Azeotropes or constant boiling mixtures is a mixture of two or more liquid which cannot be separated by simple distillation. This happens because when azeotrope is boiled, vapor has same proportion of constituents as unboiled mixture.

Maximum boiling azeotropes:

These are obtained from solution that shows negative deviation from ideal solution. We know, vapor pressure is inversely proportional to boiling point. Since first type of mixture showing negative deviation have lowest vapor pressure, they form maximum boiling azeotropes. Here the mixtures will boil at the temperature above boiling temperature of components from which they are made and the mixture will boil undistilled. Read more

Types Of Mixtures (for distillation)

Miscible liquid mixtures are of three types which can be revealed by plotting the vapor pressure against mole fraction of component.

1. First type of mixture:

The Vapor pressure curve exhibit minimum area. If we take mixture which has excess of ‘x’ (more volatile compound), we are somewhere at ‘C’ on the curve. On distillation, vapor will contain excess of ‘x’ and thus the remaining mixture will get richer in ‘y’. Finally we reach the point ‘D’ where vapor pressure is minimum and thus the boiling point is maximum. Here the mixture will distill unchanged in composition. Read more