THE CHEMISTRY OF PHOTOSYNTHESIS 303 



gen in the "nascent" condition and potassium hydroxide. The presence 

 of potassium hydroxide is necessary, according to these authors, for the 

 formation of potassium bicarbonate which is reduced, rather than the 

 carbon dioxide. They seem to regard the condition of the potassium 

 bicarbonate ("in Entstehung begriffen") as well as the "nascent" state of 

 the hydrogen as essential to the formation of formaldehyde. The appli- 

 cations which are made of these conclusions to the photosynthetic process 

 are somewhat fanciful especially because of the "nascent" hydrogen re- 

 quired. In a later publication Stoklasa alters his scheme to describe the 

 reactions of photosynthesis. He points to the fact that an alkaline solu- 

 tion of formaldehyde is oxidized to formic acid and the latter in ultra- 

 violet light is oxidized to carbon dioxide. This he regards as the re- 

 versal of the photosynthetic reactions. The latter he consider progresses 

 as follows : 



K3CO3 H- CO2 -\- H2O = 2KHCO3 



2KHCO3 + Light = K3CO3 + HCOOH + O 

 HCOOH + Light rr HCOH + O 

 n(HCOH) = (HCOH)n. 



Stoklasa thus considers that formic acid is an intermediate step in the 

 reduction of carbonic acid (i.e., potassium bicarbonate) to formaldehyde. 

 It is important to note, however, that Stoklasa gives no experiments to 

 show that formic acid on illumination with ultra-violet light yields formal- 

 dehyde. Stoklasa also reports that by illuminating potassium bicarbonate 

 he obtained a hexose. Into 300 cc. of a 7 per cent of potassium hydroxide 

 solution was run a stream of carbon dioxide (the source of the carbon 

 dioxide is not given) and to the solution was added 80 cc. of a 15 per cent 

 solution of ferrous sulfate, while the whole was illuminated for 8 hours. 

 After precipitating the inorganic salts with potassium phosphate and 

 alcohol he obtained an alcoholic extract containing 0.219 gram of reducing 

 substance giving a phenylosazone melting at 204-205° and analyzing for a 

 hexosazone. 



Recently Baly, Heilbron and Barker ^-* claim to have obtained a direct 

 synthesis of formaldehyde from carbon dioxide and water by the use of 

 ultra-violet light. Their results are more analogous to those of Usher 

 and Priestley than to those of Berthelot and Gaudechon or of Stoklasa 

 in that they do not use hydrogen, which is considered essential for the 

 formation of formaldehyde by the three last mentioned. In the opinion 

 of Baly and his collaborators the formation of formaldehyde takes place 

 in light of very short wave length {I = 220 \i\i) and the polymerization 

 of formaldehyde in light of longer wave length (?t = 290 \i\i). The 

 quantity of formaldehyde formed from carbon dioxide is, according to 



^Baly, Heilbron and Barker, Jour. Cliem. Soc, 119, 1025 (1921). Nature, 112, 

 323 (1923) ; Jour. Sac. Chem. Ind., 40, 2,77 (1921) ; Ind. and Eng. Chem., 16, 1018 

 (1924). 



