Synthesis by Sunlight in Relationship to the Origin of Life. 165- 



Acting on the hypothesis outlined above, experiments with a view to 

 testing the synthetic action of sunlight in presence of inorganic colloids were 

 commenced by us in November, 1911, but for over a year only negative 

 results were obtained, on account of difficulties in adjusting proper concen- 

 trations of solution, securing adequate illumination in vessels made of 

 suitable material, and obtaining delicate enough methods for separating and 

 identifying formaldehyde. After overcoming these experimental difficulties, 

 and with the aid of the brighter sunshine, a large number of positive results 

 have been obtained, within the past few weeks, and the synthesis of formal-, 

 dehyde under the conditions to be described below has been shown quite 

 unmistakably by all the usual colour-reactions for formaldehyde. 



It has also been shown that it is the ultra-violet rays which are most, 

 effective. The use of quartz flasks as containers for the colloid gives, with 

 the same intensity of insolation, definite results in a much shorter period, and 

 lately we have found that a " Uviol " mercury arc, in a " Uviol " glass 

 protecting vessel, immersed in an outer wider cylinder of glass so as to. 

 produce a thin layer of the colloid, through which the carbon dioxide is 

 passed, gives quite clearly positive reactions for formaldehyde by all the 

 colour tests, with an exposure to light of only four or five hours. 



The results are obtained either with colloidal hydrated ferric oxide, or 

 colloidal oxide of uranium, in exceedingly dilute solution. For example, in 

 the case of uranium, - 028 per cent, of the oxide, and, in the case of the iron, 

 0'113 jjer cent, of ferric oxide were the concentrations used. 



Controls carried out in the absence of light gave no formaldehyde, and all 

 precautions were taken to exclude contamination in any way. The same 

 point is shown by our earlier unsuccessful experiments in which the illumina- 

 tion was inadequate. 



Formaldehyde in small amounts has already been synthesised from 

 inorganic sources in several reactions in which hydrogen in the nascent 

 condition, or adsorbed in palladium, has been present. But there is here 

 chemical energy as such, presented by the hydrogen, and so far as we are 

 aware there is no case known of utilisation of light energy by an inorganic 

 catalyst which does not itself become altered in the reaction. 



Thus Bach* obtained formaldehyde from hydrogen-palladium and carbon 

 dioxide, Fentonf obtained it by the action of carbon dioxide and water on 

 metallic magnesium, and other observers have obtained it by the interaction 

 of dilute sodium amalgam and moist carbon dioxide. 



The only experiment approaching more closely to our own as recorded 



* 1 Comptes Bendus,' 1898, vol. 126, p. 79. 



t ' Journ. Chem. Soc. Trans.,' 1907, vol. 91, p. 687. 



