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How to reconstruct a crystal

  1. Sep 22, 2014 #1
    Suppose I have a substance that has been crystallized. Now suppose I break down those crystals into powder, grains, etc. How can I reconstruct that powder into a crystal again? Do I just dissolve it into a solvent and then evaporate the solvent?

    Another quick question - is it possible to manipulate the appearnace of the crystal based on what solvent I use, the amount of solvent I use, etc?
     
  2. jcsd
  3. Sep 22, 2014 #2

    Borek

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    Staff: Mentor

    Either that, or melt and cool down to solidify.

    Let me put it this way - crystal form can depend on the solvent used and/or other substances dissolved. I have heard organic chemists say "If you have not seen other crystalline forms of your substance, you have not tried hard enough". Those working in pharma told me horror stories about products that were approved for use, but one day started to crystallize in another form and they were unable to find the reason (and as far as I know you can't sell different form, you have to sell the one you have permission for). But it is not easy to predict.
     
  4. Sep 22, 2014 #3
    To be specific, the compound the I am trying to crystallize is usually comprised of nearly opaque, pearly crystals. When it is in its base form, it is dissolved in diethyl ether, then precipitated in its hydrochloride form by adding an acetone/HCL acid solution (or by bubbling dry HCL gas through the solution). This results in opaque-ish, pearly crystals. My problem is, if I were to break these crystals down and reassemble them by crystallizing them in, say, methanol (or IPA), the result is transparent crystals which bear no resemblence to the original crystals. How can I reassemble the crystals so that they look the same as the original?
     
  5. Sep 23, 2014 #4

    Borek

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    The most logical approach would be to neutralize the hydrochloride and recrystallize by adding HCl (that is, by repeating the same procedure). Note it is not guaranteed to work.

    What do you need these crystals for? If you are getting clear ones they are probably 'better' - less inclusions and impurities.
     
  6. Sep 24, 2014 #5

    DrDu

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    Last edited: Sep 24, 2014
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