272 COMPOUNDS DERIVED FROM NITRIC ACID. 



On the other hand 



C 6 + H 6 + N + 2 = C 6 H 6 N0 2 (liquid) x 



H 2 + = H 2 (liquid) +69 



Sum ... + 69 + x 



whence, x = + 4*2 for 123 grms. 



5. Decomposition ly heat. We know that nitrobenzene 

 is not, properly speaking, an explosive substance. It may be 

 distilled at a certain temperature. If, however, it is subjected 

 to great heat, a powerful reaction is effected between the oxygen 

 of the nitrous molecule and the hydrocarbon elements of the 

 benzene molecule. But the products of this reaction are im- 

 perfectly known. 



6. The heat of complete combustion of nitrobenzene is cal- 

 culated from the above data ; that of the elements being 



12C + 120 2 = 12C0 2 4-564-0 



i(5H 2 - 50 = 5H 2 0) + 172-5 



+ 736-5 



On subtracting the heat of formation of nitrobenzene + 4'2 we 

 get 



J (2C 6 H 5 N0 2 liquid + 250 = 12C0 2 + 5H 2 liquid + ET 2 ) gives 

 off + 732-3 Cal. 



This weight relates to 123 grms. For 1 grm. we should get 

 5952 cal. 



2. Dinitrobenzene, C 6 H 4 (N0 2 ) 2 . 



This substance was prepared by dissolving a known weight 

 of nitrobenzene in nitrosulphuric acid. The apparatus was the 

 same as for nitrobenzene, and the experiment was performed in 

 exactly the same manner. In the platinum cylinder were placed 

 35 grms. of a mixture previously prepared from 1500 grms. of 

 nitric acid similar to that already described, and 2944 of boiled 

 sulphuric acid. 



In these 35 grms. of nitro-sulphuric acid were dissolved : in 

 one experiment, T262 grm., and in another 2'534 grms. of 

 nitrobenzene. The elevations of temperature were 73 and T44 

 respectively. 



It was proved that the nitrobenzene was entirely converted 

 into dinitrobenzene. The calculations and corrections for 

 obtaining the quantity Q were made as previously (p. 270). 

 'The calculation of q (p. 271) is somewhat complicated. In 

 fact, the formation of the dinitrobenzene, in this case, produces 

 two phenomena : it changes the hydration of the nitrosulphuric 

 acid and also alters the relation between the nitric and sulphuric 

 acids, causing the latter to predominate, as a portion of the 

 nitric acid disappears, owing to the fact of the combination. In 



