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 117 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.

117 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.

Fig. 119b. Making Hydrogen Chloride Gas

This water dissolves the rest of the gas in the flask and more water is forced up until the bottle is nearly full of it, all of which produces a very mysterious and at the same time a mighty pretty effect.

How to Make Hydrogen Chloride Gas

To make this gas take another bottle and fit a two hole stopper into it; in one hole put a funnel and in the other an L tube as shown at B 119.

In the bottom of the bottle put 1/3 of a cup of common table salt; put a straight tube down into the Florence flask you want to fill and connect this tube and the L tube with a piece of rubber tube as is also shown at B.

The apparatus set up, pour sulphuric acid down the funnel, a very little at a time until the salt is all gone and then fit the cork with the long nozzle tube and the medicine dropper in it, into the mouth of the bottle filled with the hydrogen chloride gas.