Glycerol can be separated from spent-lye in soap industry by:
A. Crystallisation
B. Sublimation
C. Different extraction
D. Chromatography
E. Distillation under reduced pressure

Hint: Glycerol can be separated by a method in which the pressure above the liquid mixture that is to be separated is reduced to less than its vapour pressure, that causes evaporation of the most volatile liquid.

Complete Step by step solution:
- As we know that Glycerol is high boiling liquid and is having a high boiling point. It can be separated from the spent lye by the method of distillation. It is found that in this method, the liquid is made available to boil at a low temperature than that of its normal temperature.
- Lye is actually an alkaline salt solution. Spent lye is basically Glycerol containing liquor that is formed on saponification of fats with boiling lye.
- It is found that Glycerol can be separated from spent-lye by the process of fractional distillation under reduced pressure.
- It is also seen that Glycerol is having a high melting point, so for its isolation Spent lye is heated under reduced pressure so that the temperature of the liquid is lowered.

- Hence, we can say that the correct option is (E) that is Glycerol can be separated from spent-lye in soap industry by Distillation under reduced pressure.

Note:
- We can see that if the external pressure is reduced, then the boiling point of the liquid is found to be lowered. Therefore, at high-temperature glycerol can be obtained without its decomposition.