MAHLER'S CALORIMETER. 63 



stances, and are saturated with aqueous vapor when they enter 

 the bomb. From the calorific capacity of the different parts 

 we obtain that of the whole, the glass and enamel being 

 omitted. 



Soft steel 3945 grams. 3945 X 0.1097 = 43 2 '/6 



Brass 545 " 545XO.O93 = 50.68 



Mercury, plati- 

 num, and lead 72 * 72X0.03 = 2.16 



Sum 485. 60 grams. 



The coefficient 0.1097 is the one adopted by the College 

 of France, from Berthelot and Vielle's experiments, for a steel 

 of similar quality. We have given above (page 14) the 

 calculations relative to the valuation in water. By direct 

 method of mixing water of different temperatures Mahler 

 found the equivalent to be 470 and 484, and assumed the 

 mean 481. 



By the method of burning a body of known composition 

 and heat of combustion he obtained with naphthalin 9688 

 calories within ^Vir of that given by Berthelot (9692). 



The equivalent in water may also be obtained by burning I 

 gram of known composition and heat of combustion naph- 

 thalin for instance.* We may also, after Berthelot, burn a sub- 

 stance of fixed composition at two trials with different weights 

 of water in the calorimeter. Two equations are thus formed, 

 from which the heat of combustion of the body used is elimi- 

 nated, and the heat sought obtained. 



In using naphthalin care must be taken to weigh it only 

 after being gently fused in the capsule. It is so light that if 

 not agglomerated some would be blown away by the oxygen. 

 In practice the tests are made rapidly. The water equivalent 

 once determined may be verified by combustion of cane- 



*This practical method has the advantage of automatically eliminating 

 causes of error. 



