Oct 3o, 1933 Soil Reaction in Relation to Calcium Adsorption 
103 
The hydrogen-ion concentration of the suspension of the ignited soil 
was very nearly the same as that obtained on the original soil in Experi¬ 
ment 5. This shows that the acid-producing substance was not de¬ 
stroyed by ignition. The hydrogen-ion concentration of the extract 
from the ignited soil was greater than it was in the original soil. This 
indicates that ignition increased the solubility of the acid-producing sub¬ 
stance. However, the addition of the same quantities of Ca(OH) 2 to 
the ignited soil produced a greater increase in the hydroxyl-ion concen¬ 
tration. This was due to the decreased adsorption of calcium. The 
amount of calcium adsorbed by the ignited soil was approximately two- 
thirds that adsorbed by the original soil. The adsorptive capacity was 
lessened by the destruction of colloidal structure brought about by igni¬ 
tion. It is also possible that ignition alters the structure of the silicates 
in such a way that less chemical combination with calcium is possible. 
It is recognized that a too general statement can not be based on this 
experiment with only one soil. However, it is clear that while the 
hydrogen-ion concentration was not decreased by ignition, the adsorptive 
power for calcium was materially decreased. 
EXPERIMENT 13.—IGNITED SOIL+CALCIUM HYDROXID-f POTASSIUM CHLORID 
The manner of procedure in this experiment was the same as in Expeir- 
ment 12 except that KC1 was added. The results obtained are pre¬ 
sented in Table XIII. The effect of KC 1 in increasing the hydrogen-ion 
concentration and decreasing the amount of calcium adsorbed was rela¬ 
tively the same on ignited soil as on the untreated soil. Ignition, how¬ 
ever, decreased the solubility of calcium in a solution of KC 1 . In the 
original soil a solution of KC 1 dissolved 14 mgm. calcium per 10 gm. of 
soil, but in the ignited soil the amount dissolved was only 3.9 mgm. 
Thus while ignition increased the solubility of the acid-producing sub¬ 
stances in a solution of KC 1 it decreased the solubility of calcium in the 
same solution. Preceding experiments have shown that calcium ad¬ 
sorption was decreased by the presence of KC 1 and also by ignition. 
This experiment shows that KC 1 added to the ignited soil results in a 
further decrease of calcium adsorption. This apparently means that 
while basic exchange took place less readily in the ignited soil, the 
substances formed were more highly ionized. 
Table XIII.— Ph suspensions and extracts of ignited soil-\-Ca(OH) 2 -\-KCl, also titra¬ 
tions and calcium content of extracts and calcium adsorbed from Ca(OH) 2 
Calcium added. 
Suspension. 
Extract. 
0.05N HCl 
Calcium in 
Extract. 
Calcium not 
adsorbed. 
Calcium 
adsorbed. 
Mgm. 
Ph 
Pn n 
Cc. 
Mgm. 
Mgm. 
Mgm. 
O . 
4. 82 
5-83 
0*3 
3-9 
O. O 
O. 0 
4 . 
6. 17 
7. 00 
. O 
6.9 
3-0 
I. O 
8. 
7. 76 
7 - 59 
.4 
9-7 
6.8 
I. 2 
12. 
8.88 
9. 18 
i -3 
12.3 
8.4 
3-6 
16. 
10.05 
10. 02 
2.9 
14. 7 
10. 8 
5-2 
20. 
10.43 
11. 03 
7.6 
17 . 5 
13. 6 
6.4 
28. 
10. 90 
11. 20 
9.6 
21. 8 
17.9 
IO. 1 
36. 
11. 14 
11. 51 
13.8 
27. 1 
23. 2 
12. 8 
48. 
11.44 
11. 61 
17. 2 
32. 1 
28. 2 
19. 8 
60. 
11. 68 
n- 95 
30. 1 
42. 6 
38. 7 
21 . Z 
