PHYSICAL PROPERTIES OF HAWAII SOILS 
27 
Yoder, and has given good dispersion with some soils. The second 
method is being used rather extensively, especially by English work- 
ers, and is a part of the official pipette method. " The third method 
has been suggested by Bouyoucos (5, p. 32J), and consists of dis- 
persing the soil in a specially constructed cup having baffles in the 
form of copper wires on its wall to act as obstructions! The machine 
used in connection with this method was a drink mixer with a rate of 
10,000 revolutions per minute. 
In every case 50 grams of soil oven dried at 110° C. for 18 hours or 
longer was used. The chemical treatment in each case was the same — 
that is, 5 cubic centimeters of normal potassium hydroxide in about 
400 cubic centimeters of distilled water. 
After dispersing for the required length of time the soil suspension 
was poured into graduated cylinders 45 centimeters high by 6 centi- 
meters in diameter, and the volume was made up to 1,130 cubic 
centimeters with distilled water. At this concentration the hydrom- 
eter was graduated to read grams of solid matter in suspension. 
The suspension was then vigorously shaken for half a minute or so, 
the palm of the hand being used as a stopper. The cylinder Avas 
then immediately placed on the table, and the time was noted with a 
stop watch. The settling period was always 15 minutes, when the 
hydrometer reading was taken and the temperature correction made. 
Results are expressed as grams solid matter remaining in suspension 
per unit volume (1 liter) at the end of the settling period. Table 10 
gives the results of these determinations. The first column repre- 
sents the reading obtained when no mechanical means were used, the 
soil being simply shaken in the cylinder with the required amount 
of water (plus potassium hydroxide) for about half a minute and 
allowed to settle for the time prescribed. 
Table 10. — Degree of dispersion 
[Results expressed in grams per liter of solid matter in suspension] 
RUBBING IX MORTAR WITH RUBBER PESTLE 
Solid matter dispersed in — 
Soil No. 

minutes 
15 
minutes 
30 
minutes 
45 
minutes 
60 
minutes 
2 
6 
Grams 
7.4 
8.5 
5.7 
5.4 
0.2 
Grams 
20.2 
21.7 
11.5 
14.2 
23.7 
Grams 
21.3 
21.6 
13.2 
17.3 
28.1 
Grams 
24.9 
25.3 
14.4 
19.4 
30.9 
Grams 
27.3 
27.3 
37 
42 
48 
15.0 
20.5 
31.9 
USING END-OVER-END SHAKER 
Soil No. 
Solid matter dispersed in— 
hours 
6 hours 
12 hours 
18 hours 
24 hours 
2 
6 
37 
7.4 
8.5 
5.7 
5.4 
6.2 
30.5 
37.5 
19.0 
30.7 
38.7 
20.2 
33.1 
41.1 
21.1 
24.6 
38.1 
32.7 
41.7 
21.2 
42 
24. , 25. 7 
35.0 
25.2 
48 
38.7 
