Azeotrope

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.