Azeotrope

An azeotrope is a liquid mixture of two or more components which has a unique constant boiling point. This azeotrope may boil at a higher, lower, or intermediate temperature, relative to the constituent liquids, and the liquid retains the same composition as it is boiled. As a consequence, the vapor has the same composition as the liquid and simple distillation will not separate the constituents as it would with most liquid mixtures.

The word azeotrope comes from the Greek "zein tropos", or "constant boiling". An azeotrope is said to be positive if the constant boiling point is at a temperature maximum, and negative when the boiling point is at a temperature minimum. The vast majority of azeotropes are minimum boiling.

The azeotrope maximum for alcohol is 192 degrees proof. This is due to the fact that alcohol is so anhydrous that it will absorb moisture from the air. Anhydrous alcohol can only be produced by using a molecular sieve or through the addition of harmful chemicals such as benzene.