230 



Dr. S. B. Schryver. The Photochemical [Nov, 18, 



hydrazine reagent was necessary, indicate that the aldehyde is contained in 

 the chlorophyll in the state of someivhat stable combination. 



The Photochemical Formation of Formaldehyde by Chlorophyll. 



In the earlier researches on this subject by Uslier and Priestley, the 

 formation of aldehyde was demonstrated by allowing chlorophyll films 

 extended on gelatin plates, or on the surface of water, to remain exposed to 

 light in the presence of carbon dioxide. It is conceivable that, in the 

 experiments carried out in the first-named manner, some of the aldehyde 

 may have been derived from the gelatin.* In the experiments described 

 below, the formation of formaldehyde can be demonstrated when films of 

 chlorophyll alone are employed. 



It has been already stated that a sample of chlorophyll fi'om grass 

 collected on a foggy morning contained only very small traces of the 

 aldehyde. furthermore, formaldehyde gradually disappeared on keeping 

 from ethereal solutions of chloropliyll, which were originally rich in the 

 aldehyde. The experiments were carried out with such formaldehyde-free 

 chlorophyll solutions. 



Each test was carried out with 1 c.c. of an ethereal solution of chlorophyll, 

 which was allowed to evaporate at room temperature on a strip of glass 

 (about 140 by 20 mm.). Some films thus prepared were kept in the dark, 

 others were exposed to moist carbon dioxide in sunlight, others to sunlight 

 over lime or soda lime, and others, again, were exposed to moist carbon 

 dioxide in the dark. For testing for formaldehyde two films were usually 

 employed, and in each case either warmed for a few minutes or allowed to 

 stand for some hours with a mixture of 10 c.c. water and 2 c.c. of the 

 phenylhydrazine reagent, and the test was then completed in the usual 

 manner. The results are tabulated below. 



Conditions of experiment. 



Besult. 



Kept, in tlic diirli i-itlier in presence or absence 

 of moist CO;j 



Kept in sunliglit over liuio or soilii lime 



No formation of HCHO 



ForniiU ion of very minute ([iiiintities of IICHO 

 Formaldehyde reiietion distinct 



It will bo seen that formaldehyde is formed when the chlorophyll film is 

 exposed to sunlight cither in ])rcsence oi- a,bscnce of carbon dioxide. In tlio 

 latter case, tliO iiuantity of ahUibydo foiMiicd is so minute that its presence 

 coubl only be denioiiHtratod witli certainty after dilution of tlie reaction 

 * CoiniKin; iMeisling, ' Ileviie G6n6ralo (k.s Scioticos,' May LO, 1909 



