Illustrated Glossary of Organic Chemistry

Distillation: A process for separating components of a mixture, in which the components are evaporated and the vapors condensed. The most volatile substance (the substance with the lowest boiling point) is vaporized first, and hence removed from the mixture first.

In simple distillation, all of the material which is evaporated and then condensed (the distillate) is collected together as a single fraction. Labeling code: (1) Heat source. (2) Still pot. (3) Still head. (4) Thermometer. (5) Condenser. (6) Cooling water in. (7) Cooling water out. (8) Distillate receiver. (9) Vacuum adapter. (10) Still receiver. (11) Heat controller. (12) Stirrer controller. (134) Stirrer/hot plate. (14) Heating bath. (15) Stir bar. (16) Cooling bath. Click here for a larger version.

A still for making moonshine (illegal hard liquor) uses simple distillation. The silver cylinder is the still pot (which is heated by a wood fire), the copper tube is the condenser, and the green barrel is the still pot. Distillation of legal liquor is conducted in a distillery.

Fractional distillation operates much like simple distillation, except that the distillate is divided into fractions. Each fraction might be a pure compound, or a mixture with a different boiling point range than other fractions.

Diagram of a refinery's fractional distillation column. An oil refinery uses fractional distillation to separate crude oil into material that have different boiling point ranges. Gasoline, composed mostly of C4 to C12 hydrocarbons, is the fraction whose boiling point range is about 40oC to about 200oC, while the kerosene/jet fuel fraction is composed mostly of C12 to C16 hydrocarbons and has a boiling point range is about 200oC to about 250oC.

A rotary evaporator (rotovap) uses simple vacuum distillation to remove solvent from a sample. As the ambient pressure is lowered, boiling point is also lowered, so the solvent evaporates more readily.