I added 3 grams of adipic acid to 150ml deionized water with heating + mixing until it was completely dissolved. This was then boiled and cooled to allow crystals to form. The maximum amount of adipic acid recovered was 2.62g. Is there a way to recover more of the acid without completely boiling off the solution? Does decreasing the pH decrease the solubility of adipic acid?
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$\begingroup$ The solubility of a substance in pure water depends only on the temperature. But adding some strong acid like hydrochloric acid decreases the solubility of weak acids like adipic acid (Le Chatelier's principle) $\endgroup$– MauriceCommented Feb 20, 2023 at 17:33
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2$\begingroup$ Add salt - sodium chloride. See en.wikipedia.org/wiki/Salting_out $\endgroup$– WaylanderCommented Feb 20, 2023 at 18:05
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$\begingroup$ Why dissolve it in the first place? And how do you know how much you had before you dissolved it? $\endgroup$– Karsten ♦Commented Mar 22, 2023 at 23:04
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1 Answer
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Yes it will. Protonated adipic acid is less soluble in water than sodium adipate. Colder temperatures also make it less soluble.
It can be extracted into a non-polar solvent that is more easily evaporated. Drying under excessive heat may degrade adipic acid. Vacuum may be better.
Some adipic acid will remain in solution if water is still present, but with multiple batches, losses can be reduced by using the same "mother liquor".
Try putting your re-crystallization solution in the refrigerator.
answered Feb 20, 2023 at 19:44