6 H. A. SPOEHR 



dealt with gaseous carbon dioxide, it is practically certain that 

 in the plant we are dealing with a substance of quite different 

 properties, that is, carbon dioxide dissolved in water, carbonic 

 acid or its salts. 



Of a very similar nature are the recent experiments which 

 have been carried out by the use of ultraviolet light from the 

 quartz mercury vapor lamp. The results obtained by various 

 investigators are, however, by no means congruous. Usher and 

 Priestley 1^ report that by exposing a saturated solution of car- 

 bon dioxide, in quartz tubes, to ultraviolet light they obtained 

 ''an easily recognizable quantity of formaldehyde, most of 

 which was in the polymerized form." From this very simple 

 experiment they conclude that "the primary products of photol- 

 ysis of aqueous carbon dioxide are formaldehyde and H2O2, that 

 the evolution of O 2 is due to the decomposition of the latter sub- 

 stance by catalase, and that up to this point the process is entirely 

 non-vital, and can be reconstructed in vitro J'' 



Berthelot and Gaudechon^' found that CO2 can be split into CO 

 and O2 by means of ultraviolet light, and that: 



2H20^2H2+02. and 

 CO+H2-^CH20. 



They state that they were able to obtain formaldehj^de from CO 2 

 only in the presence of hydrogen. 



The recent experiments of Stoklasa^^ and his co-workers, with 

 ultraviolet light have received a great deal of attention, and 

 have, in fact, been quoted as finally establishing the formalde- 

 hyde theory of photosynthesis. For this reason these experi- 



1' Usher, F. L., and Priestley, J. H., The Mechanism of Carbon Assimilation. 

 Proc. Roy. Soc. 84: B. 101-12, 1911. 



" Berthelot, D., and Gaudechon, H., Sj'nthese photochimique des hydrates de 

 carbon aux depens des elements de I'anhydride carbonique et de la vapeur d'eaii, 

 en I'absence de chlorophyll; synthese potochemique des composes quarternaires. 

 Comp. rend. 150: 1690-3, 1910. 



" Stoklasa, J., und Zdobnicky, W., Ueber photochemische Synthese der Koh- 

 lenhydrate aus CO2 und H2 in Anwesenheit von KOH, und in Abwesenheit von 

 Chlorophyll. Monatsh. f. Chem. 32:53-75, 1911. Ueber die photochemische 

 Synthese der Kohlenhydrate unter Einwirkung der Ultra-violetten Strahlen. 

 Biochem. Zeitschr. 41 : 333-72, 1912. 



