[ 385 ] 

 LVI. Oji the Metamorphoses of Indigo*. 

 Production of Organic Bases ixhich contain Chloi'ine and Bro- 

 mine. By Dr. August Wilhelm Hofmann, Assistant in 

 the Giessen Laboratory ■\. 



THE changes which result from the action of various 

 bodies upon indigo have for a series of years engaged 

 the attention of chemists. It may be even said that this sub- 

 ject has been selected with preference for investigation ; and 

 when we consider the rich harvests already obtained by a 

 great number of celebrated chemists, there would appear, at the 

 first glance, scarcely anything to be gleaned. It is however 

 the character of every rapidly-advancing science, that each 

 discovery becomes the source of numerous others, and that 

 the solution of every question gives rise to others which must 

 in their turn be answered. It was thus that the further in- 

 vestigation of the products from the decomposition of indigo, 

 which had been already so thoroughly studied in many points 

 by Laurent and Erdmann, led to results which appeared to 

 me worthy of publication. 



Before proceeding, however, to the description of these re- 

 sults, it may be advantageous to make a few preliminary ob- 

 servations for the purpose of showing the reasons for which 

 these investigations have been undertaken. 



Among the various theories which have of late years 

 claimed the attention of chemists, that of substitution occu- 

 pies a very prominent place. It is not my intention to exa- 

 mine the numerous phases of this discussion, for the most 

 part carried on in France, nor to consider minutely the vari- 

 ous consequences which had their rise in this originally ex- 

 tremely simple question. The problem which forms the basis 

 of the present investigation is a more general experimental 

 establishment of a single substitution theorem. 



If we examine carefully the origin of the theory of substi- 

 tutions, we shall be able to trace it to the endeavour to pre- 

 determine, by means of certain laws experimentally esta- 

 blished, the changes to be produced upon a body through the 

 action of chlorine, bromine, oxygen, &c. In the course of 

 such investigations it was however perceived, that in order to 



* Communicated by the Chemical Society j having been read February 

 3, 1845. 



•j- I have had the pleasure of witnessing the care and accuracy with 

 which the author of tliis paper has proceeded in making his observations 

 and establishing his facts. 



It appears to me that he has produced a definite and irrefragable proof 

 that the chemical character of a compound does not depend, as the electro- 

 chemical theory supposes, upon the nature of the elements it contains, but 

 solely on the manner of their grouping. — Justus Liebig. 



Phil. Mag. S. 3. Vol. 26. No. 174. May 184-5. 2 D 



