The process used to separate the substances composing
a mixture; it involves a change of state, e.g. liquid
to gas, and subsequent condensation.
A simple distillation
apparatus consists of three parts a flask in which
the mixture is heated, a condenser in which the vapor
is cooled, and a vessel in which the condensed vapor,
called distillate, is collected.
Upon heating, the
substances with a higher boiling point remain in the
flask and constitute the residue. When the substance
with the lowest boiling point has been removed, the
temperature can be raised and the process repeated
with the substance having the next lowest boiling
point. The process of obtaining portions in this way
is called fractional distillation.
distillation various solid substances, such as wood,
coal and oil shale, are heated out of free contact
with air, and the portions driven off are collected
separately. Distillation is used in refining petroleum
and in preparing alcoholic beverages.