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Dr. Edward Schunck on 



colouring matter, leaving behind the cellular tissue of the 

 leaves mixed with sand and debris. The extract was filtered 

 boiling hot, and, being left to stand some time so as to 

 allow fatty matters and other impurities to deposit, was 

 filtered again. The extract thus obtained did not show the 

 bright green colour characteristic of solutions of pure un- 

 changed chlorophyll from fresh leaves, but had a yellowish- 

 green tint. Its absorption spectrum also differed in more 

 than one respect from that of chlorophyll. 



a B C D E F 



The absorption spectrum of chlorophyll shows four 

 bands, the first of which in the red is very dark, whilst the 

 fourth, near the line E, is faint. The alcoholic extract of 

 the leaves from the Ship Canal deposit, on the other hand, 

 showed a tolerably dark band near E, while the third band 

 between D and E appeared very faint and further away 

 from the red end ; its absorption spectrum coincided in fact 

 with that of so-called " modified chlorophyll." There can be 

 no doubt that modified chlorophyll is a product of the action 

 of acids on chlorophyll. When a solution of pure chlorophyll 

 is mixed with a little hydrochloric acid it loses its bright green 

 colour, and soon becomes yellowish-green ; it then exhibits 

 the spectrum of modified chlorophyll. Weak acids produce 

 the same effect, but more slowly. Hence it appears probable 

 that in the case of the leaf deposit, the chlorophyll had 

 come into contact with some acid conveyed possibly by 

 infiltration from above, or formed, perhaps, in consequence 

 of the oxidation of some leaf constituent or other, and thus 

 become modified. Modified chlorophyll, like all derivatives 

 of the colouring matter, is much more stable than the 



