General Guidelines for a Recrystallization

Here are some general rules to follow for purifying any solid compound. 

Put the solid in an Erlenmeyer flask, not a beaker. If you recrystallize compounds in beakers, you may find the solid climbing the walls of the beaker to get at you as a reminder. A 125-ml Erlenmeyer usually works. Your solid should look comfortable in it, neither cramped, nor with too much space. You probably shouldn t fill the flask more than one fifth to one fourth full. 

Heat a large quantity of a proven solvent (see preceding) to the boiling point, and slowly add the hot solvent. Slowly A word about solvents Fire Solvents burn No flames A hot plate here would be better. You can even heat solvents in a steam or water bath. But—No flames  

Carefully add the hot solvent to the solid to just dissolve it. This can be tricky, since hot solvents evaporate, cool down, and so on. Ask your instructor. 

Add a slight excess of the hot solvent (5-10 ml) to keep the solid dissolved. 

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