378 



Formaldehyde as an Oxidation Product of Chlorophyll Extracts. 

 By Charles Horne Warner, B.Sc, F.I.C. 



(Communicated by Prof. V. H. Blackman, F.R.S. Received February 3, — 

 Bead March 5, 1914.) 



(From the Department of Plant Physiology and Pathology, Imperial College of Science 



and Technology.) 



Of recent years the action on carbon dioxide of chlorophyll in vitro has 

 assumed some importance as possibly throwing light on the nature of the 

 photo-synthetic process of green plants. Thus Usher and Priestley* have 

 stated that films of extracted chlorophyll in the presence of moist air and 

 carbon dioxide produce formaldehyde and hydrogen peroxide under the 

 influence of light. The earlier work' of these authors has been adversely 

 commented upon by several writers, notably by Ewart,f to whose criticisms 

 Usher and Priestley have replied with a number of additional experiments 

 and arguments, referring also to the work of Schryver,^ subsequent to that 

 of Ewart, as affording strong confirmation of their views as far as the 

 synthesis of the aldehyde is concerned. The facts set forth in the present 

 paper came to light during an attempt to confirm and extend the observa- 

 tions of Usher and Priestley and of Schryver. 



Grass was extracted with alcohol, usually in the cold and in the presence 

 of calcium carbonate. In some experiments the alcoholic liquid was 

 evaporated to dryness under reduced pressure and the residue extracted 

 with ether ; in others a solution of chlorophyll in light petroleum was 

 obtained by shaking the alcoholic solution with that liquid. The method of 

 experiment was based upon that described by Schryver, the ether or 

 petroleum extract being allowed to evaporate on glass plates and exposed to 

 light under the various conditions to be mentioned below. As was the case 

 in the later experiments of Usher and Priestley themselves, the test which 

 has been relied upon for the detection of formaldehyde is the very delicate 

 one devised by Schryver, who has found that the reaction is not given by 

 such other members of the series as have been examined up to the present. 

 It has been assumed in the course of these experiments, as in the work 

 of the investigators already mentioned, that the aldehyde produced is 



* 'Boy. Soc. Proc.,' B, vol. 77, p. 369 (1906) ; vol. 78, p. 318 (1906) ; and vol. 84, p. 101 

 (1911). 



t Ibid., vol. 80, p. 30 (1908). 

 % Ibid., vol. 82, p. 226 (1910). 



