Lunar caustic \(\left({AgNO}_{3}\right)\) is used as reagent hare to distinguish \({Cl}^{-}, {Br}\) and \({I}^{-}\)respectively as follows.
\({Cl}^{-}({aq}) \stackrel{{AgNO}_{3}}{\longrightarrow} {AgCl} \downarrow_{{ppt}}\) white
\({Br}^{-}({aq})\stackrel{{AgNO}_{3}}{\longrightarrow} {AgBr} \downarrow_{{ppt}} {pale}\) yellow
\({I}^{-}({aq}) \stackrel{{AgNO}_{3}}{\longrightarrow} {AgNO}_{3} {AgI} \downarrow_{{ppt}}\) Dark yellow
(પરમાણ્વીય દળ :- $Ag =108, Br =80\, g\, mol ^{-1}$ )