PHYSICAL PROPERTIES OF HAWAII SOILS 31 
Table 12 shows that increase in concentration of hydroxyl ions 
does not increase the degree of dispersion. Charlton (12, p. 9) ob- 
served similar phenomenon, noting that " increasing the concentra- 
tion of ammonia does not increase the dispersion of clay." 
The use of hydrogen peroxide is recommended by some investi- 
gators to oxidize the organic matter present, which has a flocculating 
effect on the fine material. The use of hydrochloric acid is also 
advocated to remove certain bases, such as calcium, which has a sim- 
ilar effect. Fifth-normal and twentieth-normal hydrochloric acid 
have been used by various workers to remove calcium. The objec- 
tion to the use of stronger concentration has been repeatedly raised, 
due to the solvent effect of the acid upon the iron and aluminum 
compounds. 
In order to learn whether the organic matter present interfered 
with the work of obtaining perfect dispersion, in view of the large 
amount of humus contained in many Hawaii soils, the degree of 
dispersion was determined after the organic matter had been treated 
with superoxol (30 per cent solution of hydrogen peroxide). The 
flocculating effect of calcium in the dispersion was also determined 
by removing the calcium with cold hydrochloric acid. The two 
concentrations" of acid used were fifth normal and twentieth normal. 
The soils were treated as follows : Fifty grams of oven-dried soil 
was placed in a 400 cubic centimeter beaker. About 40 cubic centi- 
meters of superoxol was added and thoroughly mixed with the soil. 
The mixture was then heated in a sand bath on an electrical hot 
plate and kept there until the evolution of oxygen was no longer 
noticeable. During heating, the beaker was covered with a watch 
glass to prevent loss by spattering. After the mixture cooled, 250 
cubic centimeters of acid solution was added, and the whole was 
stirred and allowed to stand overnight. During the day the mix- 
ture was stirred several times. The following morning the mixture 
was poured into a porous filtering dish, and the acid was removed 
by suction. The filtrate was tested for calcium with ammonium 
oxalate solution. The soil was repeatedly leached with the acid 
solution until the filtrate gave no test for calcium. Thereupon the 
excess acid was removed by washing with distilled water until the 
filtrate gave no test for chlorides. The soil was then transferred 
to a dispersing cup, the alkali solution was added, and the soil was 
dispersed for one hour. After the usual settling period, the degree 
of dispersion was read by means of the hydrometer. 
Table 13 shows the effect of the treatment with hydrogen peroxide 
and the removal of calcium by hydrochloric acid upon the degree of 
dispersion. Column 2 gives the degree of dispersion when neither 
the organic matter was affected nor the calcium removed, and the 
soil was dispersed with the aid of potassium hydroxide alone. 
Column 3 gives the dispersion with treatment by hydrogen peroxide 
but without removal of the calcium. Columns 4 and 5 give the dis- 
persion with the calcium removed by fifth-normal and twentieth- 
normal hydrochloric acid, respectively, but without the hydrogen 
peroxide treatment prior to the acid treatment. Column 6 shows 
the degree of dispersion after both hydrogen peroxide and acid 
treatments. Column 7 shows the percentage loss due to superoxol 
treatment of the soil. 
