232 DR. EDWARD SCHUNCK ON INDIGO-BLUE. 



employed for its extraction ; and it seemed to me^ therefore, 

 highly probable that the plant would be found to contain 

 some glucoside similar to indican. 



Bletia Tankervillice is not difficult to procure, being fre- 

 quently grown for the sake of its handsome brown and white 

 flowers and its general beauty. The leaves of the plant 

 having been cut in pieces and ground with water between 

 two stones to a pulp, which is strained through calico, yield a 

 green muddy liquid which, heated to near the boiling-point, 

 gives a thick green coagulum. The liquid filtered from this 

 coagulum is clear, of a deep yellow colour, with a slight acid 

 reaction and an acrid taste. When this liquid is mixed 

 with sulphuric or hydrochloric acid and left to stand, it 

 deposits dark-coloured flocks consisting of indigo-blue 

 mixed with a substance which imparts a purple colour to 

 boiling alcohol, probably indirubine. The presence of 

 glucose may be detected in the filtrate by the usual test, 

 while the same test applied before the addition of acid 

 shows no indication of its presence. It may hence be 

 inferred that the liquid contains in solution a glucoside 

 similar to, if not identical with, indican. It undergoes, 

 like indican, a complete change when submitted to the 

 action of alkalies ; for if its watery solution be mixed with 

 caustic alkali and boiled, then with an excess of sulphuric 

 acid and again boiled, it deposits brown flakes, which are 

 found to contain but little indigo-blue, while in the filtrate 

 only a trace of glucose can be detected. The same change 

 takes place gradually when the watery solution is left to 

 stand for several days at the ordinary temperature. 



The gradual formation of indigo-blue in the leaves of 

 Bietia Tankervillice may easily be traced in the same way 

 as with those of Polygonum tinctoriwn, by placing the lower 

 ends, immediately after cutting, in dilute hydrochloric acid 

 and leaving them freely exposed for a few days. The acid. 



