GASEOUS FUELS. 99 



The proportion of nitrogen in these gases reaches 56 to 

 60 per cent ; that of carbonic oxide, 2 1 to 32 per cent ; that of 

 of hydrogen, from traces to 17 per cent. The theoretical 

 calculation for the combustion of carbon in air to a gas con- 

 taining only carbonic oxide and nitrogen gives for the first 

 34.7 and for the second 65.3 per cent. 



By adopting for the composition of air the round numbers 

 79 and 21, and for the weight of oxygen 1.430 grams per 

 litre, for carbon the atomic weight of 12, and for oxygen 16, 



12 : 16 = 1000 grams : 1333 grams. 



A kilogram of carbon needs, then, i kilograms of oxygen. 

 A litre of oxygen weighing 1.430 grams, 1333 grams would 

 occupy 932 litres. These 932 litres will give with carbon a 

 double volume, or 1864 litres carbonic oxide. Multiplying 

 932 litres by the coefficient 4.77 (see Table XIV), we obtain 

 the volume of the air corresponding, or 4445 litres. The 

 gases of combustion will be composed then of these 4445 

 litres of air and the 932 litres of increase in volume, or 5377 

 litres for I kilogram of carbon. The 4445 litres of air will 

 contain (at 79 per cent) 3513 litres of nitrogen, or 65.3 per 

 cent.* 



The calculation is more complicated when we have fuel 

 containing hydrogen, as one portion of the oxygen disappears 

 by its combination with the hydrogen to form water. Take 

 for example, a coal containing 90 per cent of carbon, 5 per 

 cent of hydrogen, and 5 per cent of oxygen. Suppose I 

 kilogram of this coal, under theoretical conditions, burnt in a 

 gasogene, i.e., with perfect transformation of the carbon into 

 carbonic oxide and no residues. This coal contains 900 

 grams carbon, 50 grams hydrogen, 50 grams oxygen. 900 



* One pound of carbon requires 1.333 Ibs. of oxygen; I cubic foot of 

 oxygen weighs 0.08926 Ib. ; 1.333 lb s. measure 14.93 cu. ft. These would 

 give 29.86of CO. 14.93 X 4-77 = 71.216, and 71.216 -f 14.93 = 86.146, volume 

 of gases of combustion. These contain 56.26 cu. ft. of nitrogen. 



