Lassaigne’s test

This test is employed to detect the presence of nitrogen,sulphur,halogens and phosphorus in an organic compound. These elements are present in the covalent form in an organic compound. These are converted into ionic form by fusing the compound with sodium metal.

Na+ C +N→ NaCN

Na+ S+C+N→ NaSCN

2Na+S→ Na₂S

Na+ X→ NaX

(X= Cl, Br, I)

The cyanide,sulphide and halide of sodium formed are extracted from the fused mass by boiling it in distilled water. The extract so obtained is called lassaigne’s extract. This lassaigne’s extract is then tested for the presence of nitrogen, sulphur, halogens and phosphorus.