3 (NH4)2S + K2Cr2O7 + 7 H2O → 6 NH4OH + 2 Cr(OH)3 + 3 S + 2 KOH

This is an oxidation-reduction (redox) reaction:

3 S-II - 6 e- → 3 S0 (oxidation)

2 CrVI + 6 e- → 2 CrIII (reduction)

(NH4)2S is a reducing agent, K2Cr2O7 is an oxidizing agent.

Reactants:

  • (NH4)2S
  • K2Cr2O7 – Potassium dichromate(VI) source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02
    • Other names: Potassium dichromate source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04, Chromium potassium oxide source: wikidata, accessed: 2019-09-02, Dipotassium dichromium heptaoxide source: wikidata, accessed: 2019-09-02
    • Appearance: Red-orange crystalline solid source: wikipedia, accessed: 2019-09-27; Orange-to-red crystals source: ICSC, accessed: 2019-09-04
  • 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

Products:

  • NH4OH
    • Names: Ammonium hydroxide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-07, Ammonia solution source: wikidata, accessed: 2019-09-07, Ammonium hydroxide (10%-35% solution) source: ICSC, accessed: 2019-09-04
    • Appearance: Colourless liquid source: wikipedia, accessed: 2019-09-27; Very volatile colourless ammonia solution in water with pungent odour source: ICSC, accessed: 2019-09-04
  • Cr(OH)3 – Chromium(3+) hydroxide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02
    • Other names: Chromium(III) hydroxide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02, Chromium (iii) hydroxide hydrate source: ICSC, accessed: 2019-09-04, Cr(OH)3 source: wikidata, accessed: 2019-09-02, Chromic (III) hydroxide hydrate source: ICSC, accessed: 2019-09-04
    • Appearance: Green, gelatinous precipitate source: wikipedia, accessed: 2019-09-27; Blue-to-green powder or black particles source: ICSC, accessed: 2019-09-04
  • S
    • Names: Sulfur source: wikidata, accessed: 2019-09-07source: ICSC, accessed: 2019-09-04, S source: wikidata, accessed: 2019-09-07, Sulphur source: wikidata, accessed: 2019-09-07source: ICSC, accessed: 2019-09-04
    • Appearance: Yellow solid in various forms source: ICSC, accessed: 2019-09-04
  • KOH – Potassium hydroxide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02
    • Other names: Caustic potash source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02, Lye source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02, Potash lye source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02
    • Appearance: White solid, deliquescent source: wikipedia, accessed: 2019-09-27; White hygroscopic solid in various forms source: ICSC, accessed: 2019-09-04; Odorless, white or slightly yellow lumps, rods, flakes, sticks, or pellets. [Note: May be used as an aqueous solution.] source: NIOSH NPG, accessed: 2019-09-02