Question

Explain about principle and reactions involved in carius method of estimation of sulphur. Carius method:

Answer 1

1. Principle:

A known mass of the organic substance is heated strongly with fuming HNO₃.C and H get oxidized to CO₂ and H₂O while sulphur is oxidised to sulphuric acid as follows.

C \(\underset{HNO_3}{\stackrel{Fuming}{\rightarrow}}\) CO₂

2H \(\underset{HNO_3}{\stackrel{Fuming}{\rightarrow}}\)H₂O

S \(\longrightarrow\)SO₂ \(\overset{O+H_2O}{\rightarrow}\) H₂SO₄

2. The resulting solution is treated with excess of BaCl₂ solution, H₂SO₄ present in the solution is converted into BaSO₄ . From the mass of BaSO₄, the percentage of sulphur can be calculated.