MAHLER'S CALORIMETER. 6 1 



even under a variation of several hundred grams in amount of 

 water used. 

 The law* is 



1. The decrease in temperature observed after the maxi- 

 mum represents the loss of heat of the calorimeter before the 

 maximum and for a certain minute, with the condition that 

 the mean temperature of this minute does not differ more than 

 one degree from the maximum. 



2. If the temperature considered differs more than one 

 degree but less than two degrees from the maximum, the 

 number representing the rate of decrease dimminished by 

 0.005 will b e tne correction. 



The two preceding remarks suffice in all cases with Mah- 

 ler's apparatus. The variation of heat in the first half-minute 

 after kindling may also be corrected by the same law. 



The agitator must be worked continually during the ex- 

 periment, being careful of the thermometer. 



When through, the conical valve is opened and then the 

 bomb. Wash the inside with a little distilled water to collect 

 the acids formed. The proportion of acids carried away by 

 the escaping oxygen at the opening may be neglected. De- 

 termine the acids volumetrically. 



When experimenting with substances low in hydrogen and 

 incapable of furnishing sufficient water to form nitric acid, it 

 is advisable to put a little water in the bomb, or hyponitric 

 acid would be formed. 



All the data being obtained, we proceed to the calculation 

 of the calorific power Q. 



Let A be the observed difference of temperature ; 

 a, the correction for cooling ; 

 P, the weight of water in the calorimeter; 

 Pj the equivalent in water of the bomb and acces- 

 sories; 



* It is evident that the rule must be modified for apparatus notably dif- 

 ferent from that used by Mahler. 



