296* DIAZO-COMPOUNDS. 



This fact is in accordance with the general result ; according 

 to which the carburets, that are only slightly hydrogenated, and 

 the carbonaceous substances, retain a considerable portion of the 

 energy of their complex generators ; their energy exceeds more 

 or less that of the elements themselves. 



This remark, which was at first made concerning acetylene, 

 has a very wide application in pyrogeneous decompositions ; it 

 explains the singular conditions under which certain endothermal 

 compounds are generated, at the very moment that organic com- 

 pounds are destroyed by heat. 



15. Seat of total combustion. Combustion was started by 

 galvanic ignition of a fine platinum wire, in an atmosphere of 

 pure oxygen. It gave off, for 167grms. (1 equiv.), + 783 -9 Cal. 

 at constant volume (two experiments), which gives 782*9 Cal. 

 at constant pressure ; or, for 1 grm., 469 f 4 cal. at constant 

 volume. 



If the oxidation is complete, the reaction may be represented 

 by the following equation : 



i[2C 6 H 5 N 2 N0 3 + 230 = 12C0 2 + 5H 2 + 3NJ 



The Jieat of combustion lyy oxygen with reproduction of nitric 

 acid 



C 6 H 5 lSr a N03 + 70 2 = 6C0 2 + 2H 2 + 1ST 2 + HlSTOg, 



would give off, in addition, the heat of formation of nitric acid 

 combined with two equivalents of water 



HN0 3 , 2H 2 0, 

 or + 46-6 ; altogether + 829'5 Cal. 



