mCHAIlDS. — HEATS OF COMBUSTION OF ORQANIC SUBSTANCES. 591 



The very wide diflerence between the absolute heats of combustion 

 of sugar as given by Stohmann and Fischer makes a calculation of 

 the absolute value for benzol from the combination of our results with 

 either of theirs a somewhat uncertain matter. If Stohmann's value 

 for sugar be accepted, 41.89 kilojoules is computed as the heat of 

 combustion of a gram of benzol ; but if Fischer's be accepted, 42.13 kilo- 

 joules must be taken as the true value. No attempt will be made in 

 the present paper to decide this discrepancy, which is probably due 

 either to different standards of temperature or to different standards 

 of heat capacity in the two cases. 



In conclusion, it is a pleasure to express our indebtedness to the 

 Rumford Fund of the American Academy of Arts and Sciences for 

 pecuniary support at the commencement of these experiments, and to 

 the Carnegie Institution of Washington for further assistance during 

 their continuation. 



Summary. 



1. The adiabatic method of calorimetry devised by Richards, Hen- 

 derson, and Forbes, as applied to the determination of heats of com- 

 bustion with the calorimetric bomb, was improved and thoroughly 

 tested. 



2. The efficiency of this method in eliminating all corrections for 

 heat exchange with the surroundings, and for thermometric lag, was 

 established. 



3. A new method was devised for burning an accurately weighed 

 quantity of a liquid in the calorimetric bomb, by sealing it in a thin 

 completely filled bulb, and exploding this by the combustion of a small 

 amount of sugar. 



4. The effect of an inert gas, nitrogen, on the heat of combustion of 

 substances was noted for the first time. 



5. In the calorimetric combustion of substances needing much 

 oxygen it was shown that the presence of nitrogen may involve a very 

 considerable error. 



6. Benzol was found to evolve at least 2.534 times as much heat as 

 an equal weight of sugar on burning. 



