114 THE WONDERFUL HOUSE THAT JACK HAS 



of our bodies nor other fuel will burn readily in air 

 that contains much of the latter gas? A few simple 

 experiments will plainly prove these facts. 



In a previous paragraph we learned that a large 

 amount of oxygen is in the earth's crust. Chlorate 

 of potash and manganese dioxid are two solids that 



Preparation of oxygen. 



contain a great deal of oxygen. Half fill a large test- 

 tube with equal parts of these substances, and, using 

 apparatus similar to that shown in the cut, heat 

 the test-tube over a gas-jet or alcohol lamp flame. 

 The oxygen, being set free by the heat, will pass 

 through the connecting tubes and fill the inverted 

 glass bottle. Remove the bottle, being careful not 

 to allow the oxygen to escape. If a lighted candle 

 be lowered into the gas thus collected, it will burn 

 with many times its ordinary brightness. Lower into 

 a jar of oxygen a small piece of coal that has been 

 kindled, and it will blaze up as if it were charcoal. 

 Tie a small splinter of wood to a fine wire, and, after 

 lighting the splinter, lower both quickly into a jar 



