I 



144 GENERAL SCIENCE 



Fill one bottle full of water, another half full of water, and place only a small 

 amount of water in a third. Arrange a gas generator as shown in the dia- 

 gram. Collect the gas in the three bottles, over water. Hydrogen gas may 

 be*1ade by placing a small amount of zinc in the generator and adding hydro- 

 chloric acid and water. 



Test each bottle with a lighted taper. Note what happens to 



1. The bottle of pure hydrogen; 



2. The bottle half hydrogen and half air; 



3. The bottle nearly full of air and a slight amount Af hydrogen. 



Burning of Gas. Light a c.andle. After a few moments blow it 

 out and hold a lighted ma^ch in-the stream of gas a little way from the 

 wick. The vapor will take fire, carrying the flame to the wick. 

 This gas can be made to burn at some distance from the flame if 

 the candle is placed in a lamp chimney which has a few sticks under 

 the chimney to allow the air to enter. (Why?) Carefully blow 

 out the candle, or extinguish it with a piece of glass tubing. Allow 

 the " smoke " or " gas " to rise to the top of the chimney. Light 

 it with a match. The flame will burn down to the wick and relight 

 the candle. The candle may be called a little gas generator. The 

 wax does not burn, but melts where the wick extends out of the wax. 

 A little cup forms to hold this melted wax which is drawn up the 

 wick by a process known as capillarity. 



Place one end of a lump of sugar in a drop of ink. The ink will rise to the ' 

 top of the sugar. Blotters absorb ink in the same way. Rough towels dry 

 the body more quickly than smooth towels. The water rises from the subsoil to 

 the top soil in the same manner. The liquid rises because the attraction 

 of the little particles of the substance always pulls it up between the tiny spaces. 

 Water will rise higher in a glass tube which has a very small hairlike bore than 

 in one with a large bore. 



When the liquid wax reaches the upper part of the wick the heat 

 changes it to a gas and it is this gas which burns. This furnishes 

 an excellent illustration of how gasoline burns. The gas of gaso- 

 line has been known to take fire 50 feet from a person cleaning 

 clothes. The fire will travel along the stream of gas to the vessel 

 containing the gasoline. The gas of gasoline is much heavier than 

 air. 



Kerosene burns just above the liquid where there is a gas and 



