70 CALORIFIC POWER OF FUELS. 



heat developed by a current with intensity 7 and electro- 

 motive force E is 



4.17 



/ being reckoned in seconds. If / was appreciable, this should 

 be considered at least in exact determinations. But, actually, 

 t is very small ; the contact is hardly established before the 

 iron is burnt and the contact broken.* 



Mahler cites two successive tests made on the same coal 

 with his bomb and with the bomb of the College of France, 

 as furnishing proof of the accuracy of his method. 



The following results were obtained : 



Scheurer-Kestner 



at the Mahler, 



College of France. 



Coal (pure) from Bascoup, Belgium ____ 8828 8813. 



The calculations may be rendered simpler and the obser- 

 vation more rapid, still being exact enough for industrial uses. 

 Take the equation 



Q, = (A + a)(P+ P') - (o.2 3 / + I.6/), . . (i> 

 arranging the terms in order of the corrections 



(2. = 4(P + P') + a(P+ P ) - (0.2 3 / + 1 .6/). (2> 

 It is clear that the calculation of the calorimetric operation 



* In exact researches this heat can be easily determined if wished. It 

 will be sufficient to measure the electromotive force in volts. Then put 

 an amperemeter in the line which connects the bomb and kindle the com- 

 bustible as usual. The displacement of the needle shows the intensity of 

 the current under the conditions of the test, and also the time during which 



the current was closed. The formula - / will give the quantity of heat 

 sought. 



