A hot solution of a substance on cooling, deposits crystals of the pure substance. This process is called crystallisation.
Take about 25 ml of water in a beaker. Add salt, stir and heat. At one point no more salt will mix into the solution. Such a solution is said to be saturated. Filter the hot salt solution through a filter paper. Collect the filtrate in a china dish and allow it to cool. Fine crystals of pure salt will be formed in the china dish. The crystals can be separated on filtration. The liquid left after the removal of the crystals is called mother liquor.
1. Separation of crystals of alum from impure samples.
2. Purification of salt from sea water.
In cities drinking water is obtained from water works. The above figure represents supply of drinking water from water storage tank.