44 CAROTINOIDS AND RELATED PIGMENTS 



ether and carbon disulfide solutions of the chloroplastid pigments from 

 plantain (Plantago) and dead nettle (Lainium album) leaves Tswctt 

 has shown that at least three and possibly four xanthophylls accom- 

 pany carotin. He has provisionally designated these a, u', a", and (3 

 xanthophylls, respectively. Tswett has characterized these pigments 

 further, as follows: 



Xanthophyll a. This pigment is least adsorbed by the CaC0 3 and 

 is closest to carotin in this respect, which is not adsorbed at all. Its 

 adsorption zone is the lowest in the column of the xanthophyll zones 

 and has an orange-yellow color when carbon disulfide is the solvent. 

 It is hypophasic in the Kraus separation, i.e., remains in the alcohol 

 layer. It shows three well marked absorption bands, the first two of 

 which, in alcohol or petroleum ether solution, lie at 485-470|i(j, and 

 455-440^1. Its alcoholic solutions are merely bleached on addition of 

 con. HC1. 



Xanthophylls a' and a". These pigments lie very close together 

 in the column but above the zone of xanthophyll a. In CS 2 their 

 zones are yellow. They are similar in properties to xanthophyll a, 

 i.e., in the Kraus separation and spcctroscopically, but their absorp- 

 tion bands are shifted slightly towards the violet. The effect of HC1 

 on the alcoholic solutions is not mentioned but the author (1914g) 

 has found that for xanthophyll a , at least, no color reaction is 

 produced. 



Xanthophyll /?. This pigment shows the greatest adsorption affinity 

 for CaC0 3 (exists in the largest colloidal aggregates) and comprises 

 the highest yellow zone in the column. This pigment is hypophasic 

 in the Kraus separation like the other xanthophylls, but may be dif- 

 ferentiated from them by the fact that its alcoholic solution gives a 

 blue color on addition of con. HC1, and also by the fact that its 

 absorption bands are shifted perceptibly towards the violet from those 

 of xanthophylls a, a', and a", the first two bands lying at 475-462|j|i 

 and 445-430(i(.i, when in alcoholic solution. The xanthophyll (5 of 

 Tswett appears to be identical with th.e "yellow xanthophyll" of Sorby 

 and the Y. xanthophyll of C. A. Schunck, but bears no relation what- 

 ever to the xanthophyll (3 of Kohl. According to Tswett (1908b) the 

 latter is not a xanthophyll at all, in fact does not exist in the plant 

 but is merely a post-mortem decomposition product derived from 

 colorless chromogens whose alkali salts are yellow and which assume 

 a dark color on oxidation. 



The relative solubility properties of carotin and xanthophylls as 



