XANTHOPHYLL 



243 



stances erythrophyll and chrysophyll described by Bougarel 

 and Schunck respectively. 



It absorbs 34^3 per cent of its weight of oxygen, being 

 converted into a colourless substance. With iodine it forms 



the compound 

 prisms. 



C 40 H 56 I 2 , which crystallizes in dark violet 



XANTHOPHYLL 



This substance is closely related to carotin, having the 

 molecular formula C 40 H 56 O 2 . Ewart * has, indeed, shown that 

 xanthophyll may be converted into carotin by the action of 

 zinc dust or magnesium powder and water. 



It is a neutral substance, reacting neither as an alcohol nor 

 as an acid. 



It absorbs 36*55 per cent of its weight of oxygen, and 

 forms an additive compound with iodine of the formula 

 C 40 H 56 O 2 l2, which crystallizes in dark violet tufts. 



The more important physical constants and solubilities of 

 carotin and xanthophyll are given in the appended table, 

 compiled by Willstatter : 



Xanthophyll. 

 Pleochroic dark reddish- 

 brown plates. 



Appearance 



Colour by transmitted 

 light .... 



Melting-point . 



Solubility in light pe- 

 troleum 



Solubility in alcohol 



Solubility in acetone 

 Solubility in carbon di- 

 sulphide 



Carotin. 

 Copper coloured leaflets. 



Red. 



167-5-168. 



Appreciably soluble. 

 Practically insoluble in 



cold ; very sparingly 



soluble in hot. 

 Very sparingly soluble. 



Yellow to orange. 

 172. 



Insoluble. 



Sparingly soluble in cold ; 



fairly readily soluble in 



hot. 

 Readily soluble. 



Very readily soluble. Sparingly soluble. 



FUCOXANTHIN C^H^. 



This substance was first isolated from fresh brown algse by 

 Willstatter and Page.f It is more difficult to extract this 

 substance from dried algae. Fucoxanthin is a brownish-red 

 substance, which crystallizes from methyl alcohol or light 

 petroleum, and melts at 159*5 to i6o - 5. It absorbs iodine 



* Ewart: " Proc. Roy. Soc.," 1915 [B], 89, i. 

 t Willstatter and Page: "Annalen," 1914, 404, 237. 

 l6 * 



