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Author: Subject: Acetic acid/ sodium hydroxide
The_Davster
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[*] posted on 18-7-2004 at 12:56


I assume you made your sodium acetate the same way I make mine, baking soda and vinigar:D. I have about 1.5L of this solution to boil down still.:( It is taking a long time because I am using a 600mL beaker for my boiling.

Edit: anyone else notice this thread has three pages but on the "reagents and apparatus aquisition" page only 1 page and 23 posts are apparent.

[Edited on 18-7-2004 by rogue chemist]
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[*] posted on 19-7-2004 at 11:52


I noticed it.

I did use baking soda and vinegar.:P

This is slightly off topic, but I think that baking soda and vinegar will make some acetic anhydride. Look at the AA thread. Sodium acetate would be there, and so would CO2, so why not AA if the soln. is cold enough. I noticed a fruity smell when doing this reaction that wasn't sodium bicarbonate or vinegar. Does AA smell fruity?




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[*] posted on 19-7-2004 at 12:04


acetic anhydride has nearly the same odor as acetic acid
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[*] posted on 19-7-2004 at 16:35
Experiment


I just mixed about 1 g NaC2H3O2 and 2 g H2SO4 (94%) in a test tube, the sulfuric acid attacked the sodium acetate and the mix turned black. Then it was distilled for about 20 min. Actually it was more like refluxing, because the distillate kept on condensing before it even reached the condenser.:(

A ridiculously small amount of distillate (about 0.25 ml) made it to the test tube at the end of the condenser, which was in an ice bath.

Now the distillate ought to be nearly pure acetic acid, and it ought to be a solid at icy temp. It did smell and taste like acetic acid, but the stuff was a liquid, even at near zero temperatures. :mad:

What am I missing?

Perhaps the sulfuric acid started losing water during the distillation, and the water ended up in the distillate?
Near the end of the process, I noted some SO3 fumes coming off, water might have been there too?




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[*] posted on 19-7-2004 at 17:06


Just to tell you- i know the MP of acetic acid is supposedly around 20 deg C. But I cooled down glacial acetic acid (analytical grade) to 4 deg C, and it stilll wouldnt crystllise/solidify. I guess if takes time, even more so if it is impure. Quite similiar to diethanolamine, which supposdely melts at 26 deg C, and yet failed to solidify at 4 deg C for 10 days...



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[*] posted on 20-7-2004 at 12:49


Cool, I was searching some info about toluene/water azeotropes and this thread came up :)

First of all, H2SO4/acetate salt is very hard to upscale from a testtube. Since the stuff will be solid (as Cyrus already said) and heat transfer will be a problem.
I checked mp of sodium citrate and it's >300*C so, citric acid would give same problem.
Just a suggestion, what if one uses a solvent for this, with high bp... like acetamide... :P it would make reaction mix liquid.

I have prepared 96% acetic acid from 24% like a year ago.. this wasn't that fun..
First, acid was extracted with ethyl acetate on evaporation of solvent, this gave ~60% AA. This was then destilled with ethyl acetate and 96% prod was obtained. Though it seems like alot of AA goes away with ethyl acetate. And some solvent decomposes...
There are some info about ethyl acetate/water azeotrope on the address already posted in this thread. Though they've choosen to use methyl isobutyl ketone, it seems to be more effective (I have no source for it).

Btw, obtained wet ethyl acetate was dried by freezing out the water, very effective and fast (I did this to reuse solvent..)
I have some experimental results somewhere if anyone is interested..

Oh, finally, what about using toluene to remove water? This azeotrope boils at 85*C. A bit higher than mentioned 76*C.. but my 24% AA boils above 100*C IIRC, so there seems to be no azeotrope (can't beliave noone tested this yet, gonna do this tomorrow to be sure..)...

EDIT:
This may be interesting:
http://separationprocesses.com/Distillation/DT_Chp06c07.htm

Where they use n-butyl acetate/water azeotrope (90,2*C) to remove water from AA. Nothing mentioned about the one with AA/water..

[Edited on 20-7-2004 by frogfot]

[Edited on 20-7-2004 by frogfot]
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[*] posted on 20-7-2004 at 13:58


A good part of the smell of neutralised vinegar is butane dione (AKA biacetyl, AKA diacetyl)
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[*] posted on 21-7-2004 at 11:15


Oki, tryed to distil 24% acetic acid, it came at about 100*C. Also checked CRC book (don't remember year, but it was new), it said no azeotrope formed between acetic acid and water.
However heres some interesting azeotropes:
water/toluene bp=84,1*C tol. content=86,5%(w)
acetic acid/toluene bp=100,6*C tol. content=71,9%(w)

So, I think toluene would be great to dry AA. I'm currently destilling 100 ml 24% AA with 150 ml toluene, stuff destills at about 85*C, and thats without any defligmator or column.. and pretty fast it goes :) will se how it goes..

