Upsilon - 13-9-2015 at 20:18
Acetic acid is known to be a huge pain to concentrate from household vinegar because of the azeotrope it forms. I've been thinking about it, and I've
come up with a possible theory. If I have copper(II) acetate available, I could dehydrate it with heat. Then I could add the anhydrous salt to the
vinegar, where the dehydrated salt will take on water out of the azeotrope until it is hydrated once again. Would this actually work? Am I overlooking
something here?
Cou - 13-9-2015 at 21:01
Couldn't you just react vinegar with a sodium salt to form sodium acetate, boil it off to leave it behind, and then use the methods to make GAA from
sodium acetate?
UC235 - 13-9-2015 at 21:03
Acetic acid doesn't form an azeotrope with water. The problem is merely that there is only an 18C difference in boiling points between it and water.
It takes a very large column to efficiently separate the two and there is very little yield since white vinegar is only 5% acetic acid and 95% water.
Copper acetate doesn't simply dehydrate when heated. It loses acetic acid and forms basic copper acetate or oxides.
Are you suggesting to add enough (if it was possible to make) anhydrous copper acetate to white vinegar to use up all the water? There are about 60
moles of water in white vinegar for every mole of acetic acid. It would take about 10kg of starting hydrated copper acetate to process a single liter
of vinegar, which if perfectly recovered would yield 50ml of GAA.
If you want to concentrate the acetic acid, add baking soda to convert the acetic acid into non-volatile acetate, then boil the solution all the way
down to dry sodium acetate (which you can buy in cleaner condition on ebay for little money and without all the effort), roast it in an oven to expel
all remaining water, and distill from concentrated sulfuric acid.