The best way to determine the presence of halogens is by adding a silver nitrate solution to the solvent. This is because all halogens, except for fluorine, produce a precipitate with silver nitrate solution.
Chlorine produces a white precipitate, bromine produces a pale cream colored precipitate and iodine produces a yellow colored precipitate.
If further testing is required, concentrated sulfuric acid may be added. The sulfuric acid will produce misty fumes with fluorine and chlorine, brown fumes with bromine and purple fumes with iodine.