How will you test the presence of halogen in an organic compound by Lassaigne's test?
Lassaigne's test:
This test involves following two steps;
1. Preparation of Lassaigne's or sodium extract:
where X may be Cl, Br or I.
2. Test for halogen: The Lassaigne’s filtrate is boiled with concentrated nitric acid, cooled and then treated with silver nitrate solution. Formation of precipitate indicates the presence of halogen.
(i) White precipitate soluble in ammonium hydroxide indicates the presence of chlorine in the compound then treated with silver nitrate solution. Formation of precipitate indicates the presence of halogen.
(ii) Light yellow precipitate partially soluble in ammonium hydroxide indicates the presence of bromine in the organic compound.
(iii) Bright yellow precipitate insoluble in ammonium hydroxide indicates the presence of iodine in the compound.
