6 H2O2 + 2 KI + 2 H2S2O3 → I2 + K2S4O6O4 + 8 H2O

This is an oxidation-reduction (redox) reaction:

4 SII - 10 e- → 4 S9/2 (oxidation)

2 I-I - 2 e- → 2 I0 (oxidation)

12 O-I + 12 e- → 12 O-II (reduction)

H2S2O3 is a reducing agent, KI is a reducing agent, H2O2 is an oxidizing agent.

Reactants:

  • H2O2 – Hydrogen peroxide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: NIOSH NPG, accessed: 2019-09-02
    • Other names: Dioxidane source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02, Oxidanyl source: wikipedia, accessed: 2019-09-27, Perhydroxic acid source: wikipedia, accessed: 2019-09-27
    • Appearance: Very light blue color; colorless in solution source: wikipedia, accessed: 2019-09-27; Colourless liquid source: ICSC, accessed: 2019-09-04; Colorless liquid with a slightly sharp odor. [Note: The pure compound is a crystalline solid below 12°F. Often used in an aqueous solution.] source: NIOSH NPG, accessed: 2019-09-02
  • KI
    • Names: Potassium iodide source: wikidata, accessed: 2019-09-02, KI source: wikidata, accessed: 2019-09-02, Thyrosafe source: wikidata, accessed: 2019-09-02
  • H2S2O3 – Sulfurothioic O-acid source: wikipedia, accessed: 2019-09-28, Dihydroxidooxidosulfidosulfur source: wikipedia, accessed: 2019-09-28
    • Other names: Thiosulfuric acid source: wikipedia, accessed: 2019-09-28source: wikidata, accessed: 2019-09-02, Sulfurothioic O source: wikipedia, accessed: 2019-09-28, O-acid source: wikipedia, accessed: 2019-09-28

Products:

  • I2
    • Names: Iodine source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02, Jod source: ICSC, accessed: 2019-09-04, Iode source: ICSC, accessed: 2019-09-04
    • Appearance: Bluish black or dark purple crystals with pungent odour source: ICSC, accessed: 2019-09-04; Violet solid with a sharp, characteristic odor. source: NIOSH NPG, accessed: 2019-09-02
  • K2S4O6O4
  • H2O – Water, oxidane source: wikipedia, accessed: 2019-09-27
    • Other names: Water (H2O) source: wikipedia, accessed: 2019-09-27, Hydrogen hydroxide (HH or HOH) source: wikipedia, accessed: 2019-09-27, Hydrogen oxide source: wikipedia, accessed: 2019-09-27
    • Appearance: White crystalline solid, almost colorless liquid with a hint of blue, colorless gas source: wikipedia, accessed: 2019-09-27