98 CAROTINOIDS AND RELATED PIGMENTS 



carried out on five different preparations of fucoxanthin gave the fol- 

 lowing results in comparison with several theoretical values. 



The investigators prefer the formula C 40 H 54 6 over C 40 H 5G O (; , 

 although the latter expresses the closer empirical relation to carotin, 

 but admit, at the same time, that their data correspond most closely 

 to the formula containing one additional carbon atom. In any case 

 the close chemical relation of fucoxanthin to the other carotinoids is 

 clearly established. 



The observations of Tsw r ett and of Willstatter and Page show that 

 great care must be taken in the isolation of fucoxanthin to prevent 

 the formation of the post-mortal phycophain. This was prevented by 

 Willstatter by dehydrating the fresh plants with 30 per cent acetone, 

 after which the material was macerated and extracted at once with 

 pure acetone. The extract containing the combined chlorophyll and 

 carotinoids was then diluted witli ether which was washed free from 

 acetone with water. The ether extract was now diluted with an equal 

 volume of low boiling petroleum and the mixture submitted to a modi- 

 fied Kraus separation using 70 per cent methyl alcohol. In this con- 

 nection Willstatter and Page made the valuable observation that 

 fucoxanthin is quantitatively removed by 70 per cent alcohol in the 

 Kraus separation, leaving the other carotinoids practically quantita- 

 tively in the petroleum ether, especially if ether is also present. It is 

 clear that this discovery not only permits the separation of fucoxan- 

 thin but does not interfere with the subsequent separation of xan- 

 thophyll and carotin by the usual procedure using petroleum ether 

 and 80 per cent methyl alcohol. 



Fucoxanthin isolated on the above principle was found to crystal- 

 lize readily from methyl alcohol or acetone in dark red regular 

 hexagons, containing water or alcohol of crystallization, the latter 

 being lost only in high vacuum at 105 C. By precipitating the pig- 

 ment from ether with low boiling petroleum, in which it is insoluble, 

 compact needles without any solvent of crystallization were obtained. 



A study of the characteristic color reaction with HC1 showed it to be 



