86 



THE PRODUCTION AND USE OF HEAT 



wipe it dry, and allow the gas to flow into a dry bottle containing air. 

 Cover this bottle as well as possible. Take the hydrogen generator 

 apart, fill the flask with water to dilute the acid and stop the action. 

 Pour the dilute acid into the sink, rinse the unused zinc with fresh 

 water and save the metal for future use. 



Study the hydrogen as follows: 



(a) The Burning of Hydrogen. Light a splinter of wood. Lift 

 one of the full bottles of hydrogen from the water, and, keeping the 

 mouth of the bottle down, bring the flame of the splinter to the mouth 



FIG. 68. Apparatus for generating hydrogen. 



of the bottle. Pay no attention to the noise, but look for the flame 

 of burning hydrogen playing about the mouth of the bottle where it is 

 uniting with the oxygen of the air. The experiment may be repeated 

 with other bottles of the gas. 



(6) The Burning of a Mixture of Hydrogen and Air. Prepare an- 

 other burning splinter. Lift from the water the bottle which was 

 filled half full of hydrogen, keeping the mouth of the bottle down. 

 What enters the bottle as the water runs out? Allow the air and 

 hydrogen a few seconds in which to mix ; then ignite them by means of 

 the flame. The result illustrates the burning of a mixture of hydro- 

 gen and air. The noise is due to the sudden rush of the products of 

 the burning from the bottle. The outrush is due to the heat gener- 

 ated by the combustion. Such a mixture is said to be EXPLOSIVE. 

 Such mixtures should be ignited only in bottles having wide mouths 

 to allow the easy escape of the products of the burning. 



