Schunck . — The Chemistry of Chlorophyll . 1 1 9 
tains zinc and some kind of fatty acid. The various phyllo- 
cyanin compounds which I have described are chlorophylls 
which contain either zinc, iron, copper, or silver, and an acid, 
which may be either an organic acid or phosphoric, or even 
exceptionally carbonic acid. Of these compounds the cupric 
ones approach anilophyll in stability, while the zinc com- 
pounds, as before mentioned, closely resemble natural chloro- 
phyll in more than one respect. If the properties of the 
ferrous compounds corresponded more nearly with those of 
natural chlorophyll, it would be permissible to suppose that 
the latter is an iron compound, for though the percentage 
of ferric oxide in the ash of chlorophyll is but small, the 
amount might perhaps suffice to form a saturated compound 
with phyllocyanin, the atomic weight of which is probably 
very high. The properties of the ferrous compounds, however, 
differ too widely from those of chlorophyll to allow of this 
supposition. The only probable conclusion therefore is, that 
the factor y in the formula of natural chlorophyll represents 
an organic base, perhaps choline, as suggested by Hoppe- 
Seyler. Were this base known there would be some hope 
of our being able to build up a compound which should be 
identical with natural chlorophyll. 
I venture in conclusion to bring forward one more hypo- 
thesis ; it is this, that the factor x in the chlorophyll formula 
may represent carbonic acid. A weak acid like carbonic 
acid would form with phyllocyanin, itself a weak base, and 
the unknown base y> also perhaps weak, a compound the 
proximate constituents of which would probably not be very 
firmly united, and which would therefore easily split up when 
exposed to any disturbing influence. It is possible that the 
first stage of the decomposition of chlorophyll — the one which 
it undergoes by the action of heat alone or of very weak 
acids — may consist simply in the elimination of C0 2 , and 
that it is this loss which renders it incapable after being kept 
in solution for some time of forming anilophyll on being 
brought into contact with aniline. It may be too the re- 
moval of the loosely combined C0 2 after leaves have been 
