# 3.6B: Crystallization Summary


 Heat some solvent on a heat source to a boil (include boiling stones). To the impure solid in an Erlenmeyer flask, add a small portion of hot solvent. If a hot filtration step is expected, use boiling stones with the impure solid, or a boiling stick or stir bar if a filtration is not expected. Put both flasks on the heat source and bring to a boil. Add the minimum amount of boiling solvent needed to dissolve the impure solid, with swirling. For $$100 \: \text{mg}$$-$$1 \: \text{g}$$ quantities, add $$0.5$$-$$2 \: \text{mL}$$ solvent each time. For smaller scales, add solvent dropwise. Wait for each portion of solvent to come to a boil before adding more. Possibly use charcoal and hot filtration at this point if colored or insoluble impurities are present. When dissolved, remove the solution from the heat source and remove the boiling stick or stir bar if used. Allow the solution to slowly cool atop some paper towels, and with a small watch glass over the mouth of the Erlenmeyer. If a hint of cloudiness is seen in the solution, or if the solution has cooled a good deal without crystallizing, scratch with a glass stirring rod to initiate crystallization. A proper crystallization takes between 5-20 minutes to complete. When the solution is at room temperature, place it in an ice bath for at least 10 minutes to maximize crystal formation. Also chill a rinse solvent in the ice bath. Collect the crystals by suction filtration.

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