186 Dr. Schunck on the Formation of Jndigo-hlue. 



animal charcoal until it had lost the yellowish tint which it pos- 

 sessed at first. The liquid having been again filtered was mixed 

 with acetate of lead and ammonia, which produced a milk-white 

 precipitate. This precipitate, after being filtered off, was redis- 

 solved in a mixture of alcohol and acetic acid, and by the addition 

 of a small quantity of ammonia a white precipitate was again 

 produced, which was filtered off and washed with alcohol. 



1-0230 grm. of this precipitate, dried in vacuo, gave 0-4780 

 grm. carbonic acid and 0-1510 water, 



0-6095 grm. gave 0-5780 grm. sulphate of lead. 

 In 100 parts it contained, therefore, — 



Carbon 12*74 



Hydrogen 1'64 



Oxygen 15*85 



Oxide of lead 69-77 



100-00 

 If the oxide of lead, the amount of which stands in no simple 

 relation to that of the other constituents, be deducted, the com- 

 position of the body combined with it will be represented by the 

 formula C'^H^'O", which is that of anhydrous indiglucine, as 

 will be seen from the following calculation : — 



Eqs. Calculated. Found. 



Carbon ... 12 72 42-60 42-14 

 Hydi-ogen. . . 9 9 5*32 5*42 



Oxygen ... 11 ^ 52-08 52*44 

 169 10000 10000 

 The manner in which indiretine and indifuscine are formed 

 from indicanine needs no explanation, since the composition of 

 the latter differs from that of indican merely by the elements of 

 1 equivalent of indiglucine. It is, however, difficult to explain 

 why indicanine, by decomposition with acids, should yield only 

 these products, and no indigo-blue, indirubine or indifulvine, 

 which might,, as far as their composition is concerned, be pro- 

 duced at the same time, and I am quite unable to assign any 

 cause for this phsenomenon. It seems to me very probable 

 that the indiretine and indifuscine which are formed when pure 

 indican in large quantities is decomposed with acids, owe their 

 origin to the conversion of a portion of the indican into indica- 

 nine before the acid has had time to effect the more complete 

 decomposition of this portion into indigo-blue, or indirubine and 

 indiglucine. 



Indican is decomposed, when its \vatery solution is heated for 

 a length of time, in exactly the same manner as by means of 

 alkalies. After the solution has been heated for some time, it 



