Dr. Schunck on the Formation of Indigo-blue. 123 



indifuscone might not be inappropriate for the body whose com- 

 position is expressed by the second formula, C^^H^°NO^. Though 

 this is the only way in which I am able to explain these discre- 

 pancies, still I failed in all my efforts to separate any specimen 

 of the substance having an intermediate composition into two 

 distinct constituents, as every such specimen behaved towards 

 all reagents as if it were one single substance. By treating, 

 however, a specimen of this kind with a boiling solution of 

 caustic soda for a length of time, the per-centagc of carbon was 

 increased by about 2-5, showing that the body whose formula is 

 Q24 jjio NQS^ has a tendency to loss carbonic .acid and be con- 

 verted into the one whose composition is expressed by the for- 

 mula C^"^ H'" NO^. The substance used in this experiment was 

 that employed for the analysis No. III. It was dissolved in 

 caustic soda ; the solution was boiled for some time, and then 

 mixed with an excess of muriatic acid. The precipitate produced 

 by the acid was dissolved in alcohol and ammonia, and the solu- 

 tion having been mixed with an excess of acid, deposited a brown 

 powder, which after being collected on a filter, washed and dried, 

 was analysed, when it was found to contain 63-23 per cent, of 

 carbon. 



Indirefine. 



This body, the most striking properties of which have been 

 already mentioned in the first part of this paper, appears on eva- 

 poration of its alcoholic solution in the form of a dark brown, 

 shining resin, which is transparent only in very thin layers. It 

 resembles iudifulvine in appearance, but is distinguished from 

 the latter by its being easily soluble in all alkaline liquids. When 

 heated on platinum-foil it melts, swells up very much, and burns 

 with a yellow smoky flame, leaving some charcoal which slowly 

 burns away. When heated in a tube, it swells up and gives 

 strong-smelling fumes, together with an oily sublimate resem- 

 bling that obtained from iudifulvine, which when cool becomes 

 half solid. Concentrated sulphuric acid dissolves it in the cold, 

 forming a brown solution, which when boiled becomes black, 

 and disengages sulphurous acid. Boiling nitric acid decomposes 

 it with an evolution of nitrous acid, giving a yellow solution, 

 which on evaporation leaves a brown residue consisting of a re- 

 sinous substance insoluble in water and a little picric acid. 

 When it is treated with boiling caustic soda-lye only a trace of 

 ammonia is given off, but when heated with soda-lime there is a 

 much stronger evolution of ammonia. A boiling solution of bi- 

 chromate of ])0tash, to which sulphuric acid has been added, slowly 

 decomposes it with an evolution of gas, while the liquid becomes 

 green. The solution in ammonia is brown, and gives browu 



