8o Schunck . — The Chemistry of Chlorophyll . 
The Decomposition of Chlorophyll by Acids and 
the Products formed thereby. 
A few simple experiments should suffice to convince any- 
one conversant with the chemistry of plants that by the action 
of acids chlorophyll undergoes a complete change. If a small 
quantity of hydrochloric acid be added to an alcoholic or 
ethereal solution of chlorophyll, the colour of the solution is 
completely altered, and the absorption-bands are seen to be 
different in number and position ; the change too is a perma- 
nent one, for the original colour and the original absorption- 
spectrum cannot be restored by the addition of an excess of 
alkali. The colour, moreover, though not so brilliant as before, 
is now remarkably stable under ordinary conditions, pre- 
senting in this respect a marked contrast to the bright colour 
of the original chlorophyll-solution which disappears rapidly 
in sunlight. To an unprejudiced observer such facts alone 
suffice to prove that here a marked change of chemical pro- 
perties has taken place of a kind, such as workers with com- 
plex organic substances are familiar with ; and yet the 
alterability of chlorophyll by acids has by some observers 
been completely denied or ignored. Unfortunately the 
subject of chlorophyll has been too much in the hands of 
persons unaccustomed to weigh chemical evidence, and too 
easily satisfied with a superficial examination of chemical and 
physical properties. The somewhat unfortunate use of the 
word ‘ modification 5 may also have led to confusion and mis- 
understanding, as so often happens when the same term is 
employed in different senses. To my mind modified chloro- 
phyll is no longer chlorophyll ; to those who think otherwise 
the proposition — indigo is a modification of chlorophyll — • 
might perhaps prove acceptable. Professor Stokes was the 
first to point out that the chlorophyll of the earlier observers 
was in fact a product of decomposition due to the action of 
acids ; he too, I think, first obtained a derivative of chloro- 
phyll in a crystalline form. On referring to the memoirs of 
