2 FeS₂ + 15 KNO₃ → Fe₂O₃ + 4 SO₃ + 15 KNO₂

This is an oxidation-reduction (redox) reaction:

FeS₂ is a reducing agent, KNO₃ is an oxidizing agent, FeS₂ is a reducing agent.

Reactants:

• FeS₂
  • Names: Ferrous disulfide , Fool's gold , Iron disulfide ... show moreIron persulfide , FeS2 show less
• KNO₃ – Potassium nitrate
  • Other names: Saltpeter , Saltpetre , Nitrate of potash ... show moreNitric acid, potassium salt , Niter , Salt peter , Nitre show less
  • Appearance: White solid ; Colourless-to-white crystalline powder

Products:

• Fe₂O₃ – Iron(III) oxide
  • Other names: Ferric oxide , Hematite , Ferric iron ... show moreRed iron oxide , Rouge , Maghemite , Colcothar , Iron sesquioxide , Rust , Ochre , Iron oxide dust and fume (as Fe) , Iron oxide red , Red oxide , Anhydrous ferric oxide , Iron (III) oxide , Diiron trioxide , Iron trioxide , Ferric sesquioxide , Iron(III) oxide [Iron oxide dust and fume (as Fe)] , Iron(III)oxide [Rouge] show less
  • Appearance: Red-brown solid ; Reddish brown-to-black crystals or powder ; Reddish-brown solid. [Note: Exposure to fume may occur during the arc-welding of iron.] ; A fine, red powder of ferric oxide. [Note: Usually used in cake form or impregnated in paper or cloth.]
• SO₃ – Sulfur trioxide , Sulfonylideneoxidane
  • Other names: Sulfuric anhydride , Sulfur(VI) oxide , SO3 ... show moreSulphur trioxide , [SO3] , Sulphuric (acid) anhydride , Sulfuric oxide show less
  • Appearance: Colorless to white crystalline solid which will fume in air.{{ ; Fuming hygroscopic colourless liquid or colourless-to-white crystals
• KNO₂
  • Names: Potassium nitrite , Nitrous acid potassium salt
  • Appearance: White or slight yellow solid | deliquescent ; White-to-yellow deliquescent solid in various forms