Carius method for the estimation of halogens: A known mass of the organic compound containing halogens is heated with an excess of fuming nitric acid and silver nitrate in a sealed tube called Carius tube. Cabron, hydrogen and sulphur (if present) are oxidised to CO₂, H₂O and H₂SO₄ respectively whereas halogen forms a precipitate of silver halide. The precipitate is separated, washed with distilled water, dried and weighed. The percentage of halogens is then calculated. Calculations:
Let the mass of the compound taken = Wg Let the mass of halide (AgX) formed = ag

Atomic mass of halogen = x

Molecular mass of AgCl = 108 + 35.5 = 143.5 g mol^-1.
Now 143.5 g AgCl contains 35.5 g chlorine
  0.5740 g AgCl would contain
                 
Mass of organic compound is =0.3780

Mass of organic compound 0.15g
Mass of AgBr = 0.12g
Molecular mass of AgBr = 108+80 = 188 g mol^-1
Now 188g AgBr contains 80 g bromine

Mass of the compound  = 0.15 g,   Mass of silver iodide = 0.2682 g
The molecular mass of silver iodide. 
              (Ag I) = 108 + 127 = 235
              
235g of AgI contains  = 127 g of iodine