An azeotrope ( /əˈziːətroʊp/ ə-ZEE-ə-trohp or /ˈeɪziətroʊp/ AY-zee-ə-trohp) is a mixture of two or more liquids in such a way that its components cannot be altered by simple distillation. This happens because, when an azeotrope is boiled, the vapor it produces has proportionate constituents as the original mixture.
Because their composition is unchanged by distillation, azeotropes are also called (especially in older texts) constant boiling mixtures. The word azeotrope is derived from the Greek words ζέειν (boil) and τρόπος (state) combined with the prefix α- (no) to give the overall meaning, "no change on boiling".
Azeotropic mixtures of pairs of compounds have been documented. (See Azeotrope (data)). Many azeotropes of three or more compounds are also known.
Read more about Azeotrope: Distillation of Mixtures, Phase Diagrams, Heteroazeotropes, Deviation From Raoult's Law, Separation of Azeotrope Constituents, Use of Azeotropes To Separate Zeotropic Mixtures, Why Azeotropes Exist, Complex Azeotrope Systems, Examples of Azeotropes