174 CALORIFIC POWER OF FUELS. 



carbonic oxide. In doing so it is supposed that carbon in 

 combining with two atoms of oxygen generates the same 

 quantity of heat with one as with the other, only in the first 

 case part of the heat is used in vaporizing the carbon. This 

 heat is found by subtracting the heat of combustion of the 

 solid carbon from that of the carbon supposed gaseous in 

 carbonic oxide. 



One kilogram of carbon unites with 1.333 kilograms of 

 oxygen to form 2.333 kilograms of carbonic oxide. With 

 diamond there is generated 2405 calories. The 2.333 kilograms 

 of carbonic oxide in becoming carbonic acid generates 2.333 X 

 2435 5680 calories. Then I kilogram of carbon in passing 

 from carbonic oxide to carbonic acid generates 5680 calories. 

 We have seen, on the other hand, that I kilogram of diamond 

 carbon generates 2405 calories in becoming carbonic oxide. 

 The difference, then, 5680 2405 = 3275(5895 B. T. U.) cal- 

 ories, represents the heat of vaporization of diamond carbon. 

 With wood charcoal it becomes 5680 2489 = 3191(5743.8 

 B. T. U.). 



The heat of combustion will be then 7859 -f- 3275 = 1 1 134 

 calories (20041 B. T. U.) for diamond, and 8137 -f- 3191 

 11328 calories (20390 B. T. U.) for wood charcoal. 



EVAPORATIVE POWER OF FUEL. 



The evaporative power of a fuel represents the number of 

 pounds of water at 212 F. that can be evaporated or con- 

 verted into steam by one pound of the fuel. Water at that 

 temperature is sufficiently heated to vaporize, but needs an 

 addition of force equivalent to that required for the vaporiza- 

 tion. This quantity varies for the pressure of the barometer 

 and the temperature of the water, but for the purposes of cal- 

 culation is considered to be taken at 30 inches of mercury and 

 212 F. Experiment has shown the equivalent to be 965.7 

 heatunits (B. T. U.). 



