Hydrogen chloride fountain

Water quickly flows into the flask and changes color

Scientific name: Dissolving hydrogen chloride in water causes pressure to fall in the flask


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Wear eye protection goggles. Use gloves. Hydrogen chloride is a poisonous gas! If possible, use a hood or carry out the experiment outdoors.

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

Reaction formula

HCl + H2O → H3O+ + Cl-

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. Obtain hydrogen chloride. Pour approximately 10 grams of sodium chloride into a flask and add 25 ml of concentrated sulfuric acid. Close the flask with a stopper equipped by a tap with a tube. Lower the other end of the tube into an empty liter flask. Hydrogen chloride is heavier than air, so the flask should be kept neck up while filling.
  2. Close the flask filled with hydrogen chloride.
  3. Fill a large evaporation dish with two liters of water.
  4. Dissolve a small amount of litmus in water.
  5. Replace the stopper of the flask with hydrogen chloride with a stopper equipped by tap with a tube.
  6. Attach the flask with hydrogen chloride on the stand upside down.
  7. Lower the other end of the tube into the evaporation dish with water.
  8. Observe the filling of the flask and the color change of the indicator from purple to red.

Scientific background

Hydrogen chloride is highly soluble in water. Pressure drops in the flask when hydrogen chloride dissolves in water. Due to the pressure difference water starts to flow into the upper flask.The indicator changes color due to the change of the reaction medium from neutral to alkaline.


Published on 30 April 2015

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