1. Halide Anion Tests

2. What are we testing to find?
Halides are salts that contain halogens, which include chlorides, bromides and iodides.
Chlorides, bromides and iodides are negative ions - negative ions are called anions.
This test is used to identify the presence of chloride, bromides and iodides.

3. How do we do the test? Place the sample solution in a test tube.
First add a few drops of nitric acid using the dropper.
Then add silver nitrate solution to the sample, using a dropper.
Observe if a precipitate is formed and note the colour of the precipitate.

4. What results might we get?
If a precipitate is formed it will be a particular colour, dependent upon what halide ion is present.
Chloride Cl- bright white
Bromide Br- cream
Iodide I- yellow

5. Why does this test work?
The halides of silver are noted for being insoluble. They form distinctive colours according to which halogen is present.
Silver chloride (AgCl) is a white solid
Silver bromide (AgBr) is an off-white or cream-coloured solid
Silver iodide (AgI) is a yellow solid

6. Watch this video to see the test in action

7. Ionic Equations
We can write the equations for these reactions by just referring to the ions which react to form the insoluble salt. This is because we are only interested in the halide ions and the silver ions
Ag+ (aq) + Cl- (aq) → AgCl (s)
Ag+ (aq) + Br- (aq) → AgBr (s)
Ag+ (aq) + I- (aq) → AgI (s)

8. Summary
Samples may be tested by adding silver nitrate solution in the presence of nitric acid in order to identify if they contain halide ions (chloride, bromides or iodides). If present each halide will give a distinctive coloured precipitate.