Ag2S + 4 HNO3 → 2 AgNO3 + 2 NO2 + S + 2 H2O

This is an oxidation-reduction (redox) reaction:

S-II - 2 e- → S0 (oxidation)

2 NV + 2 e- → 2 NIV (reduction)

Ag2S is a reducing agent, HNO3 is an oxidizing agent.

Reactants:

  • Ag2S – Silver(I) sulfide, Silver sulfide source: wikipedia, accessed: 2019-09-28
    • Other names: Silver sulfide source: wikipedia, accessed: 2019-09-28source: wikidata, accessed: 2019-09-02, Ag2S source: wikidata, accessed: 2019-09-02, Silver(I) sulfide source: wikidata, accessed: 2019-09-02
    • Appearance: Grayish-black crystal source: wikipedia, accessed: 2019-09-28
  • HNO3 – Nitric acid source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: NIOSH NPG, accessed: 2019-09-02
    • Other names: Aqua fortis source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: NIOSH NPG, accessed: 2019-09-02, Spirit of niter source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02, Eau forte source: wikipedia, accessed: 2019-09-27
    • Appearance: Colorless, yellow or red fuming liquid source: wikipedia, accessed: 2019-09-27; Colourless-to-yellow liquid with pungent odour source: ICSC, accessed: 2019-09-04; Colorless, yellow, or red, fuming liquid with an acrid, suffocating odor. [Note: Often used in an aqueous solution. Fuming nitric acid is concentrated nitric acid that contains dissolved nitrogen dioxide.] source: NIOSH NPG, accessed: 2019-09-02

Products:

  • AgNO3 – Silver(I) nitrate, Silver nitrate source: wikipedia, accessed: 2019-09-28
    • Other names: Silver nitrate source: wikipedia, accessed: 2019-09-28source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04, Nitric acid silver(1+) salt source: wikipedia, accessed: 2019-09-28, Lapis infernalis source: wikipedia, accessed: 2019-09-28
    • Appearance: Colorless solid source: wikipedia, accessed: 2019-09-28; Odourless colourless or white crystals source: ICSC, accessed: 2019-09-04
  • NO2 – Nitrogen dioxide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02
    • Other names: Nitrogen(IV) oxide source: wikipedia, accessed: 2019-09-27, Deutoxide of nitrogen source: wikipedia, accessed: 2019-09-27, Nitrogen peroxide source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02
    • Appearance: Brown gas source: wikipedia, accessed: 2019-09-27; Reddish-brown gas or brown or yellow liquid with pungent odour source: ICSC, accessed: 2019-09-04; Yellowish-brown liquid or reddish-brown gas (above 70°F) with a pungent, acrid odor. [Note: In solid form (below 15°F) it is found structurally as N2O4.] source: NIOSH NPG, accessed: 2019-09-02
  • 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
  • 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