Question

Glycerol is purified by which method?

• A. Distillation under reduced pressure
• B. Steam distillation
• C. Fractional distillation
• D. Simple distillation

Answer 1

Answer:

A. Distillation under reduced pressure

• Distillation under reduced pressure (also known as Vacuum Distillation) is the standard industrial method used for the purification of glycerol.

• Glycerol has a high boiling point of approximately 290°C. At this temperature, glycerol tends to undergo thermal decomposition or dehydration.

• By reducing the pressure above the liquid, the boiling point of glycerol is significantly lowered. This allows it to vaporize at a much lower temperature where it remains chemically stable, preventing its breakdown.

• This technique is specifically utilized because glycerol is a common byproduct in the soap manufacturing process (saponification of fats).

• Other Distillation Techniques:

  • Simple Distillation: Used for liquids with a large difference in boiling points.

  • Fractional Distillation: Used for separating components with boiling points close to each other, like crude oil refining.

  • Steam Distillation: Used for heat-sensitive organic compounds that are immiscible with water, such as essential oils and volatile organic compounds.