FORMALDEHYDE 61 



With a view to throwing some light on the mechanism 

 of photosynthesis, Wager* has studied the decomposition of 

 chlorophyll on exposure to oxygen both in the light and in 

 the dark, with the result that he finds that the process is not 

 catalytic. Oxygen is absorbed and aldehydes are formed, and 

 it is suggested that the sugars produced during assimilation 

 are not formed directly from carbon dioxide and water but 

 by the polymerization of aldehydes produced in this way. 

 Warner f also has found that formaldehyde is produced when 

 chlorophyll is exposed to sunlight or electric light in air; 

 since this substance is produced both in the presence and in 

 the absence of carbon dioxide, it would appear that the latter 

 plays no part in the production of formaldehyde by photo- 

 synthesis outside the plant, and that the formaldehyde is in 

 reality an oxidation product of the chlorophyll. 



The above-mentioned investigations were carried out with 

 impure chlorophyll, Jorgensen and Kidd,| on the other hand, 

 used chlorophyll a and. (see p. 227) in a state of purity which 

 satisfied Willstatter and Stoll's criteria. They experimented 

 with a chlorophyll sol with water as the dispersion medium. 

 On exposing this sol, contained in glass vessels and in contact 

 with various gases, to light, they found that formaldehyde was 1 

 only produced in the presence of oxygen. In the case of con- 

 tact with carbon dioxide, phaeophytin (see p. 231) was pro- 

 duced, and there was no' further change. In oxygen the 

 chlorophyll turned yellow, due to the presence of phaeophytin, 

 and ultimately was bleached ; when the bleaching is in pro- 

 gress, formaldehyde occurs in but small quantity, but when the 

 bleaching is complete, there is an increase in the amount of 

 formaldehyde. They suggest that the formal'dehyde arises 

 chiefly from the phytol which probably is split off from the 

 chlorophyll under the action of light and oxygen. 



In conclusion, mention may be made of a simple way of 

 demonstrating the production of formaldehyde from chloro- 

 phyll, due to Osterhout. 



* Wager: " Proc. Roy. Soc.," B., 1914, 87, 386. 



t Warner : id., 378. 



Jorgensen and Kidd : id., 1916, 89, 342. 



Osterhout: " Amer. J. Bot.," 1918, 5, 511, 



