Bee. io, 1913 
Selective Adsorption by Soils 
185 
From the data obtained in this experiment (see fig. 1) we find that 
from the zero concentration of potassium chlorid, where necessarily the 
adsorption of potassium is zero, the loss of potassium during contact 
increases regularly with the concentration to a certain point and then 
remains practically constant, the surface of the soil particles having 
apparently taken up the greater part of the potassium possible at this 
point. The point at which the adsorption of potassium becomes prac¬ 
tically constant is much lower in the case where a sandy loam is used 
than when a silt loam is used. The percentage of potassium adsorbed 
increases asymptotically as the concentration of potassium chlorid 
Pig, i. Curves showing the effect of concentration on the selective adsorption of potassium from solutions 
of potassium by Norfolk sandy loam and by Marshall silt loam. 
decreases, and it may be concluded that the adsorption of potassium 
becomes practically complete at very low concentrations of potassium 
chlorid. Chlorin was determined in several cases and was found to have 
remained unchanged. 
SERIES No. 4 
In series No. 4, 35-gram portions of a subsoil of Cecil clay, a subsoil of 
Marshall silt loam, a subsoil of Norfolk sandy loam, a subsoil of Decatur 
clay loam, and a subsoil of Carrington loam were placed in 200 c. c. 
bottles with solutions of potassium chlorid of about the same concen¬ 
tration and treated as in series No. 3. The results are given in Table III. 
Table III .—Effect of amount of surface exposed on adsorption. 
Type of soil. 1 
Cecil clay. 
Decatur clay loam. 
Marshall silt loam.. 
Carrington loam. .. 
Norfolk sandy loam, 
Quantity of KC 1 equivalent to 
the quantity of K per 100 c. c. 
of solution. 
Before contact. 
After contact. 
Grams. 
6 - 7350 
6 ■ 5550 
6. 6950 
6. 4300 
6. 2580 
Grams. 
6. 4100 
6. 3 I 5 0 
6. 2450 
6. 2050 
6.1100 
Difference. 
Grams. 
o. 3250 
. 2400 
.4500 
.2250 
. 1480 
1 The soils in this table are arranged in order of the relative amount of surface exposed. 
