Mivcter — Determination of the Heat, etc. 



347 



Art. XXXVI.— On the Determination of the Heat of Dissocia- 

 tion and of Combustion of Acetylene, Ethylene and Methane ; 

 by W. G. Mixter. 



[Contributions from the Sheffield Laboratory of Tale University.] 



The heat of formation of an organic compound is deduced, 

 as is well known, from its neat of combustion and that of its 

 constituents, since it is impossible to form any hydrocarbon 

 under conditions at which the thermal effect may be measured. 

 The determination of the heat evolved when acetylene is 



decomposed is, however, one of the easiest of calorimetric 

 experiments, giving at once the heat of combination^ as the 

 thermal change of dissociation equals that of combination. 



Moreover, it is pi 



obable that the direct measurement of the 



change is less liable to error than the indirect method, which 

 involves burning the gas. The thermal effect of thedissocia- 

 tion of other hydrocarbon gases may be found by mixing them 



