What is the difference between distillation, distillation under reduced pressure and steam distillation?

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Hint: The three methods distillation, distillation under reduced pressure and steam distillation are used to separate or purify a variety of organic compounds from a mixture of compounds based on the boiling point of the organic compound we want to purify.

Complete step by step answer:
The differences between the distillation, distillation under reduced pressure and steam distillation are tabulated as below.
S. No.DistillationDistillation under reduced pressureSteam distillation.
1Distillation is a process used to distinct volatile organic liquids from non-volatile impurities or from a mixture of liquids that have adequate difference in boiling points.Distillation under reduced pressure is used to purify a liquid that has a habit of decomposing on boiling. At the conditions of the reduced pressure, the liquid will boil at a lower temperature than its boiling point and therefore the liquids will not decompose. Steam distillation is used to purify an organic compound, which should be steam volatile and the organic compound should be immiscible with water. On passing steam through the organic compound, the compound gets heated up with the steam and gets condensed to water. After a while, the mixture of water and organic liquid starts to boil and passes via the condenser. Later this condensed mixture of water and organic liquid are then separated by separating funnels.
2. A mixture of kerosene and petrol are separated by using this method.The boiling point of Glycerol is 593 K and at this temperature glycerol is going to decompose. By using reduced pressure, Glycerol boils at 453 K without change in its composition.By using steam distillation a mixture of water and aniline can be separated easily.


Note:
The principle behind all these techniques is not the same. We have to choose the method according to the property of the organic compound or liquid which we are going to purify. If the organic compound is volatile we have to choose distillation. If the organic compound is not stable at higher temperature we have to use distillation under reduced pressure.