Dr. Schunck on the Formation of Indigo-blue. 98 



Acetate of lead produced iu the alcoholic solution a cream- 

 coloured precipitate, which was separated by filtration ; and on 

 adding a small quantity of ammonia to the filtered liquid, a 

 cream-coloured precipitate again fell, which was collected on a 

 filter, washed with alcohol, and dried in vacuo. On analysing 

 it I obtained the following results : — 



0'3705 grm., burnt with oxide of copper and chlorate of pot- 

 ash, gave 0-2670 grm. carbonic acid and 00730 water. 



0"3800 grm. gave 0"0680 grm. chloride of platinum and am- 

 monium. 



0'2680 grm. gave 0"2160 grm. sulphate of lead. 



In 100 parts it contained, therefore, — 



Carbon 19-65 



Hydrogen 2-18 



Nitrogen 1-12 



Oxygen 17*75 



Oxide of lead 59-30 



100-00 

 After deducthig the oxide of lead, the amount of which stands 

 in no simple relation to that ofthe other constituents, the organic 

 substance combined with the oxide of lead will be found to have 

 a composition expressed by the formula C^° H-^ NO^^, as will be 

 seen by the following calculation : — 



Eqs. Calculated. Found. 



Carbon .... 40 240 48-38 48-28 

 Hydrogen ... 26 36 5-24 5-35 



Nitrogen ... 1 14 2-82 2-75 



Oxygen .... 27 216 43-56 43-62 



496 100-00 100-00 

 This body is therefore formed from indican by the latter taking 

 up 3 equivalents of water and then losing 1 equivalent of sugar, 

 as will be evident from the following equation : — 

 1 eq. indican C^^ W^ NO^^ 1 _ / C^ W^ NO^' 

 3 eqs. water H^ O^ J-^ CMI'" 0'^ 1 eq. sugar. 



Qaa 1136 N 039 C*2 H36 1^ o^** 



It is perfectly conceivable that an additional equivalent of 

 sugar may separate from the body C'*'' H^^ NO^'' before the de- 

 composition is finally completed ; that is to say, that there exists 

 another intermediate body containing 28 equivalents of carbon. 

 Of the red colouring matter, which I have called indirubine, 

 I have not yet obtained a sufficient quantity for analysis. 



I have several times submitted indihumine, obtained on differ- 

 ent occasions, to analysis, but without being able to arrive at 

 any positive conclusion regarding its composition. The difficulty 

 of doing so arises from the circumstance of this substance form- 



