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How to Perform a Recrystallization

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How to Perform a Recrystallization - Introduction
A Buchner funnel may be placed on top of a Buchner flask (filter flask).

A Buchner funnel may be placed on top of a Buchner flask (filter flask) so that a vacuum may be used to separate or dry a sample.

Eloy, Wikipedia Commons
Recrystallization is a laboratory technique used to purify solids based on their different solubilities. A small amount of solvent is added to a flask containing an impure solid. The contents of the flask are heated until the solid dissolves. Next, the solution is cooled. A more pure solid precipitates, leaving impurities dissolved in the solvent. Vacuum filtration is used to isolate the crystals. The waste solution is discarded.

Summary of Recrystallization Steps

 

  1. Add a small quantity of appropriate solvent to an impure solid.
  2. Apply heat to dissolve the solid.
  3. Cool the solution to crystallize the product.
  4. Use vacuum fitration to isolate and dry the purified solid.

Let's take a look at the details of the recrystallization process.

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