NITROBENZENE. 269 



three groups was measured and found to differ according to the 

 diversity of functions of the bodies experimented on. 



2. NiTRO-COMPOUNDS IN GENERAL. 



Nitro-compounds result from the action of nitric acid upon 

 organic substances, with separation of water. For instance, 

 C 6 H 6 4- HN0 3 - H 2 ; one, two, three, or four equivalents of 

 nitric acid may thus enter into combination with either a hydro- 

 carbon, an acid, an alcohol, an alkali, etc. Compounds of this 

 class are formed principally in the aromatic series, i.e. in the 

 series of compounds derived from benzene, or rather, condensed 

 acetylene. Up to the present the terms of this series are the 

 only ones which have been employed in connection with ex- 

 plosive substances ; they are also the only ones that have been 

 studied by the author. 



It will be recollected that when nitro-compounds are treated 

 with alkalis, they do not reproduce nitric acid, but various 

 bodies of a special character, and nitrogenous, like the generators 

 themselves. Treated with reducing agents, nitro-compounds do 

 not reproduce the original body, but an amide. 



1. Nitrobenzene, C 6 H 5 N0 2 . 



1. The reaction for the production of this compound is as 

 follows : C 6 H 6 + HN0 3 = C 6 H 6 N0 2 + H 2 0. 



This was performed in a little platinum cylinder, floating in 

 a platinum calorimeter containg 500 grms. of water. The same 

 conditions were observed as in the calorimetric experiments. 

 The density of the acid used was 1*5, and its composition corre- 

 sponded to the formula, HN0 3 + -335H 2 0. 



Fifteen grms. of this acid were poured into the little platinum 

 cylinder, which was then closed with a cork coated with 

 paraffin. The temperature of the water in the calorimeter was 

 taken by means of a thermometer sensitive to ^J<j of a degree ; 

 and the temperature of the nitric acid with a smaller thermo- 

 meter sensitive to ^ of a degree. 



The two temperatures being made to agree, the cork was then 

 removed, and the benzene allowed to drop into the nitric acid 

 through a pipette having a very tapering mouth, and only allow- 

 ing exceedingly small drops to pass through. During this 

 procedure the acid was continually stirred, so as to mix it 

 gradually with the benzene ; the water in the calorimeter was 

 also stirred. In this way a known weight of benzene was intro- 

 duced 1-835 grm. and 3*670 grms. respectively in two different 

 experiments the operation of pouring in lasting, in all, two 

 minutes. 



The cylinder was then corked up and worked through the 



