—The Effect.—You show an empty bottle, or Florence flask, and then push a cork with two holes in it into the mouth of the bottle. Next push a glass tube having a nozzle on one end through one of the holes in the cork until the nozzle nearly touches the bottom of the bottle.
Through the other hole in the cork push a medicine dropper, or fountain pen filler. The end of the long tube projects down into a bowl containing water which you have colored blue[122] either with indigo or with copper sulphate or you can make a beautiful violet by dissolving in it a little potassium permanganate. The arrangement of the apparatus is shown at [A in Fig. 119].
[122] Any kind of colored water will do for this experiment.
Fig. 119a. the mystic fountain
Now when you squeeze the bulb of the medicine dropper the colored water rushes up the tube and squirts out of the nozzle into a pretty fountain until the flask is nearly full.
The Cause.
—Instead of the bottle being empty as it looks to be, you have previously filled it with hydrogen chloride gas of which 500 volumes will dissolve in 1 volume of water.
The medicine dropper is filled with water and when you squeezed it a few drops of water is forced into the bottle and dissolves a large part of the gas that is in it. This leaves a vacuum when, of course, the atmospheric pressure on the colored water in the bowl forces it up through the nozzle to fill the vacuum.
