Testing For Anions

Chemistry

Test for Carbonates

Add dilute acid to the substance. Carbon dioxide gas will be produced, causing effervescence. The gas can be tested by bubbling it through limewater, which turns milky.

Test for Sulfates

Add dilute hydrochloric acid (for the purpose of reacting with and removing carbonate or sulfite ions, which would otherwise form an interfering white precipitate with barium ions). Then add barium chloride solution. A white precipitate of barium sulfate will form.

Test for Sulfites

Add dilute acid to the substance and warm. Sulfur dioxide gas is produced, which will turn acidified potassium manganate solution from purple to colourless.

Test for Nitrates

Add sodium hydroxide solution and aluminium foil to the substance, then warm gently. Ammonia gas will be produced, which turns damp red litmus paper blue.

Test for Halides (Process)

Add dilute nitric acid to remove interfering ions. Then add silver nitrate solution. If a halide ion is present a precipitate will form.

Test for Halides (Results)

Chloride ions form a white precipitate (silver chloride).

Bromide ions form a cream precipitate (silver bromide).

Iodide ions form a yellow precipitate (silver iodide).