Organic compound is heated with fuming nitric acid in the presence of silver nitrate in carius method. Lunar caustic (AgNO3) is used as reagent hare to distinguish Cl−,Br and I− respectively as follows.
Cl−(aq)⟶AgNO3AgCl↓ppt white
Br−(aq)⟶AgNO3AgBr↓ppt pale yellow
I−(aq)⟶AgNO3AgI↓ppt Dark yellow