PROPERTIES AND METHODS OF IDENTIFICATION 225 



and formic acid. Well colored solutions in low boiling petroleum 

 arc difficult to secure because of the low solubility of the pigment 

 in this solvent, crystalline xanthophyll being almost insoluble in this 

 solvent. However, xanthophyll in the amorphous state or contami- 

 nated with lipoids can be dissolved quite readily even in petroleum 

 ether. The solutions in all these solvents, except carbon disulfide 

 and formic acid, are yellow. These solutions are distinguished from 

 the corresponding carotin solutions by showing a strong greenish tinge 

 on great dilution. The solution in formic acid, which is mentioned 

 only by Montevcrde and Lubimenko (1913b), is green. Carotin and 

 lycopin do not dissolve in this solvent. Carbon disulfide solutions 

 of xanthophylls are orange to orange-red, never blood red or bluish 

 red like carotin and lycopin. 



The relative color intensities of solutions of carotin and xanthophyll 

 at equi-molar concentrations in different solvents varies considerably 

 with the depth of the solutions. Willstatter and Stoll have compared 

 crystalline xanthophyll and carotin solutions and have obtained the 

 following results. 



5 X ID' 5 MOLAR SOLUTIONS IN CARBON DISULFIDE 



Layer of carotin Layer of xantho- Relative 



in mm. phyll in mm. intensity 



12 50 1 



25.5 87 1 



38.5 120 1 



85 180 1 



4.1 

 3.4 

 3.1 

 2.1 



5 X ID' 5 MOLAR SOLUTIONS, CAROTIN IN PETROLEUM ETHER-ETHER, 

 XANTHOPHYLL IN ETHER 



10 20 1 



40 60 1 



91 120 1 



2.0 

 1.5 

 1.3 



Xanthophyll can be obtained in aqueous colloidal solution in the 

 same manner that colloidal carotin solution is obtained, according 

 to van den Bcrgh, Muller and Broekmeyer. Egg yolk and blood 

 serum xanthophyll were used as the source of pigment in the experi- 

 ments by these investigators. 



Only very strong alkali seems to affect alcoholic solutions of xan- 

 thophylls adversely. Saponification of xanthophyll solutions with 

 20 per cent alcoholic potash solutions to remove admixed fat, ap- 

 parently does not affect the general properties of the pigments. Will- 

 statter and Mieg found, however, that heating amyl alcohol solu- 

 tions of crystalline xanthophyll with sodium decolorized the pigment, 

 and heating benzene solutions with granulated potassium in an at- 



