ABSORPTIVE POWER OF THE SOIL 337 
Experiments to ascertain how much of a substance the soil is able to 
absorb are mide by putting a known amouut of the dry soil (e. g. 100 
grms.) in a bottle with a given volume (e. g. 500 cubic cent.) of solution 
whose content of substance has been accurately determined. The solu- 
tions are most conveniently prepared so as to contain as many grms. of 
the salt to the liter of water as corresponds to the atomic weight ot 
equivalent of the former, or one-half, one tenth, ctc., of that amount. 
The soil and solution are kept in contact with occasional agitation for 
some hours or days, and then a measured portion of the liquid is 
filtered off and subjected to chemical analysis. 
The absorptive power of the soil is exerted unequally 
towards individual substances. Thus, in Peters’ experi- 
ments ( Vs. St., IT., 140), the soil he operated with absorb- 
ed the bases in quantities diminishing in the following 
order: 
Potash, Ammonia, Soda, Magnesia, Lime. 
Another soil, experimented upon by Kiillenberg 
(Jahresbericht uber Agricultur. Chemie, 1865, p. 15), ab- 
sorbed in a different order of quantity, as follows: 
Ammonia, Potash, Magnesia, Lime, Soda. 
As might be expected, different soils exert absorptive 
power towards the same substance to an unequal extent. 
Rautenberg (Hennebverg’s Jour. fiir Landwirthschaft, 
1862, p. 62), operated with nine soils, 10,000 parts of which, 
under precisely similar circumstances, absorbed quantities 
of ammonia ranging from 7 to 25 parts. 
The time required for absorption is usually short. 
Way found that in most cases the absorption of ammonia 
was complete in half an hour. Peters, however, observed 
that 48 hours were requisite for the saturation of the soil 
he employed with potash, and in the experiments of Hen- 
neberg and Stohmann (Henneberg’s Journal, 1859, p. 35), 
phosphoric acid continued to be fixed after the expiration 
of 24 hours. 
The strength of the solution influences the extent of 
absorption. The stronger the solution, the more substance 
is taken up from it by the soil. Thus, in Peters’ experi- 
15 i 
