3 CdS (s) + 8 HNO₃ (aq) → 3 S (s) + 2 NO (g) + 3 Cd(NO₃)₂ (aq) + 4 H₂O (l)

This is an oxidation-reduction (redox) reaction:

3 S^-II - 6 e^- → 3 S⁰ (oxidation)

2 N^V + 6 e^- → 2 N^II (reduction)

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

Reactants:

CdS
- Names: Cadmium sulfide , Cadmium(II) sulfide , Greenockite
- Appearance: Yellow-orange to brown solid. ; Light yellow or orange crystals or yellow-to-brown powder
HNO₃ – Nitric acid
- Other names: Aqua fortis , Spirit of niter , Eau forte
- 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.]

Products:

S
- Names: Sulfur , S , Sulphur
- Appearance: Yellow solid in various forms
NO – Nitrogen monoxide , Oxidonitrogen(•) (additive)
- Other names: Nitric oxide , Nitrogen(II) oxide , Nitric oxide (radical)
- Appearance: Colourless gas ; Colourless compressed gas ; Colorless gas. [Note: Shipped as a nonliquefied compressed gas.]
Cd(NO₃)₂ – Cadmium(II) nitrate
- Other names: Cadmium nitrate , Nitric acid , Cadmium salt
- Appearance: White crystals, hygroscopic
H₂O – Water, oxidane
- Other names: Water (H2O) , Hydrogen hydroxide (HH or HOH) , Hydrogen oxide
- Appearance: White crystalline solid, almost colorless liquid with a hint of blue, colorless gas

3 CdS (s) + 8 HNO3 (aq) → 3 S (s) + 2 NO (g) + 3 Cd(NO3)2 (aq) + 4 H2O (l)