VIII.] 



ABSORPTION OF AMMONIA 



215 



pure clay when shaken with 300 c.c. of ammonium 

 chloride solution of varying strengths. 



Thus from the weaker solutions a smaller total but a 

 larger proportion of the ammonia was removed by the 

 clay, and the removal was never complete. Of course, 

 in the field the amount of soil is so enormously in excess 

 that the absorption of ammonium salts applied as 

 manure is practically complete. Thus at Rothamsted 

 the presence of ammonia in the drainage water is rarely 

 detected, even when heavy rain immediately follows the 

 application of the manures. 



With humus, ammonium salts interact in a very 

 similar fashion, calcium coming into solution, and the 

 ammonium forming some insoluble compound with the 

 complex " humic " acids. 



With calcium carbonate a double decomposition of 

 the type — 



(NH 4 ) 2 S0 4 + CaC0 3 ^Z± (NH 4 ) 2 C0 8 + CaS0 4 



— takes place, not only with such substances as 

 ammonium sulphate, but also with humic and zeolitic 

 compounds of ammonium, and though the proportion 

 converted into carbonate is small, it is constantly 

 renewed as the ammonium carbonate is nitrified, so that 

 eventually the whole of the ammonium salt applied to 

 the land undergoes this change. 



