Dragendorff reagent

Preparation of Dragendorff reagent

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Safety

Wear eye protection and lab gloves. Avoid contact of acid with skin.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Step-by-step instruction

  1. Prepare a mixture of water and acetic acid 4/1.
  2. Mix 100 ml of this mixture with 1.7 g of bismuth oxynitrate. This is the first solution.
  3. Dissolve 40 g of potassium iodate in 100 ml of water. This is the second solution.
  4. Mix together 5 ml of both the first and the second solutions, add 20 ml of acetic acid and 70 ml of water.
  5. Add a few drops of the prepared solution into the test tube with an alkaloid solution (for example, quinine). An orange precipitate is formed.

Scientific background

Bismuth oxynitrate (commercially available Bi5O(OH)9(NO3)4) reacts with potassium iodide in an acidic solution and forms potassium bismuth iodide (typically represented as BiI4K) solution. The orange mixture prepared in this experiment is the Dragendorff's reagent used for detection of alkaloids in a test solution.

Actually a number of modifications of this reagent exist. Nitric, hydrochloric, tartaric acid may be used for the preparation of Dragendorff's reagent.

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Published on 03 May 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst