CALCULATION OF THE HEAT UNITS. l6l 



A correction of the same kind as that applied to the tem- 

 perature of the feed-water must be applied. We do not 

 wish the total calories, only those taken up from the coal. 

 From the observed temperature T we must deduct the 

 original temperature t before entering the fire. So that 



The general formula then becomes 



C = [(1.256^)0.244 -f (1.966^)0.217 -f- (1.2 5 1 z/')o. 245 



~N~ ~~CoT~ CO 



.43000-217] (T-t). 



As an example, suppose the following composition : 



Nitrogen 81.25 \ _ j Air in excess 23.04 (4.84 X 4.761) 



Oxygen 4.84 j - ( Nitrogen 63. 05 (81.254.84 23.04) 



Carbonic acid. . 13.08 13.08 



Carbonic oxide. 0.83 0.83 



100.00 100.00 



and that the temperature (T t) is 130. Then 



Nitrogen 1.256 X .8125 X 0.244 = 0.249 



Carbonic acid .... 1.966 X . 1308 X 0.217 = 0.055 

 Carbonic oxide. . . 1.25 I X .0083 X 0.245 = O.OO2 

 Oxygen l -43 X .0484 X 0.217 = 0.015 



i.oooo 0.321 



The value in water for I cubic metre is 0.321 kilogram, 

 which at 130 give 



0.321 X 130 = 41.7 calories. 



If the volume of the gases was 8.938 cubic metres per 

 kilogram of coal, the calories carried to the chimney would be 



8.938 X 41-7 



100 



= 372 calories. (669.6 B. T. U.) 



