Oct. 20, >923 
Soil Reaction in Relation to Calcium Adsorption 
101 
placed in a tall 8-liter bottle, and distilled C 0 2 -free water added until 
the bottle was nearly full. The bottle was then shaken for one hour, 
after which the soil was allowed to settle for one week. The super¬ 
natant liquid, still turbid with colloidal clay, was siphoned off without 
disturbing the soil in the bottom. The bottle was again filled with 
water and the process of shaking, settling, and removal of supernatant 
liquid repeated 12 times in as many weeks. As far as could be observed, 
the supernatant liquid was as turbid the last time it was siphoned off 
as it was the first time. The soil was transferred, using a small amount 
of water, to 1-gallon earthenware jars, and allowed to evaporate and 
dry completely at room temperature. Oswego silt loam, Bates very 
fine sandy loam, and Bates loam were thus treated. The resulting dry 
soil was very friable and loose. Determinations showed that only a 
small percentage of the soil had been removed as colloidal matter in the 
washing process. 
In a preliminary trial Ca(OH) 2 was added in varying amounts to the 
three washed soils, but the differences in the data from the washed soils 
as compared with those from the untreated were relatively the same for 
the three soils. Table XI gives the results obtained on the Oswego 
silt loam. 
Table; XI.— Ph of suspensions and extracts of washed soil -f Ca(OH) 2 ; also titrations 
and calcium content of extracts , and calcium adsorbed from Ca(OH) 2 
Calcium added. 
Suspension. 
Extract. 
0.05N. 
HC 1 . 
Calcium in 
extract. 
Calcium not 
adsorbed. 
Calcium 
adsorbed. 
Mgm. 
Pn 'o 
Ph • 
Cc. 
Mgm. 
Mgm. 
Mgm. 
0.0. 
4.89 
7-32 
O. O 
O. 4 
O. O 
O. O 
2-5 . 
5 - 94 
7-35 
. I 
• 5 
. I 
2. 4 
5 -o. 
6. 07 
8. 03 
. I 
• 7 
•3 
4 . 7 
8.0. 
6. 14 
7. 76 
. 2 
1. 1 
•7 
7-3 
12.0. 
7. 19 
8. 13 
.3 
1.4 
1. 0 
11. 0 
16.0. 
7. 62 
8. 47 
•3 
1. 6 
1. 2 
14. 8 
20.0. 
8. 03 
8. 30 
. 2 
1. 7 
i -3 
18.7 
28.0. 
8. 94 
8. 34 
• 4 
2. 6 
2. 2 
25. 8 
36.0. 
9. 99 
9 - 59 
1. 5 
4-4 
4 . 0 
32. 0 
48.O. 
10. 87 
10. 40 
2. 5 
5-3 
4-9 
43 . 1 
60.O. 
11. 24 
11. 34 
9 - 5 
14. 1 
i 3.7 
46. 3 
80.0. 
11. 68 
11. 68 
22. 8 
27. 1 
26. 7 
53-3 
Comparing the figures of Table XI with those in Table V it will at 
once be apparent that the hydrogen-ion concentrations obtained, when 
different amounts of Ca(OH) 2 were added to the soil, were greater for 
the washed soil than for the untreated. This means that the washing 
process increased the solubility of the acid-producing substance. Since 
the acid-producing substance is slightly soluble, a small amount was 
removed in the washing process. However, this removal resulted in an 
increase, rather than a decrease, in the hydrogen-ion concentration ot 
the suspensions and the extracts. This indicates a continuous and in¬ 
creasing solubility of the acid-producing substance. (See fig. 6.) 
The differences in the figures for calcium adsorption obtained on the 
washed soil as compared with the untreated are practically within the 
limits of the experimental error. If there is any real difference, washing 
has decreased the adsorptive capacity of soil for calcium. This was 
probably due to the removal of colloidal clay. 
