38 CAROTINOIDS AND RELATED PIGMENTS 



which he called a, p, y, 8 and e xanthophyll, respectively, although he 

 concluded from the fact that each pigment showed two absorption 

 bands showing no significant spectro-analytical differences that they 

 were probably identical substances. Kohl (1902c) later considered 

 all these xanthophylls to be carotin, but a comparison of the meas- 

 urements of the spectrum bands of y and 8 xanthophyll as given by 

 Tschirch (1885) would indicate that the former may have been due 

 to carotin, but that the latter was undoubtedly one of the xantho- 

 phylls as now recognized. 



In his next paper Tschirch (1896) regarded all the yellow chromo- 

 lipoids as xanthophylls and distinguished between two, one of which 

 was obtained in metallic glistening crystals, which he called xantho- 

 carotin. This pigment showed three beautiful absorption bands, the 

 measurements of which correspond with those now recognized for 

 xanthophyll. The other xanthophyll could not be obtained in crystal- 

 line form and its solutions were characterized by showing no absorp- 

 tion bands, only end absorption of the violet and ultra-violet. 

 Tschirch used fresh grass as the source of his material for this study. 



In his most recent paper T.schirch (1904) turned hi* attention to a 

 comparison of his xanthocarotin and xanthophyll with the carotin 

 from carrots. Spectroscopic absorption properties only were considered. 

 There has always been a question in the author's mind as to which 

 group of carotinoids Tschirch'* xanthocarotin belongs. Tschirch him- 

 self considered that it might be identical with the carotin from car- 

 rots, inasmuch as the absorption spectra of the crystalline pigment 

 which he isolated from carrots and that of his xanthocarotin from 

 grass were identical. Kohl (1902d) believed that Tschirch's xantho- 

 carotin was carotin contaminated with phytosterin, and Tswett 

 (1911a) apparently also regarded the pigment as a carotin although 

 he recognized the absorption spectra of Tschirch's carrot carotin did 

 not correspond exactly with the measurements given by other inves- 

 tigators. Willstatter and Mieg (1907) also regard the xanthocarotin 

 as carotin, but with these views the author is not in agreement on the 

 following grounds. The author believes that Tschirch's carotin crys- 

 tals from carrots were xanthophyll, not carotin, for he obtained them 

 merely by spontaneous evaporation of an ether extract of sugar-free 

 carrots, which would be more likely to yield xanthophyll crystals than 

 carotin. Moreover, the crystals had the reddish yellow color and steel 

 blue reflection described by Willstatter and Mieg for crystals of xantho- 

 phyll. In addition the absorption spectra of these crystals correspond 



