Question 12.26: Explain the reason for the fusion of an organic compound with metallic sodium for testing nitrogen, sulphur and halogens.

Nitrogen, sulphur, and halogens are covalently bonded in organic compounds. For their detection, they have to be first converted to ionic form. This is done by fusing the organic  compound with sodium metal. This is called “Lassaigne’s test”. The chemical equations involved in the test are


                                                                         Na + C + N  NaCN
Na + S + C + N  NaSCN
2Na + S  Na2S
Na + X  NaX)
                    ( X = CI,Br,I ) 


Carbon, nitrogen, sulphur, and halogen come from organic compounds.