Testing for halide ions

Here’s how to test for halide ions in a sample:

1. Add a few drops of dilute nitric acid (HNO3) to the sample.

  • This step removes any carbonate ions that could cause a false positive result

2. Add a few drops of dilute silver nitrate (AgNO3) solution.

3. Observe the colour of the precipitate that forms. The colour of the precipitate identifies the halide ion present in the sample.

The table below shows the precipitate colour for each halide ion.

Halide ionPrecipitate colourEquation
Chloride (Cl⁻)WhiteAg⁺ (aq) + Cl⁻ (aq) → AgCl (s)
Bromide (Br⁻)CreamAg⁺ (aq) + Br⁻ (aq) → AgBr (s)
Iodide (I⁻)YellowAg⁺ (aq) + I⁻ (aq) → AgI (s)