In the estimation of element $$\mathrm{X}$$ in an organic compound, $$0.8 \mathrm{~g}$$ of the compound containing $$\mathrm{X}$$ was heated with fuming $$\mathrm{HNO}_3$$ and the cooled product was treated with barium chloride. The mass of barium sulphate precipitated was $$1.2 \mathrm{~g}$$. What is the percentage of element $$\mathrm{X}$$ and what is the formula of the violet-coloured compound formed when Lassaigne's extract of the organic compound is treated with sodium nitroprusside?

Presence of halogen in organic compounds can be detected using