76 Schunck . — The Chemistry of Chlorophyll. 
certainty is arrived at. Still, I do not deny that chlorophyll — 
using the term in the same sense as Mr. Sorby does — may 
consist of several closely-allied substances ; indeed some of 
my own experiments on the derivation of chlorophyll seem 
to countenance this view. 
Derivatives of Chlorophyll. 
Most observers who have taken up the subject of chloro- 
phyll agree in considering it to be a body the molecules of 
which are in a state of unstable equilibrium, any disturbance 
of the equilibrium causing the molecules to re-arrange them- 
selves so as to form compounds of a more stable character. 
External influences of an apparently slight character cause it 
to undergo considerable change, so much so that it may be 
considered liable to spontaneous decomposition. To this 
circumstance the difficulty of isolating it and ascertaining its 
properties and composition is mainly attributable. Chloro- 
phyll is probably a body of complex constitution and high 
atomic weight, such as might be expected in the case of a body 
playing so important a part in the vegetable economy. When 
difficulties, such as here present themselves, are met with, the 
founders of modem organic chemistry have laid it down as a 
rule that the only way to arrive at definite conclusions is to 
submit the body to be examined to a definite process of de- 
composition, or to several such processes, and to ascertain the 
exact nature and composition of the products resulting there- 
from. When this has been done the fragments resulting from 
the splitting up of the complex may be recombined, in 
theory at least, if not actually, so as to enable us to under- 
stand the constitution of the original compound. This is the 
method which, as regards chlorophyll, has been applied with 
more or less success by Fremy, Hoppe-Seyler, and others, and 
it is the one which I have endeavoured to carry out in my 
experiments. Our knowledge of chlorophyll-derivatives is 
still very incomplete ; indeed, we may say that their study has 
only just commenced, so that a short account will suffice to 
