4 H3PO3 → 3 H3PO4 + PH3

This is an oxidation-reduction (redox) reaction:

PIII + 6 e- → P-III (reduction)

3 PIII - 6 e- → 3 PV (oxidation)

H3PO3 is both an oxidizing and a reducing agent (disproportionation (dismutation)).

Reactants:

  • H3PO3 – Phosphonic acid source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-04
    • Other names: Phosphorous acid source: wikipedia, accessed: 2019-09-27, Dihydroxyphosphine oxide source: wikipedia, accessed: 2019-09-27
    • Appearance: White solid | deliquescent source: wikipedia, accessed: 2019-09-27

Products:

  • H3PO4
    • Names: Phosphoric acid source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02, Orthophosphoric acid source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02, Phosphoric(V) acid source: wikidata, accessed: 2019-09-02
    • Appearance: Hygroscopic colourless crystals source: ICSC, accessed: 2019-09-04; Thick, colorless, odorless, crystalline solid. [Note: Often used in an aqueous solution.] source: NIOSH NPG, accessed: 2019-09-02
  • PH3 – Phosphane source: wikipedia, accessed: 2019-09-27
    • Other names: Phosphine source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02, Phosphamine source: wikipedia, accessed: 2019-09-27, Phosphorus trihydride source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02
    • Appearance: Colorless gas source: wikipedia, accessed: 2019-09-27; Colourless compressed liquefied gas source: ICSC, accessed: 2019-09-04; Colorless gas with a fish- or garlic-like odor. [pesticide] [Note: Shipped as a liquefied compressed gas. Pure compound is odorless.] source: NIOSH NPG, accessed: 2019-09-02