72 Schunck . — 77 ^ Chemistry of Chlorophyll . 
the peculiar absorption-spectrum about which so much has 
been written, and which need not be here described. 
There can be little doubt that chlorophyll contains nitrogen 
in addition to carbon, hydrogen, and oxygen, but the percentage 
is certainly not large. How widely the analyses of so-called 
pure (crystallised) chlorophyll differ may be seen on compar- 
ing the two latest determinations of its composition, which 
gave the following numbers : — 
Carbon 
Hydrogen . 
Nitrogen . 
Ash . 
Gautier. 
73-97 % 
9-8° % 
4-i5 % 
i-75 % 
Hansen. 
67-26 % 
10-63 % 
5-120 %' 
It is evident that the substances, the composition of which is 
represented by these two analyses, taking for granted that each 
was pure, could not have been one and the same. 
That iron, in some form or other, is an essential constituent 
of chlorophyll has been repeatedly asserted and as often denied. 
The uncertainty in this respect is of course due to our being 
unable to obtain chlorophyll in a state of purity. When a 
solution of chlorophyll is evaporated to dryness, and the residue 
is incinerated, the ash is always found to contain a minute 
quantity of ferric oxide ; but whether the latter was derived 
from the chlorophyll or from some other substance accom- 
panying it and following it into solution must remain doubtful. 
There is much to be said on both sides of the question, but on 
the whole I incline to the opinion that iron is not an essential 
constituent of chlorophyll. 
Most of those who have worked with chlorophyll agree in 
stating that, when burnt, it leaves an ash containing phosphates. 
When the residue left on evaporation of an ethereal solution 
of chlorophyll, prepared as above described, is incinerated, it 
leaves an ash containing a little ferric oxide and a relatively 
large quantity of calcium and magnesium phosphates. I in- 
1 These were the calculated numbers after deducting the ash, which amounted to 
1076 % and consisted partly of sodium carbonate. 
