Posted: 24 January 2001

A process in which a liquid is vapourised and the vapour subsequently condensed to produce a purified form of the liquid or one of its constituents. Distillation is a natural part of the hydrological cycle. Energy supplied by the sun causes the water to evaporate. The vapour is carried up into the atmosphere until it is cool enough to condense as water droplets. These droplets are pure water, although the original source may have been salty or polluted. Distillation is the principal method of purifying liquids. It is the most common process used in desalination, and has been used increasingly by domestic consumers to provide fresh drinking-water.