Estimation of Sulphur in Organic Compounds

A known mass of an organic compound is heated in a Carius tube with sodium peroxide or fuming nitric acid. Sulphur present in the compound is oxidised to sulphuric acid. It is precipitated as barium sulphate by adding excess of barium chloride solution in water.

The precipitate is filtered, washed, dried and weighed. The percentage of sulphur can be calculated from the mass of barium sulphate.

Let the mass of organic compound taken = m g

The mass of barium sulphate formed = m1 g

1 mol of BaSO4 = 233 g of BaSO4 = 32 g of sulphur

m1 g of BaSO4 contains 32m1/233 g sulphur