Crystallization

Theory

Crystalization is a separation technique used to purify solid compounds. Crystallization relies on the principle that compounds tend to be more soluble in hot solvents. Then, if allowed to cool, the compound will form crystals. As it cools, the dissolved molecules come out of solution and try to stick to the crystal. If the geometry of the molecule matches that of the crystal then it is less likely to go back into solution. This is illustrated in the picture below.