228 



sume years agij by Dr. Schunck 'i; liis results did Di.ir, agrée with 

 those obtained by Beijerinck, and I bave been enabled to elear up the 

 cause of the différences of thèse two observers, Beijerinck's expe- 

 riment is carried out as follows. Fresh leaves of Isatis tinctoria are 

 thrown iiitn Ixiiling u ater and the mixture kept at tlie bnil fur sume 

 minutes, filtered of( and the filtrate treated at unee witli an aqueous 

 solution of isatin. Very soon there is formed a red precipitate, 

 which is collected on a filter. washed well with water and dried. 

 The colouring matter obtained is next crystallised twice froni boiling 

 acetic acid. It does not difler in any respect from iiidirubin ob- 

 tained by Baeyer's svnthesis and possesses the same composition 

 as will be seen from the following analysis. 



0. 1024 gr. gave 0.0378 gr. H,0 and 0.2757 gr. Cü., 

 found 4.10"/o H.,0 a 73.437o C 

 calcul, for C„.H,„N._,0., 3.85% „ 73.28o/o 



Quite a différent resuit is obtained when operating with dued 

 leaves, that is. when the conditions are observed which led Dr. 

 Schunck to the discovery of indican. I opeiated as fcjllows. Leaves 

 of Isatis tinctoria which were left to dry first at ordinary tempe- 

 rature and then in a water stove were pulverised and extracted 

 with boiling alcolml. The filtrate was evaporated under reduced pres- 

 sure, the residue extracted with boiling water. filtered and the fil- 

 trate boiled with a solution of isatin. There was formed after 

 some time a dark precipitate which was filtred off, washed with 

 boiling water. tlien with a dilute solution of caustic soda and 

 again with water. Tho dry colouring matter was next dissolved 

 in boiling phénol, filtered and the solution precipitated with ether, 

 quickly filtered cjff and dried. The colouring matter which may 

 for the présent be called isatocvanin possesses the following pro- 

 perties. It represents a blackish brown powder easily soluble in 

 aeetic acid with a blue coiour. with greater difficulty in alcohol 

 and ether, and insoluble in alkalis. In conc. sulphuric acid it dis- 

 solves at first with a yellowish coiour but after standing the solu- 

 tion turns blue. The following table contains some of the charac- 

 teristic reactions of indirubin and isatocyanin; it will be seen that 

 the two colouring matters differ very materially in many l'espeets. 



') Comp. Chem. News. 1900, p. 176. 



