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Author: Subject: Ammonium Acetate, what went wrong
highpower48
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[*] posted on 1-5-2021 at 15:32
Ammonium Acetate, what went wrong


Made some ammonium acetate by naturalizing 10% ammonia with white vinegar. Boiled from 1000ml to around 50ml it turned a golden brown. It's been sitting in a beaker to finish evaporating but shows no sign of crystallization. For such a simple reaction, what went wrong?

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njl
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[*] posted on 1-5-2021 at 16:26


Ammonium acetate is notoriously difficult to dry (deliquescent even) and I expect you will have to continue to heat it to get it out. The brown color is probably from an impurity in the vinegar either becoming more concentrated or decomposing, although it could be the product decomposing. Another way would be to add acetone and cool the solution as low as possible.



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Amos
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[*] posted on 1-5-2021 at 17:14


A lot of people are under the impression that white vinegar is just acetic acid and water, but it also contains all sorts of yeast waste products. The golden brown color is perfectly normal, so no worries. You’ve got ammonium acetate, just try boiling it down to a more syrupy consistency and then chill it. It’s 5 times more soluble at 80C than at 0C, so do this correctly and you should get a massive crop of crystals.
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S.C. Wack
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[*] posted on 2-5-2021 at 13:41


It would surprise me if any solid can ever be obtained by boiling off water from pure solutions of ammonia and the acid...the pH of such a distillate could be interesting to follow.



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Fyndium
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[*] posted on 2-5-2021 at 14:01


Some vinegar products contain only diluted acetic acid, while some contain a significant residue. I've faced both.

Ammonium acetate and ammonium formate cannot be effectively dried simply by boiling. They need to be vacuum distilled with high vacuum and low heat to prevent decomposition, and/or dried finally with vacuum desiccator. Heating too much will decompose them to acetamide and formamide.

One method is to bubble ammonia gas into pure acetic or formic acid, with inverted funnel and very effective cooling and stirring, because the reaction will generate enough heat to evaporate the acid. It will form a solid sludge, and it could possibly be diluted with anhydrous inert solvent to keep them workable, and evaporating the solvent to obtain powder form. If the intended use does not warrant anhydrous reagent, it can be used wet, just determining the approximate content, or as a limiting reagent in excess.
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