$C{{H}_{3}}-N{{H}_{2}}+2HONO\,\to C{{H}_{3}}-ONO+{{N}_{2}}+2{{H}_{2}}O$

while dimethylamine and trimethyl amine form insoluble compound with hinsberg reagent and $KOH$.

${{R}_{2}}NH\,+\,{{C}_{6}}{{H}_{5}}S{{O}_{2}}Cl\,\xrightarrow{O{{H}^{-}}}$ ${{C}_{6}}{{H}_{5}}S{{O}_{2}}N{{R}_{2}}$

${{R}_{3}}N\,+\,{{C}_{6}}{{H}_{5}}S{{O}_{2}}Cl\,\xrightarrow{O{{H}^{-}}}\underset{insoluble}{\mathop{{{R}_{3}}N}}\,$

Azo dyes are not formed by secondary amines.