32 
BULLETIN 6 2, HAWAII EXPEKIMEXT STATION 
Table 13. — Effect of hydrogen peroxide (superoxol) and hydrochloric acid upon 
dispersion as compared icith dispersion by the use of KOH alone 
[Results expressed in grams per liter solid matter in suspension after 15 minutes] 
Solid matter in suspension after treatment with— 
Loss 
due to 
superoxol 
treatment 
Soil No. 
KOH 
alone 
Superoxol 
plus 
KOHi 
N/5 HC1 
plus 
KOH 
N/20HC1 
plus 
KOH 
Superoxol 
plus N/20 
II CI plus 
KOH i 
Grams 
34.0 
42.5 
26.0 
30.0 
39.5 
Grams 
32.7 
43.3 
26.1 
30.4 
41.2 
Grams 
31. 9 
44.6 
30.4 
33.1 
41.1 
Grams 
35.6 
44.0 
30.4 
33.6 
41.1 
Grams 
35.7 
44.8 
30.7 
34.2 
42.5 
Per cent 
0.43 
6 
1.52 
37 
3.39 
42 
3.46 
48 
2.00 
1 Figures were corrected for loss due to superoxol treatment, assuming that all the loss was borne by the 
fraction that stayed in suspension after the settling period. 
In a study of Table 13, several points are noteworthy : 
Treatment with hydrogen peroxide solution apparently does not 
increase the degree of dispersion even in the case of soils containing 
from 9 to 11 per cent organic matter. A special determination of 
the effect of superoxol on a highly organic soil was made to supple- 
ment this table. Soil No. 9, containing 18.5 per cent organic matter, 
was treated in the manner described, and the dispersion was deter- 
mined. In this case the soil treated with hydrogen peroxide gave a 
dispersion of 30.5 per cent as compared with 29.5 per cent without 
the treatment. According to these findings, the treatment of organic 
matter with hydrogen peroxide is not necessary except, perhaps, in 
soils containing upward of 15 per cent organic matter. 
The use of acid to remove calcium is necessary to obtain maximum 
dispersion. On an average, 2.6 per cent more solid matter is kept 
in suspension in the case of acid-treated soils than in untreated soils 
after the dispersion has been completed. 
Twentieth-normal hydrochloric acid was just as effective in the 
removal of calcium as was the fifth normal. As a matter of fact, 
of 21 soils treated in this manner, only in one instance — soil No. 77 — 
was the twentieth-normal acid not sufficiently strong to remove all 
calcium. In this case fifth-normal acid was used. 
These results are in good agreement with those obtained by other 
investigators, notably Charlton (12, p. 9), and Puri and Amin 
(28, p. 15) , working with tropical lateritic clays in India. 
ESTIMATION OF COLLOIDS BY THE WATER- VAPOR ADSORPTION 
METHOD 
It has long been realized that certain soil properties are due largely, 
if not wholly, to the colloidal fraction of the soil. To such properties 
belong heat of wetting, base exchange, and adsorption. This fact 
suggests the possibility of estimating the amount of colloids by de- 
termining one of these properties in the soil and also in a representa- 
tive portion of the colloidal fraction of the soil that has been ex- 
tracted. The ratio of the two figures obtained would give the 
percentage of colloidal material in the soil. 
Several assumptions had to be made that such methods would yield 
even approximately correct figures: (1) It had to be assumed 'that 
the extracted colloid is representative of the whole colloidal complex 