EDIT:
Some results from AA drying mentioned above..

I have boiled away about 100 ml liquid, separated clear toluene and returned it back into destilling flask. This was done 4 times, and I got 77 ml water solution which showed to be 15% AA. Next 4,9 ml collected aqueous solution was 20% AA.

Remaining aqueous solution in destilling flask, that was separated after cooling was 15 ml 55% AA (it was turbid, because of some solid precipitate..).

Results is not the best, but remember, this was a simple destillation setup. Think what one could do with a fractionating column or at least vigreoux column.. Any thoats on this? It boiled at 84-85*C for me, while theoretically it should be 84,1*C and I did it pretty fast which is not adviseable when separating liquids by destillation.. IMO yield can be improved.

Btw, would it be promicing to add ethanol into the system? This way we get new azeotrope:
water/ethanol/toluene bp=74,4 water content 12%

So, we get an azeotrope with approx. same water content but it'll boil 9,7*C lower.. ofcaurse there will also form ethanol/toluene bp=76,7*C ..oh, and it would be harder to separate toluene from resulting destillate.. dunno..

[Edited on 21-7-2004 by frogfot]

[Edited on 22-7-2004 by frogfot]
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[*] posted on 22-7-2004 at 09:23


Oops, if I said that the contents of the test tube (sodium sulfate, acetic acid, and sulfuric acid) were a solid, I made a mistake. When I added the sodium acetate, there was some solid, but after distilling for a minute or two, all of the solid sodium acetate had disappeared, the contents acted like a liquid, after being cooled down, they acted like a mush.

I still think this process could be scaled up pretty easily.




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[*] posted on 22-7-2004 at 11:19


Aha, sorry I assumed it was solid. So you had NaHSO4 in the end, cool. Since it melts at 240*C, you're right, it can be easily upscaled in a flatbottomed flask.

Btw, decomposing NaHSO4 would give off water and pyrosulfite, which would in turn decompose to SO3.. as discussed in acetic anhydride thread. So, there could happen a dilution of your product.
I'd also try with larger ammounts, since I think half of your yield was stuck on the walls..

[Edited on 22-7-2004 by frogfot]
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[*] posted on 22-7-2004 at 15:53


Um, this may be a dumb question, but if the bp of acetic acid is near 100 deg. C, and the mp of NaHSO4 is more than 200 deg C, how is the NaHSO4 going to melt if there is any acetic acid left?
:o

Could the H2SO4 might affect the phase of the NaHSO4?

[Edited on 22-7-2004 by Cyrus]




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[*] posted on 23-7-2004 at 06:57


AA will leave and it will gradually melt.. first by dissolving in AA, and then on its own..
Important part is that it'll melt in the bottom of flask giving good heat conductivity for the rest of mass. As example, this was actually the main problem for me when making acetone from Ca acetate.. stuff was in powder form.. and even if reaction required 400*C my 1500*C burner couldn't drive reaction to completeon..

Btw, today I checked newer book on azeotropes (year 2002) and it said water/AA gives an azeotrope with bp of 77*C with 3% AA content.. :( (Oh, IIRC someone mentioned this already)
So, this could be checked using a column..

[Edited on 23-7-2004 by frogfot]
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[*] posted on 23-7-2004 at 10:39


I tried the reaction again with larger amounts- 17 g sodium acetate, an excess of sulfuric acid, when added the sulfuric acid attacked the sodium acetate again, leaving a black gunk/liquid.

I am assuming this residue is carbon, how can this be prevented? I don't like losing all of my acetic acid yields just to make carbon!




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[*] posted on 24-7-2004 at 06:08


The black gunk is probably from impurities (sugars etc) left over from the vinegar being attacked by th sulphuric acid.
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[*] posted on 28-1-2005 at 22:30


woudent Aluminum hydroxide and sodium acetate work (possiply work to make other acids to)

[Edited on 30-1-2005 by kclo4]
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[*] posted on 1-2-2005 at 20:09
acetic acid from vinegar


I have been attempting to obtain glacial acetic acid from vinegar (5% acetic acid).
I first tried a simple distillation of 250 mL. Everything came over at 100 C and I left 12 mL in the pot. The distillate and the pot residue smelled about like the starting vinegar.

