Distillation under reduced pressure - Purification of organic compounds

This process is employed for the purification of high boiling liquids and liquids that decompose at or below their boiling points. The crude liquid is heated in distillation flask fitted along with a water condenser, receiver and vacuum pump. Since the pressure is reduced, the liquid begins to boil at a much lower temperature as compared to its normal boiling point. The vapour is condensed through water condenser and the pure liquid collects in the receiver.

Glycerol that decomposes at its boiling point (563 K) within atmospheric pressure can be distilled with no decomposition at 453 K under 12 mm of Hg. Likewise, sugarcane juice is concentrated in sugar industry by evaporation under reduced pressure that saves a lot of fuel.