These are a mixture of two liquids having the same composition in liquid as well as the vapour phase and boil at the constant temperature. This liquid mixture cannot be separated into pure component even by fractional distillation.
Types of Azeotropes
Minimum boiling azeotrope:
The solution which shows large positive deviation from Raoult’s Law. Example: solution of 95% ethanol in water.
Maximum boiling azeotropes:
The solution which shows large negative deviation from Raoult’s Law. Example: solution of 68% nitric acid and 32% water by mass.