Fire and Heat 81 



When oxygen combines with substances both in slow and 

 rapid combustion, the resulting products of the process are com- 

 pounds known as oxids. The yellowish powder produced by 

 burning lead in the air or in oxygen is the compound lead oxid, 

 familiar in commerce as litharge. Burning sulfur in the air 

 or in oxygen produces a disagreeable gas, which is also a com- 

 pound called sulfur dioxid. The prefix di means two, and 

 when so used, means that two unit parts of oxygen are com- 

 bined with one unit part of sulfur. Charcoal is practically 

 all carbon, and so, too, is the charred stick. These burning 

 in oxygen give as a product carbon dioxid. 



Oxygen and life. Oxygen is indispensable in the processes 

 of life. In living organisms oxidation or slow combustion occurs 

 in the production of energy necessary for all kinds of activity 

 and for bodily heat. The human organism is, in fact, an 

 engine which utilizes food as fuel ; but in doing this the food 

 must be burned or oxidized. The oxidation of food fuel or of 

 living tissues, into which food is converted, is carried on by the 

 aid of oxygen received from the lungs and circulated throughout 

 the body by the blood. The blood also carries off and eliminates 

 with the help of the lungs the waste products of oxidation. 

 Thus our lungs perform a double service to life, receiving 

 oxygen and throwing off oxids or waste products of combustion. 



Oxygen in medicine. Oxygen is frequently administered 

 in medical practice to accelerate combustion in the living body. 

 A good whiff of oxygen just at the beginning of a sprint or a 

 long run gives additional energy and endurance. It is ex- 

 hilarating, almost intoxicating, in the outburst of energy 

 thus liberated. In medicine it is utilized for relief from suf- 

 focation, asphyxiation, and drowning, and for many other 

 purposes. Describe the pulmotor and its use in resuscitation 

 of individuals overcome by smoke or poisonous gas. 



Oxygen in industry. You may infer from your study of 

 oxygen that the greater the amount of it added to a burning 

 substance, the more rapidly the substance burns and the more 

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