FRACTIONAL DISTILLATION
PRINCIPLE
It differs from simple distillation as in simple distillation, vapour pass through condenser & gets condensed which is collected into receiver while in fractional distillation, vapour pass through fractional column where partial condensation of vapours occur & a part of condensing vapour goes to the still. This process is also known as rectification because a part of vapour is condensed & returned as liquid.
APPARATUS
On small scale, the apparatus consists of a still in which liquid is boiled, a fractional column which is inserted between still & condenser & a condenser which is used to condense vapours.
WORKING
The mixture of liquids with different boiling point is heated with high pressure. The mixture starts to boil & form vapour. The vapours rise to the fractional column. The vapour condenses in a condenser column. The distillate is finally received in a receiving flask.
The fractionating column acts as a hurdle to the raising gas. It will stop non pure condensation from passing through it. The gas creates in the packing material in the fractionating column and will be again warmed up by the hot gas that will evaporate again unless it becomes pure.
DIFFERENCE BETWEEN SIMPLE DISTILLATION & FRACTIONAL DISTILLATION
USES
• Used to separate mixtures containing volatile liquids having different but close boiling points.
• Used for separation of miscible liquids, such as alcohol and water, acetone and water, chloroform and benzene.
ADVANTAGES
• Highly effective & efficient.
• Easy to use.
DISADVANTAGES
• High capital cost
• Not flexible
• Not easy to sterilize.
• Not preferred for heat sensitive products.
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