youngjunky (Member)
12-04-98 02:50
No 90051
      acetic acid from vinegar?  Bookmark   

my nearest source of acetic acid is about 200 miles away. got no car. iv got the recipe posted in rhodiums site but it is not a complete proceder. also did a search here but that also came up short. so here is my delema. i need to make the acetic acid ester of pseudo. can this be done just using vinegar? if not could vinegar be fractionally distilled? if not could somebody please give a little more info about the recipe on rhodiums page or just stear me in the right direction. thanks much.
12-04-98 11:27
No 90052
      Re: acetic acid from vinegar?  Bookmark
    Mickey Finn
12-07-98 08:07
No 90053
      Re: acetic acid from vinegar?  Bookmark   

Distillation of acetic acid from vinegar is not feasable because it forms an annoying azeotrope with water which prevents seperating; possibly, one could form the sodium salt from the vinegar by adding sodium hydroxide until neutral, or slightly acidic, and then evaporating.  With the sodium acetate one should be able to add concentrated sulphuric acid and then distill over the mixture to obtain acetic acid. I would be interested if someone knows a better way to remove the water from vinegar as this is of interest to me as well.  Thanks.
12-07-98 14:55
No 90054
      Re: acetic acid from vinegar?  Bookmark   

MF. thanks for the info on the azetrope. i to found out about that hypothetical recipe from rhodiums page. it would be easy to do if i knew a couple of things. how much H2SO4 would i add to the sodium acetate. and what are the boiling points of acetic acid and H2SO4.
commodium. thanks for the site but in no way will i order chems to my house. for those that will this is an excellent mor many things! makes me want to go in to photograghy. you should tell more people about this site.
    Mickey Finn
12-08-98 10:08
No 90055
      Re: acetic acid from vinegar?  Bookmark   

The chemicals needed to do this are extremely easy to get. Vinegar, lye (red devil), and conc. sulfuric acid (super drain cleaner at Menard's or some other large building supply center --- great for getting other solvents as well, is trichloroethane (carbosol) as good as dichloromethane?)Anyway add lye dissolved in a little water (this gets hot) to vinegar until it turns lightly yellow, then add vinegar small amounts at a time until the yellow discoloration dissipates, that way you know your mixture is not basic, excess NaOH will react with the H2SO4 and one of the products of that reaction is water which we are trying to get rid of, excess vinegar will just evaporate. Then dry the solution to leave the sodium acetate. Add just enough sulfuric acid to the sodium acetate so that it dissolves, this is not too critical; however using too much acid will introduce excess water to the mix as the concentrated acid has some water About 6% allthough I don't believe that this can be driven off the acid too easily as sulfuric acid is extremely hydrophyllic (loves water). The distillation is fairly easy as the boiling points of the two liquids are well separated.  Acetic acid boils at 118 C and Sulphuric acid boils at 338 C (however the dihydrate of sulfuric acid boils at 167 C but this is still a 49 degree difference which is far enough to effect a good separation by distillation.  I hope that information helps.
12-08-98 15:37
No 90056
      Re: acetic acid from vinegar?  Bookmark   

Mickey Finn thanks much. that was my last hurdle in this hypothetical thingy i would like to dream. thanks much. and yes menards is a great place for a chemhack.
    Mdm. Atom
03-07-99 16:09
No 90057
      Re: acetic acid from vinegar?  Bookmark   

How would the Sodium Acetate be dried?  Reflux?
Would this yield galcial?
Sure would be nice to know.
You know, for educational purposes!
(Synaptic Self-Mutilator)
11-21-02 16:54
No 382006
      Drying acetic acid  Bookmark   

There is no azeotrope formed with water and acetic acid that I could find. The Perry's lists this as the data on acetic acid:

liquid vapor            liquid vapor
Temp   mol frac         w/w
118.3  0      0         100.0  100.0
110.6  0.1881 0.3063     93.5   88.3
107.8  0.3084 0.4467     88.2   80.5
105.2  0.4498 0.5973     80.3   69.2
104.3  0.5195 0.658      75.5   63.4
103.5  0.5824 0.7112     70.5   57.5
102.8  0.6750 0.7797     61.6   48.5
102.1  0.7261 0.8239     55.7   41.6
101.5  0.7951 0.8671     46.2   33.8
100.8  0.8556 0.9042     36.0   26.1
100.8  0.8787 0.9186     31.5   22.8
100.5  0.9134 0.9409     24.0   17.3
100.2  0.9578 0.9708     12.8    9.1
100    1      1           0      0

The problem is that they don't separate easily. ie distilling a liquid of 88% acetic acid only gives a 93% vapor. Piss-poor separation. Fortunately if you you only need to boost the concentration 5% or so, a really long column will allow you to dry your acetic acid (ie to get the last of the water out).
11-21-02 17:15
No 382017
      Industry  Bookmark   

As was mentioned in Post 249833 (lugh: "Study More Chemistry!!!", Chemistry Discourse), the industrial method of manufacturing glacial acetic acid uses sulfuric acid as a drying agent smile
(Hive Bee)
11-21-02 18:11
No 382036
      distilling, than freezing out  Bookmark   

For most laboratory uses this procedure is sufficient:

- distill with a good fractionating columm, you should reach about 90% to 95%.
- freeze the acetic acid out by putting it in a freezer (not deep-freezer) and waiting until it starts solidifying. Do this in a squeezable plastic bottle as now you squeeze the slush and pour away the water. Repeat this sometimes. Done.

If your vinegar seems to be contaminated with something and for getting better results in didtillation it may be favorable to add some high boiling alcohol to the vinegar. Perhaps you loose something by an azeotrope but the middle fraction (acetic acid) will be much cleaner. As this should be be done in a big setup for making any sense I see no problem if 5 or 7 liters are procesed.


now or never
11-22-02 13:37
No 382358
(Rated as: excellent)

A calculated amount of potassium or sodium bisulfate may bee used instead of concentrated sulfuric acid, in producing the so called "soda acid" smile Prior to the introduction of synthetic acetic acid, this was the most anhydrous form of glacial acetic acid available. Some patented methods of distillation are Patent DE220705, Patent US1463209, Patent FR612595, Patent FR449035 and Patent US1196329 smile Electrolytic purification methods can bee found in Patent US1104978 and Patent US1210792 smile Some methods of concentration by distillation of acetic acid are Patent GB218271, Patent GB218272, Patent FR594925, Patent GB204196, Patent GB187603, Patent US1477076, Patent GB230447, Patent GB296794, Patent GB3000923, Patent GB356741 and Patent GB298137 smile Some non patent references are Chem Ztg 55 881 (1931), Chem and Met Eng 36 657 (1929), Ind Eng Chem 24 722 (1932) & 23 482 (1931) and Z Agnew Chem 20 148 (1916) smile Concentration of acetic acid by adsorption is disclosed in Patent GB332983 and Z Physikal Chem 29 326 (1925) smile Removal of water by selective adsorption is patented in Patent GB314913, Patent US1492717, Patent US1492718, Patent US1817993, Patent GB338187, Patent DE230171, Patent DE282263 and Patent DE292959 smile  Concentration of acetic acid by freezing is the subject of Patent GB378463 and Patent GB378463 smile Some more applicable references are Patent US2275802, JACS 54 1429 (1932), 53 2881 (1931) & 58 2585 (1936), JCS 1751 (1910) and Ind Eng Chem 20 1379 (1928)smile Probably the most effective drying agent available to most bees would be anhydrous copper sulfate laughsmile
(Synaptic Self-Mutilator)
11-22-02 23:11
No 382519
      Ideas  Bookmark   

I've spent some time looking at these patents, but I find them next to unreadable. frown I'm used to chem abstracts...

You mention drying agents, I don't like these ideas as they are rather messy and need to be regenerated. You mention special membranes, which sound cool, but are out of reach. Adsorption is cool, I remember how acetic acid is preferentially taken up my adsorbants like activated charcoal.

In one of the patents, using the azeotrope of trichloroethylene/dichloroethylene/etc and water is mentioned to concentrate formic, acetic and propanoic acid. IIRC, the azeotrope forms somewhere around 70C with perc. Is azeotropic distillation a reasonable way to proceed? Can you recommend it?

I didn't see any examples on mixing sulfuric acid and an acetate salt, but I imagine if mixing bisulfate with acetate will make acetic acid, only a small molar excess would be required.

11-23-02 02:47
No 382553
      Details  Bookmark   

It's stated you use the calculated amount of sulfuric acid in making "soda acid"; since this was/is the traditional route from long ago, no one's going to publish it smile Here's the abstract from Patent GB378463

Dilute acetic acid such as vinegar is concentrated by passing the pre-cooled solution through a heat exchanger at a sufficient speed and rate of heat exchange to cause the formation of ice crystals which are carried along by the liquid stream and separated. The crystals are washed with some of the initial solution and may then be mixed with alcohol, the mixture being used to pre-cool the solution, and afterwards being returned to the vinegar plant so as to supply the alcohol and a part of the water needed for the process while saving the remaining acetic acid. In an example, the concentration of 10 per cent vinegar is effected by passing the solution, pre-cooled to -2 DEG C. through a heat exchanger at 3 feet per second, the heat transfer being 500-1000 calories per square metre of cooling surface per hour. To control or limit the rate of cooling, the cooling surfaces may be coated with material of low conductivity such as rubber or enamel. More than one heat exchanger may be used; for instance the first may cool the liquor to -5 DEG C. and the second to -15 DEG C. giving a vinegar of 40 per cent.

