Power of Ooal and of Coke. 



38 



Tabular View of the Working. 



In this trial, which lasted for seven hours, 50 lb. of coke 

 were used, and 370 lb. of water were evaporated from 42, and 

 W = 7.4 — accordingly, for each lb. of coke consiuned, 7.4 lb. 

 of water were driven off in steam. 



In another trial, conducted with equal care and for the 

 same time, the result was very nearly the same. 



The coke used, it has been already stated, contained 81 per 

 cent, of fixed carbon. Now, according to the experiments of 

 Despretz, 1 lb. of carbon will evaporate 12.3 lb. of water from 

 32, and the number of degrees of heat in the steam beyond 

 that point is 1136 ; the water which I employed was at 42, 

 consequently the degrees of heat in the steam beyond it were 

 only 1126 ; the coke should therefore have evaporated only 

 7.33 instead of 7.4 ; supposing the temperature of the water 

 supplied to the boiler to have been at 32, 



and as 100 : 12.^: : 81 : 9.96, 

 accordingly, the coke ought to have evaporated 9.96, provided 

 the whole of the carbon were consumed, and provided also the 

 whole of the heat evolved by the combustion were taken up 

 by the water ; but the quantity was only 7.33, therefore there 

 was a loss of about 26 per cent. 



Similar trials were then made with the coal. The follow- 

 ing is a tabular view of the most satisfactory :-— 



VOL. XXXIIIr NO, LXV.-— JVLY lS42r 



