Vacuum distillation

Working of Vacuum distillation

1. Vacuum Distillation

2. Vacuum Distillation: Principle: Vacuum distillation is a special method of separating compounds at pressure lower than the standard atmospheric pressure. Under this condition, the compounds boil below their normal boiling temperature. Hence, vacuum distillation is best suited for separation of compounds with higher boiling points (more than 200°C), which tend to decompose at their boiling temperature.

3. Vacuum distillation is a method of distillation performed under reduced pressure. As with distillation, this technique separates compounds based on differences in boiling points. This technique is used when the boiling point of the desired compound is difficult to achieve or will cause the compound to decompose. For examples The boiling point of ethanol is 79°C and under vacuum (28 inHg ) it drops to around 34°C.

4. Construction and working: The crude liquid is heated in distillation flask fitted with a water condenser, receiver and vacuum pump. As the pressure is reduced, the liquid begins to boil at a much lower temperature than its normal boiling point. The vapor is condensed by water condenser and the pure liquid collects in the receiver.

5. Vacuum distillation can be conducted without heating the mixture, as is usually followed in other distillation types. For the separation of some aromatic compounds, vacuum distillation is used along with steam distillation. When vacuum distillation is combined with fractional distillation method, components of a mixture get separated very easily.

6. Applications: This method is used for the purification of high boiling liquids and liquids which decompose at or below their boiling points.