668 
Journal of Agricultural Research 
Vol. XI, No. 12 
Table VIII .—Effects of an excess of a solution of calcium hydroxid on the amount of 
calcium oxid used by acid soil 23 
VARYING QUANTITIES OR CALCIUM OXID, SOIL CONSTANT 
Erlenmeyer flask No. 
Weight of 
soil taken. 
Quantity 
of calcium 
hydroxid 
taken. 
Quantity 
of water 
added. 
Titer of 
filtrate 
(cubic 
centi¬ 
meters of 
hydro¬ 
chloric 
add). 
Quantity 
of calrium 
hydroxid 
used by 
soil. 
Percent¬ 
age of 
applied 
calcium 
hydroxid. 
Quantity 
of calrium 
oxid used 
per 
2,000.000 
pounds 
of soil. 
Gm. 
C. c. 
C. c. 
C. c. 
Pounds. 
I . 
c 
2 
10 
2. O 
100 
2 . 
c 
4 
20 
A. O 
100 
3 . 
0 
5 
6 
30 
0. 2 
1 
S-8 
97 
2,320 
4 . 
5 
8 
40 
.6 
7-4 
92 
2, 960 
5 . 
5 
10 
50 
2.4 
7.6 
76 
3 > ° 4 ° 
6. 
5 
12 
60 
3-6 
8.4 
70 | 
3 > 3 6 ° 
7 . 
S 
14 
70 
5-5 
8-5 
61 
3> 4 °° 
8. 
5 
16 
80 
7*7 
8-3 
52 
3 > 3 2 ° 
VARYING QUANTITIES OR SOIL, CALCIUM OXID CONSTANT 
1. 
1 
2 
20 
0. 75 
■2$ 
. 1 
2. 2 < 
2 * 75 
2. 0 
75 * 0 
91. 6 
96.6 
100. 0 
4 > 5 °° 
2,748 
1 > 93 ° 
2. 
2 
O 
2 
20 
2 . 
7 
O 
2 
20 
O 
A . 
O 
4 
O 
3 
2 
20 
y 
O 
C . 
T 
5 
20 
O 
V 0 
100. 0 
O 
0 
It is evident that the soil continues to take up calcium oxid after the 
solution becomes alkaline to phenolphthalein, but the quantity used 
(Table VIII) soon reaches a maximum and remains quite constant. 
Soil acidity is undoubtedly neutralized when an excess of calcium oxid 
is found in the solution. A second reaction must then take place which 
is complete when the maximum amount of calcium oxid is taken. It 
will be observed from the table that this maximum amount increases 
with the concentrations of the solutions in contact with the soil. The 
quantity of calcium oxid required to neutralize 2,000,000 pounds of 
soil 23, as determined by the indirect-titration method with a different 
concentration of limewater than was used in Experiment III, is 2,160 
pounds, an amount comparable to that used by the soil in this experi¬ 
ment when the solution becomes slightly alkaline. 
Two generalizations can be drawn from the data given: 
(1) A definite quantity of calcium oxid is required to neutralize an 
acid soil, with phenolphthalein as the indicator; and this quantity is 
„ independent of the concentration of the limewater used. 
(2) Beyond the neutral point the amount of calcium oxid used varies 
directly with the concentration of the limewater solution bathing the 
soil; hence, it appears that the first generalization deals with a chemical 
reaction, and the second with a physical reaction. However, mass 
action may cause a chemical reaction when an excess of calcium oxid 
is present. 
