66 Schunck . — Chemistry of Chlorophyll. 
review of what has already been done may prove of interest to 
the readers of this journal, should it merely serve to show how 
defective our knowledge is, and how much still remains to be 
discovered. 
What is Chlorophyll? 
Before commencing the discussion of any subject it is 
desirable to define precisely what the subject comprises, what 
are its limits, and in what sense terms relating to it are 
employed. The subject to be considered being the chemistry 
of chlorophyll, the question naturally arises : What is 
chlorophyll? To this question a physicist, a chemist, and 
a physiologist might return different answers. Pelletier and 
Caventou, who invented the term chlorophyll, express them- 
selves as follows : — ‘ II suit des faits contenus dans cette notice, 
que la matiere verte des vegetaux, improprement appelee 
fecule ou resine, est une substance particuliere qui doit etre 
classee parmi les substances vegetales tres hydrogenees ; 
qu’elle se rapproche de plusieurs matieres colorantes, telles 
que celle de l’brcanette, du curcuma, du santal rouge, et 
qu’elle merite, par ses proprietes et le role qu’elle joue dans 
l’economie vegetale, d’etre consideree comme un principe im- 
mediat des vegetaux. Nous proposons de lui donner le nom 
de chlorophylle V It is evident therefore that Pelletier and 
Caventou considered chlorophyll to be simply an organic 
colouring matter, a bod y sui generis like indigo or alizarin, but 
distinguished by its green colour, and their definition should, 
I think, be adhered to. Some later chemists have given a 
wider meaning to the term chlorophyll, and made it apply to 
the sum of the coloured constituents of green leaves, soluble 
in alcohol and ether, but insoluble in water ; and it has accord- 
ingly been proposed to call that constituent, the colour of 
which inclines more to blue, kyanophyll , while that constituent 
or group of constituents which gives solutions of a yellow or 
greenish-yellow tint, should be named xanthophyll. In works 
Annales de Chimie et de Physique, IX. 194. 
