Question

Give the principle involved in the estimation of halogen in an organic compound by Carius method.

Answer 1

Estimation of halogens: carius method:

1. A known mass of the organic compound is heated with fuming HNO₃ and AgNO₃ .

2. C, H and S gets oxidised to CO₂ , H₂O and SO₂ and halogen combines with AgNO₃ to form a precipitate of silver halide

X\(\underset{AgNO_3}{\stackrel{Fuming\,HNO_3}{\rightarrow}}\)AgX↓

3. The precipitate AgX is filtered, washed, dried and weighed.

4. From the mass of AgX and the mass of organic compound taken, the percentage of halogens are calculated.

5. % of chlorine = \(\frac{35.5}{143.5}\times\frac{wt.\%of\,chlorine}{wt.\,of\,organic\,compound}\) x 100

% of Bromine = \(\frac{80}{188}\) x \(\frac{wt.\,\%of\,bromine}{wt.\,of\,organic\,compound}\)x 100

% of Iodine = \(\frac{127}{235}\) x \(\frac{wt.\,\%\,of\,Iodine}{wt.\,organic\,compound}\) x 100