0.2 g of an organic compound is subjected to estimation of sulphur by the Carius method, giving 0.6 g of BaSO₄. Calculate the percentage of sulphur in the compound.

The Carius method is a classical analytical technique used for determining the amount of sulphur present in an organic compound. In this method, sulphur present in the compound is converted into sulphate ions, which are then precipitated as barium sulphate (BaSO₄). By measuring the mass of BaSO₄ formed, the amount of sulphur can be calculated.

Given:

• Mass of organic compound = 0.2 g
• Mass of BaSO₄ formed = 0.6 g

First calculate the molar mass of BaSO₄:

BaSO₄ = 137 + 32 + (4 × 16)

= 233 g mol^-1

From the formula, 233 g of BaSO₄ contains 32 g of sulphur.

Therefore, sulphur present in 0.6 g BaSO₄ is:

Mass of S = (32 × 0.6)/233

= 0.0824 g

Percentage of sulphur:

%S = (0.0824/0.2) × 100

= 41.2%

Nearest integer:

= 41%

The Carius method remains important in analytical chemistry because it provides accurate quantitative estimation of sulphur and halogens in organic compounds. The calculation is based on stoichiometric relationships between the precipitated compound and the element being estimated.

Percentage of Sulphur = 41%