Glycerol and KMnO₄

Summary

A puddle of glycerol is poured on a pile of potassium permanganate in a porcelain cup. After about 30 seconds, the reaction bursts into purple flame.

Hazards

Potassium permanganate is a strong oxidizer.

Chemicals and Solutions

  • 15 g potassium permanganate
  • 2-3 mL glycerol

Materials

Porcelain dish

Procedure

  1. Place KMnO₄ in dish.
  2. Add glycerol on top of potassium permanganate.
  3. Stand back. After 30 sec. the reaction mixture will burst into a purple flame.
  4. If larger crystals of potassium permanganate are used the reaction is much slower. (For this reason you can use this demonstration while teaching kinetics.)

Hint: This reaction can be delayed if the crystal size of the potassium permanganate is large.

Discussion

The reaction:

\( \ce{14KMnO4 + 4C3H5(OH)3 -> 7K2CO3 + 7Mn2O3 + 5CO2 + 16H2O } \)