Then I tried a fractional distillation using a column packed with a stainless steel scouring pad. Same results although this time I took the pot to very near dryness. Again the temperature at the still head stayed at 100 C. Based on these results it looks like there is indeed an azeotrope at about 97% water. However, if there is I would say its temperature is very close to 100 C, not the 76 C reported in my CRC! I will go to the library to see if I can get some help on this issue.

I also prepared some calcium acetate using 250 mL vinegar reacted with a stoichiometric amount of hydrated lime [Ca(OH)2]. Yield of Ca(Ac)2 is 79%. I will try to make glacial acid out of this using H2SO4.

Has anyone else been doing some experimentation in this area?




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[*] posted on 2-2-2005 at 12:46
vinegar distillation


Vinegar at 5wt% acetic acid is 1.6 mole% in acid. According to the vapor-liquid equilibrium data I found at the library the liquid and vapor composition at this liquid concentration are very nearly equal. This I believe makes concentration of the acid by distillation impossible or at least impractical.

I also checked "Azeotropic Data" by Gmehling et al (1994). There were 52 citations! Pressures ranged from 1.07 kPa to 5864.7 kPa with 31 citations at 101.7 kPa (atmospheric pressure). All of the references indicated "none" for existence of an azeotrope.

Needless to say I'm giving up on distillation of vinegar.




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[*] posted on 3-2-2005 at 16:02


Attempted to make glacial acetic acid out of the Ca(Ac)2 I made a few days ago. Decided to use hydrochloric acid instead of sulfuric after reading Muspratt in the MSDB library (I love that reference). Set for distillation using a fractionating column and stainless steel packing (scouring pad from Fred Meyer). Noticed that the column was tending to plug and a dark green (Malachite) colored liquid flowed down the column when I cut the heat. Fearing a plugged column with consequent flask or colum burst, I aborted. Examination of the packing showed that it had been nearly eaten away in the lower part of the column. I saved the pot liquid and will try again when I get some glass beads.



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[*] posted on 4-2-2005 at 19:31


I found some glass beads (hollow cylinders about 2mm dia x 7mm high) at the local bead shop. Repacked my Hempel fractionating column with the beads and distilled my crude acetic acid. All the water came off at 100 C then the nasty mix started foaming and looked like it might plug the fiberglass support plug in the bottom of the column. So I aborted. Also at that time there was a strong smell of acetic acid in the lab! What's left in the pot is very crude glacial acetic acid (~ 10 mL). The Fe, Cr, and Ni acetates generated from the old stainless steel packing are contributing the black/dark green color I believe. The acid quickly froze at room temperature. I may try to clean this up and redistill. I'll use a simple distillation as all the water is gone. :D

There is a solid mass of CaCl2 mixed with my acetic acid in the bottom of the flask. I think it's time to scrap this batch. I may try another larger batch next week.

[Edited on 5-2-2005 by Magpie]




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[*] posted on 5-2-2005 at 08:39
Critique


Re: glacial acetic acid preparation

There's a big difference in following some school recipe and striking out on your own into a long abandoned method. For one thing you have to be much more on your guard to protect your safety and that of your equipment.

I think removing the water from my reaction mix by fractional distillation was a mistake. Once that water was gone there wasn't much liquid left in the flask but a whole lot of CaCl2. If I would have kept the heat on another minute I could likely have cracked my expensive Kontes 250 mL RBF with ground glass joint. That would have really pissed me off. I've also told my wife that if she ever sees me in the lab without my safety glasses on to kick my ass!




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[*] posted on 5-2-2005 at 09:51


What if one dries dilute acetic acid in excicator above CaCl2? The air inside will be saturated by AA and water, while only the latter will stick to the drying agent..
Will take ages, but this should theoretically work..
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[*] posted on 5-2-2005 at 11:27


Frogfot what you suggest might work. I don't know if CaCl2 is more hydgroscopic than acetic acid, however.

My current plan is to proceed as before only use a double batch (500 mL) of vinegar charge. Once I get the Ca(Ac)2 powder I will react it with 31.45% HCl (muriatic acid). I will then codistill off the water and acetic acid using a simple distillation. Muspratt says this distillate will be about 45% acetic acid IIRC. Then I will fractionally distill this distillate. That way I'll get rid of the the CaCl2 and be working with a clear product.




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[*] posted on 5-2-2005 at 19:57


Why not mix your calcium acetate with sulfur and do a dry distillation?
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[*] posted on 6-2-2005 at 11:45


Icarus says:


Quote:

Why not mix your calcium acetate with sulfur and do a dry distillation?


I don't understand how this would produce acetic acid. Please provide chemical equation.




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[*] posted on 6-2-2005 at 11:58


It would make sense if he meant sulphuric (acid).
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