Recrystallizing out of methanol

  • #1
Hi, I am trying to recrystallize salt from methanol. I am having trouble. This is exactly what I did:

I dissolved a gram of salt into 20 ml of methanol (the bottle I have says methyl hydrate but I read online that it's the same thing as methanol). Then I made a hot water bath. I put a pyrex dish into a pot of boiling water. Using an eye dropper, I dropped a few drops into the pyrex beaker. I expected the methanol to evaporate almost immediately, leaving me with a thin flakey crystal that can easily be scraped off. But at best, I am left with a small piece of crust that is impossible to scrape off the pyrex dish. What is wrong?
 
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Answers and Replies

  • #2
Borek
Mentor
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No idea why you expected dried out substance to easily separate from the glass. It may, but it doesn't have to.
 
  • #3
397
21
What are you planning on getting out of this process? It seems to me that you are just spinning your wheels. Making a solution and evaporating the solvent leaves you with the material you started with minus some time and energy.

Recrystallizations are typically done to purify something from a mixture and requires either some background knowledge of the system (what your compound is, what impurities might be there etc) or a bunch of trial and error.

See Wikipedia for a intro discussion: Recrystallization
 
  • #4
Thanks for the replies! I have read a lot about crystallization and I will be doing some experiments over the next couple of days. I will update this thread if I have any questions.
 

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