180 CAROTINOIDS AND RELATED PIGMENTS 



was isolated by the methods of Arnaud and Escher. The crystals 

 melted at 168 C., and gave an iodide of definite composition. The 

 elementary analyses of a large number of samples obtained from 

 Crustacea of various kinds showed the pigment to be a hydrocarbon in 

 which the ratio of C:H 5:7. The molecular weight determination 

 performed on the iodides by the ebulloscopic method showed that the 

 carotin of Crustacea is the same as that of vegetables, with the form- 

 ula C 40 H 56 . Among its most significant reactions was the formation 

 of a violet-brown iodide. The pigment exhibited the same spectro- 

 scopic absorption bands as vegetable carotin. It was not attacked 

 by alkalis and oxidized with great ease. 



These statements are certainly sufficient to establish the carotin 

 identity of the crustacean pigment. It is to be hoped, however, that 

 the details of this study will soon be made available. Certain of the 

 points mentioned in connection with the general properties of the pig- 

 ment are quite at variance with the findings of numerous previous 

 investigators who were presumably studying the same crustacean pig- 

 ment. Either Verne was working with a different pigment, or the 

 methods used by previous investigators were decidedly at fault. It is 

 important that these divergencies be explained. 



Summary 



A chemical relationship between an animal chromolipoid and a 

 specific plant carotinoid was shown for the first time by Schunck's 

 (1903) comparative spectroscopic studies of flower "xanthophylls" 

 and the yellow pigment of the egg yolk and blood scrum of fowls. 



Chemical studies of crystals of egg yolk pigment by Willstiitter and 

 Escher (1912) showed a complete correspondence with plant xantho- 

 phyll in all properties except melting point, but the results of the ele- 

 mentary analyses and molecular weight determinations of the egg 

 yolk pigment can only be regarded as approximations to the theoreti- 

 cal values for a substance with the formula C 40 H 56 2 . A considera- 

 tion of these divergencies in the light of the biological relationship 

 between egg yolk pigment and plant xanthophyll leads to doubts 

 regarding the alleged isomerism of the two pigments. 



A possible chemical relationship between certain animal chromo- 

 lipoids and plant carotin was recognized by several workers before 

 Escher (1913) definitely established the chemical identity of the cor- 

 pus luteum pigment (of the cow) with plant carotin. 



