46 CAROTINOIDS AND RELATED PIGMENTS 



dence available on this question indicates, however, that xanthophyll 

 (3 may have formed a considerable proportion of the crystalline prep- 

 aration. Willstatter and Mieg mention the fact that their prepara- 

 tion dissolved in strongly alcoholic HC1 with a blue color, a reaction 

 which is apparently characteristic of xanthophyll (3 only. In the Sorby 

 and C. A. Schunck separation, however, the pure pigment differen- 

 tiated itself almost equally between the alcohol and carbon disulfide 

 layers, a reaction which obviously characterizes the a group of xan- 

 thophylls because of their lesser adsorption from this solvent by 

 CaC0 3 . Still further evidence of a mixture of xanthophylls in the 

 Willstatter and Mieg preparation is the fact that its spectroscopic 

 absorption bands apparently lie in an intermediary position between 

 the bands of xanthophylls a and (5 as recorded by Tswett. 



The isolation of the various members of the xanthophyll group in 

 crystalline form seems greatly to be desired in order that the dif- 

 ferences existing between the individual members of this class of 

 carotinoids may be determim-d. The relative adsorption properties 

 of these pigments offers the most promising method for accomplishing 

 this result but the experimental work would have to be conducted on 

 a very generous scale. The xanthophylls are unquestionably either 

 isomorphic or isomeric forms of the same empirical composition, 

 C 40 H S6 2 , as Willstatter and Stoll (1913) have pointed out. The 

 author believes that Willstatter and Escher (1912) have already iso- 

 lated pure xanthophyll a in the form of their so-called lutein from 

 egg yolk, as will be discussed more fully in a later chapter. 



It is not likely that more than four xanthophylls characterize the 

 chloroplastid for the author (1914g) has found only four on applying 

 the chromatographic method to extracts from an entirely different 

 plant than Tswett used, namely, the leaves of alfalfa (Medicago 

 sativa). The possibility of other xanthophylls being present in non- 

 chlorophyllous organs is indicated, however, by a chromatographic 

 analysis which the author (1914g) carried out on the xanthophyll 

 fraction (obtained by the Kraus separation) of the pigments of the 

 carrot root, in which no less than eight distinct yellow or orange 

 zones characterized the chromatogram. The possibility remains to 

 be investigated, however, whether this result was influenced in any 

 way by the method of preparation of the material or other experi- 

 mental steps in the procedure employed. The author regards the 

 adsorption phenomenon of the carotinoids as colloidal so that it may 

 not be possible to secure these pigments in every case in the same 



