8 HNO₃ + 3 CaS → 3 Ca(NO₃)₂ + 2 NO + 3 S + 4 H₂O

This is an oxidation-reduction (redox) reaction:

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

Reactants:

• HNO₃ – Nitric acid
  • Other names: Aqua fortis , Spirit of niter , Eau forte ... show moreHydrogen nitrate , Acidum nitricum , Nitric acid (> 70% in water) , Fuming nitric acid , Engravers acid , HONO2 , Red fuming nitric acid , RFNA , White fuming nitric acid (WFNA) show less
  • Appearance: Colorless, yellow or red fuming liquid ; Colourless-to-yellow liquid with pungent odour ; 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.]
• CaS – Calcium sulfide
  • Other names: Calcium monosulfide , Hepar calcies , Sulfurated lime , Oldhamite
  • Appearance: White crystals | hygroscopic

Products:

• Ca(NO₃)₂
  • Names: Calcium nitrate , Kalksalpeter , Nitrocalcite ... show moreNorwegian saltpeter , Lime nitrate , Anhydrous calcium nitrate , Lime saltpeter , Saltpeter , Calcium(II) nitrate (1:2) , Calcium saltpeter , Norway saltpeter , Norge saltpeter , Nitric acid, calcium salt , Calcium dinitrate , Calcium (II) nitrate show less
  • Appearance: Colorless solid | hygroscopic ; Colourless-to-white hygroscopic crystals
• NO – Nitrogen monoxide , Oxidonitrogen(•) (additive)
  • Other names: Nitric oxide , Nitrogen(II) oxide , Nitric oxide (radical) ... show moreMononitrogen monoxide , (.)NO , EDRF , Nitrogen monooxide , [NO] , Oxido de nitrogeno(ii) , NO(.) , Oxido nitrico , Stickstoff(ii)-oxid , NO , Oxyde azotique , Oxyde nitrique , Stickstoffmonoxid , Nitrosyl , (NO)(.) , Monoxido de nitrogeno , Endothelium-derived relaxing factor , Nitroxide radical , Nitroxyl , Nitrosyl radical , Hydroxyamine , Nitrogen oxide , Nitrogen protoxide , Nitrosyl hydride , Nitric Oxide show less
  • Appearance: Colourless gas ; Colourless compressed gas ; Colorless gas. [Note: Shipped as a nonliquefied compressed gas.]
• S
  • Names: Sulfur , S , Sulphur ... show moreElement 16 , Flowers of sulfur , Flour sulfur , Brimstone show less
  • Appearance: Yellow solid in various forms
• H₂O – Water, oxidane
  • Other names: Water (H2O) , Hydrogen hydroxide (HH or HOH) , Hydrogen oxide ... show moreDihydrogen monoxide (DHMO) (systematic name) , Hydrogen monoxide , Dihydrogen oxide , Hydric acid , Hydrohydroxic acid , Hydroxic acid , Hydrol , Μ-oxido dihydrogen , Κ1-hydroxyl hydrogen(0) show less
  • Appearance: White crystalline solid, almost colorless liquid with a hint of blue, colorless gas