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the extract became yellowish, and now showed the bands 
of ‘acid chlorophyir as distinctly as did the ethereal ex- 
tract after several days. An alcoholic extract of fresh grass 
after being kept in the dark for several days had not 
changed in the least, and still showed the ordinary chloro- 
phyll bands. On exposing the extract of grass for a few 
hours to sunlight it gradually lost its green colour, became 
of a pale yellow, and then showed hardly a trace of absorp- 
tion bands, the band I being only just discernible. On ex- 
posing the alcoholic Eucalyptus extract, after being kept in 
the dark for 24 hours, to sunlight, it also became much 
paler in colour, but the bands I,. II, and IN a, were quite 
as distinct as before insolation, and in addition to these the 
broad band IV b between the lines E and F of the spectrum, 
which also belongs to the so-called ‘ acid chlorophyll,’ now 
came out very neatly, it having been previously invisible on 
account of the great obscurity in that part of the spectrum. 
It appears then that an alcoholic or ethereal extract of Euca- 
lyptus leaves undergoes even in the absence of light a change 
whereby the normal chlorophyll contained in it is converted 
into a substance which shows the same absorption bands as, 
and is perhaps identical with, ‘ acid chlorophyll.’ I am in- 
clined to attribute the change which takes place to the large 
amount of essential oil contained in the leaves and conse- 
quently in the extracts. Essential oils, it is well known, con- 
vert inactive oxygen into ozone, and ozone, according to Ger- 
land, produces a change in alcoholic solutions of chlorophyll 
similar to the one I have described, whilst under the same 
conditions ordinary oxygen is without effect, which Sachsse 
seeks to explain by supposing that the ozone in Gerland’s 
experiments led to the formation of some organic acid which 
reacted on and modified the chlorophyll. Fresh Eucalyptus 
leaves contain no acid soluble in water, for a watery decoction 
of the leaves does not redden blue litmus paper and remains 
neutral even on exposure to the air for some days ; but the 
