Chapter : 2. Is Matter Around Us Pure
Purification by Crystallisation
Separation by filtration :
Separation by centrifugation :
Separation by Evaporation :
Purification by crystallisation : The process of cooling a hot, concentrated solution of a substance to obtain crystals is called crystallisation. The process of crystallisation is used for obtaining a pure solid substance from impure sample.
(a) The impure solid substance is dissolved in the minimum amount of water to form a solution.
(b) The solution is filtered to remove insoluble impurities.
(c) The clear solution is heated gently on a water bath till a concentrated solution or saturated solution is obtained (This can be tested by dipping a glass rod in hot solution from time to time. When small crystals form on the glass rod, the solution is saturated). Then stop heating.
(d) Allow the hot, saturated solution to cool slowly.
(e) Crystals of pure solid are formed. Impurities remain dissolved in solution.
(f) Separate the crystals of pure solid by filtration and dry.
Separation by chromatography :
Separation by distillation :
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