Grocery store vinegar is not very clean

I've been working with store-bought 'distilled white vinegar' for a year and a half and have only just now linked it to all the impurities that keep appearing in my metal acetates.

Maybe this should've been obvious, but the impurity only makes itself apparent when pyrolyzed or treated with certain chemicals under unknown conditions.


Brown material that forms on pyrolysis.


Various metal acetates affected by the vinegar impurity (left) compared to clean water (right). Recrystallization is effective for purifying sodium acetate and perhaps copper acetate, but few of the others.

With calcium acetate I've tried with isolation with hot water, cold water, and various solvent extractions such as hot 90% isopropanol, to no avail.

Now I get to save up for a liter of ACS grade acetic anhydride, since apparently it's only about twice as expensive per gram of acetic acid compared to store-bought vinegar.

DudaDiesel

Quote: Originally posted by Deathunter88

It's sugar left over from fermentation + also added for taste. Wreaks havoc when trying to dry sodium acetate (as you've experienced).

Actually I think sodium acetate itself is somewhat hygroscopic. I measured the dissolved solids content of my store-bought vinegar at only 0.57 ± 0.10 g/L (which, to be fair, is a lot for something meant as a streak-free window cleaner!), which I knew months ago but ignored because it seemed so innocuous.




Pictured above is 0.008 grams of the impurity. It's colorless, but as I said in the original post, I suspect that the nasty brownish-green colors emerge on pyrolysis and/or exposure to certain chemicals over time.

Quote: Originally posted by Texium

Yep. It’s very well known on this forum that food grade vinegar is not pure. I’m surprised that you weren’t already aware. As for buying acetic anhydride to make acetic acid though, that is pure sacrilege! You can buy clean glacial acetic acid online for cheap. My favorite source: https://www.dudadiesel.com/search.php?query=acetic It works great and it’s a much better $/mol than vinegar too.