What are azetropics mixture??

An azeotrope (/?'zi??tro?p/ ?-zee-?-trohp or /'e?zi?tro?p/ ay-zee-?-trohp) is a mixture of two or more liquids in such a way that its components cannot be altered by simple distillation.[1] This happens because, when an azeotrope is boiled, the vapor has the same proportions of constituents as the unboiled 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 ??e?? (boil) and t??p?? (turning) combined with the prefix a- (no) to give the overall meaning, "no change on boiling". Azeotropic mixtures of pairs of compounds have been documented.[2] Many azeotropes of three or more compounds are also known.[3] they are binary mixtures having the same composition in liquid and vapour phase and boil at a constant temperature. In such case it is not possible to separate the components by fractional distillation. There are two types of azeotropes called minimum boiling azeotrope and maximum boiling azeotrope. The solution which show a greater positive deviation from Raoult`s law form minimum boiling azeotrope at a specific composition. For example ethanol-water mixture (obtained by fermentation of sugars) on fractional distillation gives a solution containing approximately 95% by volume of ethanol. Once this composition, has been achieved, the liquid and vapour have the same composition, and no further separation occurs. The solutions that show large negative deviation from Raoult`s law form maximum boiling azeotrope at a specific composition. Nitric acid and water is an example of this class of azeotrope. This azeotrope has the approximate composition, 68% nitric acid and 32% water by mass, with a boiling point of 393.5 K.