Dr. Hofmaun on the true Composition of Clilorindatmit, 21 



tion of the preparation and analysis, until I found the object 

 could be attained by a much more convenient way. 



For this purpose I must here mention some results ob- 

 tained by Erdmann in his excellent investigation on indigo. 



If indigo suspended in water be treated with chlorine, it is 

 transformed, as is known, into a reddish yellow mass, which 

 is a mixture of different substances. On submitting this to 

 distillation with water, chlorisatine and dichlorisatine remain 

 in the retort, whilst another body volatilizes with the watery 

 vapour, which according to Erdmann contained no nitrogen. 

 He called this substance chlorindoptene*, and gave for it the 

 following formula : 



C32 Hg Clg O4. 



By later experiments Erdmann found however that on di- 

 stilling chlorindoptene with potash or carbonate of potash it is 

 decomposed into a neutral body which passes over, and an acid 

 which remains in the retort united to the potash. The latter 

 is chlorindoptenic acid (chlorophenisic acid of Laurent) ; the 

 former Erdmann called chlorindatmit, and gave it the for- 

 mula Cj2 H4 Clg O2. 



Whence comes this body ? In what relation does it stand to 

 the other members of the indigo or phenyle series ? Among 

 the many derivatives of indigo made known to us by the inves- 

 tigations of Erdmann and Laurent it stands quite isolated. 



On comparing the properties which Erdmann described as 

 belonging to chlorindatmit with those I had observed in tri- 

 chloraniline, it appeared to me in the highest degree proba- 

 ble that these bodies were identical. The properties of both 

 bodies correspond exactly, and the method of formation is 

 extremely alike. The production of trichloraniline, as well 

 as that of chlorindatmit, is accompanied by the formation of 

 chlorindoptenic acid. Erdmann had determined the carbon, 

 hydrogen and chlorine in chlorindatmit. His numbers cor- 

 respond completely with the composition of trichloraniline. 

 For comparison I placed together the theoretical numbers of 

 this body and the analytical results of Erdmann. 



Chlorindatmit. Tiichloraniline. 



Carbon . . =36-42t Carbon . . =36*66 



Hydrogen . = 2-23 Hydrogen . = 2*03 



Chlorine . . =53-58 Chlorine . . =54-09 



Loss . . . = 7-79 Nitrogen . . = 7-22 



100-00 100-00 



* Journ.fur Pralct. Chem., vol. xix. p. 334. 

 t The equivalent of carbon is here taken as 75. 



i 



