Why is an organic compound fused with sodium for testing nitrogen, halogens sulphur?

Explanation

When an organic compound is fused with metallic sodium, these elements present in the compound are converted into their water sodium salts (NaCN, NaX and `Na_(2)S`). The presence of cyanide ion `(CN^(-1))` , halide ion `(X^(-))` and suphide ion `(S^(2^(-))` in the solution can then be confirmed by using suitable reagents.