8 INTRODUCTION TO GENERAL SCIENCE 



5. OXYGEN ITS USES AND ACTION 



Oxygen means acid-producing material, and it is found in 

 nearly all the acids. Its use in the atmosphere, of which it 

 composes about one fifth, is to support combustion. There 

 can be no ordinary burning without the presence of oxygen. 

 The oxygen combines with the carbon in the wood, coal, or 

 other combustible, producing carbon dioxide, which passes 

 off as a gas. It is the combination of the carbon and oxygen 

 which produces the heat we obtain from our fires. Oxygen 

 also causes the slow combustion which takes place in animals, 

 producing animal heat, and burning up waste material ab- 

 sorbed by the blood. When water is thrown on the fire, it 

 puts the fire out, simply because the water lowers the tem- 

 perature of the burning substance and forms a film upon it 

 which prevents the access of oxygen. Similarly, carbon 

 dioxide bombs, which are exploded to extinguish fires, keep 

 out oxygen, because the carbon dioxide is heavier than the 

 oxygen and coats the surface of the combustible. See Section 

 90, The Chemical Engine. 



Experiment 3. Oxygen and Combustion. 



Apparatus: Test tube 8" X 1", stopper, with one hole to 

 fit test tube, test-tube holder, or clamp, ring stand, glass tube 

 3" long, rubber tube VI" long, bread pan (pneumatic trough), 

 four wide-mouthed, half-pint bottles, tweezers, deflagrating 

 spoon, lamp, four glass plates 4" X 4". 



Materials: Powdered potassium chlorate, granulated 

 manganese dioxide, wood splinters, charcoal in small pieces, 

 powdered sulphur, iron picture cord, magnesium ribbon, 

 phosphorus. 



a. Mix equal parts of potassium chlorate and manganese 



