distillation

Distillation is a physical separation process that relies on differences in volatility to separate components of a liquid mixture. By heating a mixture, the more volatile component vaporizes first; the vapor is then cooled and condensed back to liquid in a separate container. The technique can either concentrate a single component or separate a mixture into fractions with different boiling points. The central concept is relative volatility, the tendency of components to vaporize at different rates due to their boiling points.

Common forms include simple distillation, fractional distillation, steam distillation, and vacuum distillation. Simple distillation is used when the boiling points are markedly different; fractional distillation uses a fractionating column to create multiple theoretical plates and achieve finer separation. Steam distillation blends a volatile compound with water to lower its effective boiling point, useful for heat‑sensitive substances such as essential oils. Vacuum distillation lowers boiling points by reducing ambient pressure, enabling distillation at lower temperatures to limit decomposition.

Industrial and laboratory applications include purification and isolation of liquids, production of alcoholic beverages, purification of solvents, and the separation of liquid hydrocarbons in petrochemical refining. Distillation is also used in desalination and water purification. Limitations include energy intensity, potential formation of azeotropes that cannot be fully separated, and decreased efficiency with heat‑sensitive mixtures without special designs.