joeflsts
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Purification of Benzoic Acid
I'm relatively new to chemistry and would like some input. I'm hopeful that this isn't too basic a question. I just completed the synthesis of
Benzoic Acid from toluene, water and Potassium Permanganate and crystalized the Benzoic acid from the final solution (after lots of filtering to
remove MnO2).
I used HCl to acidify the Benzoic Acid solution. This caused immediate percipitation but I've noticed after drying that a strong HCl odor is present.
My understanding is that Benzoic Acid should have a pleasant odor. This isn't exactly pleasant.. unless you compare it to a nose full of pepper.
Actually it isn't all that bad....
Is there a way to further purify the Benzoic Acid? I know that it is slightly soluable in water and quite soluable in acetone so I'm thinking of
creating the acetone / benzoic acid solution then allowing the Acetone to evaporate. Would this remove the excess Hydrochloric Acid? From my
research it doesn't appear that an accidental by-product would be acetone peroxide. I'm quite interested in keeping the digits.
Thank you,
Joe
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The_Davster
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To get rid of the HCl just let the crystals sit in a warm area for a week or so.
Hexane (Camp fuel?) works wonders for recrystalizing benzoic acid, nice crystalls often inches long form.
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BromicAcid
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I recently converted a large amount of sodium benzoate to benzoic acid. The process is very simple and if you have some extra NaOH on hand you can
duplicate it to purify your benozic acid. You'd dissolve it in a NaOH solution, and filter, watching out for organics floating on top that you would
have a pipette off. Then after filtering add HCl to precipitate and wash with corpious amounts of water. My benozic acid had the slightest of
smells, the flighty powder burned my nostrils though on the inside badly, be wary, it hurts the throat too.
[Edited on 4/5/2006 by BromicAcid]
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joeflsts
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Thank you!
Joe
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Positon
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Interressant thing about benzoic acid is that you can find this product in soft drink .
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Swany
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Yeah, negligible amounts as a preservative. Another interesting thing is somehow it reacted with whatever in there to create benzene, in tiny tiny
amounts, like PPB amounts. Naturally, they went postal.... It was all over the news, and I was depressed.
But yes, I would second the basification/acidification, and then recrystallization.
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