CHAPTER XL 



AIR SUPPLIED AND GASEOUS PRODUCTS OF COM- 

 BUSTION. 



VOLUME OF AIR NECESSARY TO COMBUSTION. 



Four elements are to be considered in calculating the 

 theoretical volume of air for combustion: carbon, hydrogen, 

 oxygen, sulphur. The last is sometimes wanting in coal, but 

 not usually. 



Carbon. The atomic weights of carbon and oxygen are 

 as 12 and 1 6, and 2 atoms of oxygen are needed to form car- 

 bonic acid with I atom of carbon. Then 



12 : 32 = i : 2.666. 



i kilogram of oxygen occupies 0.699 cubic metre (Table IV); 

 i kilogram of carbon needs 



0.699 X 2.666 = 1.863 cubic metres of oxygen. 



Hydrogen. The atomic weights of hydrogen and oxygen 

 being respectively i and 16, and water being formed of 2 

 atoms of hydrogen and I of oxygen, we have 



2 : 16= i : 8; 



and as I kilogram of oxygen occupies 0.699 cubic metre, I 

 kilogram of hydrogen requires 



8 X 0.699 5-59 2 cubic metres of oxygen. 



125 



