FORMATION OF INDIGO-BLUE. 207 



III. 0.2760 grm. of a third preparation gave 0.6190 grm. 

 carbonic acid and 0.1420 water. 



These numbers correspond with the following composi- 

 tion : — 



Eqs. Calculated. 



Carbon... 36 216 61.02 



Hydrogen 20 20 5.64 



Nitrogen.. 1 14 3.95 



Oxygen... 13 J^ 29.39 



354 100.00 100.00 100.00 



Assuming C36 H20 NO13 to be the correct formula for indi- 

 retine, then the formation of this substance from indican, or 

 rather from its hydrates, can only be explained by supposing 

 that carbonic acid is evolved during the process. If we 

 take, for instance, the substance represented by the formula 

 C52 H37 NO40, 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 : — 



Cgg H20 NO13 1 eq. Indiretine. • 



t.52 «37 ^^^40- )^^ Q^ 4 ^^^ Carbonic Acid. 



H7 O7 7 eqs. Water. 

 C52 H37 NO40 



I have certainly not observed the disengagement of car- 

 bonic acid during the formation of indiretine, but the evo- 

 lution of gas might easily elude observation during the 

 long-continued boiling, which is necessary for the production 

 of this substance. 



The want of material has, for the present, interrupted the 

 further prosecution of my experiments. As soon as I shall 

 have obtained an additional quantity of the fresh plant, it is 



