PROBLEMS OF MODERN SCIENCE 



the materials available are the carbon dioxide 

 and water vapour of the atmosphere. Experiment 

 in the laboratory has shown that these simple 

 materials may be converted by the action of light 

 to oxygen and a very simple carbon compound 

 termed formaldehyde. The molecular composi- 

 tion of formaldehyde is simple ; it contains carbon, 

 hydrogen, and oxygen in the relative amounts 

 indicated by the formula CH 2 O, and its formation 

 by this process may be represented as follows : 

 CO 2 + H 2 O = O 2 + CH 2 O. It has been known 

 for many years that oxygen is given off by the 

 leaves of the growing plant, and search for this 

 formaldehyde in green leaves soon proved that 

 this substance was present in small quantity. It 

 seems probable, therefore, that the first step taken 

 by the plant in the assimilation of carbon has been 

 detected. In the process the reaction between the 

 materials is brought about by light, which is un- 

 doubtedly assisted in its catalytic action by the 

 chlorophyll of the leaves, but the precise role of 

 the latter substance is not yet fully understood. 



The fact that light can excite chemical reaction 

 has been known for very many years, but this 

 discovery of the production of formaldehyde 

 seems to have drawn the attention of organic 

 chemists to the possibility of its use as a synthetic 

 reagent, and at the present time our knowledge 

 of the photochemistry of organic compounds is 

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