CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT. 323 



similar absorption bands in the violet region of the spectrum. The 

 bands of the xanthophylls, however, were all shifted somewhat 

 towards the blue with respect to the bands of crysophyll, the amount 

 of shifting depending on the xanthophyll, L xanthophyll being shifted 

 the least and Y xanthophyll the most. Schunck found the absorption 

 bands of the different xanthophylls especially characterized by the 

 action of their alcoholic solutions in the presence of HC1 and HNO 3 

 the details of which are given in his latest paper. 1 



Schunck also made the very interesting discovery that the yellow 

 pigment of egg yolk and fowl serum shows the identical properties 

 of L xanthophyll both with respect to the position of the original 

 absorption spectra and also the action of acids upon the spectra. . 



One of the most interesting and important studies of chlorophyll 

 and its accompanying yellow pigments was made by Tswett 2 who 

 discovered and thoroughly investigated the adsorption properties of 

 these pigments. He was able to demonstrate the presence of at least 

 four different xanthophylls which he designates as xanthophylls 

 * ' a" and B. A more detailed review of this work will be given 

 in connection with a report of the present investigations. It is of 

 interest here especially on account of its historical position with respect 

 to the establishment of the chemical constitution of the xanthophylls. 

 It was Willstatter and Meig 3 who isolated and identified the 

 crystalline xanthophyll pigment accompanying the carotin in green 

 plants and leaves, and, as noted above, Eiiler and Nordenson 4 have 

 recently found xanthophyll crystals in their extracts from the carrot, 

 thus indicating a more general distribution of the xanthophylls in 

 connection with carotin than has been believed. 



The results of the study of the crystalline xanthophyll show that 

 it is composed of carbon, hydrogen and oxygen in the proportion 

 C 4t H 56 O 2 and is thus merely carotin dioxide. 5 The pigment is further 

 distinguished from carotin by the color and shape of its crystals, which 

 are yellow or orange trapesium plates sometimes spear or wedge-shaped 

 which are characterized by a steel blue reflection. The pigment ex- 

 hibits an entirely different solubility toward petroleum ether and abso- 

 lute alcohol than carotin, being insoluble in the former and readily 

 soluble in the latter solvent. According to these authors, the pure 



1. Proc. Roy. Soc. 72 (1903). 



2. Ber. Botan. Gessel, 24, pp. 316 and 384 (1906). 



3. Ann. der. Chemie, 355, p. 1 (1907). 



4. Loc. cit 



5. Willstatter and Meig point out the probable identity of xanthophyll with 

 the hitherto unexplained hydrocarotin found by Husemann. 



