38 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 



the soil in one hour. Such a fertilization, however, amounts 

 to 560 pounds nitrogen per acre half-foot of soil, a quantity- 

 far in excess of any ever used in agriculture. The quantity 

 of calcium absorbed in one hour in this test is equivalent to 

 600 pounds CaO per acre half-foot of soil. 



Ulpiani regards the change as taking place with the inter- 

 mediate formation of calcium cyanamide carbonate: 



(CN. NH),Ca +. CO2 = CN. NH, -f CaCN,CO,, 

 CaCN^CO, + H,0 = CN. NH, + CaC03 



Whatever the mechanism of this hydrolysis there is no 

 question but that the result is free cyanamide, and conse- 

 quently the following investigations on the decomposition of 

 cyanamide in the soil were made with the free cyanamide, 

 CN.NH2. 



SECOND AND THIRD STAGES OF DECOMPOSITION. 



The following experiment by Ulpiani^ was made to deter- 

 mine the rate of decomposition of cyanamide: 100 grams of 

 earth carefully dried at laboratory temperature, and sieved 

 through a screen with holes of i mm. diameter, was placed in 

 a glass tube and to it was added 20 cc. of a solution of pure 

 cyanamide containing 4.2 per cent, cyanamide. The liquid 

 reached almost to the bottom of the tube, hence the soil was 

 not quite saturated. A series of tubes so prepared was stop- 

 pered with cork and set in a thermostat at 28° C. After 

 various periods of time the content of cyanamide remaining in 

 the tubes was determined as follows : 80 cc. of distilled water 

 was added and thoroughly stirred with the contents of the 

 tube. After exactly an hour the contents were filtered with 

 suction. Of the filtrate (about 70 cc), two portions of 25 cc. 

 each were analyzed for cyanamide. The following results 

 were obtained : 



1 Gaz. Chim. Ital. XL, Parte i, 1910. 



