Test for Anions

• Carbonate ion CO3 2-

  • add dilute acid
  • effervescence observed, colourless odourless gas forms a white precipitate when bubbled into limewater, gas evolved is carbon dioxide
• Chloride Ion Cl-

  • add dilute nitric acid followed by aqueous silver nitrate
  • white precipitate forms (silver chloride)
• Iodide ion I-


  • add dilute nitric acid followed by aqueous silver nitrate
  • yellow precipitate forms (silver iodide)
• Nitrate ion NO3-

  • add aqueous sodium hydroxide followed by a piece of aluminium foil, warm the mixture
  • effervescence observed, pungent gas that turns damp red litmus paper blue is evolved, gas is ammonia gas as nitrate ion is reduced to ammonia
• Sulfate ion SO4 2-


  • add dilute nitric acid followed by aqueous barium nitrate
  • white precipitate forms, which is barium sulfate