PRELIMINARY AND MINOR PAPERS 



A NITROGENOUS SOIL CONSTITUENT: 

 TETRACARBONIMID 



By Edmund C. Shorey and E. H. Walters, 

 Scientists, Soil-Fertility Investigations, Bureau of Soils 



In 1913 brief mention (Shorey, 1913a)' was made of the isolation 

 from a soil of a nitrogenous compound that had the properties of tetra- 

 carbonimid (C4H4N4O4). Since then this compound has been isolated 

 from a number of soils and its identity as tetracarbonimid has been 

 confirmed. 



In the isolation of this compound an alkaline extract obtained by 

 treating the soil with a 2 per cent solution of sodium hydroxid for 24 

 hours at room temperature was used. This extract was made acid with 

 sulphuric acid and filtered. The acid filtrate was shaken out with ether 

 to remove the acids and other compounds that are soluble in this solvent, 

 and a solution of mercuric sulphate in dilute sulphuric acid was added 

 until no further precipitate was formed. The precipitate was filtered off, 

 well washed, suspended in water, and decomposed with hydrogen sulphid. 



After the removal of mercuric sulphid by filtration, the dark-colored 

 filtrate was concentrated to a smaller volume and excess of a solution 

 of neutral lead acetate added. The dark-colored precipitate thus formed 

 was removed by filtration and ammonia added to strong alkahnity. 

 The white or cream-colored precipitate thus formed was filtered off, 

 well washed, and decomposed by hydrogen sulphid, the lead sulphid 

 was filtered off, and the filtrate was evaporated almost to dryness and 

 allowed to stand. Crystals formed in this semisoHd mass in a short time, 

 and after standing a number of hours several volumes of alcohol were 

 added and the solution was filtered. The alcoholic filtrate was con- 

 centrated to a small volume, and from this solution crystals separated 

 in a short time. These were separated by filtration, dissolved in hot 

 water, the solution filtered and concentrated to the crystallizing point 

 and allowed to stand several hours, when the compound separated in a 

 fairly pure form. By repeating this operation several times it was 

 obtained in the form of small plates or prisms free from color. 



Several points in this method as thus briefly outlined are deserving of 

 further comment. The original acid filtrate from the humus extract 

 is usually dark colored, and the treatment with mercuric sulphate in acid 

 solution produces a dark-colored precipitate that removes nearly all 

 color from the solution. When this precipitate is decomposed with 

 hydrogen sulphid, a dark-colored solution again results from which 

 neutral lead acetate precipitates most of the color without apparently 

 removing the compound under discussion. This is mentioned because 



' Bibliographic citations in parentlieses refer to "I^iterature dted," p. 178. 



Journal of Agricultural Research, Vol. Ill, No. 3 



Dcpt. of Agriculture, Washington, D. C. Nov. 16, 1914 



(17s) H-3 



