In Carius tube, an organic compound ' X ' is treated with sodium peroxide to form a mineral acid ' Y '. The solution of BaCl 2 is added to ' Y ' to form a precipitate ' Z '. ' Z ' is used for the quantitative estimation of an extra element. ' X ' could be

Step-by-step solution

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. Z is BaSO 4 and Y is H 2 SO 4 It is clear that " X " must contain sulphur. Methionine is C 5 H 11 NO 2   S , a sulphur contaning am