THE CHEMISTRY OF CHLOROPHYLL 



447 



In addition to carotin, Willstatter also succeeded in isolating 

 another pigment, XantJiophyll, with composition corresponding 

 with the formula C 4 oH 3 oO. It is closely related in composition, 

 therefore, to carotin. It was obtained from the mother-liquors 

 of a chlorophyllin preparation, by mixing the alkaline alcoholic 

 extract of leaves after addition of alkali and separation of the 

 potassium salt, with ether, washing out alkali and alcohol from 

 the ethereal extract, and finally precipitating the pigment from 

 this by light petroleum. The precipitate was purified by dis- 

 solving in hot acetone, and adding wood-spirit to the solution : 

 from this mixture the xanthophyll separated. 



Both carotin and xanthophyll are unsaturated, and the opinion 

 is expressed that carotin may act as an oxygen carrier, and be 

 converted into xanthophyll, which may, under suitable conditions, 

 again yield up the oxygen. The general properties of the two 

 substances are summarised in the accompanying table : 



Carotin. Xanthophyll. 



General Conclusions 

 Chlorophyll is a magnesium derivative, from which the 

 metal is readily eliminated by means of acids. It is assumed by 

 Willstatter that magnesium plays an important part in the 

 synthetic functions of the green pigment, acting in a manner 

 similar to that in which it acts in Grignard's reaction ; the iron 

 in the allied pigments of blood, on the other hand, is assumed to 

 play an important part in oxidation. The magnesium is re- 

 moved with very great difficulty by alkalis. 



