134 



CALORIFIC POWER OF FUELS. 



must be used; but usually only the oxygen, carbonic oxide, 

 and carbonic acid are required. In normal combustion with 

 sufficient air the quantity of hydrocarbons is very trifling, and 

 need not be considered. This occurs usually with a supply 

 of 15 cubic metres of air per kilogram (240 cubic feet per 

 pound) of coal, and should produce a waste gas containing 10 

 to 14 per cent of carbonic acid, in which case the unburnt 

 hydrocarbons amount to less than I per cent. 



The Orsat apparatus or its modifications may be used to 

 determine the oxygen, carbonic acid, and carbonic oxide. By 

 using Winckler's modification the hydrocarbons may be deter- 

 mined. For exact analyses of the gases the Hempel apparatus 

 may be used. For general work, however, the Orsat appa- 

 ratus or the Orsat-Muencke is the best and most easily 

 transported and handled. Directions for using this apparatus 

 need not be given here, as they can be found in all works on 

 gas analysis, or can be had of the dealers. 



The following table gives analyses made by Scheurer- 

 Kestner of waste gases from Ronchamp coal. The gases for 

 examination were collected by means of the apparatus described 

 above (pp. 128 et seq.) and shows the average for a whole 

 day's run. 



