The Kjeldahl's method for the estimation of nitrogen can be used to estimate the amount of nitrogen in which one of the following compounds?
(1)

Kjeldahl's method is not applicable to:Nitrogen in nitro groups ($-{\text{NO}}_2$).Nitrogen in azo groups ($-\text{N}=\text{N}-$).Nitrogen in the ring (pyridine, quinoline).This is because the nitrogen in these cases cannot be converted quantitatively to ammonium sulfate. Aniline (primary aromatic amine) can be estimated via this method.