Julys, I9I7 Isolation of Cyanuric Acid from Soil 87 



precipitates. The compounds thus formed were shown to be identical 

 with a previously described silver-ammonium compound having the 

 formula Ag2C3HN303.2NH3 (i, p. 1268), which when analyzed gave the 

 following results: 



Preparation from soil compound : 



(a) 0.15295 gm. yielded 0.08900 gm. of silver; 



(b) 0.14825 gm. yielded 0.08635 g°^- o^ silver. 

 Preparation from synthetic cyanuric acid : 



(c) 0.2615 gm. yielded 0.1510 gm. of silver; 



(d) 0.1335 gm. yielded 0.0778 gm. of silver; 



(e) 0.1257 gm. yielded 0.0720 gm. of silver. 



Silver 

 (per cent). 



Calculated for Ag2C3HN303.2NH3 . . . .' 57. 2 



Found in the salt derived from soil compound : 



(a) 58-2 



(b) 582 



Found in salt from synthetic cyanuric acid: 



(c) 57-7 



(d) 57-5 



(e) 57-3 



The largest amount of pure cyanuric acid isolated from one of the 23- 

 kgm. lots of the Indiana soil by the above method was about 0.150 gm. 

 Since the isolation must entail some losses, even this should be taken as a 

 minimal value. This quantity of cyanuric acid represents 6.5 p. p. m. 

 and corresponds approximately to 26 pounds per acre-foot, by assuming 

 the weight of an acre-foot to be 4,000,000 pounds.^ 



It should be mentioned in passing that the properties of cyanuric acid 

 are very similar to those of tetracarbonimid as reported by Scholtz (8) 

 and by Schittenhelm and Wiener (7). By accepting the descriptions of 

 tetracarbonimid given by these workers, both compounds when anhydrous 

 have the same percentage composition, and both give similar precipitates 

 when treated with salts of some of the heavy metals. Both compounds 

 when subjected to dry heat decompose with the formation of a white 

 sublimate and acid vapors. On the other hand, cyanuric acid crystallizes 

 from water with two molecules of water of hydration, whereas no mention 

 is made of water of hydration in the case of tetracarbonimid. Further- 

 more, the neutralization equivalent, which is essentially a molecular- 

 weight determination, should ser\-e to distinguish between cyanuric acid, 

 which has the formula C3H3N3O3, and tetracarbonimid, which has the 

 formula C4H4N4O4, and the silver-ammonium derivative of cyanuric acid 

 described above has a composition diJGferent from that of any theoretically 

 possible silver derivative of tetracarbonimid. 



' The soil contained 0.0744 Per cent of total nitrogen. When extracted with a 2 per cent sodium- 

 hydroxid solution , the soil yielded 56 per cent of the total nitrogen to the alkaline solution. On acidification 

 with sulphuric acid and filtration, only 31 per cent of the total nitrogen was found in the acid solution. 

 When treated with mercuric sulphate in dilute sulphuric acid, the acid solution yielded a precipitate which 

 retained approximately 14 per cent of the nitrogen originally present in the soil. The cyanuric acid isolated 

 corresponds to about 0.30 per cent of the total nitrogen in the soil. 



