White crystalline salt imparts violet colour to a Bunsen flame, and hot concentrated $H_{2}S{O}_4$ forms a pungent Gas. On treatment with $AgN{O}_3$ solution, this forms a white precipitate readily soluble in $N{H}_3$. The white crystalline salt may be

A white crystalline salt imparts a violet colour to a Bunsen flame and with hot concentrated ${\mathrm{H}}_2{\mathrm{SO}}_4,$forms a pungent gas. On treatment with ${\mathrm{AgNO}}_3$solution, this gas forms a white precipitate readily soluble in ${\mathrm{NH}}_3$. The white crystalline salt may be $\mathrm{KCl}$.