In Lassaigne’s test for the detection of halogens, the sodium fusion extract is first boiled with concentrated nitric acid. This is

Step-by-step solution

For the test of halogens, it is necessary to remove sodium cyanide and sodium sulphide from the sodium extract if N and S are present. It is possible by boiling sodium extract with cocn. H N O 3 as follows N a C N + H N O 3 → N a N O 3 + H C N ↑ N a 2 S + 2 H N O 3 → 2 N a N O 3 + H 2 S ↑