Sim-pie Laboratory Experiments on Leaf Pigments. 31 



By saponification with hot alkali isochlorophyllins are formed 

 which are fluorescent. They are complex magnesium compounds 

 of phytochlorin e and phytorhodin g. On the addition of acid to 

 the isochlorophyllins, these two important dissociation products 

 are themselves formed. 



The process can also be effected by addition of acid first and 

 subsequent saponification with hot alkali. 



The following scheme may help to make clear the relations 

 between these various derivatives in the case of chlorophyll a. An 

 exactly similar scheme may be made for the case of chlorophyll b. 



[MgN,C,,H3„0]{COOCH,)(COOC.„H33) ->[N,C3,H330](COOCH.)(COOC.,H.,) 



With acid 

 chlorophyll a phaeophytin a 



[MgN,C3,H3„0](COOH)(COOH) >[N,C3,H,,0](COOH)(COOH) 



With acid 

 isochlorophyllin a phytochlorin e 



The relation between chlorophyll and isochlorophyllin is not 

 as simple as that expressed in the above scheme as the alkali not 

 only saponifies the two ester gi'oups but also produces an alteration 

 in the lactam ring grouping, as indicated by the appearance of the 

 brown phase. 



Another difference between saponification with cold alkali and 

 with hot alkali is that during the latter process the yellow pigments 

 are destroyed. If water is added after the saponification and the 

 solution shaken up with ether, the ether should remain colourless. 



We have gone into the explanation of the changes taking place 

 in this experiment in some detail, because importance attaches 

 to the two dissociation products phytochlorin e and phytorhodin g. 

 It was the formation of these substances that led Willstatter 

 to the discovery that phaeophytin, and also chlorophyll, is a mixture 

 of two components. The experiment, moreover, is also of importance 

 as a modification of the method is used in the quantitative 

 estimation of the green pigments in the leaf. 



Experiment 9. Substitution of other metals for the magnesium 

 in chlorophyll. 



Two c.c. of an ether solution of chlorophyll are shaken with a 



