Question

Discuss about Lassaigne's test.

Answer 1

Hey !!

In this test, a fleshly cut pea-size sodium metal is placed in a fusion tube and strongly heated till it forms a shining globule. The fusion tube is withdrawn from the flame and a pinch of organic halide added. The fusion tube is again heated in the flame to red-heat and then plunged into distilled water and filtered. The filtrate thus obtained is called ''Lassaigne's extract''

The Lassaigne's extract is then boiled with the dil. HNO₃ to expel gases, if evolved. The solution is then cooled and AgNO₃ solution added to it.

(a) A white precipitate soluble in NH₄OH indicates the presence of chlorine.

(b) A pale yellow precipitate partially soluble in NH₄OH indicates the presence of bromine.

(c) A bright yellow precipitate insoluble in NH₄OH indicates the presence of halogens.

Good luck !!

Answer 2

The sodium fusion test, or Lassaigne's test, is used in elemental analysis for the qualitative determination of the presence of foreign elements, namely halogens, nitrogen, and sulphur, in an organic compound. It was developed by J. L. Lassaigne....