A SIMPLE METHOD OF DEMONSTRATING THE PRO- 
DUCTION OF ALDEHYDE BY CHLOROPHYLL AND 
BY ANILINE DYES IN THE PRESENCE OF 
SUNLIGHT! 
W. J. V. OSTERHOUT 
In 1906 it was stated by Usher and Priestly^ that chlorophyll, 
extracted from leaves and spread out in thin films (under special 
conditions), can decompose CO2 and produce formaldehyde in sunlight. 
In the following year the writer attempted to repeat their experi- 
ments but found the method unsatisfactory; as a result a simpler 
method was devised which proved so successful that it has been em- 
ployed by his classes ever since. 
The method consists in extracting chlorophyll from fresh leaves 
by means of alcohol ; shaking the alcohoP with carbon tetrachloride, 
drawing off the latter, sprinkling it on filter paper, and allowing it to 
evaporate. For this purpose the filter paper is stretched in a suitable 
manner (or merely hung over two parallel glass rods) and the extract 
sprayed over it until the paper is saturated. In the course of a few 
minutes, when most of the solvent has evaporated, the paper is again 
sprinkled with the extract. This is repeated until the paper acquires 
a deep green color, comparable with that of a leaf. 
When the paper is dry it is placed in a bell jar, forming a lining 
which covers the entire surface : it is then wet with water (which in- 
cidentally helps to keep it in position by making it adhere to the glass). 
The bell jar is then inverted over a glass plate on which is a large 
petri dish containing about 5 cc. of water. The edges of the bell 
jar are sealed by means of vaseline. It is desirable to use a large bell 
jar and to cover the inside completely with filter paper. Several are 
prepared, some of which are placed in the light while others, kept in 
the dark, act as controls. 
Those which are placed in the light are allowed to remain undis- 
1 An abstract appeared in Science n, ser. 42: 68. 1915. 
2 Proc. Roy. Soc. Lond. B, 77: 369. 1906; 78: 318, 1906. 
3 The addition of water to the alcohol may be necessary to ensure separation. 
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