26 
BULLETIN 1193, U. S. DEPARTMENT OF AGRICULTURE. 
certain amount of contamination was also more or less inevitable in 
treating 50 to 100 grams of soil with 100 to 200 liters of water, with- 
out special refinement in equipment. For the purposes of the com- 
parison in Table 8 it was assumed that the slight loss or gain of soil 
material applied to the soil as a whole, i. e., it was distributed among 
the soil separates in the proportions the separates were present in 
the soil. In calculating for Table 8 the quantities of dye, water, 
and ammonia that would be adsorbed by 1 gram of the combined 
soil separates a correction was applied on this assumption regarding 
the gain or loss in material during fractionation. 13 
Table 8. — Adsorption by the untreated soil and by the combined soil separates. 
Description of material . 
Cecil clay loam, soil: 
Untreated soil 
Combined soil separates 
Cecil clay loam, soil (duplicate determination): 
Untreated soil 
Combined soil separates 
Htmtington loam, soil: 
Untreated soil 
Combined soil separates 
Huntington loam, subsoil: 
Untreated soil 
Combined soil separates 
Sassafras silt loam, subsoil: 
Untreated soil 
Combined soil separates 
Sharkey clay soil: 
Untreated soil 
Combined soil separates 
Sharkey clay, soil (separation by supercentrifuge): 
Untreated soil 
Combined soil separates 
Vega Baja clay loam, soil (separation bv supercentri- 
fuge) 
U: 
ntreated soil 
Combined soil separates. 
Amount adsorbed by 
combined soil sep- 
Adsorption per gram of 
arates relative to 
material 
amount adsorbed by 
untreated soil taken 
as 100. 
Dye. 
H 2 0. 
NH 3 . 
Dye. 
HoO. 
NH 3 . 
Gram. 
Gram. 
Gram. 
0.0078 
0.0442 
0. 0034 
100 
100 
100 
.0090 
.0305 
.0029 
115 
69 
85 
. 0078 
.0442 
100 
100 
.0094 
.0359 
121 
81 
.0245 
.0533 
.0104 
100 
100 
100 
.0243 
.0487 
.0092 
99 
92 
88 
.0182 
.0792 
.00S3 
100 
100 
100 
.0191 
.0742 
.0066 
105 
94 
80 
.0276 
. 0668 
.0074 
100 
100 
100 
.0289 
. 0551 
.0063 
104 
96 
85 
.1997 
. 1755 
.0345 
100 
100 
100 
.2048 
.1742 
.0327 
103 
99 
95 
. 212S 
.1984 
. 0358 
100 
100 
100 
.1773 
.1683 
.0303 
83 
85 
85 
. 0369 
.1805 
.0147 
100 
100 
100 
.0378 
.1873 
. 0146 
102 
104 
99 
In most cases the quantities of dye, water, and ammonia, adsorbed 
by the combined separates appear to agree with the quantities of 
these substances adsorbed by the untreated soil as closely as could be 
expected, considering the accuracy of the adsorption methods 
employed. However, the relative figures for the adsorptions by the 
untreated soils and the combined separates disclose what seems to 
be a significant fact. The adsorption of dye by the combined 
separates in almost every case is slightly higher than that of the un- 
treated soil, while the adsorption of ammonia by the combined 
separates in every case is slightly or considerably less than that of 
the untreated soil. Adsorption of water by the combined separates 
in 7 of 8 cases is slightly less than that of the untreated soil. 
If these results are significant and not due to experimental error, 
they show that the procedure of separation has rendered the colloidal 
w For example: The Huntington soil separates totaled 96.2 per cent of the whole soil (see Table 4). The 
dye adsorption of 1 gram of the combined separates was thus taken as being the sum of 0.103X0.0949, 
0.219X0.0288, and 0.64X0.0114, divided by 0.962. 
