94 
Journal of Agricultural Research 
Vol. 26, No. 3 
EXPERIMENT 4.—SOIL+CALCIUM CARBONATE+POTASSIUM CHLORID 
In this experiment KC 1 was added to the soil in addition to the CaC 0 3 , 
and the time of contact was 24 hours. The results for P H titrations 
and calcium are presented in Table IV. 
Table IV.— Ph on suspensions and extracts of soil-\~CaC 0 3 made with a solution of KCl; 
also the titration and calcium content of the extracts 
Calcium added. 
Oswego silt loam. 
Bates very fine sandy loam. 
Suspen¬ 
sion. 
Extract. 
0.05 N 
HC 1 . 
Cain 
extract. 
Suspen¬ 
sion. 
Extract. 
0.05 N 
HC 1 . 
Ca in 
extract. 
Mgm. 
Ph 
Ph 
Cc. 
Mgm. 
Ph 
Ph 
Cc. 
Mgm. 
2 -5 . 
5-6 
7-3 
0. 0 
14. I 
5-2 
5 - 1 
—O. I 
8. 2 
5 -°- . 
6. 0 
7.6 
—. 1 
17 - 7 
5-6 
6 -3 
—. I 
9.4 
10.0. 
7 - 1 
8.3 
. 0 
19. 8 
7. 2 
8.4 
. O 
13. 6 
20.0. 
7-5 
8.4 
•4 
20. 4 
7.8 
8.4 
•4 
18. 7 
40.0. 
7.6 
8.5 
•4 
24.4 
8.0 
8.4 
•S 
19. 6 
When salts like KCl, NaCl and CaCl 2 , each composed of a strong base 
and a strong acid, are added to soil the H-ion concentration of the soil 
suspension is increased. CaC 0 3 is a salt of a strong base and a weak 
acid. When carbonates were added to soil (Experiment 13) the H-ion 
concentration of the suspension was decreased. In Experiment IV the 
KCl increased the hydrogen-ion concentration, even in the presence of 
CaC 0 3 . The calcium in the extract was dissolved by KCl partly from the 
soil and partly from the added CaC 0 3 , but only a part of the added 
CaC 0 3 was dissolved. When 40 mgm. of calcium were added in the form 
of CaC0 3 , the amount obtained in solution was only about 10 mgm. 
more than when 2.5 mgm. were added. 
The titrations with 0.05N HC 1 were made on the same solutions in 
which the calcium was determined. Each cc. of this standard HC 1 
solution is stoichometrically equivalent to 1 milligram of calcium as a 
carbonate or as a hydroxid. The small values of the titer figures show 
that very little calcium was present in such forms. The KCl furnishes the 
conditions essential for changing the calcium to CaCl 2 and it is probable 
that the calcium was present in the form of a neutral salt. The high 
hydroxyl-ion concentrations obtained with the larger amounts of CaC 0 3 
were due to the presence of the ions HCO s , C 0 3 , and Ca, which are ions 
of a weak acid and a strong base. 
EXPERIMENT 5.—SOIL+CALCIUM HYDROXID 
In this and the following experiments Oswego silt loam was used 
unless a statement to the contrary is made. The Ca(OH) 2 solution 
was added to the soil in increasing amounts, beginning with 2.5 mgm. 
and running up to 80 mgm. of calcium equivalent for 10 gm. of soil. 
These amounts represent from one-third ton to 20 tons equivalent of 
CaC0 3 per acre. The results are given in Table V. 
