In my own experience, some compounds crystallize easily, while others are just plain stubborn, tending to form amorphous solids or oils. For good crystals to form, they need to grow slowly. There are a number of popular techniques:
- Dissolve the solid in a small volume of hot solvent and cool.
- Dissolve in a suitable solvent and allow volume to reduce by slow evaporation.
- Dissolve in a "good" solvent and add a miscible "bad" solvent and let stand.
This method works well if the good solvent is more volatile than the bad solvent and can be slowly evaporated. - Allow a more volatile "bad" solvent to slowly diffuse into a solution of the compound in a "good" solvent.
Crystal growing is a craft learned by practice and experience, or, in my case, a matter of luck!
I did not know any particular good websites about crystal growing, but a Google search on ["crystal growing" technique] turns up a good variety. Here are a couple:
Tips for Crystal Growing:
http://www.cryst.chem.uu.nl/growing.html
Crystal Growing for Students (linked in above site):
http://www.xray.ncsu.edu/student_xtal.html
Steve
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