In Carius tube, an organic compound ' X ' is treated with sodium peroxide to form a mineral acid…

Barium chloride is used estimate sulphur content in the molecule. In Carius tube test, a known mass of sulphur present in an organic compound with Silver Nitrate is heated into a sealed tube known as Carius tube with silver. The organic compound is then converted to Sulphuric acid which then reacts with excess Barium Chloride solution and produces a precipitate of Barium Sulphate. $\mathrm{Z}$ is ${\mathrm{BaSO}}_4$ and $\mathrm{Y}$ is ${\mathrm{H}}_2{\mathrm{SO}}_4$

It is clear that " $\mathrm{X}$ " must contain sulphur. Methionine is ${\mathrm{C}}_5{\mathrm{H}}_{11}{\mathrm{NO}}_2 \mathrm{S}$, a sulphur contaning amino acid