TO THE ORIGIN OF LIFE 41 



dioxide. He adduces no direct experimental evidence of the 

 presence of formaldehyde in the solution, but makes the hypothesis 

 that the carbonic acid by the action of light forms formaldehyde 

 and per-carbonic acid. Then the per-carbonic acid decomposes 

 and forms peroxide of uranium. Lastly, the formaldehyde attacks 

 uranic oxide forming lower oxides recognisable by their colour in 

 the precipitate of mixed oxide. In confirmation he shows that when 

 peroxide of uranium and actually added formaldehyde are exposed 

 to sunlight a reduction to lower oxide occurs with production first 

 of a green and then a violet colour. 



It will be observed, first that the crystalloidal salt of uranium 

 employed undergoes permanent change, and secondly that there 

 is no clear evidence of formation of formaldehyde, although our 

 experiments recorded below show that Bach's hypothesis is probably 

 a correct one. All the experiment actually proves, however, is 

 that acetate of uranium in crystalloidal solution, in presence of 

 carbon dioxide and sunlight, is decomposed, yielding a mixture of 

 oxides of uranium. At the same time it is an important pioneer 

 experiment in this field. 



In a later experiment, Bach obtained evidence of the formation 

 of formaldehyde by exposing to light a solution of dimethylaniline 

 in dilute sulphuric acid through which carbon dioxide was passed. 

 There is here, however, the objection of using an organic body as 

 catalyst, although the reaction is interesting as a photo-synthesis. 



The same objection holds as to the presence of the acetic acid 

 anion in the uranium acetate solution used above, since this might 

 serve as a source of formaldehyde. 



A considerable increase in our knowledge was given in the papers 

 of Usher and Priestley quoted above, in which they repeated and 

 extended Bach's experiment. 



The experiments of Bach were repeated and confirmed by these 

 authors, both as to the production of peroxide and formaldehyde. 

 The amount of decomposition obtained in three weeks in bright 

 weather was extremely small, and this was ascribed to the poorness 

 of the uranium as a catalyst, and the non-removal of the separated 

 oxygen which remained as uranium peroxide and acted as a de- 

 structive 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 

 2-i hours, suspended outside a south window, in bright sunlight. 



