CHAP. V. 



OF THE ATOMIC WEIGHT OF AZOTE, AND 

 THE SPECIFIC GRAVITY OF AZOTIC GAS. 



I SHALL begin this chapter with an account of 

 the experiments to determine the true specific 

 gravity of azotic gas. The specific gravity of 

 common air is always reckoned unity, and we 

 have seen in the third chapter of this work, that 

 the true specific gravity of oxygen gas is 1-1 11. 

 Now, as air is a mixture of oxygen and azotic 

 gases, it is obvious that, in order to obtain the 

 true specific gravity of azotic gas we have only 

 to determine by rigid experiments what is the 

 true ratio between the volumes of oxygen and 

 azotic gases in common air. Many experiments 

 have been made upon this subject ; but che- 

 mists do not seem to have employed the requi- 

 site precautions to ensure a successful result. 



1. In order to have common air in a state of Composi- 

 tion of com- 

 purity, I collected a quantity of it from above mon air de- 



the middle of a green field, at some distance 

 from all houses. The hydrogen gas, which was 

 employed to remove the oxygen, was prepared 

 from a mixture of purified zinc, and pure sul- 

 phuric acid diluted with distilled water. The 

 retort in which the gas was extricated, was quite 



