash to 'pure' IPA could be an interesting exercise in fractionated distillation: there appears to be no IPA/water azeotrope but
the fairly close BPs would require quite a few theoretical plates.
Oooops! There IS an IPA/water azeotrope at 87.9 w% IPA:
http://en.wikipedia.org/wiki/Isopropyl_alcohol
[Edited on 25-12-2009 by blogfast25]
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JohnWW
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Perrys Chemical Engineers' Handbook, chapter 13, also mentions that constant-minimum-boiling-point azeotrope, but lists it as having 31.46% water and
68.54% isopropyl alcohol. It is possible that some additional concentration may be obtainable by distillation with benzene or something, in a similar
way to purification of ethanol above its azeotrope of 89.43%. Isopropyl alcohol is sold as "rubbing alcohol" at a concentration of about 70%.
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Panache
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Quote: Originally posted by Sedit  | Third.
Panache, Did you use Bisulfate to "dry" distill the AcOH out or did you use H2SO4? If you used Bisulfate I suggest adding some H2SO4 and stir it to a
slush first to aid in heat transfer or else you will have many many problems. The time issue you see is why im starting to resort to aq extraction of
the AcOH instead. I have gotten it now to the point where it is not as messy as when I first started experimenting but it still requires a few steps.
The best part about the aq extraction though is that you can add drying agent while its still in the non polar with ease to make sure its dry before
you distill it.
I would like to heat a report of it passing the Glacial test because I have a very hard time getting it to do this on the first run and resort to
adding MgSO4 to the AcOH and slowly redistilling just above the temperature of AcOH to not release the water trapped in the MgSO4. After this you
should be able to get it to crystalize to its dimmer with relative ease.
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Yeah its glacial. However i cheated and combined greater than equimolar bisulfate and around 200mL of glacial i already had. Initially it worked great
and the first 250mL came over with little effort, the next 10mL took an hour, i then added around 100mL conc h2so4 (around 200g worth), the remainder
of the distill took several hours of cycling between full vacuum and no vacuum. Sorry to not have mentioned the drying of the sodium acetate before, i
thought everyone knew!!
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blogfast25
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| Quote: Originally posted by JohnWW | | Perrys Chemical Engineers' Handbook, chapter 13, also mentions that constant-minimum-boiling-point azeotrope, but lists it as having 31.46% water and
68.54% isopropyl alcohol. It is possible that some additional concentration may be obtainable by distillation with benzene or something, in a similar
way to purification of ethanol above its azeotrope of 89.43%. Isopropyl alcohol is sold as "rubbing alcohol" at a concentration of about 70%.
|
Wikipedia mentions cyclohexane as an azeotroping agent in it's IPA entry. Presumably distilling the 87.9 w% azeotrope with cyclohexane separates a
cyclohexane/water azeotrope and the dry IPA.
Yes, rubbing alcohol is another OTC containing IPA.
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entropy51
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You can buy 91% (or higher) IPA at the drugstore. There are threads here on removing the last of the water, even to anhydrous. Search and you will
find.
There are also posts lurking here about making esters in aqueous reactants. It definitely works for making ethyl acetate.
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blogfast25
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| Quote: Originally posted by entropy51 | You can buy 91% (or higher) IPA at the drugstore. There are threads here on removing the last of the water, even to anhydrous. Search and you will
find.
There are also posts lurking here about making esters in aqueous reactants. It definitely works for making ethyl acetate.
|
Buying stuff like that here in Britain from a 'farmacy' can be tricky w/o prescription, it's a real Nanny State when it comes to chemicals. What's the
91 % grade used for? Rubbing alcohol?
What about spray cans of windshield de-icer, wouldn't that be mainly IPA (apart from the driver gas)?
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entropy51
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| Quote: | | Buying stuff like that here in Britain from a 'farmacy' can be tricky w/o prescription, it's a real Nanny State when it comes to chemicals. What's the
91 % grade used for? Rubbing alcohol? |
In the US, it's normally on the shelf next to the 70% rubbing alcohol.
No prescription needed.
Over here they also sell Iso-Heet in the hardware stores, used to prevent gasoline lines from freezing. It with the auto supplies, and is essentially
anhydrous IPA. You can dry it and distill if need be. The other Heet product is near pure methanol, so read the labels. I have no idea if this is
available in the nanny state, but I'd sure look.
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