2 HI + Fe₂(SO₄)₃ → I₂ + 2 FeSO₄ + H₂SO₄

This is an oxidation-reduction (redox) reaction:

HI is a reducing agent, Fe₂(SO₄)₃ is an oxidizing agent.

Reactants:

• HI – Iodane
  • Other names: Hydroiodic acid , Hydrogen iodide , Hydronium iodide ... show moreHI , Anhydrous hydriodic acid show less
  • Appearance: Colorless liquid ; Colorless gas ; Colourless compressed liquefied gas with pungent odour
• Fe₂(SO₄)₃ – Iron(III) sulfate
  • Other names: Ferric sulfate , Sulfuric acid , Iron(3+) salt (3:2) ... show moreDiiron tris(sulphate) , Iron tersulfate , Iron sesquisulfate , Iron persulfate , Ferric tersulfate , Ferric sesquisulfate , Ferric persulfate , Diiron trisulfate , Iron(III) sulfate(VI) , Ferric sulfate anhydrous show less
  • Appearance: Grayish-white crystals

Products:

• I₂
  • Names: Iodine , Jod , Iode ... show moreIodio , Yodo , Iodine crystals , Molecular iodine show less
  • Appearance: Bluish black or dark purple crystals with pungent odour ; Violet solid with a sharp, characteristic odor.
• FeSO₄ – Iron(II) sulphate
  • Other names: Iron(II) sulfate , Ferrous sulfate , Green vitriol ... show moreIron vitriol , Copperas , Melanterite , Szomolnokite , Ferrous sulfate , Iron sulfate (1:1) , Iron(II) sulfate (1:1) , Ferrous sulfate (anhydrous) , Ferrous sulfate (anh.) , Iron(2+) sulfate (anh.) , FeSO4 , Fe(II)SO4 , Ferrous sulfate anhydrous show less
  • Appearance: White crystals (anhydrous) | White-yellow crystals (monohydrate) | Blue-green crystals (heptahydrate)
• H₂SO₄ – Sulfuric acid
  • Other names: Oil of vitriol , Sulfuric acid, concentrated (> 51% and < 100%) , H2SO4 ... show moreSulphuric acid , Battery acid , Hydrogen sulfate , [SO2(OH)2] , [S(OH)2O2] , Sulfuric acid (aqueous) show less
  • Appearance: Clear, colorless liquid ; Odourless colourless oily hygroscopic liquid ; Colorless to dark-brown, oily, odorless liquid. [Note: Pure compound is a solid below 51°F. Often used in an aqueous solution.]