Spontaneous Combustion

Burns with purple flames.

 

 

 

Category - Chemicals & Reactions

Key Idea - Redox

 

Purpose - Cool and quick oxidation reaction.  Also shows and extreme exothermic reaction.
Nature -  Demonstration
Materials -  Potassium permanganate KMnO4, Glycerol C3H5(OH)3, Heat proof tile, Mortar and Pestle, Spatula
Method - 
  1. Grind up approximately 20 gm of Potassium permanganate using the mortar and pestle.
  2. Pile this on the heat proof mat and use the stirring rod to make a small volcano shape.
  3. Fill the crater of the volcano with glycerol and stand back.
  4. It takes a few moments for the reaction to occur, but when it does you'll be impressed.
Safety - A great deal of heat is produced so be aware of the potential for burns.  The fumes given off are best avoided, so doing this outside or in the fume cupboard is a good idea.
Explanation - There is an exothermic reaction that takes place between the potassium permanganate and the glycerol as summarized below -

14KMnO4 + 4C3H5(OH)3 => 7K2CO3 + 7Mn2O3 + 5CO2 + 16H2O
Notes - The purple colour of the flame is indicative of potassium.