What is the process of recrystallization?

Recrystallization is a purification technique primarily used to refine solid compounds. The process begins by dissolving the target solid in a hot solvent, which allows the impurities to remain in solution while the desired substance dissolves. As the solution cools slowly, the solubility of the solid decreases, leading to the formation of pure crystals.

The ability to control the cooling process is crucial in recrystallization, as slow cooling allows the crystals to grow larger and purer. These larger crystals are typically more uniform and have less incorporated impurities compared to smaller or rapidly formed ones. Once crystallization is complete, the pure crystals can then be separated from the solution, often through filtration.

This method is particularly advantageous in chemistry because it combines thermal dynamics and solubility principles to achieve purification, making it suitable for a wide variety of organic and inorganic compounds. Other methods mentioned in the choices involve different mechanisms: reverse osmosis is based on membrane separation, grinding is a physical process, and transforming solid into gas pertains to sublimation or other chemical changes not related to recrystallization.