THE CHEMISTRY OF CHLOROPHYLL 



443 



Work of Tswett and more recent Work of Marchlewski 

 Tswett has devised another method for investigating chloro- 

 phyll derivatives — the so-called method of adsorption analysis 

 Solutions of the pigment are made to pass through a filter of 

 adsorbent material — calcium carbonate being most commonly 

 used. The more readily adsorbed pigment will be retained in 

 the upper layers of the filter, the less readily adsorbed in the 

 lower layers. The layers are then divided after filtration, the 

 pigment re-extracted from each, and then submitted to spectro- 

 scopic examination. By this method, Tswett claims to have 

 separated two main constituents, chlorophyllin a and chlorophyllin 

 /3 from chlorophyll, and has studied the action of acids and 

 alkalis on these substances, and expresses the relationship of the 

 various chlorophyll derivatives to one another according to the 

 following scheme : 



Willstatter's Rhodophyllin 



[Alkalis at 

 200 c ] 



Chlorophyllin acid a -» 



[Alkali] 



Chlorophyllin a 



[Weak acids] 



[Mixture Willstatter's 

 Chlorophyllin] 



Chlorophyllan a -» 



[Strong acids] 

 Phyllocyanin (Schunck) 



Mixture. 



Hoppe-Seyler's Chlorophyllan. 



Willstatter's Phneophytin 



Phylloporphyrin (Schunck) 

 t 



[Alkalis at 200 ] 



Chlorophyllic acid /3 



[Alkali] 

 Chlorophyllin £ 

 [Weak acids] 



<- Chlorophyllan |S 



(Schunck's Phylloxanthin) 



[Alkalis] 



Willstatter's Phytochlorins and Phytorhodins 



It must be remarked that this scheme depends chiefly on 

 the adsorption analysis method, and spectroscopic examination. 

 The chemical evidence upon which it rests appears at the 

 present moment to be somewhat slender. 



Marchlewski has recently examined the phaeophytin as pre 

 pared by Willstatter's method. He has suggestedjthat for this 



