CHAPTER V 

 SUBSTANCES FORMING THE BODY; OXIDATION 



82. Oxidation. You learned that oxidation is the process 

 of forming a union of oxygen with some other substance. 

 When iron oxidizes, iron-rust is formed. When wood de- 

 cays, the carbon in it oxidizes and carbonic acid gas is 

 formed. When wood burns, the oxidation is more rapid. 

 When hydrogen is oxidized, water is formed. For in- 

 stance, kerosene oil contains hydrogen, and, by burning it 

 in a lamp, water is formed which collects on the chimney 

 when the lamp is first lighted, before the glass has become 

 hot. You learned that animal life seems to be based upon 

 a process of slow oxidation taking place in the tissues of 

 the body. Oxygen has great affinity for many substances, 

 and its union with, them is accompanied by the production 

 of heat; thus the heat of the body is kept up. 



83. Plant and Animal Life. In plant life there is more 

 of deoxidation than of oxidation. Carbon when alone is a 

 solid like coal, charcoal, or plumbago ; oxygen when alone 

 is a gas. When joined together they make a gas called 

 carbonic acid gas, or carbon dioxid. The leaves of a plant 

 absorb the carbon dioxid, and by the aid of the sunlight 

 the green coloring matter of the leaf separates the carbon 

 from the oxygen. The carbon remains as a part of the 

 plant, while the oxygen escapes from the leaves as a gas, 

 and is ready to burn the carbon in wood or sugar or ani- 

 mal tissue, and form carbon dioxid again. Just as much 

 heat, or energy, will be given back in the oxidation as was 

 furnished by the sun to the plant to enable it, in the leaf, 



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