Synthesis by Sunlight in Relationship to the Origin of Life. 167 



the non-removal of the separated oxygen which remained as uranium 

 peroxide and acted as a destructive agent upon the formaldehyde. 



The authors accordingly took tubes of Jena glass, cooled them in liquid 

 air, passed in carbon dioxide, sealed, and exposed for 24 hours, suspended 

 outside a south window, in bright sunlight. A precipitate appeared after 

 15 minutes' exposure, and in 24 hours the reaction was complete. The 

 tubes on opening were found to contain uranium peroxide and formic acid, 

 but no formaldehyde. 



Usher and Priestley then repeated their experiments using uranium 

 sulphate instead of the acetate. Carbon dioxide was passed through a 2-per- 

 cent, crystalloidal .uranium sulphate solution, and the solution was exposed 

 to sunlight on a roof for nearly a fortnight. Several grammes of a precipitate 

 of mixed oxides of uranium were obtained of a pale violet colour. The 

 greater part was a mixture of uranous and ordinary uranic hydroxides 

 soluble in acetic acid. The insoluble residue was a hydrate of uranium 

 peroxide. The nitrate from all these mixed hydroxides was distilled and 

 examined for formaldehyde. None, however, was found, though the liquid 

 reduced Fehling's solution and silver nitrate. It was subsequently found to 

 contain formic acid, the lead salt of which was prepared and identified. The 

 undistilled residue was then evaporated down, and when nearly solid was 

 repeatedly extracted with dry ether in order to remove any formic acid 

 which had not evaporated. The residual solid was extracted with absolute 

 alcohol, and the solution on evaporation left a small quantity of a brown 

 syrup, bitter to the taste, which reduced Fehling's solution. It could not 

 be proven that this formed an osazone, but it closely resembled in its 

 properties a substance called " methylenitan " obtained by Butlerow from form- 

 aldehyde and milk of lime. The body was obtained in minute amount only. 



This experiment constitutes a distinct advance, since the organic substances 

 (formic acid and the body above mentioned) were obtained by the action of 

 light on purely inorganic substances. 



The points still left against the results, from the aspect mentioned at the 

 outset of tbe present paper, are that the catalyst is an extremely rare one 

 in nature, that it was used in high concentration in crystalloidal solution, 

 and that it underwent changes in itself and was precipitated as the result of 

 the reaction. The fact that formic acid was obtained instead of formalde- 

 hyde, looked at from our point of view, is relatively unimportant, since both 

 are organic bodies of increased energy content. 



By the use of many times more dilute colloidal uranic hydroxide, we have 

 been able now to obtain formaldehyde, and this without precipitation or 

 other visible change in our catalyst. Compared with a stronger solution of 



