Estimation of Halogen

Carius Method:

Principle: A known mass of organic compound is heated with fuming nitric acid (HNO₃) in the presence of silver nitrate (AgNO₃) in a Carius tube → carbon and hydrogen oxidised to CO₂ and H₂O → halogen present reacts with AgNO₃ to form the corresponding silver halide (AgX).

Silver halide is filtered, washed, dried, and weighed.

Formulas:

\[\%X=\frac{\text{At wt of halogen}\times\text{wt of AgX formed}\times100}{\text{Mol. wt of silver halide}\times\text{wt of organic compound}}\]

\[\%Cl=\frac{35.5\times\text{wt of AgCl}\times100}{143.5\times w}=\frac{24.74\times\text{wt of AgCl}}{w}\]

\[\%Br=\frac{80}{188}\times\frac{\text{Mass of AgBr}\times100}{\text{Mass of compound}}=\frac{42.55\times\text{wt of AgBr}}{w}\]

\[\%I=\frac{127}{235}\times\frac{\text{Mass of AgI}\times100}{\text{Mass of compound}}=\frac{54\times\text{wt of AgI}}{w}\]