Dragendorff's reagent is a color reagent to detect alkaloids in a test sample or as a stain for chromatography plates.DR is a solution of potassium bismuth iodide composing of basic bismuth nitrate (Bi(NO₃)₃), tartaric acid, and potassium iodide (KI), and when contact with alkaloids DR produces an orange or orange red precipitate. DR is a solution of potassium bismuth iodide composing of basic bismuth nitrate (Bi(NO₃)₃), tartaric acid, and potassium iodide (KI), and when contact with alkaloids DR produces an orange or orange red precipitate.