Fractional crystallization is a chemical purification technique based on differences in solubility of substances in a solvent at varying temperatures. Re-crystallization is similar, relying on the reduced solubility of a compound to separate it from impurities when cooled. Seed crystals can be used to trigger crystallization in supersaturated solutions.
Fractional crystallization is a technique used in chemistry to purify compounds by exploiting the differences in solubility of substances at different temperatures. Typically, the substance to be purified must be more soluble at higher temperatures.
When the temperature is lowered, the substance precipitates out of solution, leaving impurities that remain dissolved. This process can be applied to a wide variety of compounds, including both inorganic substances like potassium bromide (KBr) and organic substances like antibiotics and enzymes.
A related process is re-crystallization, in which a solution is created by dissolving the impure compound in a hot solvent. Upon cooling, the desired substance crystallizes out. The impurities, being more soluble, do not crystallize and remain in solution. Seed crystals can be added to a supersaturated solution to induce crystallization, providing a starting point for the solid to form.
Both fractional crystallization and re-crystallization are important for achieving high levels of compound purity in various scientific and industrial applications, such as the manufacture of pharmaceuticals and the production of fine chemicals.
The probable question may be:
How does fractional crystallization work in chemical purification, and what is the role of temperature variations in separating substances based on differences in solubility?