Ammonia fountain experiment – compared with HCl and N₂

ChemistryInorganic ChemistryAges 16–17

An inverted round-bottomed flask full of NH₃ gas has a tube dipping into a trough of water containing phenolphthalein. Squeeze the dropper to add a few drops of water: NH₃ is extremely soluble (≈ 700 volumes per volume of water), so the pressure in the flask drops sharply and water is forced up as a pink fountain. Switch to HCl gas (with litmus or methyl orange) or to poorly soluble N₂ to compare; a pressure gauge and a p(t) graph update continuously.