Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the heating of solid materials to produce gaseous products (which may condense into liquids or solids); this may involve chemical changes such as destructive distillation or cracking. Distillation may result in essentially complete separation (resulting in nearly pure components), or it may be a partial separation that increases the concentration of selected components; in either case, the process exploits differences in the relative volatility of the mixture's components. In industrial applications, distillation is a unit operation of practically universal importance, but is a physical separation process, not a chemical reaction. An installation used for distillation, especially of distilled beverages, is a distillery. Distillation includes the following applications:

• The distillation of fermented products produces distilled beverages with a high alcohol content, or separates other fermentation products of commercial value.
• Distillation is an effective and traditional method of desalination.
• In the petroleum industry, oil stabilization is a form of partial distillation that reduces the vapor pressure of crude oil, thereby making it safe for storage and transport as well as reducing the atmospheric emissions of volatile hydrocarbons. In midstream operations at oil refineries, fractional distillation is a major class of operation for transforming crude oil into fuels and chemical feed stocks.
• Cryogenic distillation leads to the separation of air into its components – notably oxygen, nitrogen, and argon – for industrial use.
• In the chemical industry, large amounts of crude liquid products of chemical synthesis are distilled to separate them, either from other products, from impurities, or from unreacted starting materials.