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



removed with sulphuretted hydrogen, leaving on evaporation a 

 residue which is insoluble in alcohol. It differs, however, in 

 composition, according as the solution of indican has been eva- 

 porated spontaneously or with the assistance of heat. The body 

 which is formed when a watery solution of indican is sponta- 

 neously evaporated in contact with' the air, I propose to call — 



Oxindicanine. 



So much of this body is produced during the preparation of 

 indican, that I found it unnecessary to prepare it purposely. 

 "When the residue left after the evaporation of the watery solu- 

 tion of indican by means of a current of air, as described above, 

 is treated with cold alcohol, the greatest part of the oxindica- 

 nine formed during the process remains undissolved. It may 

 be purified simply by dissolving it in a little water and precipi- 

 tating again with a large quantity of alcohol. Its appearance is 

 that of a brown glutinous substance, which on being left to stand 

 over sulphuric acid becomes almost dry, and assumes the appear- 

 ance of gum. It is insoluble in absolute alcohol, and only 

 slightly soluble in dilute alcohol. When heated on platinum it 

 swells up very much and burns, leaving a considerable carbon- 

 aceous residue. It yields, when heated in a tube, strong-smell- 

 in"- fumes, but only a slight trace of crystalline sublimate. Its 

 taste is naxiseous, but not bitter. Its watery solution gives with 

 acetate of lead a copious, dirty-yellow precipitate, and the filtered 

 liquid gives a pale, primrose-yellow precipitate on the addition 

 of ammonia, or of a large excess of alcohol. When the watery 

 solution is mixed with sulphuric acid and boiled, it slowly de- 

 posits brovra flocks, which have the properties of indifuscine, 

 while the liquid contains iudiglucine. For the purpose of de- 

 termining its composition I employed the lead compound, pre- 

 pared by adding acetate of lead to the watery solution, filtering, 

 and washing with water. 



I, 0-8515 grm. of this precipitate, dried fii-st in vacuo and 

 then at 100° C, gave 0-7310 grm. carbonic acid and 0-1735 

 water. 



1*1640 grm. gave 0-2575 grm. chloride of platinum and am- 

 monium. 



0-5185 grm. gave 0-3460 grm. sulphate of lead. 



II. 1-2640 grm. of another preparation gave 1*0495 gi*m. 

 carbonic acid and 0-2430 water. 



1*5500 grm. gave 0*2505 grm. chloride of platinum and am- 

 monium. 



0-7730 grm. gave 0-5250 grm. sulphate of lead. 

 Hence the composition in 100 parts was as follows : — 



