PHYSICAL PROPERTIES OF HAWAII SOILS 
39 
The temperature of the outside — that is, the room — was very nearly 
that of the thermostat. The glass cylinder used for the modified 
pipette method was 45 centimeters in height, 6 centimeters in diam- 
eter, and had a 1,000 cubic centimeter capacity. At the 100-milli- 
meter depth a glass stopcock one-fourth inch in diameter was fitted 
into a circular opening extending into the interior of the cylinder 
about one-sixteenth of an inch. Sampling was done through this 
stopcock instead of a pipette to avoid cumbersome operations in the 
thermostat. 4 At the time of sampling the first 10 drops of suspen- 
sion in the stopcock were discarded. Only four samplings were 
taken to give the colloidal, very fine silt, fine silt, and silt fractions. 
The sand fraction was obtained by difference. The results are sum 
marized in Table 17. 
Table 17. — Comparison of the rapid hydrometer method and the pipette method 
of mechanical soil analysis 
Soil No. 
2--. 
6 
9 
12 
15— 
17... 
21 
23 
31 
33. 
37 
42- 
48 
49 
56 
57 
65 
66- - 
69 
76 
77 
Average 
Mechanical analysis by 
hydrometer 
Mechanical analysis by pipette method 
Colloids 
Per cent 
61. 
80 
30 
23 
25 
19 
44 
38 
72 
30 
48.3 
Silt 
Per cent 
17 
13 
40 
16 
17 
21 
24 
30 
17 
33 
17 
17 
31 
22 
21 
21 
31 
20 
10 
26 
22 
22. 
Sand 
Colloids 
<(0.002 
milli- 
meter) 
Per cent Per 
.22 
I 7 
30 
61 
58 
60 
32 
32 
11 
37 
44 
30 
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 
29.5 
31.4 
Very fine 
silt (0.002 
to 0.005 
milli- 
meter) 
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 
12.1 
Fine silt 
(0.005 to 
O.Olmilli 
meter) 
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 
Silt (0.01 
to 0.02 
milli- 
meter) 
Per cent 
8.8 
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 
10.8 
Sand 
>(0.02 
milli- 
meter) 
Per cent 
25.2 
1.-,. 7 
34.0 
55. 
68. 5 
89. 5 
58. 5 
45.5 
16.5 
54.0 
40.9 
34.0 
11.2 
56. 7 
12.8 
16.2 
26. 7 
42.2 
14.2 
28.2 
53.0 
36.1 
Table 17 shows a fair agreement between the tAvo methods. Tak- 
ing the over-all averages it is seen that the colloids indicated by 
the hydrometer method included all the very fine silt fraction and 
half the fine silt fraction of the pipette method. Since the sand 
fraction was obtained in both instances by subtraction, it is not 
strictly comparable, yet the disparity exhibited is not great. 
The detailed hydrometer method was also compared with the 
pipette method. Only the colloidal and the three silt fractions were 
determined, the sand fraction having been obtained by subtraction. 
The data obtained are given in Table 18. 
* This method of sampling was checked against the original method of sampling by 
means of a pipette, and the agreement between them was found to be so close as to permit 
duplicating the results with considerable accuracy. 
