476 Mr. C. A. Schunck. The Yellow Colouring Matters 



the violet and ultra-violet, the first two and least refrangible of which 

 are slightly but distinctly shifted towards the violet compared to the 

 first two bands in the crude solution, while the other two occupy 

 approximately the same positions (Plate 5, A, 3) ; but it is only in a few 

 instances they are plainly visible on the photographic plate, usually 

 they are more or less obscured, only the first band being distinct and 

 well defined (Plate 6, F, 2). The obscuration is no doubt due to the 

 yellow colouring matter before mentioned, the greater quantity of which 

 remains in the alcohol after the CS 2 fractionation, being more soluble 

 in the former than in the latter. Its presence in a considerable 

 quantity tends further to obscure the bands, and it can then be 

 detected at once by the alcoholic solution after fractionation, being- 

 more of a straw colour than the usual pale yellow. This spectrum is 

 not stable, for, after standing a few days the least refrangible band 

 fades and finally disappears, and, after a further lapse of time, the other 

 three bands, more especially the third and fourth, became intensified 

 and well defined, the rest of the ultra-violet being obscured (Plate 6, 

 F, 4) ; but in some cases when there is very little obscuration present, 

 an additional band is discernible in the ultra-violet (Plate 5, A, 4). 

 This change, however, only takes place, as a rule, after fractionation, as 

 the crude solution can be kept a considerable time without any change 

 taking place, pointing to the capability of one colouring matter in 

 protecting a less stable one in a mixture. The same change, however, 

 can be effected at once by adding a very small quantity of HC1 to the 

 alcoholic portion, when the colour of the solution immediately becomes 

 a paler yellow, but in a few hours all the bands disappear and 

 the solution becomes a peacock-blue colour which, in a day or two, 

 likewise fades leaving the solution finally colourless. This blue 

 coloration is a characteristic of the colouring matter left in the 

 alcohol after fractionation. By agitating the alcoholic portion with 

 ether and adding water till a separation takes place, the ether takes up 

 the greater quantity of the colouring matter, and, on spontaneous 

 evaporation, an amorphous lemon-yellow substance is deposited which 

 also gives this same spectrum. The last of the CS 2 fractions when 

 taken into alcohol in some cases likewise give this spectrum. 



The question whether the normal spectrum of the alcoholic portion 

 represents a single colouring matter I have been unable to decide 

 definitely by spectroscopic means, but I think the above facts tend to 

 prove that on standing or by the action of HC1 a definite colouring 

 matter is formed therefrom giving the above changed spectrum, and 

 from it, by the further action of acid, a blue colouring matter is pro- 

 duced. I also think the experiments tend to show that this colouring 

 matter does not pre-exist in the leaf, but is formed subsequently, either 

 spontaneously or by the action of the acid juices during or after the 

 process of extraction, which is supported by the fact that from extracts 



