Combustion of Sulfur in Molten Nitrate

A bright glow of the tube

Scientific name: Oxidation of sulfur by potassium nitrate


Горение серы в расплаве селитры


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Wear eye protection goggles. Work away from flammable objects in a hood or outdoors.

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

Reaction formula

2 KNO3 + 2S → K2SO4 + N2 + SO2

Step-by-step instruction

WARNING! This experiment is dangerous! You should NOT perform this at home. ONLY carry out this experiment, if you are a trained chemist, and you understand local safety and legal requirements, which are required to perform such experiments

  1. Pour 3 grams of potassium nitrate into a test tube.
  2. Fix the test tube on a stand.
  3. Melt potassium nitrate using a spirit lamp or a gas burner.
  4. Slowly add small pieces of sulfur.
  5. Observe a bright glowing. The test tube may begin to melt.

Scientific background

Potassium nitrate is a common oxidizing agent which can reduce sulfur. Due to the fact that both of materials are solid, the reaction doesn't occur at room temperature, due to the small contact area between the reactants. Therefore, you need to melt the potassium nitrate. The reaction is very exothermic, so you can observe a bright glow.


Published on 13 June 2015

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