*2oO ANNUAL OF SCIENTIFIC DISCO VEKY. 



pose will require a little close attention to a chemical formula ; but It 

 is very interesting. 



If nitre-benzol is acted upon by water and by iron, of which I have 

 put down the symbols here, nitro-benzol -f- water -j- iron = C 12 H 5 

 (NO 4 ) -|- 2HO -f- 4Fe, the iron takes away all the oxygen from the 

 water, and the oxygen from the oxide of nitrogen. There are six 

 equivalents of oxygen, which the iron takes to itself and forms iron- 

 rust with it. The rust remains, and the two of hydrogen of the water 

 now joins itself to the C 12 H N, and produces this body here, C 12 H 7 N, 

 aniline. That is to say, the iron takes away the oxygen, and leaves 

 oxide of iron and aniline as the result. 



Now, this aniline is a most important body. It was first investi- 

 gated by Dr. Hoffmann, who has made with regard to it a series of 

 the most brilliant researches, out of which have arisen these coal-tar 

 colors with which we are now acquainted. Aniline is an ammonia. 

 It is a body exactly resembling the base ammonia, but it is what 

 is termed a compound ammonia. Here is the constitution of ammo- 

 nia : 



H 



H 



I put down the three atoms of hydrogen separately. Now, if I take 

 away one of these atoms of hydrogen, and substitute it by one of 

 something else which plays the part of hydrogen, I form a com- 

 pound ammonia. I will do so in this case. 



C 12 H 5 



(H 



I have replaced one atom of hydrogen with a compound radical 

 which chemists call phenyle, and I obtain what is termed aniline. 

 This aniline is, therefore, a compound ammonia in which the radical 

 phenyle replaces one of hydrogen. 



Now, it is out of this aniline that we produce mauve, magenta, 

 roseine, azuline, bleu de Paris, and the various colors which have 

 received arbitrary names. It was known for a long time that the 

 products of distillation of coal had a strong tinctorial power. Here, 

 for instance, I have two of them, a body called pyrrole. I have here 

 a piece of pine wood, made for a theatrical purpose, in the shape 

 of a dagger. I will now moisten this with muriatic acid, and then 

 place it in a deep vessel which contains a few drops of pyrrole. You 

 see that it suddenly gets as it were covered witj^ blood. Now, this 

 tinctorial power has been known, in fact, for a long time, but the 

 mode of manufacturing the substance readily and economically was 

 not known. Here I have a small quantity of aniline, and I agitate it 

 with water ; and now, if I add to that a solution of bleaching powder, 

 you will see the effect it produces. It was long known that this ani- 

 line gave a purple color with bleaching powder. The color comes 

 after a little while ; it does not come immediately, but you see, as I 

 add it, that the aniline produces a mauve or a purple color ; and this 

 was known for many years, before persons knew how to make it for 

 commercial purposes. This is now a color used in the arts. The first 



