CHAPTER IV 

 BURNING OR OXIDATION 



Why things burn. The heat of our bodies comes from the 

 oxidation of the food we eat; the heat for cooking and for 

 warming our houses comes from coal. The production of heat 

 through the burning of coal, or oil, or gas, or wood, is called 

 combustion. Ordinary combustion cannot occur without the 

 presence of a substance called oxygen, which exists rather abun- 

 dantly in the air; that is, one fifth of our atmosphere consists of 

 this substance which we call oxygen. We throw open our win- 

 dows to allow fresh air to enter, and we take walks in order to 

 breathe the pure air into our lungs. What we need for the 

 energy and warmth of our bodies is the oxygen in the air. 

 Whether we burn gas or wood or coal, the heat which is pro- 

 duced comes from the combination of these various substances 

 with oxygen. We open the draft of a stove that it may " draw 

 well " ; that it may secure oxygen for burning. We throw a 

 blanket over burning material to smother the fire; to keep 

 oxygen away from it. Burning, or oxidation, is combining 

 with oxygen, and the more oxygen you add to a fire, the hotter 

 the fire burns, and the faster. The effect of oxygen on com- 

 bustion may be clearly seen by thrusting a smoldering splinter 

 into a jar containing oxygen; the smoldering splinter instantly 

 flares and blazes, while if it is removed from the jar, it again 

 burns quietly. 



How to prepare oxygen. Mix a small quantity of potas- 

 sium chlorate with an equal amount of manganese dioxide and 

 place the mixture in a test tube. Close the mouth of the tube 



