CHEMICAL RELATI<)\* />'/' VI I' /:/: .Y CAROTINOIDS 179 



than AVillstattcr and Mieg obtained in their analyses of tho carotin 

 from cither green leaves en- carrots. Although Kscher was unable to 

 carry out any molecular weight determinations because of lack of 

 material, there can be no doubt from these data that the ovarian 

 carotin is identical in composition with the carotin of vegetable origin. 



Escher's observations of the melting-point of ovarian, carrot and 

 leaf carotins are of interest. By heating crystalline preparations from 

 each source together in the same bath using a shortened thermometer 

 he found that they all melted at exactly the same temperature, but 

 that this temperature was about 175 C. (corrected). This tem- 

 perature is appreciably higher than the figure reported by Willstatter 

 and Mieg for the carotins of plant origin, namely, 167.5-168 C., 

 which corresponded with the earliest observations of Arnaud, Kohl 

 and others. Escher explained his results on the grounds that con- 

 siderable variation in melting point can be obtained by modifying the 

 method of heating, so that in reality the melting point of crystals of 

 different carotinoids should be determined under comparative con- 

 ditions to secure comparable results. These results may indicate, 

 therefore, that the slight difference in the melting point of carotin 

 and xanthophyll crystals may not be of great importance in distin- 

 guishing the two forms of carotinoid. 



The general properties of the ovarian carotin also correspond exactly 

 with the carotin from carrots and leaves. The crystalline form; 

 solubility of the crystals in various solvents; response to the phase 

 test (being practically quantitatively epiphasic between petroleum 

 ether and 80-90 per cent alcohol); position of the absorption bands; 

 formation of a crystalline tri-iodide (C 40 H 56 I 3 ) in carbon disulfide 

 solution, melting at 133.5-135 C., and showing 40.6 per cent iodine 

 (calculated value 41.5 per cent) ; and its ready oxidation to a grayish- 

 yellow powder, soluble in alcohol and containing 36 per cent oxygen, 

 all corresponded exactly with the properties of carotin from leaves 

 and carrots. There can be no doubt whatever that the carotin from 

 the corpus luteum of the cow is identical with the carotin so widely 

 distributed in the vegetable kingdom. 



Crustacean carotin. As stated in Chapter V in connection with the 

 chromolipoids of Crustacea, Verne (1920) has recently stated that the 

 red pigment in the hypodermis of the higher Crustacea, such as lob- 

 sters, crabs and crayfish, is identical with carrot carotin. The analyti- 

 cal data are not presented. In support of his conclusion, however, 

 Verne makes, in substance, the following assertions. The pigment 



