ESTIMATION OF COLLOIDAL MATERIAL TN SOILS. 
21 
contained, as near as could be judged by observation, very few 
particles larger than 0.3 micron. Hence the difference between the 
colloidal material obtained in previous extractions and that obtained 
in this separation consisted in the fact that in the first case the upper 
limit of size of particles was in the neighborhood of 0.3 micron while 
in the latter case the upper limit of size was 1 micron. 
The finer and coarser soil particles above colloidal size were col- 
lected in separate fractions as in the previous separation, but in this 
separation a quantitative recovery of these fractions was attempted. 
The samples of soil fractionated in this way consisted of 50 grams of 
Sharkey soil and 100 grams each of Cecil soil, Huntington soil, 
Huntington subsoil and Sassafras subsoil. 
Table 4 shows the quantities of colloidal, fine and coarse materials 
separated from each soil, together with the adsorptive capacities of 
these materials and of the unfractionated soils. Included in this 
table, also, are the results obtained with two samples of soil — the 
Vega Baja soil and a second sample of Sharkey soil — which were 
fractionated according to the method described on pages 16 to 17; 
that is. the colloidal material was graded by the supercentrifuge, so 
the upper limit of the particles was about 0.3 micron instead of 1 
micron. 10 
Table 4. — Adsorptive capacities of soils and soil fractions. 
Description 
of soil fractions. 
Part 
of whole 
soil. 
Adsorption per gram 
of material. 
,. 
Dye. 
H 2 0. 
NH3. 
Cecil clay loam, soil: 
Whole soil 
Per cent. 
100.0 
9.4 
7.6 
83.8 
100.0 
9.4 
10.4 
78.3 
100.0 
10.3 
21.9 
64.0 
100.0 
13.3 
19.4 
63.3 
100.0 
14.4 
20.6 
61.9 
100.0 
42.4 
53.1 
100.0 
31.5 
38.9 
31.8 
100.0 
30.5 
38.6 
31.8 
■ Gram. 
0.0078 
.0840 
.0154 
.0000 
.0078 
.0975 
.0007 
.0000 
.0245 
.0949 
.0288 
.0114 
.0182 
.0918 
.0143 
.0053 
.0276 
.1398 
.0222 
.0053 
.1997 
.3790 
.0657 
.2128 
.3592 
.1075 
.0825 
.0369 ! 
.0530 
.0492 
.0094 
Gram. 
0.0442 
.2439 
.0714 
.0028 
.0442 
.2834 
.0509 
.0042 
.0533 
.2221 
.0476 
.0215 
.0792 
.2996 
.0665 
.0292 
.0568 
.2732 
.0546 
.0041 
. 1755 
.2956 
.0772 
.1984 
.3037 
.1280 
.0834 
.1805 
. 2974 
.2332 | 
.0260 
Gram. 
0.0034 
Colloid 
Fine fraction 
.0165 
.0076 
Coarse fraction 
Cecil clay loam, soil (duplicat 
Whole soil 
e determination): 
.0010 
Colloid 
Fine fraction 
Huntington loam, soil: 
Whole soil 
Colloid 
Fine fraction 
.0104 
.0270 
.0098 
Coarse fraction 
Huntington loam, subsoil: 
Whole soil 
.0062 
.0083 
Colloid 
Fine fraction 
.0226 
.0072 
Coarse fraction 
.0031 
Sassafras silt loam, subsoil: 
Whole soil 
.0074 
Colloid 
Fine fraction 
.0293 
.0079 
Coarse fraction 
Sharkey clay, soil: 
Whole soil 
Colloid 
Fine fraction 
.0004 
.0345 
.0520 
.0172 
Sharkey clay, soil (separation 
Whole soil 
by supercentrifuge): 
.0358 
Colloid 
.0514 
Fine fraction 
.0244 
Coarse fraction 
.0168 
Vega Baja clav loam, soil (separation by supercentrifuge): 
Whole soil 
C oil oi d 
Fine fraction 
.0147 
.01S7 
.0196 
Coarse fraction 
.0044 
10 In the case of the Sharkey soil absolutely all the extractable colloidal material was not isolated, sine* 
the fractionation was undertaken chiefly for the study, to be described later, on the "alteration in adsorp- 
tive capacity of the colloid produced by extraction."" 
57580—2 
