PHYSICAL PROPERTIES OF HAWAII SOILS 
13 
the facts that they were lying near the border line of two or more 
classes and the experimental error involved or the inherent nature 
of the methods used caused these soils to be put in different classes. 
Furthermore, the rapid hydrometer method does not take into con- 
sideration the specific gravity of the soil. With soils like most of those 
of the United States this would introduce only small error, because the 
range there in the fluctuation of the specific gravity is small. How- 
ever, in the case of Hawaii soils, where the specific gravity might 
vary between 2.2 and 3.4, this variation introduces considerable 
error. As will be shown later (p. 40), in the case of the detailed 
hydrometer method where the factors of temperature and specific 
gravity have been given due consideration, the agreement between 
the two methods is very good. 
It is customary, especially with a large number of soil samples, to 
show diagrammatically the distribution of soils into the different 
soil classes on the basis of mechanical analysis, the equilateral tri- 
angle method being used for the purpose. Figure 6 shows graphi- 
cally the distribution of 71 soils into the principal soil classes, and 
their percentage composition of sand, silt, and clay. 
In order to obtain a better picture of the fine fraction of these 
soils, a mechanical analysis was made in which the silt fraction was 
divided into three groups. All particles below 0.002 millimeter equiv- 
alent diameter were considered as colloidal and were classed as such. 
This limit for colloids has been retained throughout the bulletin. 
Table 3 gives the detailed mechanical analysis, the classification 
obtained therefrom, the percentage of organic matter, and the soil 
reaction, expressed as pH values, of 21 Hawaii soils. 
Table 3. — Mechanical analysis, 1 percentage of organic matter, soil reaction 
expressed as pH, and classification of 21 Hawaii soils 
Mechanical subdivision 
Organic 
matter 
Reaction 
pH 
Soil No. 
Sand 
(0.02 
milli- 
meter) 
Silt (0.01 
to 0.02 
milli- 
meter) 
Fine silt 
(0.005 to 
0.01 milli- 
meter) 
Very fine 
silt (0.002 
to 0.005 
milli- 
meter) 
| 
Colloids 
(0.002 mil- 
limeter) 
Soil classes * 
2 
Per cent 
25.2 
15.7 
34.0 
55.0 
68.5 
69.5 
38.5 
45.5 
16.5 
54.0 
40.9 
34.0 
11.2 
55.7 
12.8 
16.2 
26.7 
42.2 
14.2 
28.2 
53.0 
Per cent 
8.0 
3.9 
12.5 
12.0 
8.0 
7.2 
10.1 
15.0 
6.9 
15.0 
9.1 
8.0 
14.7 
9.8 
9.2 
9.4 
18.9 
10.9 
8.4 
21.6 
6.9 
Per cent 
8.7 
6.4 
10.5 
7.0 
5.4 
2.5 
12.1 
12.0 
11.6 
9.0 
10.7 
8.7 
20.6 
6.0 
11.8 
10.9 
11.6 
7.6 
13.6 
8.6 
6.8 
Per cent 
5.8 
7.4 
16.0 
11.0 
8.6 
9.0 
15.4 
12.0 
15.6 
5.0 
16.2 
16.8 
23.4 
7.2 
18.2 
14.4 
7.7 
8.7 
14.9 
15.8 
5.2 
Per cent 
51.5 
66.6 
27.0 
15.0 
9.5 
11.8 
23.9 
15.5 
49.4 
17.0 
23.1 
32.5 
30.1 
21.3 
48.0 
49.1 
35.1 
30.6 
48.9 
25.8 
28.1 
Per cent 
3.94 
3.89 
18.52 
15.75 
25.52 
8.49 
13.36 
12.45 
8.15 
10.95 
11.56 
9.07 
6.67 
2.34 
7.10 
6.27 
5.09 
2. 32 
1.22 
7.70 
1.91 
8.23 
8.73 
4.80 
5.87 
5.77 
6.50 
6.55 
7.17 
7.40 
6.70 
6.36 
6.50 
5.97 
5.77 
4.75 
5.03 
7.42 
7.25 
7.77 
7.72 
7.74 
Clay. 
6 
Do. 
9 
Clay loam. 
12 
15 
17 
Sandy clay loam. 
Do. 
Sandy loam. 
21... 
Clay. 
23 
Do. 
31 
Do. 
33 
Do. 
37 
Do. 
42... 
Do. 
48..- 
Do. 
49 
Do. 
56 
Do. 
57. 
Do. 
65 - 
Do. 
66 
Do. 
69 
Do. 
76 
Do. 
77 
Sandy clay loam. 
1 Mechanical analysis by a modified pipette method. 
2 Soil classes according to specifications given by R. O. Davis and H. H. Bennett (75). 
