GASEOUS FUELS. 93 



grades of coal, and all variations in quality may be eliminated, 

 a uniform product being had by storing the gas in a holder, or 

 by making proper arrangement of different generators so that 

 an average will be obtained. In several cases where hand-fed 

 coal fires have been tried against fires burning gas from the 

 same coal, better results have been obtained, due to the possi- 

 bility of more closely adjusted regulation. The tests made 

 at Brieg may be cited. Here each boiler had 141.25 square 

 feet of heating-surface and steam-pressure 6 to 7 atmospheres. 

 No. i boiler was hand-fired ; No. 2 was gas-fired. The 

 evaporation in pounds per pound of fuel was : 



No. i 8.34 8.74 8.28 4.02 2.569 2.764 



No. 2 9.86 9.73 10.07 5-44- 3.251 3.158 



Increase... 18$ 12$ 20$ 35$ 25$ 



HEAT OF COMBUSTION OF GASES FROM ANALYSIS. 



When the chemical composition of a gas is known exactly, 

 its heat of combustion can be correctly calculated ; but in 

 absence of a correct analysis, the calorimeter must be used. 



Knowing the proximate composition of a combustible 

 gas, that is, the proportion of chemically defined components 

 as well as their heats of combustion, it is sufficient to add the 

 numbers obtained for each constituent gas. Take, for 

 example, the analysis of illuminating gas of Manchester as 

 given by Bunsen: 



Hydrogen 45-58 



Marsh gas (CH 4 ) 34-9O 



v Carbonic oxide 6.64 



Ethylene (C 2 H 4 ). 4.08 



Butylene (C 4 H.) 2.38 



Sulphydric acid 0.29 



Nitrogen 2.46 



Carbonic acid., 3.67 



100.00 



