94 A YEAR IN SCIENCE 



Sulphur + oxygen = sulphur dioxide 



S + 2 X = SO 2 

 Iron -f- oxygen = oxide of iron - 



Rapid oxidation is always accompanied by heat and 

 light. To fully appreciate this statement you need but 

 recall the methods employed in heating our homes. 

 Wood, coal, coke, etc., are burned in a furnace. Burn- 

 ing is rapid oxidation. In other words, the oxygen of 

 the air combines with the carbon of the wood, coal, or 

 coke, and the home is made comfortable with the heat 

 evolved in the process. If more heat is desired, we in- 

 crease the burning or oxidation by admitting more 

 oxygen to the fuel through the draughts. If less heat 

 is desired, the draughts are closed, admitting a smaller 

 amount of oxygen, thus reducing oxidation. 



If, however, oxidation is very slow, as in the rusting 

 .of iron or the decay of wood, it is not accompanied by 

 any noticeable amount of heat or light, though the 

 sum total of the heat evolved during the process of 

 decay is as much as would be given off were the same 

 piece of wood completely burned in a few minutes. 



Uses. Oxygen is absolutely necessary to life. Only 

 a few very minute forms of plant life can exist with- 

 out it. Oxidation goes on in the bodies of living organ- 

 isms in very much the same manner as it does in the 

 furnace. Of course, it is not accompanied by light, 

 but the results are the same. In the process of respi- 

 ration, oxygen is taken into the lungs, where some of 



