Explain cryatallization and sublimation phenomena whilch are used in the purification of organic compounds.

Explanation

Crystallisation: The principle used here is that the impurities are insoluble or soluble in the given solvent at any temperature, but the substance to be purified is sparingly soluble at room tempera- - ture but highly soluble at highest temp. i.e.) almost near the boiling temp. of the solvent. This method is useful to purify solid compounds.
Sublimation : Some solid substances when heated pass directly into vapour state without melting. Those vapour on cooling form directly solid with out condensing to liquid. This phenomenon is called sublimation.
Impure compound is taken in a beaker covered with a watch glass and heated on an electric plate. The compound sublimates and solidifies on the lower surface of the watch glass. Impurities settle in the beaker. Pure compounds in separated by scratching the watch glass.
This is also a purification method of solids.