92 
Journal of Agricultural Research 
Vol. 26, No. 3 
Table i.— Ph on water suspensions and extracts of soils , titrations, and calcium content 
of extracts 
Soil type. 
Suspension. 
Extracts. 
0.05N 
NaOH. 
Calcium in 
extract. 
Neosho silt loam. 
Pb 
6. 48 
5. 66 
4. 82 
Pa 
■ 8. 54 
8. 50 
8. 50 
8. 61 
Cc. 
o -45 
.40 
• 50 
• 5 ° 
Mgm. 
I. 0 
Oswego silt loam. 
I. 3 
Bates very fine sandy loam. 
. 7 
Bates loam. 
7 * 56 
1.9 
Rice and Osugi (39) found that the suspensions of many soils would 
invert cane sugar, while the extracts of such soils had little or no power. 
Soils containing calcium in equilibrium with HC 0 3 and C0 2 have an alka¬ 
line reaction {23). 
In some cases, in connection with experiments reported in this paper, 
titrations were made on the water extracts used for the electrometric 
measurements. In such cases the hydrogen removed the C 0 2 , and one 
drop of the 0.05N NaOH would produce a color with the indicator. This 
means that the titrable acidity of the extracts in Table I was due to 
carbonic acid. The maximum error of titration in any experiment due 
to the presence of C 0 2 was therefore small, and when the C 0 2 was removed 
by boiling or by bubbling hydrogen it was nil. The slowness of attaining 
equilibrium when CaC 0 3 was present was evidently due to the slow decom¬ 
position of this substance under the conditions of the experiment. 
EXPERIMENT 2 .—SOIL + WATER + POTASSIUM CHLORID 
The same soils were used as in Experiment 1, but in making the sus¬ 
pensions and the extracts enough of a 3N KC 1 solution was added to 
make the liquid in contact with the soil 0.5N KC 1 . Preliminary experi¬ 
ments showed that it made no material difference at what point in the 
preparation that KC 1 was added. In all of the experiments where this 
salt was used the amount was such as to make the concentration 0.5N. 
The results obtained are presented in Table II. 
Table II. — Ph on suspensions and extracts of soils made with a solution of KCl and 
the calcium content of the extract 
Soil type. 
Suspensions. 
Extracts. 
Calcium in 
extract. 
Neosho silt loam. 
Pa 
5-83 
5. 02 
4.51 
6. 48 
Ph 
7. 29 
6. 61 
Mgm. 
8.0 
Oswego silt loam. 
14. 1 
Bates very fine sandy loam. 
4 - 95 
6.97 
7. 0 
Bates loam. 
21.5 
The presence of the neutral salt, KCl, increases the hydrogen-ion 
concentration both in the suspensions and in the extracts. This would 
indicate that the acid-forming substance is more soluble in a KCl solution 
than in water. Sharp and Hoagland (41) found that other neutral 
