Preparation of Dragendorff's reagent and testing for alkaloids

The formation of a brown solution. Color disappears with alkaloid's solution in extremely low concentration

Scientific name: The formation of the complex salt of bismuth and its reaction with alkaloids

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Make Dragendorff's reagent from Bismuth Nitrate

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Safety

Wear eye protection goggles. Work in a fume hood.

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

Reaction formula

Bi(NO3)3 + 4 KI → K[BiI4] + 3 KNO3

Step-by-step instruction

  1. Pour 0.5 g of bismuth nitrate into an empty beaker. Add about 10 ml of distilled water. The mixture should be like a suspension.
  2. Add 10 ml of concentrated hydrochloric acid. Stir the resulting mixture.
  3. Pour 4 g of potassium iodide into another beaker, add a little water and stir until KI is completely dissolved.
  4. Mix the two solutions.
  5. Observe the formation of a dark orange solution.

Scientific background

Bismuth nitrate is the most commercially available reagent of Bi. It reacts with potassium iodide in an acidic solution and forms potassium bismuth iodide (typically represented as K[BiI4] ) solution. The orange mixture prepared in this experiment is the Dragendorff’s reagent used for detection of alkaloids in a test solution.

Danger:
Coolness:
Difficulty:

Published on 30 June 2015

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