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Author Topic: Making glacial acetic acid from household vinegar  (Read 15373 times)

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bbro1997

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Making glacial acetic acid from household vinegar
« on: October 03, 2013, 04:11:31 PM »

A 1 gallon (3.78 L) mixture of 95% water, 5% acetic acid costs about $2.80 where I live. This equates to about 189 mL of potential acetic acid. This is cheaper up front than just ordering the stuff online, but I have yet to come up with a cost-effective solution for extracting acetic acid from vinegar. I have read of people using the method of adding baking soda, then concentrated sulfuric acid, to yield acetic acid but according to some calculations this is roughly 2-3 times more expensive than buying it straight-up. I also tried refrigerating the vinegar, since acetic acid freezes at about 17C, but nothing happened. Something I haven't tried is boiling the water off, however I fear that the acetic acid will evaporate, causing a low yield. Does anyone know of a better strategy?
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discodermolide

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Re: Making glacial acetic acid from household vinegar
« Reply #1 on: October 03, 2013, 07:03:48 PM »

Why not just distill the water off using a fractionating column.
Work out the energy costs in removing 3.5 L of water and compare them with the price of a bottle of glacial acetic acid.
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bbro1997

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Re: Making glacial acetic acid from household vinegar
« Reply #2 on: October 04, 2013, 02:00:45 PM »

I did some research and I found that if I pass chlorine gas through acetic acid, it will produce chloroacetoc acid and hydrochloric acid. It would also be nice to have a home source of HCl. I have a readily available supply of chlorine gas, so this won't be an issue. Chloroacetic acid at room temperature is a solid, so it would be easy to extract. Is there any feasible way to convert chloroacetic acid back to acetic acid?
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mesa

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Re: Making glacial acetic acid from household vinegar
« Reply #3 on: October 14, 2013, 09:20:19 AM »

I wouldn't suggest messing with halocarbon's unless you are quite well versed in safety procedures.  Chloroacetic acid will absorb through skin quite readily and the LD50 from literature is ~80mg/kg from memory.

Sodium/Potassium bisulfate/metabisulfite can substitute for Sulphuric acid in the NaOAc/H2SO4 reaction.  Simply mix the two powders intimately(grinding is preferable) and dry distill.  A small amount of glacial acetic acid is useful as a wetting agent, but given its the desired product, it seems somewhat counterproductive to use it :P.

The dry distillation can be done in a domestic microwave that has been suitably modified to allow for a condenser, there are tutorials on this around, Googling will work.

A method I've thought of, but not yet attempted, is using the calcium salt rather than the sodium one.  Calcium salts are notoriously difficult to dissolve, so adding sulphuric acid to calcium acetate should result in acetic acid and an insoluble precipitate which can then be filtered, forgoing the need for distillation.  The resulting acetic acid will surely be at least slightly contaminated, but still suitable for use in some applications.
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