Ion tests

• Sulfate anions (SO4 2-) are tested for using BaCl2, which reacts to form a white precipitate.
• Hydroxide anions (OH-) indicate that a substance is alkaline. They can be identified by turning red litmus blue.
• Carbonate anions (CO3 2-) are tested for by adding an acid and bubbled through limewater. CO2 is produced and so the limewater turns cloudy and effervescence is seen.
• Cl- ions form a white precipitate with acidified silver nitrate (AgNO3) and dissolves in dilute ammonia.
• Br- ions form a cream precipitate with acidified silver nitrate (AgNO3) and dissolves in concentrated ammonia.
• I- ions form a yellow precipitate with acidified silver nitrate (AgNO3) and doesn't dissolve in ammonia.
• Ammonium cations (NH 4+) are tested for by turning red litmus blue as ammonia is given off whenever there are ammonium ions present, and ammonia gas is a base. NaOH can be added to produce ammonia gas faster.
• Ca 2+ burns with a brick red flame.
• Sr 2+ burns with a red flame.
• Ba 2+ burns with a pale green flame.