NITROGEN 103 



that very characteristic, however, that much of its 

 value lies. We have seen how very rapid oxidation is 

 in pure oxygen. An atmosphere of pure oxygen 

 would be almost as disastrous as one with no oxygen. 

 A mixture of oxygen with a harmless, inactive gas 

 which will hold the oxygen in check is necessary. 

 This seems to be the chief use of nitrogen. Forming 

 as it does about four-fifths of the air, it dilutes the 

 other one-fifth, which is oxygen, and thereby guards 

 against too rapid oxidation, and consequently wide- 

 spread destruction. 



Nitrogen is necessary to plant life, and although it 

 forms a large part of the air, plants are unable to use 

 it in the free state. They obtain the element from the 

 soil from some soluble compound of nitrogen, usually 

 a nitrate. If for some reason these compounds 

 become insufficient in the soil for the proper growth 

 of plants, they must be restored in some way. This 

 is done by nitrogenous fertilizers, such as nitrate of 

 soda (Chili saltpetre) and sulphate of ammonia. 



Nitrogen is used commercially in compound form 

 in the manufacture of ice. Nitrates are also of great 

 commercial value in the making of explosives, gun- 

 powder, dynamite, and nitro-glycerin. 



Questions 



1. Name the properties of nitrogen. 



2. What are the chief sources of nitrogen? 



3. State two ways of preparing it for class use. 



