This method is called distillation. It is used for the separation of components of a mixture containing two miscible liquids that boil
without decomposition and have sufficient difference in their boiling points.
To separate a mixture of two or more miscible liquids for which the difference in boiling points is less than 25 K, fractional distillation process is used, for example, for the separation of different gases from air, different factions from petroleum products etc. The apparatus is similar to that for simple distillation, except that a fractionating column is fitted in between the distillation flask and the condenser.
A simple fractionating column is a tube packed with glass beads. The beads provide surface for the vapours to cool and condense