280 PHOTOSYNTHESIS 



"methylenitan" and from tubes containing formaldehyde and oxalic acid 

 he claims to have obtained sorbose. 



Pribram and Franke *^ obtained glycollic aldehyde by illuminating solu- 

 tions of formaldehyde in quartz vessels with ultra-violet light. 



Recently Baly, Heilbron and Barker''*' have also reported the forma- 

 tion of sugar from a solution of formaldehyde exposed to ultra-violet light. 

 To the formaldehyde solution they added calcium carbonate and found 

 that the optimum temperature during illumination was ?)7°. Baly states: 

 "With an initial concentration of 40 per cent formaldehyde the maximum 

 reducing power is 8 per cent calculated as glucose and with 20 liters of 

 formaldehyde this can often be reached after 14 days of continuous illumi- 

 nation." 



Irvine and Francis *^ have examined the mixture obtained by Baly 

 from the action of ultra-violet light on formaldehyde solutions and found 

 that the sirup behaved as though it were about 25 per cent sugar (cal- 

 culated as glucose), but this value diminished when the sirup was heated 

 with acid such as would hydrolyze a glucoside or polysaccharide. They 

 conclude: "that part of the reducing power was therefore contributed by 

 compounds other than sugars." From methylation experiments it is con- 

 cluded that there was present 9.3 per cent of sugar in the original sirup 

 and that "the bulk of the photosynthetical sirup, at least to the extent 

 of 80 per cent, consists of nonsugar compounds which contain hydroxyl 

 groups." Baly claims that glucuronic acid is present in the sirup, but 

 he does not give sufficient evidence to support this claim. 



Beyond the fact of demonstrating that it is chemically possible to 

 obtain sugars which occur in the plant, all of the large amount of chem- 

 ical work which has been done on the condensation of formaldehyde 

 with strong and weak alkalies and with light are really of little signifi- 

 cance in establishing the vahdity of Baeyer's theory. Condensing formal- 

 dehyde with strong alkalies or through the action of ultra-violet light 

 and obtaining a great mixture of substances of which only a small per 

 cent is in many cases hexose sugar, will, even to the most optimistic chem- 

 ist, appear as a rather far cry to the method by means of which the 

 plant forms glucose. Whether there are in the plant enzymes by means 

 of which the condensation is effected, whether there exist in the chloro- 

 plast areas of high alkalinity or whether the great pressures which may 

 exist in the surface layers of the cells play a role, are after all mere 

 conjectures. Baeyer's theory is a good suggestion of a possible mecha- 

 nism of photosynthesis ; the chemical evidence which has been advanced 

 in support of it may serve as a good clue for further investigations with 

 very much more highly refined methods. 



'= Pribram and Franke, Monalsh., 33, 415 (1912). Franke and PolHtzer, ibid., 



^'^' ^ Bafy.^Heilbron and Barker, Jour. Chcm. Soc, 119, 1025 (1921). Baly, Ind. 

 Ena Cheln., 16, 1016 (1924). 



« Irvine and Francis, ibid., 16, 1019 (1924). 



