4 HCl + 2 KI + Na2HAsO4 → H2O + I2 + 2 NaCl + 2 KCl + H3AsO3

This is an oxidation-reduction (redox) reaction:

AsV + 2 e- → AsIII (reduction)

2 I-I - 2 e- → 2 I0 (oxidation)

Na2HAsO4 is an oxidizing agent, KI is a reducing agent.

Reactants:

  • HCl – Chlorane source: wikipedia, accessed: 2019-09-27, Hydrogen chloride source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02
    • Other names: Hydrochloric acid source: wikipedia, accessed: 2019-09-27source: NIOSH NPG, accessed: 2019-09-02, M source: wikipedia, accessed: 2019-09-27, Uriatic acid source: wikipedia, accessed: 2019-09-27
    • Appearance: Colorless, transparent liquid, fumes in air if concentrated source: wikipedia, accessed: 2019-09-27; Colorless gas source: wikipedia, accessed: 2019-09-27; Colourless compressed liquefied gas with pungent odour source: ICSC, accessed: 2019-09-04; Colorless to slightly yellow gas with a pungent, irritating odor. [Note: Shipped as a liquefied compressed gas.] 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
  • Na2HAsO4
    • Names: Dibasic heptahydratesodium arsenate source: wikidata, accessed: 2019-09-03, Disodium arsenate heptahydrate source: ICSC, accessed: 2019-09-04source: wikidata, accessed: 2019-09-03, Disodium monohydrogen arsenate heptahydrate source: wikidata, accessed: 2019-09-03
    • Appearance: Colourless crystals source: ICSC, accessed: 2019-09-04

Products:

  • 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
  • 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
  • NaCl – Sodium chloride source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02
    • Other names: {{unbulleted list source: wikipedia, accessed: 2019-09-27, Salt source: wikidata, accessed: 2019-09-02, Table salt source: wikidata, accessed: 2019-09-02
    • Appearance: Colorless cubic crystals source: wikipedia, accessed: 2019-09-27
  • KCl
    • Names: Potassium chloride source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04, Sylvite source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02, Muriate of potash source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02
    • Appearance: White crystalline solid source: wikipedia, accessed: 2019-09-27; Colourless hygroscopic crystals source: ICSC, accessed: 2019-09-04
  • H3AsO3 – Arsorous acid source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02
    • Other names: Arsenous acid source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02, Arsenious acid source: wikipedia, accessed: 2019-09-27, Arsenic oxide source: wikipedia, accessed: 2019-09-27
    • Appearance: Only exists in aqueous solutions source: wikipedia, accessed: 2019-09-27