238 CAROTINOIDS AND RELATED PIGMENTS 



the addition of 36.5 per cent of their original weight, corresponding 

 to 13 atoms of oxygen or the formula C 40 H 56 15 . When this product is 

 recrystallized from ether it contains even more oxygen and corresponds 

 to the formula C 40 H 56 18 , and melts at 140 C. The oxidizing pig- 

 ment has a peculiar violet-like odor, at least in the case of plant xan- 

 thophyll, although Willstatter and Escher did not notice this in the 

 case of xanthophyll from egg yolk. The oxidized crystals dissolve in 

 concentrated mineral acids with a dark brown color and in dilute 

 alkalis with an intense reddish-yellow color. 



The constitution of xanthophyll, like that of carotin, is unknown. 

 Even its relation to carotin is very puzzling. While the empirical re- 

 lations between the two carotinoids suggest that xanthophyll is a sim- 

 ple oxidation product of carotin, the behavior of xanthophyll shows 

 that this is not the case. Xanthophyll fails to give a reaction for 

 carbonyl, alcohol or acid groups, which suggests that the oxygen must 

 be present in an ether-like combination. If this be accepted as prob- 

 able it would indicate that the carotinoids are not derived from each 

 other but are rather built up from a common nucleus. 



Lycopin. This red isomer of carotin crystallizes in the form of a 

 bright or dark carmine colored, velvety appearing mat of wax-like 

 crystal aggregates, consisting of elongated microscopic prisms, whose 

 ends are usually quite ragged. The crystals usually obtained from pe- 

 troleum ether are of this character and are shown in Plate 2, Figure 

 4. Figure 5, Plate 2 shows the fine needles which crystallize from 

 ether or from carbon disulfide-alcohol, which frequently occur in 

 beautiful starlike clusters, according to Monteverde and Lubimenko. 

 The powdered crystals have a dark reddish-brown color and melt at 

 168-169 C. (corrected). 



Lycopin crystals are less soluble than carotin in all the carotinoid 

 solvents. Ethyl and especially methyl alcohol are exceptionally poor 

 solvents. Low boiling petroleum ether dissolves only a small 

 amount, 10 to 12 liters taking up only 1 gram. About 3 liters of ether 

 are required for the same amount of pigment, but one can readily 

 obtain a 2 per cent solution in CS 2 , and even stronger solutions in 

 warm chloroform or benzene. The crystals are insoluble in acetone 

 and glacial acetic acid. They dissolve, however, in concentrated 

 H 2 SO 4 and HN0 3 with a deep blue or purple color, which is very 

 transient in the case of HN0 3 . 



The lycopin crystals readily oxidize with bleaching, the maximum 

 oxygen absorption amounting to about 32.5 per cent of their original 



