PHYSICAL PROPERTIES OF HAWAII SOILS 
25 
Anderson and Mattson (3, p. 36) show that a fairly constant 
relationship exists between the chemical composition and the prop- 
erties of colloids. These investigators plotted the silica-sesquioxide 
ratio against the heat of wetting of eight different inorganic soil 
colloids and obtained a fairly straight line relationship, proving that 
chemical composition affects physical properties. The water-vapor 
adsorption, which was also determined on these colloids, showed the 
existence of a rather strict parallelism between heat of wetting and 
water-vapor adsorption. The percentage of water vapor adsorbed by 
these colloids was very nearly the same numerically as the calories 
evolved per gram of colloid on wetting, indicating that heat-of- 
wetting data may be used in lieu of water-vapor adsorption. In 
magnitude they ranged from 17.5 to 5.3. 
Parks and Linebarger, as quoted by Alexander (i, p. £51) , show 
that appreciable heat of wetting is given by substances which are 
larger than colloidal dimensions. Silica, when wetted, gave the 
following heat of wetting at different dimensions : Particles of 0.1, 
0.02, 0.01, and 0.005 millimeter diameter gave 0.24, 0.89, 6.9, and 
13.8 calories, respectively, per gram of substance. This indicates that 
in the case of silica at least particles much larger than clay or colloidal 
dimensions give considerable water-vapor adsorption. It may be 
logically assumed that other substances behave similarly. 
Gore, as quoted by Alexander (i, p. 461) , showed that aluminum 
oxide, manganese oxide, and ferric oxide gave widely differing 
figures for heat evolved when wetted with water. The heat evolved 
by aluminum oxide was about ten times that of ferric oxide (1.16° 
and 0.12° C. rise, respectively). According to Wollny, as quoted by 
"Warington {35, p. 62), the rise in temperature when quartz sand, 
aluminum silicate, and hydrated ferric oxide were moistened with 
water was 0.1°, 0.83°, and 6.6°, respectively. 
In view of these facts, it is easy to see that difference in chemical 
composition of the various fine fractions of any one soil considerably 
affects their moisture-adsorption properties, especially where large 
differences are involved. 
To show that such large differences may exist, the silica-sesquioxide 
ratio was calculated for the different fractions of nine typical 
Hawaii soils. These figures are given in Table 9. 
Table 9.- 
-The SiOi/ FeiOz+AhOz (mol) ratio in the different fractions of some 
important Hawaii soil types 1 
Soil fractions 
Soil Xo. 
Clay 
Fine silt 
Silt 
Fine sand 
Coarse 
sand 
161 
1.25 
2.17 
1.97 
1.28 
1.03 
.G2 
.33 
1.59 
1.17 
1.32 
1.88 
2.00 
1.34 
.96 
1.41 
.63 
2.02 
.84 
0.07 
1.47 
1.68 
1.23 
.66 
1.67 
.51 
1.58 
.24 
0.07 
1.28 
2.54 
1. 18 
.85 
2.01 
.57 
1.67 
.22 
291 
1.04 
292 
2.31 
330 
1.12 
392 
.64 
42S 
1.78 
448 
1.13 
474 
547 
1.55 
.30 
1 These figures were calculated from the data published by McGeorge (24, p.8). 
