Nov. i6, 1914I Nitrogenous Soil Constituent 177 



Tetracarbonimid was first obtained from a sandy soil from Florida 

 devoted to orange culture. This soil was one of the series of 16 samples 

 referred to in a previous paper (1914), and in which vanillin and other 

 benzene derivatives were found. Tetracarbonimid was found in three 

 of these soils in suiEcient quantity to make its identity certain, and in six 

 other samples crystals having, so far as could be ascertained, the same 

 properties as tetracarbonimid, were obtained in small quantities by the 

 same method. This compound was also found in three out of four 

 soils from other locations than Florida which were examined for it. 

 These soils were (i) a sample of Norfolk sandy loam from Virginia, (2) a 

 Sassafras soil from the grounds of the Department of Agriculture, and (3) 

 a sample of Elkton silt loam from Maryland. These results indicate that 

 tetracarbonimid is not an uncommon or accidental soil constituent. 



The soil from the Department grounds contained more of this com- 

 pound than the others examined, and from 18 kg. of this soil 30 mg. of 

 pure tetracarbonimid were obtained. The loss in purification in this 

 separation was at least 50 per cent, so that, assuming that the treatment 

 with sodium hydroxid extracted all of this compound, there was present 

 per acre-foot of soil approximately 7 pounds of tetracarbonimid, repre- 

 senting 2.3 pounds of soil nitrogen. This soil had a total nitrogen 

 content of 0.13 per cent, or approximately 5,200 pounds of nitrogen per 

 acre-foot, and it appears that the quantity of tetracarbonimid nitrogen 

 is at any one time but a very small part of the total. 



However, in this investigation some evidence has been obtained indi- 

 cating that the quantity of tetracarbonimid fluctuates under varying 

 conditions of cultivation or crop growth. If, then, this compound is 

 formed from other compounds under certain soil conditions and its dis- 

 appearance by oxidation or other means, such as use by plants, is 

 influenced also by conditions that vary, it may, in spite of the small 

 quantity present at any one time, be an important step in the trans- 

 formations that organic nitrogen undergoes in the soil. 



Tetracarbonimid has so far not been reported in any plant or animal 

 tissue and has been made only by the mild oxidation of uric acid. Uric 

 acid has not been found in soils or plants, and while it might be added 

 to soils in human excrement, it is not a common constituent of manures 

 or fertilizers; therefore it would seem that the source of tetracarbonimid 

 in soils must be sought in some other compound. 



The close relation of uric acid to the purin bases suggests these as 

 possible sources of this compound, and there is no theoretical reason 

 for assuming that any of the purin bases might not under proper condi- 

 tions of oxidation yield tetracarbonimid. This possibihty is disclosed 

 more clearly by consideration of the structural formulas. 



Uric acid Xanthin 



(2.6.8. oxypurin) (2.6. oxypurin) 



NH-CO NH-CO 



II II 



CO C-NH. CO C-NH. 



I II /CO I II \CH 



NH-C-NH/ NH C- N *^ 



