84 CAROTINOIDS AND RELATED PIGMENTS 



the theoretical molecular weight of which is 698. A melting point of 

 173.7 C. (corrected) was found for the crystals. 



From the work of Willstatter and Escher (1910), however, it is 

 evident that lycopin is identical in general composition and molecular 

 weight with carotin, differing only in solubility in certain solvents and 

 in the position of the absorption bands and in the form of the crystals 

 as well as their color when free and in solution. There is a slight 

 difference in melting point also, lycopin melting between 168 and 

 169 C., while carotin melts at 167.5 to 168 C. The conclusion that 

 lycopin is a true isomer of carotin seems entirely justified. 



The isolation of lycopin was carried out by Willstatter and Escher 

 on their usual generous scale, starting with 74 kg. of tomato conserve, 

 from which 11 grams of pure recrystallized pigment were eventually 

 obtained. Crystals of carotin were also obtained in small amounts as 

 by-product, showing that the factor for yellowing which the red 

 tomato possesses, and which is familiar to the botanist, is due, in 

 part at least, to the usual carotin of the chloroplastids. 



The analyses and molecular weight determinations carried out by 

 Willstatter and Escher on the pure lycopin crystals were in excellent 

 agreement with theoretical composition and molecular weight of caro- 

 tin as found by Willstatter and Mieg (1907), namely, C 40 H 56 , as 

 shown by the following data. 



Mol. Wt. jound jor 

 Calculated jor Found JOT lycopin. Calculated Mol. lycopin. 



C// M (Ave. oj 4 dttns.J in. jor CW/, (Ave. oj 7 detns.) 



C = 89.48 C = 89.36 



H = 10.52 H = 10.81 536 558 



The characteristic properties of lycopin as described by Willstatter 

 and Escher may be summarized briefly as follows. The crystals are 

 dull brownish-red to carmine colored flakes and lack the metallic 

 iridescence of carotin and xanthophyll crystals. The solution in CS 2 

 retains its bluish-red color on great dilution, and while the ethereal 

 and alcoholic solutions are yellow they have a somewhat browner tone 

 than carotin or xanthophyll solutions. The solubility of the lycopin 

 crystals in the usual carotin solvents, namely, ether, petroleum ether 

 and CS 2 , is somewhat less than that of carotin, and it is even more 

 difficultly soluble in hot alcohol than pure carotin. An iodine addi- 

 tion product of constant composition and characteristic form could 

 not be obtained, the product being amorphous and having an iodine 

 content of 34-37 per cent. Lycopin readily oxidizes and bleaches like 



