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How to Increase the Crystals in a Methanol Solvent

Recrystallizing a compound from a solvent is one way to help remove impurities when preparing a sample in a chemistry lab. Methanol is a good solvent for compounds that are only moderately polar. If you've already heated your solution, filtered it and are now waiting for it to form crystals inside your test tube or flask, there are a couple things you can do to increase the number of crystals that form.

Things You'll Need

Lab coat
Goggles
Gloves
Metal spatula
Small sample of the original impure product
Container with ice

Instructions

- 1
  Scratch the walls of the flask or tube with the tip of the spatula --- but be sure you do so gently. This action creates irregularities that can serve as surfaces where crystals will form.
- 2
  Add a couple crystals of the impure substance as "seed crystals" to encourage crystal formation. Don't overdo it --- remember the impure substance contains the impurities you were trying to get rid of through recrystallization.
- 3
  Place the flask or test tube in a container full of ice to get it to cool down faster. Be careful not to do this too soon; slower cooling and recrystallization means a more pure product and is therefore desirable. Generally it's best to wait at least 20 minutes before placing in a water bath.

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