Carius method:
A known mass of the substance is taken along with fuming HNO3 and AgNO3 taken in a clean carius tube. The open end of the carius tube is sealed and placed in a iron tube for 5 hours in a range at 530 to 540 K. Then the tube is allowed to cool and a small hole is made in the tube to allow the gases to escape. The tube is broken and the precipitate is filtered, washed, dried and weighed. From the mass of AgX produced percentage of halogen in the organic compound is calculated.
X \(\underset{AgNO_3}{\stackrel{Fuming\,HNO_3}{\rightarrow}}\) AgX ↓
Calculation:
Weight of the organic compound = Wg
Weight of AgCl = a g
143.5 g AgCl contains 35.5g of Cl
a g of AgCl contain \(\frac{35}{143.5}\times9\) g of Cl
Wg of organic compound contains \(\frac{35}{143.5}\times9\) g of Cl
% of chlorine = \(\big(\frac{35}{143.5}\times\frac{a}{w}\times100\big)\%\)
Weight of silver bromide = b g
188 g of AgBr contains 80 g of Br
b g of AgBr contain = \(\frac{80}{188}\) x b g of Br
% of Bromine = \(\big(\frac{80}{188}\times\frac{b}{w}\times100\big)\)
