Dr. Hofmann on the Metamorphoses of Indigo. 515 



element is observed to pass over into the new compound. 

 From the fused hydrate of potash, which retains a portion of 

 the carbon of chh)risatine in the form of carbonic acid, there 

 distils over chloraniline, and with it the whole of the chlorine 

 existing in the former compound. In the present memoir I 

 have had frequent occasion to show the analogy which exists 

 between aniline and the chlorinated base; it extends not 

 only to the fundamental properties of both bodies, but even to 

 the products of decomposition. By the action of bromine on 



aniline tribromaniline is formed, Cj^^ g'* >N; with the chlo- 

 rinated base the same body gives chlorodibromaniline, C12 



< Cl > N, which in no respect, either in its properties or cha- 



raclers, can be distinguished from the preceding. The only 

 difference of the two compounds consists in the presence of 

 chlorine in the second body. 



On the preceding facts, when considered together, it ap- 

 pears to me that no two constructions can be entertained. 

 They prove, in an undoubted manner, that in certain circum- 

 stances chlorine or bromine can perform the part of hydrogen 

 in organic compounds. 



It is quite another question. Is every organic body capable 

 of assuming chlorine in the place of its hydrogen ? 



Further, in those organic compounds in which we see one 

 or two equivalents of hydrogen replaced by chlorine, without 

 any essential modification of their fundamental characters, is 

 it possible to make a complete substitution of these elements 

 without changing the properties of the compounds? 



For the definite solution of these questions many further 

 investigations must still be made. From the foregoing expe- 

 riments it appears, however, that the chlorine preserves, to a 

 certain extent, its electro-negative character in those com- 

 pounds in which it replaces hydrogen, and that in proportion 

 to the increase in the number of equivalents of the latter for 

 which chlorine or bromine are substituted, so is this character 

 the more impressed on the resulting compounds. The com- 

 y)ound atom aniline, Cjg H^ N, in consequence of the peculiar 

 arrangement of its elements, possesses the property of uniting 

 with an acid ; replace one equivalent of its hydrogen by 

 bromine, and we obtain bromaniline ; a body possessing like- 

 wise basic properties, but in a feebler degree. A number of 

 metallic oxides, which can be precipitated from their solutions 

 by aniline, are not affected by the brominated base. Broma- 

 niline is a less powerful base than aniline. By the assumption 



2 M 2 



