When a drop of water is introduced into flask containing ammonia it dissolves all the ammonia in the flask If water is subsequently allowed into the flask through a small inlet atmospheric pressure forces it very fast to occupy the vacuum forming a fountain If the water contains threefew drops of litmus solution the litmus solution turns blue because ammonia is an alkalinebasic gas If the water contains threefew drops of phenolphthalein indicator the indicator turns pink because ammonia is an alkalinebasic gas SulphurIVoxide and hydrogen chloride gas are also capable of the fountain experiment  If the water contains threefew drops of phenolphthalein indicator the indicator turns colourless because both SulphurIV oxide and hydrogen chloride gas are acidic gases