An organic compound $'\mathrm{A}'$ contains nitrogen and chlorine. It dissolves readily in water to give a solution that turns litmus red. Titration of compound $'\mathrm{A}'$ with standard base indicates that the molecular weight of $'\mathrm{A}'$ is $131 \pm 2$. When a sample of $'\mathrm{A}'$ is treated with aq. $\mathrm{NaOH}$, a liquid separates which contains $\mathrm{N}$ but not $\mathrm{Cl}$. Treatment of the obtained liquid with nitrous acid followed by phenol gives orange precipitate. The compound $'\mathrm{A}'$ is :