96 AZOTIC GAS. 



filled with this mixture, and a portion of the hy- 

 drogen gas was allowed to escape, before I be- 

 gan to collect it for use. The etidiometrical 

 experiments were made while the hydrogen gas 

 was coming over, and it was taken for every ex- 

 periment directly from the beak of the retort, 

 and consequently, without standing any time in 

 contact with water. 



A mixture of 100 volumes of air, and 42 vo- 

 lumes of this pure hydrogen gas, was fired by an 

 electric spark. The diminution of bulk in three 

 successive experiments was precisely 60 volumes. 

 Now, the volume of oxygen gas in the 100 parts 

 of air employed is obviously of this diminution 

 of bulk. But ^ of 60 is 20. Thus it appears, 

 that 100 volumes of air contain 20 volumes of 

 oxygen gas. The remaining 80 volumes consti- 

 tute the azotic gas of air. Air then is a mixture 

 of 



20 volumes oxygen gas 

 80 volumes azotic gas 



100 



or the 5th of the volume of common air is oxy- 

 gen gas, and four-fifths azotic gas. 



If we employ less than 42 volumes of hydro- 

 gen gas to 100 of air, the combustion is not com- 

 plete. Thus, when a mixture of 100 volumes 

 air and 40 volumes hydrogen is fired, the di- 

 minution of bulk amounts to 57 volumes, in- 



