ChemLlama
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Extraction of fumaric acid
Hello all! I'm new to these forums, nice to meet all of you 
I have some iron(II) fumarate tablets, and I'd like to convert it to fumaric acid. I was thinking about acidifying it in solution, but unfortunately
according to this link, it has a measly solubility of 1.4 g dm-3 in water at 25oC, while fumaric acid has a solubility of 6.1 g
dm-3. Since the reactant has a lower solubility in water, but not a significantly low enough to achieve a clean separation of fumaric acid
and the reactant, what else can I do to obtain fumaric acid? I can't seem to obtain data about the solubilities of these two compounds in different
solvents except that iron(II) fumarate is "very slightly soluble" in ethanol and that fumaric acid has a solubility of 54.4 g dm-3 in 95%
ethanol according to this MSDS.
Provided that I have water, ethanol, toluene, ethyl acetate, hexane, and small amounts of isopropanol and acetone as solvents, how should I carry out
the extraction and purification of the fumaric acid? Thank you!
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Tsjerk
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Assuming fumaric acid is heat stable (at least at boiling water temperatures), maybe you can add iron(II) fumarate to water to an amount that would
give around 6 grams/liter of the acid. Then acidify with HCl, around 3 molar equivalent (1.5 times the needed amount). The acid will dissolve, and
water can be boiled away making crystallization of fumaric acid possible.
FeCl2 and FeCl3 will stay in solution and excess HCl will evaporate off. Washing can be done with cold water as fumaric acid has a low solubility.
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The Volatile Chemist
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Perhaps make the solution as above, then precipitate it with a barium (or other alkaline earth) salt (this would be best only assuming you have a lot
of the fumarate), then acidify with H2SO4 and filter off the highly insoluble BaSO4.
Interesting salt, how'd you acquire it?
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blogfast25
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Crush the tablets and make a thin slurry with water.
Treat with strong ammonia. This will give highly insoluble Fe(OH)2 and ammonium fumarate, which I assume to be water soluble.
Separate by filtration.
Neutralise the clear filtrate with HCl solution, this will give the poorly soluble fumaric acid and highly soluble ammonium chloride.
Separate by filtration.
Try to always calculate the amounts of reagents used (stoichiometry).
[Edited on 1-1-2016 by blogfast25]
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AvBaeyer
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You worry too much here. Slurry the iron fumarate in water, then add acid (HCl or H2SO4) to pH 1 or so. You will preciptate the fumaric acid and the
iron chloride or sulfate will remain in solution. You may have to provide some heat to the reaction to get it to completion. You do not need a lot of
solubility of the iron fumarate to get this to work. It's a simple double-decomposition reaction. Keep in mind that the fumaric acid will have greatly
reduced solubility in the aqueous acid reaction mixture. Isolate the fumaric acid by filtration and recrystallize it from aqueous acetic acid or other
solvent of your choosing.
AvB
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ChemLlama
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Quote: Originally posted by The Volatile Chemist  | Perhaps make the solution as above, then precipitate it with a barium (or other alkaline earth) salt (this would be best only assuming you have a lot
of the fumarate), then acidify with H2SO4 and filter off the highly insoluble BaSO4.
Interesting salt, how'd you acquire it? |
Hmm, assuming that barium fumarate is insoluble enough to achieve quantitative precipitation, how will it react with aqueous
H2SO4 to form the aqueous acid? Wouldn't the BaSO4 just form an impervious coating around the barium fumarate
particles?
Oh and I don't have much of the iron(II) fumarate, I think about 4 grams of it or so. I bought it at a pharmacy, it was being sold as an iron
supplement  it says "ferrous fumarate 200mg" and nothing else, so I'm going to
weigh a tablet and hope it works out to be 0.2g, which would mean that it doesn't have any fillers. Those would be troublesome to remove since I
wouldn't know its identity...
[Edited on 1-1-2016 by ChemLlama]
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ChemLlama
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| Quote: Originally posted by AvBaeyer | You worry too much here. Slurry the iron fumarate in water, then add acid (HCl or H2SO4) to pH 1 or so. You will preciptate the fumaric acid and the
iron chloride or sulfate will remain in solution. You may have to provide some heat to the reaction to get it to completion. You do not need a lot of
solubility of the iron fumarate to get this to work. It's a simple double-decomposition reaction. Keep in mind that the fumaric acid will have greatly
reduced solubility in the aqueous acid reaction mixture. Isolate the fumaric acid by filtration and recrystallize it from aqueous acetic acid or other
solvent of your choosing.
AvB |
Hmm... Thank you, I'd consider that method Do you think the best way to purify
the resultant precipitate which likely contains the iron(II) salts and the fumaric acid I want to obtain is to dissolve it in 95% ethanol, filter, and
evaporate the filtrate? Thanks!
Happy New Year to everyone by the way 
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The Volatile Chemist
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Sorry, I guess I was assuming fumaric acid could be distilled, just had to look at its structure and realized that wasn't so. AvBaeyer's method should
work.
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