FORMATION OP INDIGO-BLUE. 22/ 



treated with acid still gives indirubine, in a state of tolerable 

 purity. 



On attempting however to prepare stance on a 



somewhat larger scale I found it difficult to arrest the pro- 

 cess at this stage. As soon as the solution ceased to give 

 indigo-blue with acids, it began to yield with acids a mixture 

 of indirubine and indiretine, and at length it gave indiretine 

 only, after which no further change took place. By allowing 

 a watery solution of indican mixed with baryta water to stand 

 until the decomposition had arrived at its last stage and then 

 treating the solution in the way just described, a substance 

 resembling the preceding was obtained, in the form of a 

 brown syrup, to which I propose to give the name of 



Indicanine. 



This substance has the following properties. Its taste is 

 bitter like that of indican. When heated on platinum it 

 swells up very much and burns leaving a bulky carbona- 

 ceous residue. When heated in a tube it gives fumes, con- 

 densing to a brown liquid, which after some time becomes 

 filled with a quantity of white crystalline needles. It is 

 perfectly soluble in alcohol and ether. The alcoholic solu- 

 tion gives with an alcoholic solution of acetate of lead a 

 bright sulphur-yellow precipitate which dissolves when more 

 acetate of lead is added and the liquid is boiled, forming 

 a yellow solution, in which ammonia again produces a 

 yellow precipitate like the first. The watery solution gives 

 only a slight precipitate with acetate of lead, but the 

 filtered liquid yields a copious yellow precipitate on the 

 addition of ammonia. When the watery solution is mixed 

 with sulphuric acid and boiled it slowly deposits a quantity of 

 brown resinous particles, which are entirely soluble in caustic 

 soda and consist of indiretine and a little indifuscine. On 

 tig caustic soda to a watery solution of indicanine it be- 

 m dark yellow and on being boiled disengages ammonia, 



