(c) Halogen
Acidify 0.5 mL of the alkaline solution from the fusion with dilute nitric acid
(indicator paper) and, if nitrogen or sulfur has been found present, boil the solution
(hood) to expel HCN or H2S. On addition of a few drops of silver nitrate
solution, halide ion is precipitated as silver halide. Filter with minimum exposure
to light on a 2.5-cm funnel, wash with water, and then with 1 mL of concentrated
ammonia solution. If the precipitate is white and readily soluble in
ammonium hydroxide solution it is AgCl; if it is pale yellow and not readily
soluble it is AgBr; if it is yellow and insoluble it is AgI. Fluorine is not detected
in this test since silver fluoride is soluble in water