232 PIGMENTS 



The recognition of magnesium as an essential constituent 

 of chlorophyll, which is due to Willstatter,* has proved of 

 immense value in the study of the degradation products of 

 chlorophyll. 



By the action of alkalies and acids respectively upon the two 

 chlorophylls, it has been found possible to divide the degrada- 

 tion products of chlorophyll into two groups : 



1. Those that retain magnesium, known as Phyllins. 



2. Those that are free from magnesium, known as Por- 

 phyrins. 



The Action of Alkalies. 



When the two chlorophylls are treated with the calculated 

 amount of concentrated methyl alcoholic potash their ester 

 groups are hydrolysed, and two isomeric tribasic acids result 

 from each which are known as chlorophyllin and isochloro- 

 phyllin a or b, as the case may be : 



/COOCH 3 /COOH 



C 31 H 29 N 3 Mg -COOCH C n H 8B N,Mg \~COOH 



NH NH 



Chlorophyll a Chlorophyllin a and 



Isochlorophyllin a 



/COOCHj /COOH 



C^HiA^Mg/ _^ C 32 H 28 2 N 4 Mg( 



\COOC W H 39 \COOH 



Chlorophyll b Chlorophyllin b and 



Isochlorophyllin b 



Chlorophyllin a when heated with alkali loses carbon- 

 dioxide, and yields two isomeric dibasic acids, glaucophyl- 

 lin and rhodophyllin, C 31 H 32 N 4 Mg(COOH) 2 , and at a higher 

 temperature it loses two molecules of carbon dioxide, yielding 

 a monocarboxylic acid, pyrrophyllin, C 31 H 33 N 4 Mg(COOH). 

 By heating with soda lime the third molecule of carbon 

 dioxide may be removed with the formation of aetiophyllin a 

 substance containing no carboxyl group at all, and to which 

 the following formula is assigned : 



* Willstatter : " Annalen," 1906, 350, 48. 



