Synthesis by Sunlight in Relationship to the Origin of Life. 175 



but this did not happen in later experiments when the heat was better 

 regulated. 



The colloidal solution was removed and tested for formaldehyde in two 

 ways. One portion was distilled as in the previously recorded experiments 

 and the distillate gave a most marked positive reaction with Schiff's reagent 

 — a deep pink coloration. A second part was simply filtered off from the 

 coagulated iron precipitate, and at once tested. It also gave a marked 

 positive reaction both with Schiff's and Mulliken's tests. 



Experiment V. — An experiment of the same type as the preceding one. 

 A colloidal solution of 1 in 20 of the same stock solution was taken, and 

 exposed to the mercury arc light as before. Illuminated during two periods 

 of 55 minutes and 2 hours 50 minutes, respectively, making 3 hours 

 45 minutes in all. Part of the solution distilled off gives a distinct positive 

 reaction with Schiff's test. Another portion coagulated by boiling, and 

 filtered from iron, but not distilled, gives a positive reaction with gallic acid 

 and concentrated sulphuric acid (Mulliken's test). 



The experiment was continued next day from 10.15 A.M. till 2.15 p.m. ; 

 at the end of this 4 hours' period the solution coagulated, owing to a failure 

 in the water circulation and the temperature rising. The coagulated fluid 

 was filtered and the filtrate tested, it gave a marked positive effect with 

 Schiff s test and also a positive result with Mulliken's test, a trace of iron 

 left over interfered with the Schryver test, but on distillation this also was 

 obtained. 



Experiment VI. — This was conducted similarly to the above experi- 

 ments IV and V for a period of 1 hour and 40 minutes. Then a trace of 

 ammonium carbonate amounting to only 1 part in 1000 was added with the 

 view of forming hexamethylenetetramin and so concentrating the formalde- 

 hyde, but even this trace coagulated the solution. 



The experiment was, however, continued for &\ hours additional. A small 

 portion was acidified and distilled. The distillate gave a marked positive 

 reaction with Schryver's test. 



Experiment VII. — A dilute colloidal solution of ferric hydroxide (1 in 15) 

 of stock solution, equivalent to 043 per cent, of ferric oxide, was exposed 

 after saturation with carbon dioxide, in a silica test-tube 3 inches away from 

 the mercury arc, during the time the lamp was bit on three days, probably 

 about 12 hours in all. A most marked reaction to all tests. The reaction 

 quantitatively is slightly less than the uranium effect, see Experiment VII 

 of previous section, and throughout it appears that the uranium catalyst is 

 somewhat more powerful than the ferric catalyst. 



