942 HOW CROPS FEED. 



ammonia was completely absorbed in the first part of the 

 experiment. After about 7 cubic feet of air had streamed 

 tlirough the soil, ammonia began to escape unabsorbed. 

 The earth thus saturated contained 0.192" |„ of ammonia. 

 A current of j^ure air was now passed through the soil as 

 long as ammonia was removeii by it in notable quantity, 

 about 38 cubic feet being required. By this means more 

 than one-half the ammonia was displaced and carried oif, 

 the earth retaining but 0.084" |^. 



Brustlein ascei'tained further that ammonia which has 

 been absorbed by a soil from aqueous solution escapes 

 easily when the earth is exposed to the air, especially 

 when it is repeatedly moistened and allowed to dry. 



100 parts of the same kind of soil as was employed in 

 the experiments already described were agitated witli 187 

 l^arts of water containing 0.889 parts of ammonia. The 

 earth absoibed O.loT parts of ;immonia. It was now 

 drained from tlie liquid :md allowed to dry at a low tem- 

 perature, which operation required eight days. It was 

 then moistened and allowed to dry again, and this was re- 

 peated four times. The progressive loss of ammonia is 

 shown by the following figures. 



100 parts of soil absorbed 0.157 parts of ammonia, 



" " " '• contained after the first dryini,' 0.083 " " " 



" " " " " " " second " 0.066 " " " 



" " " " " " " third " 0.054 " " " 



" " " " " " " fourth " 0.041 " " " 



" " " " " " " fifth " 0.039 " " " 



In this instance the loss of ammonia amounted to three- 

 fourths the quantity at first absorbed. 



The extent to wliich absorbed ammonia escapes from 

 the soil is greatly increased by the evaporation of water. 

 Bru.stlein found that a soil containing 0.067° |„ of ammo- 

 nia suffered only a trifling loss by keeping 43 days in a 

 dry place, whereas the same earth lost half its aTumonia 

 in a sliorter time by being thrice moistened and dried. 



According to Knop ( Vs. /St., Ill, p. 222), the single 



