Schunck — The Chemistry of Chlorophyll. 91 
to sunlight in a loosely stoppered bottle, the stopper being 
occasionally removed, and the contents shaken. The green 
colour of the solution gradually becomes fainter, the absorp- 
tion-bands of phyllocyanin still remaining visible. After some 
time the colour changes to yellow, but the solution still shows 
a strong band in the red, the other bands having disappeared. 
At length this band also vanishes, and there is now nothing 
to be seen but the total obscuration at the blue end of the 
spectrum which most yellow solutions show. It is the great 
stability of phyllocyanin as compared with that of chlorophyll 
which is the cause of the slow disappearance of the colour 
and absorption-bands of solutions of chlorophyll that have 
not been carefully prepared. The absorption-bands which in 
such cases remain even after a prolonged exposure, are due, 
not to chlorophyll, but to the presence of phyllocyanin, formed 
either spontaneously or in consequence of the solution con- 
taining acid. Chlorophyll and phyllocyanin stand, as regards 
stability, in the same relation to each other as indican and 
indigotin ; indican being a substance very easily decomposed, 
whereas indigotin, which is a derivative of indican, is one of 
the most stable of colouring matters. The change which 
phyllocyanin undergoes during insolation is doubtless due 
to oxidation. The process yields two products ; one being 
yellow, amorphous, resinous, soluble in alcohol, insoluble in 
water ; the other is soluble in water, has a strong acid reaction, 
and reduces Fehling’s solution. Both products may be mix- 
tures of several substances. Phyllocyanin is soluble in alkalis, 
the solutions being green, but there can be not doubt that it 
is changed by the action of alkali, since the reactions of the 
substance precipitated on the addition of acid are not those of 
the original phyllocyanin. The properties of this substance 
will be described when I come to describe the action of alkalis 
on chlorophyll. 
The behaviour of phyllocyanin towards acids shows that 
its character is that of a weak base, since it combines only 
with strong acids yielding unstable compounds which are 
decomposed by water. ............. 
