Azeotropes are the mixtures of liqids which boil at constant temperature like a pure liqid and have same parts in liqid as well as in gaseous phase.
An azeotrope is a mixture of two or more pure compounds (chemicals) in such a ratio that its composition cannot be changed by simple distillationn. This is because when an azeotrope is boiled, the resulting vapor has the same ratio of constituents as the original mixture of liquids. As the composition is unchanged by boiling, azeotropes are also known as constant boiling mixtures
Each azeotrope has a characteristic boiling point. The boiling point of an azeotrope is either less than the boiling points of any of its constituents (a positive azeotrope), or greater than the boiling point of any of its constituents (a negative azeotrope).
mixture of liquids with constant composition: a mixture of liquids that has a different boiling point from any of its components and retains its composition as a vapor