Estimation of Halogens by Carius Method

A known mass of an organic compound is heated with fuming nitric acid in the presence of silver nitrate contained in a hard glass tube, known as Carius tube, in a furnace.

Carbon and hydrogen present in the compound are oxidised to carbon dioxide and water. The halogen present forms the corresponding silver halide (AgX). It is filtered, washed, dried and weighed.

Let the mass of organic compound taken = m g

Mass of AgX formed = m₁ g

1 mol of AgX contains 1 mol of X

Mass of halogen in m₁ g of AgX = (atomic mass of X x m₁)/(molecular mass of AgX)