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



The insoluble residue, consisting of indibumine, was analysed, 

 when the following numbers were obtained : — 



0-3065 gnn., dried at 100° C, gave 07065 grm. carbonic 

 acid and 0-1300 water. 



0-3285 grm. gave 0'3765 grm. chloride of platinum and am- 

 monium. 



From these numbers it may be inferred that the composition 

 is as follows : — 



Indifuscine. 



This body so much resembles the preceding in its outward 

 appearance and most of its properties, that the two might easily 

 be confounded. Indifuscine is always obtained in the shape of 

 a dark brown powder, exhibiting sometimes a reddish tinge. It 

 is insoluble in boiling water and only slightly soluble in boiling 

 alcohol, the solution being- light brown, and depositing a great 

 part of the substance on cooling in brown flocks. It is easily 

 soluble in a mixture of alcohol and ammonia. The solution is 

 dark brown and opake; and when it is mixed with an excess of 

 muriatic or acetic acid, the greatest part of the indifuscine is 

 deposited in the form of a brown powder, while the supernatant 

 liquid retains a brown colour, which is rather darker than that 

 of the solution of the substance itself in boiling alcohol. It is 

 also soluble in watery solutions of caustic and carbonated alka- 

 lies, forming brown solutions, from which it is precipitated again 

 by acids in brown flocks. The ammoniacal solution gives brown 

 precipitates with salts of baryta, lime, magnesia, alumina, iron, 

 zinc, copper, lead, mercury and silver, the whole of the indifus- 

 cine being precipitated in combination with the respective bases. 

 When indifuscine is heated in a platinum crucible, the whole 

 mass begins to heave and is kept in a state of agitation for a few 

 moments, in consequence probably of an evolution of gas at the 

 points of contact with the metal, whereupon it burns, but with- 

 out melting, and leaves a considerable quantity of charcoal, which 

 burns away with difficulty without leaving any ash. When 

 heated in a tube, it gives fumes having a smell like that of burn- 

 ing turf, besides a little oily sublimate, unmixed with anything 

 crystalline. Concentrated sulphuric acid dissolves indifuscine, 

 forming a brown solution, which on being heated evolves sul- 



