Physiologie. 11 



Fenton, H. J. H., The Reduction of Carbon. Dioxide to 

 Formaldehyde in Aqueous Solution. (Trans. Chem. Soc. 

 London. Vol. XCI. p. 687-693. 1907.) 



Since Baeyer's hypothesis that formaldehyde is an actual stage 

 in the photosynthesis of sugar from COg in the green leaf, many 

 chemists have attacked the problem of reducing aqueous carbonic 

 acid in vitro. The author gives a short account of previous work 

 and States that hitherto no investigator has really carried this 

 reduction in aqueous Solution beyond the stage of formic acid. 



Having found that metallic magnesium quickly reduces formic 

 acid to formaldehyde, Fenton investigated the direct action of the 

 metal on water kept saturated with CÖo. Formaldehyde is produced, 

 apparently without the intervention of a formic acid stage; the 

 yield is much increased by the presence of phenyl hydrazine and 

 certain other substances. When powdered magnesium acts on 

 ammonium carbonate the formaldehyde formed condenses with the 

 ammonia to give a considerable jield of hexamethj^len tetramine. 



The author has carefully investigated the many colour tests 

 proposed for the Identification of traces of formaldehyde. He considers 

 Rimini's test, the formation of a Prussian blue colour on adding 

 Phenylhydrazine hydrochloride, sodium nitro prusside and caustic 

 soda,"to"be the most satisfactory reaction. The next best test is the 

 formation of a bright blue ring when the liquid, mixed with a little 

 alcoholic gallic acid Solution, is poured on to pure sulphuric acid. 



F. F. Blackman. 



Gibson, R. J. Harvey, A Photoelectric Theorv of Photo- 

 synthesis. (Annais of Botanjr. Vol. XXII. p. 117—120. 1908.) 



A preliminary note bringing forward the hypothesis that in 

 photosynthesis, the absorbed light-energy is first converted into 

 electric energ}^ and that this form of energy actually effects the 

 decomposition of aqueous carbonic acid to form free oxygen and 

 formaldehj^de. 



The author holds the view that the production of formaldehyde 

 in photosynthesis can be demonstrated b}^ the gallic-sulphuric acid 

 test and that the colour reaction is strongest with leaves exposed 

 to diffuse light, being feeble or absent with intense or very weak 

 light or with light that has been tiltered through another leaf. 



The author follows Loeb in holding that the silent electric 

 discharge reduces aqueous carbonic acid to formaldehj'de and 

 since electric currents of Variation are known to occur in leaves 

 when illuminated it is suggested that these are really expressions 

 of the energy utilised in photosynthesis. The evidence in support of 

 this chain of causation is to be detailed in a future paper. 



F. F. Blackman. 



Priestley, J. H. and A. A. Irving. The structure of the 

 chloroplast considered in relation to its function. 

 (Annais of Botany. Vol. XXI. p. 408—413, and 2 figs. 1907.) 



Very confiicting observations have been published upon the 

 physiologically important question of the structure of chloroplasts; 

 some investigators regarding the Chlorophyll as uniformly distributed 

 in the proteid ground substance, while others assert that it is 

 collected in a thin peripheral layer. The authors confirm Timiriazeffs 

 view that the large chloroplasts of Selaginella and Chlorophytum 



