Describe the fountain experiment with hydrogen chloride and state what it demonstrates.

A dry flask is filled with hydrogen chloride and fitted with a jet dipping into water containing blue litmus. When a few drops of water are introduced, the gas dissolves rapidly, the pressure inside falls and the coloured water rushes in as a fountain, turning red. It demonstrates that hydrogen chloride is extremely soluble in water and that the solution is acidic.

No citable source has been recorded for this record. Treat it as practice material, not as fact.

Explanation

Ammonia gives a similar fountain, but the water turns blue because ammonia solution is alkaline.