Explain about the procedure and calculation behind the carius method of estimation of sulphur.

Explanation

Carius method
(i) Procedure: A known mass of the organic compound is taken in a clean carius tube and few mL of fuming `HNO_(3)` is added and then the tube is sealed. It is then placed in an iron tube and heated for 5 hours. The tube is allowed to cool and a hole is made to allow gases to escape.
The carius tube is broken and the content collected in a beaker. Excess of `BaCl_(2)` is added to the beaker. `H_(2)SO_(4)` formed is converted to `BaSO_(4)` (white ppt.) The precipitate is filtered, washed, dried and weight. From the mass of `BaSO_(4)` percentage of S is calculated.
(ii) Calculation:
Mass of organic compound = Wg
Mass of BaSoformed= x g
233 g of `BaSO_(4)` contains 32 g of sulphur
`:.` x g of `BaSO_(4)` contain `(32)/(233) xx x g` of sulphur
`"Percentage of sulphur"= ((32)/(233) xx (x)/(w) xx 100)%`