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CHAPTEE VIII. 



HEAT OF FORMATION OF COMPOUNDS DERIVED BY THE ACTION OF 

 NITRIC ACID UPON ORGANIC SUBSTANCES. 



1. GENERAL KEMARKS. 



1. A LARGE number of artificial compounds result from the 

 association of organic principles with nitric acid. These com- 

 pounds are generally explosive, and they play an important 

 part both in warfare and in mining industry. In order to 

 estimate their explosive force, it is necessary to know the heat 

 disengaged in their decomposition. In fact, the explosive force 

 of nitro-carbon compounds results from a kind of internal com- 

 bustion analogous to that of ordinary gunpowder, from which, 

 however, it is distinguished by the fact that the nitric acid and 

 combustible principle are intimately combined, instead of being 

 simply mixed together, as in the case of ordinary gunpowder. 

 This force is greater in proportion as the combustion develops 

 more gas and more heat. Now, if all else be equal, the heat 

 disengaged by the combustion will be inversely proportional 

 to that disengaged by the previous union of the nitric acid 

 with the organic principle. 



2. The heat disengaged in the formation of the following 

 more important nitrated compounds by means of nitric acid 

 was determined nitric ether, nitroglycerin, nitro-mannite, gun- 

 cotton, nitro-cellulose or xyloidin, the nitro, dinitro, and chloro- 

 nitrobenzene, and nitrobenzoic acid. The heat of formation of 

 trinitrophenol, otherwise called picric acid, and of its salts, 

 was deduced from calculations based on certain analogies 

 which have just been confirmed by some experimental de- 

 terminations of Sarrau and Vieille. In 1871 Troost and 

 Hautefcuille had published, a few days after the author's 

 communication, some measurements relating to the heat of 

 formation of various nitrated derivatives, the results agreeing 

 very closely. 



