28 
BULLETIN 6 2, HAWAII EXPERIMENT STATION 
Table 10. — Degree of dispersion — Continued 
USING ELECTRICAL STIRRER 
Solid matter dispersed in— 
Soil No. 

minutes 
9 
minutes 
15 
minutes 
30 
minutes 
45 
minutes 
60 
minutes 
75 
minutes 
2 
7.4 
8.5 
5.7 
5.4 
6.2 
2S.4 
38.2 
17.3 
21.1 
32.3 
30.7 
40.1 
19.4 
25.9 
34.9 
32.6 
41.1 
22.8 
28.0 
37.1 
33.5 
42.1 
24.1 
28.6 
38.9 
33.9 
42.3 
26.2 
30.0 
39.7 
34.0 
« 
42.9 
37 
26.1 
42 
30.2 
48 
39.7 
The method of dispersing with an electrical stirrer is thus seen 
to be far superior to the methods of rubbing in mortar or shaking 
in an end-over-end shaker. Dispersing in an electrical stirrer for 
45 minutes was found to be equivalent in efficiency to shaking in an 
end-over-end shaker for 24 hours. Rubbing in a mortar gave the 
least efficient dispersion of the three methods studied. In subsequent 
work, therefore, the electrical stirrer was used. The figures also 
show that maximum dispersion was obtained by this method after 
stirring for 60 minutes. The relative efficiency of these various 
devices is shown graphically in Figure 10, which gives in addition 
to the individual dispersion curves, a composite average curve. 
CHEMICAL ASPECT 
Various chemicals tried, supplying a hydroxyl ion to stabilize the 
dispersed colloidal particles, included ammonia (1 per cent solution) 
potassium hydroxide and sodium hydroxide (5 cubic centimeters 
normal solution per liter of suspension), and sodium carbonate 
(0.2 per cent). Table 11 gives the magnitude of dispersion obtained 
with the aid of these deflocculents. The mechanical means employed 
was always the same, that is, stirring in an electrical stirrer for 60 
minutes. This method gave the maximum dispersion in the first 
part of the study. Bouyoucos' hydrometer was used to determine 
the degree of dispersion in the same manner as described in the 
foregoing. 
Table 11. — Effect of various chemical treatments on the degree of dispersion 
[Results expressed in grams per liter of solid matter in suspension after 15 minutes] 
Soil No. 
Solid matter in suspension when using — 
H 2 
NH 4 OH 
KOH 
NaOH 
Na 2 C0 3 
2 
Grams 
34.0 
43.7 
10.4 
25.6 
38.8 
Grams 
27.9 
37.2 
25.6 
28.3 
38.4 
Grams 
34.0 
42.5 
26.0 
30.0 
39.5 
Grams 
36.4 
44.9 
28.6 
32.8 
41.3 
Grams 
38.5 
6 
45.1 
37 
31.7 
42 
34.4 
48 
42.3 
