THE AMMONIA OF THE SOIL. 247 



'olved out nearly one-half tlie ammonia whieli tlie earth 

 at first absorbed. 



The 1st dilution removed from the soil 0.010 



"2d " " " " " ...0.009 



" 3d " " " " " 0.014 



" 4tli " " " " " 0.011 



" 5th " " " " " 0.009 



Total 0.053 



Deducting 0.053 from the quantity first absorbed, viz., 

 0.112, there remains 0.059 part retained by tlie soil after 

 five dilutions. Knop, in 11 decantations, in which the 

 soil was treated with 8 time* its weight of water, removed 

 93° !„ of the ammonia wliich the soil had previously ab- 

 sorbed. We cannot doubt that by repeating the washing 

 sufficiently long, all the ammonia would be dissolved, 

 though a very large volume of water would certainly be 

 needful. 



Causes which ordinarily prevent the Accumulation of 

 Ammonia in the Soil. — The ammonia of the soil is con- 

 stantly in motion or suffering change, and does not ac- 

 cumulate to any great extent. In summer, the soil daily 

 absorbs auimonia from the air, receives it by rains and 

 dews, or acquires it by the decay of vegetable and animal 

 matters. 



Daily, too, ammonia wastes from the soil — by volatili- 

 zation — accompanying the vapor of water which almost 

 unceasingly escapes into the atmosphere. 



When the soil is moist and the temperature not too low, 

 its ammonia is also the subject of remarkable chemical 

 transformations. Two distinct chemical changes are be- 

 lieved to affect it ; one is its oxidation to nitric acid. This 

 process we shall consider in detail in the next section. As 

 a result of it, we never find ammonia in the water of or- 

 dinary wells or deep drains, but inste-nd always encounter 

 nitric acid united to lime, and, perhaps, to magnesia and 

 alkalies. The other chemical change appears to be the 

 alteration of the compounds of ammonia with the humus 



