W. J. V. OSTERHOUT 
turbed until the chlorophyll has been bleached to a pale green or a 
pale yellow color> The bell jar is then removed and the water in the 
dish is tested for aldehyde by means of Schryver's test.^ A positive 
result is obtained in the majority of cases. 
Evidently a volatile aldehyde is produced which diffuses through 
the air and becomes absorbed by the water. Care is taken to place 
the dish so that it does not receive drippings from the filter paper. 
The experiment succeeds in many cases even without the use of a 
bell jar if the paper is simply folded into a cone and inverted over a 
small dish of water. 
The controls kept in the dark do not give the test in any instance. 
It is therefore evident that if the chlorophyll contained aldehyde be- 
fore exposure to sunlight the amount was too small to give a test. 
It seemed desirable to ascertain whether other substances could be 
substituted for chlorophyll in this experiment. Accordingly a series 
of aniline dyes were employed. A considerable number gave positive 
results. The most reliable were methyl green and iodine green. 
Aqueous solutions were sprayed upon filter paper and allowed to dry. 
This was repeated until the paper was deep green in color. The paper 
was then exposed to sunlight in the bell jar for several days in succes- 
sion until the color had practically disappeared. A positive test for 
aldehyde was obtained in the majority of cases, while the controls in 
the dark gave no test. 
It therefore appeared as if the production of aldehyde was similar 
in the case of chlorophyll and aniline dyes, and that if the experiments 
of Usher and Priestly had any bearing on photosynthesis the experi- 
ments on aniline dyes were of considerable interest. 
At that time no criticisms of Usher and Priestly's work had ap- 
peared, and the writer undertook experiments to test the validity of 
their conclusions regarding photosynthesis. These experiments showed 
^ This may require several days. 
^ The test is made as follows: Add to lo cc. of the solution to be tested: 
2 cc. of I percent phenylhydrazine hydrochloride (freshly prepared and 
filtered). 
I cc. 5 percent potassium ferricyanide (freshly prepared). 
5 cc. concentrated HCl. 
On adding a drop of amyl alcohol or chloroform and shaking vigorously, the 
pinkish color will become concentrated in the chloroform. 
The test is given by a variety of aldehydes. Cf. Schryver, S. B. Proc. Roy. 
Soc. Lond. B. 82: 226. 1910, 
