Distillation

Simple distillation

Simple distillation is used to separate a solvent from a solution. It is useful for producing water from salt solution.

Simple distillation works because the dissolved solute has a much higher boiling point than the solvent. When the solution is heated, solvent vapour leaves the solution. It is led away, cooled and condensed. The remaining solution becomes more concentrated as the amount of solvent in it decreases.

Salty water is heated.

Simple distillation

1. Salty water is heated

Fractional distillation

Fractional distillation is used to separate different liquids from a mixture of liquids. It is useful for separating ethanol from a mixture of ethanol and water, and for separating different fractions from crude oil.

Fractional distillation works because the different liquids have different boiling points. When the mixture is heated:

  • vapours rise through a column which is hot at the bottom and cooler at the top
  • vapours condense when they reach a part of the column that is below their boiling point
  • each liquid is led away from the column

Different liquids can be obtained from different parts of the column, or by continuing to heat the mixture to increase the temperatures in the column.

In the first stage of ethanol distillation, water and ethanol solution is heated.

Distillation process to separate ethanol from water

1. Water and ethanol solution is heated