Haloalkane test. Image 7 of 7. Adding concentrated ammonia to test tubes containing silver halide precipitate. The precipitates are a result of using silver nitrate to test for halogen ions. The colour of the precipitate depends on the halogen present, chloride is white, bromide pale cream and iodide pale yellow. As a double-check ammonia can be added. Dilute ammonia will only dissolve chloride, concentrated ammonia will dissolve chloride and bromide but not iodide. The precipitate in the right hand tube has not dissolved, and so is iodide. For a sequence showing the test see A500/537 to A500/543.