104 A YEAR IN SCIENCE 



4. What are the chief uses of nitrogen? 



5. What proportion by volume of the air is 

 nitrogen ? 



6. Which is* more important in the air, oxygen or 

 nitrogen ? 



7. What would probably result if the balance in 

 either direction were very much disturbed? 



8. Oxygen is 16 times as heavy as hydrogen, 

 nitrogen is 14 times as heavy as hydrogen. Air is J 

 oxygen and f nitrogen by volume. How many times 

 as heavy is a quart of air than a quart of hydrogen? 



9. From Avhat source do most plants obtain 

 nitrogen? 



10. What is a nitrogenous fertilizer ? 



