Exchange Properties of Allophanic Clays — Houng, IJehara, and Sherman 
509 
Kaolin . Sample obtained through McKesson 
and Robbins, Inc. 
Bentonite . Chiefly dioctahedral montmoril- 
lonite of uncertain origin, admixed with some 
quartz. 
Soils. Samples of four soil profiles were 
collected from the slopes of Mauna Kea, island 
of Hawaii. All of these profiles have developed 
from volcanic ash, but their mineralogies vary 
considerably with changes in climate. One of 
the soils was of the Hanipoe series (Latosolic 
Brown Forest), two were of the Waimea series, 
hereafter referred to as Waikii and Mahoelua 
(Reddish Prairie), and the fourth was of the 
Waikaloa series (Reddish Brown). The soils 
have been listed in decreasing order of weather- 
ing. The first three soils were composed chiefly 
of noncrystalline colloids; halloysite was the 
main clay mineral in the Waikaloa series. These 
soils were treated with hydrogen peroxide to 
remove organic matter, washed with water, air- 
dried, and sieved through a 60-mesh screen. 
All soils used in this study have been described 
in the Soil Survey of the Territory of Hawaii, 
1955. 
Clay fractions. The <l|x fractions of these 
soils were separated, air-dried, and ground to 
pass a 100-mesh sieve. 
Aluminum hydroxide A. Powder, obtained 
from Baker Chemical Company. X-ray diffrac- 
tion pattern showed this to be pure gibbsite. 
Aluminum hydroxide B. Precipitated from 
alkaline solution by carbon dioxide. Electrolytes 
were removed by prolonged dialysis and final 
removal was accomplished by electrodialysis. It 
was shown to be gibbsite. 
Aluminum hydroxide C. Precipitated from 
alkaline solution by hydrochloric acid at a pH 
of about 7, washed with water and acetone, and 
air-dried. It was noncrystalline. 
Aluminosilicate gels, A 1 , and A 2 . Mixed solu- 
tions of sodium silicate and sodium aluminate 
neutralized by carbon dioxide. The precipitate 
was washed free of electrolytes in Buchner 
funnels. 
Aluminosilicate gels, B lt B 2 , B s , and B /f . 
Mixed solutions of sodium silicate and sodium 
aluminate acidified to a pH of about 7 with 
hydrochloric acid. After standing overnight, 
they were washed in Buchner funnels until free 
of chloride ions. Acetone was used in the final 
washing. 
RESULTS AND DISCUSSION 
Clay Minerals and Allophanic Soils 
The results obtained on clay minerals and 
allophanic soils are shown in Figures 2 and 4. 
All leaching solutions were IN with respect to 
sodium ions, and it is fairly safe to take pH 
as the abscissa in lieu of log (M+)— log 
(H+). Without knowledge of the cation-ex- 
change capacities, the amounts of sodium ions 
held on the exchanger were plotted against the 
pH of the final leachates. 
As shown in Figure 2, the bentonite adsorbed 
the same amount of sodium ions regardless of 
the pH of leaching solutions. In comparing this 
curve with the theoretical curves shown in 
Fig. 2. Exchange curves of clay minerals and soil 
clays. C>. Bentonite; O? kaolin; (J , halloysite; ©. 
clay fraction from Waikii soil; ©, clay fraction from 
Mahoelua soil, and • , clay fraction from Waikaloa 
soil. 
