58 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 



ratio of soil solution to soil is the least; that is, when the 

 liquid film about the soil particles reaches its maximum dis- 

 tension, and the cyanamide molecules are in closest contact 

 with the soil particles (See p. 42). 



IV. The hydrolysis to urea is brought about in the soil by 

 the catalytic action of certain colloidal substances, of which 

 the most effective are the hydroxides of manganese and iron, 

 and certain natural zeolites (hydrated meta- and tri-silicates 

 of aluminium and sodium or calcium (pp. 48-56). Other 

 colloids occurring naturally in the soil have less ability of 

 transformation. Animal carbon is about as active as soil 



(P-5I)- 



V. The soil loses its power of effecting the transformation 

 when it is calcined or when it is treated with acids and alkalies ; 

 that is, when the colloids are destroyed. Upon addition of 

 the colloids again, it reacquires the property of transformation. 



VI. The conversion of cyanamide in sterile conditions is 

 entirely to the form of urea. The urea was isolated and iden- 

 tified (pp.43. 44, 50- 



VII. In the hydrolysis of cyanamide to urea, micro-organ- 

 isms do not participate, because : 



(a) The transformation proceeds most rapidly at high con- 

 centrations of cyanamide and at concentrations far above those 

 that support life (pp. 40, 43, and 46). 



(b) The transformation takes place with greatly increased 

 velocity at 100° C. (p. 43). 



(c) The transformation takes place in the presence of anti- 

 septics and sterilized materials (pp. 44, 50, and 56). 



VIII. Unless the greatest care is taken to have perfectly 

 sterile conditions, the urea is converted into the form of 

 ammonium salts. In ordinary soil this change is very rapid 

 (pp. 40, 44, and 57). 



IX. The conversion of the urea to ammonium salts hastens 

 the hydrolysis of cyanamide to urea by removing the end- 

 product of the hydrolysis (p. 57). 



