Fractional crystallization (chemistry)

Crystallization
Fundamentals
Crystal Crystal structure Nucleation
Concepts
Crystallization Crystal growth Recrystallization Seed crystal Protocrystalline Single crystal
Methods and technology
Boules Bridgman–Stockbarger method Van Arkel–de Boer process Czochralski method Epitaxy Flux method Fractional crystallization Fractional freezing Hydrothermal synthesis Kyropoulos method Laser-heated pedestal growth Micro-pulling-down Shaping processes in crystal growth Skull crucible Verneuil method Zone melting

In chemistry, fractional crystallization is a method of refining substances based on differences in their solubility. It fractionates via differences in crystallization (forming of crystals). If a mixture of two or more substances in solution are allowed to crystallize, for example by allowing the temperature of the solution to decrease or increase, the precipitate will contain more of the least soluble substance. The proportion of components in the precipitate will depend on their solubility products. If the solubility products are very similar, a cascade process will be needed to effectuate a complete separation. This technique is often used in chemical engineering to obtain pure substances, or to recover saleable products from waste solutions. Fractional crystallization can be used to separate solid-solid mixtures. An example of this is separating KNO₃ and KClO₃.

See also

• Cold Water Extraction
• Fractional crystallization (geology)
• Fractional freezing
• Laser-heated pedestal growth
• Pumpable ice technology
• Recrystallization (chemistry)
• Seed crystal
• Single crystal

References

• "Small Molecule Crystalization" (PDF) at Illinois Institute of Technology website