On the Colour of Leaves of Plants and their Autumnal Changes

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                                the leaf, alcohol extracts every trace of the red colour, the 
pieces of leaf being rendered entirely colourless. This result 
shows pretty conclusively, that the red colour is formed 
out of and at the expense of the green colouring matter.
The same result ensues when the colour is extracted by 
water only, provided the redness extends through the 
whole thickness of the leaf.
A small quantity of this red alcoholic solution obtained from the red leaf of a geranium when 
first placed in a watch glass <s>appeared to be <\s> was almost 
colourless, but when the spirit had evaporated, it was 
found that a brilliant carmine residue had made its 
appearance. This under the microscope was plainly seen 
to be composed of two colours, a bright red and an equal
ly bright yellow, each colour keeping perfectly distinct. 
The yellow was in much the smaller proportion and was 
probably derived from <s>the decomposition of <\s> the chlorophyll 
present to some extent in the red leaf which furnished 
the extract.
A few drops of a ten per cent solution of tartaric 
acid were next added to a little of the unevaporated 
almost colourless spirituous solution and this had the immediate effect of 
turning it bright red. A small quantity of a five per cent 
solution of potassium hydrate was added to a second 
quantity of the solution, and this at once caused it to 
assume a green colour. The next morning the solution was 
found to have dried up, the green colour had entirely disap=
peared and a yellow residue now alone remained. Carbonate 
                            
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Manuscript details

Author
Arthur Hill Hassall
Reference
AP/69/1
Series
AP
Date
1892
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On the Colour of Leaves of Plants and their Autumnal Changes, 1892. From The Royal Society, AP/69/1

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