Principle of Fractional distillation
- Normally the composition of vapour of any liquid mixture does not remain equal to the composition in liquid state.
- The more volatile component remains more in vapour state than that of liquid state.
- After heating, the more volatile component increase in vapour state and when this vapour is liquefied then more volatile component increase in liquid state.
- First vaporization and then condensation (liquefaction) is combinedly known as distillation. When this distillation process is repeatedly occurred, a time will come when more volatile component remain in liquid state at pure state. In this way components of liquid—liquid mixture can be separated as a pure substance by using fractional distillation method.
Let consider a liquid— liquid mixture of A and B where A is more volatile than B this mixture can be separated by the following process: