Qualitative Analysis of Bromide Ion
On adding concentrated H2SO4 to a salt, if a brown gas with pungent smell is evolved and the contents of the test solution turns reddish brown, Br– ion is present.
MBr + H2SO4 → MHSO4 + HBr
2HBr + H2SO4 → H2O + SO4 + Br2 (Bromine, reddish brown gas)
Confirmatory Test
Silver Nitrate Test
A light yellow precipitate is obtained on adding silver nitrate to water solution (after acidifying the sodium carbonate extract with dil HNO3). The precipitate is partially soluble in ammonium hydroxide.
Ag+ + Br– → AgBr ↓ (Silver bromide, light yellow)
AgBr + 2NH4OH → [Ag(NH3)2]Br + 2H2O
Organic Layer Test
The addition of chlorine water to water solution containing bromide liberates free bromine which imparts orange red colour to the test solution. On shaking with carbon tetrachloride, a reddish brown colour is imparted in CCl4 layer. The organic layer of CCl4 is obtained below the colourless aqueous layer.
2NaBr + Cl2 → 2NaCl + Br2 (Bromine, reddish brown in CCl4)