168 Mr. C. A. Schunck. The Xanthophyll [Apr. 17, 



with an indication of a fourth more refrangible, the solution becoming 

 by degrees paler and assuming a slight green tinge before becoming 

 colourless. HN0 3 on the other hand rapidly affects the colouring 

 matter, a fourth more refrangible pronounced band is formed, the first 

 and second by degrees disappear and the third becomes faint, the 

 solution in a short time assumes a green tinge and finally becomes 

 colourless (Plate 6, figs. 1014). The same reaction takes place with 

 H 2 S0 4 , H 2 2 , and nascent H, but with these reagents the action is 

 slower. On the other hand HC1 produces an immediate and striking 

 effect upon the spectra of B. and Y. xanthophyll, their solutions at once 

 became paler yellow in colour ; in the former the first band disappears 

 the resulting spectrum consisting of three distinct bands, the first 

 two a little less refrangible in position than the original second and 

 third with an indication of a fourth in the ultra-violet at M, while in 

 the latter three pronounced bands are formed, removed considerably 

 towards the violet and ultra-violet with an indication of a fourth at N 

 (Plate 6, figs. 69). 



The reaction in both cases is a most delicate one, a very small 

 quantity of acid being required, otherwise the reaction takes place 

 too rapidly to be observed. It is evidently due to the formation of 

 two other yellow colouring matters from the B. and Y. xanthophylls, 

 which are, however, unstable in the presence of the acid and are 

 rapidly destroyed, the solution becoming a greenish-blue and finally 

 colourless in a short time. A similar change takes place in these two 

 xanthophylls on standing for a time, the above two colouring matters 

 being formed spontaneously, but under these circumstances they 

 appear to be more or less stable and their alcoholic solutions can be 

 kept for a considerable time without further change taking place. 



In the case of some flowers (as coltsfoot and marigold) the extracted 

 pigment appears to be a mixture of B. xanthophyll and the colouring 

 matter formed from it by the action of acid or spontaneous change. 

 Sorby* has already noticed the formation of this colouring matter 

 from his " yellow xanthophyll " by the action of acids, but the change 

 that the Y. xanthophyll undergoes has not before been noticed I think. 

 H 2 S0 4 and HN0 3 produces in both the same effect as HC1, the action 

 being more energetic especially with the latter. 



In the separation by carbon-bisulphide the greater portion of the 

 pigment is taken up in the first fraction, the subsequent ones con- 

 taining less and less and by examining together the spectra of each 

 and the action of HC1 one can readily determine which xanthophyll is 

 present. In cases of mixtures of L. and B. and L. and Y., which occur 

 in the wallflower, daffodil and African marigold, the L. being more 

 soluble in carbon-bisulphide than the B. and Y., the latter will be found 

 more or less free from the L. in the subsequent fractions and the action 

 * ' Roy. Soc. Proc.,' rol. 21, p. 459. 



