An impure sample of Naphthalene can be purified by Sublimation.
Certain organic substances on heating change directly from a solid-state to a gaseous state without passing through the liquid state. This process is known as sublimation.
- During this process, naphthalene being sublime changes into vapours leaving behind impurities.
- Vapour can be cooled by condensation.
- This process is very helpful in separating a volatile solid from a non-volatile solid.
- The impure sublimating organic compound is taken in a china dish and covered with perforated filter paper. A funnel plugged with cotton is inverted over the filter paper to prevent the organic compound vapours from escaping.
- The china dish is heated gently.
- The organic compound sublimes and the vapours rise into the funnel through the perforations in the filter paper.
- The funnel being cooler than the dish, the vapours condense on the cooler walls of the funnel to form pure crystals of the organic compound.