Dec. io, 1913 
Selective Adsorption by Soils 
183 
In the foregoing experiments the determination of the free acid is 
unreliable, considering the fact that no indicator could be used for 
titrating which was sensitive enough and at the same time unaffected by 
carbon dioxid. The results can be considered only as approximations. 
Boiling to remove the carbon dioxid is impossible when potassium ace¬ 
tate is used, since it hydrolyzes on boiling, giving an alkaline reaction 
to indicators. Iron and titanium were determined in several cases and 
found to be present in negligible amounts in the precipitated alumina. 
The amount of chlorin present in the solution was found to be practi¬ 
cally unchanged. 
From the data obtained when the potassium chlorid is used, the amount 
of potassium chlorid equivalent to loss of potassium (0.7650—0.6950= 
0.0700 grams per 100 c. c.) during contact is greater than the amount of 
potassium chlorid equivalent to the bases dissolved from the soil (0.0107 + 
°.0353 + o.o i 57 = o.° 6 i 7 grams per 100 c. c.) by an amount (0.0700— 
0.0617 = 0.0083 grams per 100 c. c.) about equal to the amount of potas¬ 
sium chlorid equivalent to the estimated free acid (0.0112 grams per 100 
c. c.). When potassium acetate is used, the amount of potassium 
chlorid equivalent to the loss of potassium (0.7470—0.6560=0.0910 
grams per 100 c. c.) during contact is again greater than the amount of 
potassium chlorid equivalent to the bases dissolved from the soil (0.0015 + 
0.0314+0.0167 = 0.0496 grams per 100 c. c.) by an amount (0.0910— 
0.0496 = 0.0414 grams per 100 c. c.) about equal to the amount of potas¬ 
sium chlorid equivalent to the estimated free acid (0.0402 grams per 100 
c. c.). 
When potassium acetate is used, the bases dissolved from the soil are 
54.5 per cent^ P0910 X IO °^ w ^at they would be if a complete exchange 
of bases had taken place, while, when potassium chlorid is used, this per- 
( 0.0617 \ 
o 0700 X 100 J' 
SERIES No. 2 
In series No. 2, 250 grams of a Norfolk sandy loam were placed in a 
2-liter bottle. To this was added 1,000 c. c. of a solution containing 
18.38 grams of potassium chlorid and about 1 gram of sodium hydroxid 
per liter. The bottle was shaken frequently at room temperature for 
two days. The soil was allowed to settle until the supernatant liquid 
was apparently clear. Portions of the supernatant liquid were then 
pipetted off, filtered, and analyzed. 
Soil shaken with pure water showed no appreciable presence of material 
dissolved from the soil in the supernatant liquid. 
The above potassium-chlorid solution when shaken with soil showed 
a quantity of potassium chlorid equivalent to the loss of potassium of 
0.1520 grams per 100 c. c. and no appreciable loss of chlorin. The 
