94 Dr. Schunck on the Formation of Indigo-blue. 



iug compounds with alkalies and other bases which are not com- 

 pletely decomposed by acids. The analyses which I have made 

 agree best with the formula C'^ IP NO^. If this be the correct 

 formula, it differs in composition from indigo-blue by the ele- 

 ments of three equivalents of water, just as the body or bodies 

 from which it is formed differ from iudicau by containing the 

 elements of several equivalents more water. 



The analyses of indiretine led to more definite results. The 

 substance was prepared from indican, which had undergone the 

 alteration of which I have several times spoken, by treating it 

 with boiling sulphuric acid, collecting the dark brown deposit 

 which was formed on a filter, washing out the acid, treating with 

 boiling alcohol, filtering from the indihumine which remained 

 undissolved, and evaporating the alcoholic solution to dryness. 



I. 0"4420 grm., dried in the water-bath and burnt with oxide 

 of copper and chlorate of potash, gave 0'9930 grm. carbonic acid 

 and 0-2100 water. 



0"5470 grm. gave 0'3415 grm. chloride of platinum and am- 

 monium. 



II. 0-5370 grm. of another preparation gave 1-2130 grm. 

 carbonic acid and 0-2675 water. 



0-8780 grm. gave 0-4320 grm. chloride of platinum and aiu- 

 monium. 



III. 0-2760 grm. of a third preparation gave 0-6190 grm. 

 carbonic acid and 0*1420 water. 



These numbers correspond with the following composition : — 



Calculaterl. 



61-02 



5-64 



3-95 



29-39 



100-00 10000 100-00 

 Assuming C^IP°NO'^ to be the correct formula for indire- 

 tine, then the formation of this substance from indican, or rather 

 from its hydrates, can only be explained by supposing that car- 

 bonic acid is evolved during the process. If we take, for instance, 

 the substance represented by the formula C^^ IP^ N0''°, which 

 gives indiretine when treated with acids, we may suppose it to 

 split up into 1 equivalent of indiretine, 1 equivalent of sugar, 4 

 equivalents of carbonic acid, and 7 equivalents of water, as will 

 be seen by the following equation : — 



rc36H20NOi3 1 eq. indiretine. 

 C52 JJ37 N0''°= J C'^ H '° 0'2 1 eq. sugar. 



j C* 0^ 4 eqs. carbonic acid. 



L H7 07 7 eqs. water. 



Qb2 JJ37 NO"" 



