4 K2SO3 → 3 K2SO4 + K2S

This is an oxidation-reduction (redox) reaction:

SIV + 6 e- → S-II (reduction)

3 SIV - 6 e- → 3 SVI (oxidation)

K2SO3 is both an oxidizing and a reducing agent (disproportionation (dismutation)).

Reactants:

  • K2SO3 – Potassium sulfite source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02
    • Other names: E225 source: wikipedia, accessed: 2019-09-27, Potassium sulphite source: wikidata, accessed: 2019-09-02
    • Appearance: White solid source: wikipedia, accessed: 2019-09-27

Products:

  • K2SO4
    • Names: Potassium sulfate source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04, Potassium sulphate source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02, Dipotassium sulfate source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04
    • Appearance: White solid source: wikipedia, accessed: 2019-09-27; Colourless-to-white crystals source: ICSC, accessed: 2019-09-04
  • K2S – Potassium sulfide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04
    • Other names: Dipotassium monosulfide source: wikipedia, accessed: 2019-09-27source: ICSC, accessed: 2019-09-04, Dipotassium sulfide source: wikipedia, accessed: 2019-09-27source: ICSC, accessed: 2019-09-04, Potassium monosulfide source: wikipedia, accessed: 2019-09-27source: ICSC, accessed: 2019-09-04
    • Appearance: Pure: colourless | impure: yellow-brown source: wikipedia, accessed: 2019-09-27; Hygroscopic white crystals with characteristic odour. turns red or brown on exposure to air source: ICSC, accessed: 2019-09-04