If $N$ and $S$ are present in an organic compound during the Lassaigne test,then both change into:

Sodium fusion extract of which compound gives Prussian blue colour with $FeSO_4$?

$A$ solution of $m-$chloroaniline,$m-$chlorophenol and $m-$chlorobenzoic acid in ethyl acetate was extracted initially with a saturated solution of $NaHCO_3$ to give fraction $A$. The left over organic phase was extracted with dilute $NaOH$ solution to give fraction $B$. The final organic layer was labelled as fraction $C$. Fractions $A$,$B$ and $C$ contain respectively

In which of the following compounds will nitrogen not be detected by the Lassaigne test?

Statement $I$: Nitrogen in pyridine cannot be estimated by Kjeldahl’s method. Statement $II$: Nitrogen in pyridine changes to ammonium sulphate when heated with conc. $H_2SO_4$ in Kjeldahl’s method. Read the above given statements and choose the correct answer from the given options.

Which one of the following reactions does $NOT$ belong to "Lassaigne's test"?