CONTRIBUTIONS FllOM THE CHEMICAL LABORATORY OF 



HARVARD COLLEGE. 



CONCERNING THE ADIABATIC DETERMINATION OF THE 



HEATS OF COMBUSTION OF ORGANIC SUBSTANCES, 



ESPECIALLY SUGAR AND BENZOL. 



Bv Theodore W. Richards, ^Lawrence J. Henderson, and Harry 



L. Frevert. 



Presented January 9, 1907. Received December 4, 1906. 



Introduction. 



As a preliminary step to the determination of the heats of combus- 

 tion of an extended series of organic substances, desired for certain 

 theoretical considerations, measurements were made on two common 

 substances, cane-sugar and benzol. These substances were chosen in 

 order that one might represent solids and the other volatile liquids, 

 and because they may be easily obtained in a high state of purity, as 

 well as because their heats of combustion have been carefully studied 

 by other investigators. 



This investigation offered the opportunity for further testing and 

 improving the adiabatic calorimetric method recently proposed and 

 tested by Richards, Henderson, and Forbes,^ by means of which cor- 

 rections for accidental loss of heat and for the lag of the thermometer 

 are experimentally eliminated. The method was devised in the hope 

 that its use might increase the accuracy of thermochemical work ; and 

 this hope is j ustitied by the present experience. The principle of the 

 method is to cause the temperature of the surroundings of the calo- 

 rimeter to change in the same direction and at the same rate as the 

 calorimeter itself This is accomplished by surrounding the calorim- 

 eter with vessels in which a suitable warming reaction can take place 

 in a manner fulfilling the above conditions. A reaction easily regu- 

 lated and well suited to this purpose, namely, the neutralization of an 

 alkali with an acid, was chosen for this purpose. 



1 These Proceedings, 41, 3 (1905) ; Zeit. phys. Chem., 52, 551 (1905). 



