Oct.20,1923 Soil Reaction in Relation to Calcium Adsorption 105 
The hydrogen-ion concentrations were greater than those in the 
previous experiment and were due, as shown by the titration figures, to 
the larger amount of free acid present. After the acid treatment this soil 
was more colloidal than the one the used in Experiment 14. The calcium 
adsorptive capacity was nearly the same in the two soils. The acid treat¬ 
ment may be considered a case of intense leaching. Under humid cli¬ 
matic conditions soils high in calcium will ultimately lose their calcium 
to such an extent that they are as much in need of calcium as some soils 
derived from acidic rocks. 
EXPERIMENT 16.—ACID TREATED SAND+CALCIUM HYDROXID 
Ordinary river sand was chosen for this experiment. It was first 
ground to an impalpable powder in a ball mill, then digested in HC 1 . 
Further treatment was similar to that of the two preceding experiments. 
The data obtained are given in Table XVI. 
Table XVI.— Ph of suspensions of acid-treated sand-\-Ca{OH ) 2 also titrations and 
calcium on the extract, and calcium adsorbed from Ca(OH) 2 
Calcium added. 
Suspension. 
0.05NHCI 
Calcium in 
extract. 
Calcium not 
adsorbed. 
Calcium ad¬ 
sorbed. 
Mgm. 
Ph- 
Cc. 
Mgm. 
Mgm. 
Mgm. 
2. 
7.76 
-o -3 
0.8 
0.8 
1.6 
4 . 
8. 03 
—. 1 
1.4 
1.4 
2.6 
6. 
8. 40 
.6 
1.9 
1.9 
4.1 
8. 
8. 50 
1. 6 
2-5 
2-5 
5-5 
8. 84 
2. 2 
3-7 
3-7 
8-3 
16. 
9-25 
3-9 
5-2 
5-2 
10. 8 
9-35 
4-7 
6-5 
6*5 
i 3-5 
As compared with soil, sand requires a much smaller amount of 
Ca(OH) 2 to produce a corresponding change in the hydrogen-ion concen¬ 
tration. Beyond the addition of 6 mgm. calcium the titration figures 
together with the P H values show that the greater part of the calcium 
in the extract was present as Ca(OH) 2 . A small part may have been 
present as CaCl 2 . While the amount of calcium adsorbed was much 
less than that obtained with soil, the ratio adsorbed to the amount 
added was large. Finely ground sand does adsorb calcium, and the 
ratio between the amount adsorbed and the amount added corresponds 
to the adsorption law. 
GROUP C.—INFLUENCE OF CALCIUM HYDROXID AND POTASSIUM CHLORID 
ON P H WHEN USED WITH FULLER’S EARTH, ALSO ON THE TITRATION 
AND THE CALCIUM CONTENT OF THE EXTRACTS 
EXPERIMENT 17.—PULLER’S EARTH-fCALCIUM HYDROXID 
The fuller’s earth used in this experiment was a white commercial 
product labeled “chemically pure.” It was treated like the soil in 
Experiment 5. The data based on 10 grams of material are given 
Table XVII. 
