Reaction of Chlorine and Hydrogen Sulphide

Reaction between two gases gives a yellow precipitate.

Scientific name: Hydrogen sulfide is oxidized by chlorine producing sulfur and hydrochloric acid.


Double Displacement: Sodium Sulfide and HCl

Реакция сероводорода с хлором


This experiment should be performed in a fume hood or outdoors. Wear eye protection goggles and gloves.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

Na2S + 2HCl → H2S + 2NaCl

Cl2 + H2S → S + 2HCl

Step-by-step instruction

WARNING! This experiment is dangerous! You should NOT perform this at home. ONLY carry out this experiment, if you are a trained chemist, and you understand local safety and legal requirements, which are required to perform such experiments

  1. This experiment should be performed only in a fume hood.
  2. Prepare the solution of hydrochloric acid, the solution of sodium sulfide and a chlorine gas source.
  3. Pour the solution of hydrochloric acid into the jar.
  4. Fill the jar with chlorine gas and cover it with a watch glass.
  5. Add the solution of sodium sulfide to the jar.
  6. The released hydrogen sulfide gas reacts with chlorine producing a yellow precipitate of elemental sulfur.

Scientific background

When sodium sulfide solution is mixed with hydrochloric acid the components reacts forming sodium chloride and hydrogen sulfide. Hydrogen sulfide is a colorless gas with a characteristic smell of rotten eggs. Chlorine oxidizes hydrogen sulfide giving sulfur and hydrochloric acid. Sulfur is insoluble in water and precipitates on the jar walls. If chlorine is in excess sulfur chlorides also could be produced. This reaction of chlorine (in form of sodium hypochlorite as a rule) and hydrogen sulfide is used to remove hydrogen sulfide from drinking water.


Published on 15 June 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst