Recrystallization

Recrystallization - Recrystallization The following is a...

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Recrystallization The following is a graphical representation of the recrystallization process: Figure 1: Recrystallization Flow Chart The five steps of recrystallization: 1. Choose an appropriate solvent for the recrystallization 2. Dissolve the impure mixture in the solvent 3. Remove the insoluble impurities via filtration 4. Crystallize the pure compound from the solution 5. Isolate the pure compound via suction filtration
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Step 1: How to Choose a Solvent A solvent must have a number of specific characteristics in order for it to be deemed suitable for use in recrystallization. The process of finding a suitable solvent can be quite difficult and time consuming depending on the physical properties of your impure mixture. The following conditions must be met: First, it must fully solvate your compound at high temperature, but not solvate it at room temperature. Dissolution is necessary so that the crystalline lattice can be broken down and reformed in absence of the impurities. However, if the compound is soluble at room temperature, it will be exceedingly difficult to retrieve it from the solution at the end of the experiment. Second, the impurities that you are removing from the mixture must be either soluble in the solvent at room temperature or insoluble at high temperature. This temperature related contrast is essential for the proper separation of the impurities from the desired compound. In either case, the two components can be separated from one another via simple gravity filtration. Third, the solvent must be chemically inert with regards to both the desired compound and any impurities within the mixture. If your compound reacts with the solvent, a chemical transformation will occur rather than a purely physical dissolution/recrystallization.
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