184 Dr. SchuDck on the Formation of Indigo-blue. 



treated with alcohol, in which a great part dissolves, and the 

 alcoholic solution is then mixed with twice its volume of tether, 

 which causes a milkiness and produces a syrupy deposit con- 

 sisting chiefly of indiglucine. The liquid, after it has become 

 clear, is evaporated spontaneously, when it leaves a yellow trans- 

 parent glutinous residue, having a bitter taste, which cannot be 

 distinguished in outward appearance from indican itself. This 

 residue, when dissolved in water and treated with acid, still gives 

 indirubine in a state of tolerable purity. 



On attempting, however, to prepare this substance on a some- 

 what larger scale, I found it difficult to arrest the process 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 in- 

 dican 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 



Ltdicanine. 



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 carbonaceous residue. 

 When heated in a tube it gives fumes, condensing to a brown 

 liquid, which after some time becomes filled with a quantity of 

 white crystalline needles. It is perfectly soluble in alcohol and 

 Bether. The alcoholic solution gives with an alcoholic solution 

 of acetate of lead a bright sulphur-yellow precipitate, which dis- 

 solves 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 adding caustic soda to a watery solution 

 of indicanine it becomes dark yellow, and on being boiled disen- 

 gages ammonia, but exhibits no further change. The analysis 

 of the lead compound, prepared by adding acetate of lead to the 

 alcoholic solution, filtering and washing with alcohol, yielded the 

 following results : — 



0*7840 grm., dried first in vacuo and then at 100° C, burnt 

 with oxide of copper and chlorate of potash, gave 0"6115 grm. 

 Carbonic acid and 01480 water. ' 