The eutetic point of acetic acid/water is -26C, thus it seems clear that if one is starting with vinegar, that one combine these techniques, xylene is probably the most easily available solvent mentioned, the haloethylenes are somewhat more expensive. Azeotropic distillation has been used in industry for almost a hundred years, it's actually quite easy smile
11-23-02 21:37
      Form the acetate
(Rated as: off-topic)
(Synaptic Self-Mutilator)
11-23-02 22:54
No 382735
      Thanks, but...  Bookmark   

Thanks, but I'm looking for downers not uppers. smile
(Hive Addict)
11-24-02 13:07
No 382897
      Alright, I'm never using vinegar in anything I ...  Bookmark   

Alright, I'm never using vinegar in anything I eat again.  I neutralized some distillde white vinegar with abking soda, and started boiling it down.  The lower the volume got, the more it started to turn light brown.  Then the solution started to give off some kind of smell.  I know I've smelled it before, but I can't place it.  Something to do with cooking, or cookies, or something.crazy  But then I got a pretty fucking bad headache, which pissed me off.  But then I let the solution cool, and it crystallized into little rocks of sodium

A calculated amount of potassium or sodium bisulfate may bee used instead of concentrated sulfuric acid

Does that mean a bisulfate can be used on Na or K nitrate to get pure HNO3, too?coolcool

It is seductive, way too seductive.             -Eleusis
(Synaptic Self-Mutilator)
11-24-02 21:37
No 383054
      purifying dilute acetic acid  Bookmark   

Technique #1 - testing it out
You have to distill the vinegar to get sufficiently purified acetic acid (or purchase vinegar spirits)... otherwise you'll get the crap that the bacteria and yeast cells left behind in the fermentation process used to make vinegar (leaves black/brown crap on your flasks--perfectly safe to eat / drink, but not something you want in your sodium acetate). Slowly add baking soda (it bubbles) with a slight excess of acetic acid, then boil that down to get anhydrous sodium acetate.

The problem is then figuring out how to get back the acetic acid. I tried adding 1.25 eq of sulfuric acid, but it's not enough to even cover the sodium acetate. The reaction between sodium acetate and sulfuric acid is highly exothermic (careful!). It wasn't until 3 eq of sulfuric acid did it look possible to do.

Technique #2 - testing it out
Concentration by azeotropically removing the water with tetrachloroethylene was a failure for me. The setup I used is:

From the bottom to the top:
1) flask with 30ml perc, 150ml acetic acid & stir bar
2) vigreux column
3) claisen adapter (monitoring temperature in the center hole)
4) pressure-equalized addition funnel
5) reflux condenser

The perc and acetic acid formed two layers. Then I distilled it (the vapors were at 90C until the water was removed...) until all of the water was left in the pressure equalized addition funnel (draining out the perc on the bottom layer in the addition funnel occassionally so it could recycle). Eventually one layer was left in the flask. Unfortunately, the perc and acetic acid were miscible! Now I've got perc with acetic acid instead of water with acetic acid. Great, absolutely fucking useless... frown I must be missing something. I wish I was better at researching. frown
(Synaptic Self-Mutilator)
11-24-02 23:29
No 383074
      Mistaken...  Bookmark   

It was feasible to do this with only 2 H+ eq of sulfuric acid. (ie 1 mol H2SO4 for each 1 mol NaOAc)

With external cooling, to 150g NaOAc (1.8mol) in a 500ml flask, 180g H2SO4 (3.7mol H+, 2 eq H+) was ever so slowly added. All of the solids did not dissolve. Fractional distillation with magnetic stirring was started. It was possible to distill off 85g acetic acid which is a 78% yield before the flask started to fill to the top with foam (perhaps a touch more H2SO4 would have been advisable). The distillation range was 110-120C (holding mostly around 118C). There was also some white smoke produced by the reaction (??) that was a transient phenomenon and never left the distillation setup.

Except for this reaction being so time-intensive, it's a fantastic way for over the counter glacial acetic acid.

I'd love to hear some input on how to make azeotropic distillation work though... that sounds like a far easier way to purify acetic acid.
(Hive Bee)
11-25-02 08:57
No 383209
      While we are on the subject  Bookmark   

SWIM bought some distilled white vinegar.... whats the easiest way to find out how concentrated it is ?

I love the smell of Ketone in the morning.
(Synaptic Self-Mutilator)
11-25-02 09:45
No 383216
      Titration  Bookmark   

Titrate the acetic acid with NaOH to find out what percentage it is. If you just want a rough idea, figure out how many grams of baking soda react with say 100ml of vinegar. Then work backwards from that and figure out the percentage.
(Hive Bee)
11-25-02 23:38
No 383419
      Azeotropic drying of acetic acid  Bookmark   


Which patent out of lugh's* long list described azeotropic drying with chlorinated hydrocarbons ?
[Don't feel like going thru all of them]

Anyhow, I would say that while other combinations of acids & chlorinated hydrocarbons might work for drying, using tetrachloroethylene to dry acetic acid is no good: their bp's are too close [GAA 118C, perc 121 C]. So after water removal, separation of the GAA from the perc becomes a bitch. And, as can be expected from close boilers, an azeotrope is formed [61.5% GAA, bp 107C], so adding too much perc will also be a problem.

* Patent GB2182271 must be wrong cos it describes a clamping device.

Mountain Boy