242 HOW CROPS FEED. 
ammonia was completely absorbed in the first part of the 
experiment. After about 7 cubic feet of air had streamed 
through the soil, ammonia began to escape unabsorbed. 
The earth thus saturated contained 0.192°|, of ammonia. 
A current of pure air was now passed through the soil as 
long as ammonia was removed by it in notable quantity, 
about 38 cubic feet being required. By this means more 
than one-half the ammonia was displaced and carried off, 
the earth retaining but 0.084” |.. 
Brustlein ascertained 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 with 187 
parts of water containing 0.889 parts of ammonia. The 
earth absorbed 0.157 parts of «ammonia. It was now 
drained from the liquid and 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 ot SO ADSOTD EM sarcsaseis sieves: snjore wrarcisinisinalsnteinass-aveisd 0.157 parts oO a ct 
BR is si a pti the first drying........ 0.083 
re @ second. 8" essences 0.066 * & “ 
“or oe eek 3 we oe third Ree Fe Sep ete! 0. 054 4 a ty 
< & ww “ « fourth “* ... ....004 % & “ 
ob +e co we a 4 oe fifth ere 0.039 oe +e oy 
In this instance the loss of ammonia amounted to three. 
fourths the quantity at first absorbed. 
The extent to which absorbed ammonia escapes from 
the soil is greatly increased by the evaporation of water. 
Brustlein 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 ammonia 
in a shorter time by being thrice moistened and dried. 
According to Knop (Vs. S¢., III, p. 222), the single 
