176 Journal of Agricultural Research (voI.iu.no.2 



tetracarbonimid when alone and pure is precipitated by neutral lead 

 acetate. 



Further, when tetracarbonimid is pure, it is very slightly soluble in 

 alcohol, but the presence of impurities which accompany it in this method 

 of isolation afifects its solubility in alcohol to such an extent that the first 

 step in its purification is best effected by solution in alcohol. This treat- 

 ment separates it from calcium salts and other inorganic impurities that 

 always accompany it when precipitated from soil extracts by lead or mer- 

 cury salts. 



The crystals of the compound as first obtained are in the form of thin 

 micaceous scales of rather unusual appearance, but since this changes 

 when the compound is purified it can not be regarded as characteristic. 



As thus obtained from soils, tetracarbonimid is in the form of small 

 white prisms or plates rather difiicultly soluble in cold but readily soluble 

 in hot water. The crystals are very little soluble in alcohol, ether, or 

 other solvents. The compound has no definite melting point, but when 

 heated above 300° C. it decomposes, giving off acrid vapors that redden 

 blue litmus paper, a white sublimate being deposited at the same time. 

 An aqueous solution gives precipitates with silver, mercury, or lead salts. 

 Barium chlorid produces no precipitate, but on the addition of barium 

 chlorid and sodium hydroxid it is completely thrown down as a voluminous 

 white precipitate. 



Tetracarbonimid (C,H4N404) was first obtained by Scholtz (1901) by 

 oxidizing uric acid in alkaline solution with hydrogen peroxid. The 

 work of Scholtz was confirmed in 1909 by Schittenhelm and Wiener 

 (1909), who by modifying the conditions of oxidation obtained another 

 compound, carbonyldiurea (CjHgN^Og). These authors suggested that 

 tetracarbonimid and carbonyldiurea might be intermediate steps in the 

 oxidation of uric acid to urea in the human body, as shown below. 



Uric acid Tetracarbonimid Carbonyldiurea Urea 



NH— CO NH— CO— NH NHo NH, NH. 



II 1 I r \' \' 



CO C— NH-^CO CO->CO CO^CO 



I II CO I II II 



NH — C — NH NH— CO— NH NH— CO— NH NHj 



Tetracarbonimid was prepared from uric acid according to the method 

 of Scholtz and its properties compared with the compound obtained from 

 the soil. The two preparations were found to be identical in crystalhne 

 form and solubility, in being precipitated from solution by metallic salts, 

 and in their behavior on heating. Their identity was further confirmed 

 by the analysis of the barium salt and the determination of the nitrogen 

 content. 



The preparation from the soil was found on analysis to contain the 

 following percentage of nitrogen: Sample No. i, 32.59 per cent, and 

 sample No. 2, 32.47 per cent of nitrogen, the theoretical nitrogen content 

 of C4H4N404 being 32.61 per cent. The barium salt prepared by pre- 

 cipitating a hot, saturated solution of the soil compound with barium 

 hydroxid was found to contain 61.55 P^r cent of barium, the barium 

 content of C^BajN^Oj being 62 per cent. These figures, together with 

 the correspondence in properties, are sufficient to establish the identity 

 of the soil compound as tetracarbonimid. 



