28 
BULLETIN 1193, TJ. S. DEPARTMENT OF AGRICULTURE. 
calculations that the slight losses, or gains, in material taking place 
during fractionation were from the soil as a whole, and the adsorptions 
of the untreated soil given in Table 4 were decreased or increased 
from the observed values to allow for these losses or gains. 
Table 9. — Influence of extraction on the adsorptive capacity of the colloidal material. 
Soil from which colloid 
obtained. 
Cecil clay loam, soil 
Cecil clay loam, soil (dupli- 
cate determination) 
Huntington loam, soil 
Huntington loam, subsoil 
Sassafras silt loam, subsoil. . . 
Sharkey clay, soil 
Sharkey clay, soil (separa- 
tion by supercentnfuge). . . 
Vega Baja clay loam, soil 
(separation by supercentri- 
fuge) 
Gram of dye 
adsorbed 
per gram of 
extractable 
colloidal 
material. 
Gram of H ; 
adsorbed 
per gram of 
extractable 
colloidal 
material. 
Gram of Nft, 
adsorbed 
per gram of 
extractable 
colloidal 
material. 
When When | When When | When 
colloid colloid : colloid colloid colloid 
in I ex- I in ex- in 
soil, tracted.! soil, tracted. soil. 
0.0712 0.0840 I 0.3913 
,0806 I 
.0961 
, 0850 
. 1306 
0501 
091 S 
, 139S 
3790 
3592 
0530 
.3700 
.2621 
.3353 
. 2868 
.2986 
.4014 
2749 
0. 2439 
0. 0214 
. 2834 
! 2221 . 0379 
. 2996 . 0346 
.2732 .0368 
. 2956 . 0561 
When 
colloid 
ex- 
tracted 
0. 0165 
0270 
0226 
0293 
0516 
.3037 .0691 | .0514 
.2989 I .0193 .0188 
Adsorption by colloid 
when extracted di- 
vided by adsorption 
by colloid when in 
soil. 
NH 8 
Dye. 
HO. 
1.18 
0.62 
1.21 
.77 
.99 
.85 
1.08 
.89 
1.07 
.95 
1.03 
.99 
.76 
.76 
1.06 
1.09 
0.77 
The numbers in columns 8 to 10 show the extent to which the 
adsorptive capacity of the extractable colloid has probably been 
altered by the process of extracting it from the soil. These altera- 
tions, calculated on the assumption that the unextracted colloidal 
material is unaffected by the extraction process, are somewhat greater 
than the values given in Table 8, columns 5 to 7, which were calcu- 
lated on the assumption that the unextracted material was altered 
as well as the extracted. The same general conclusions, however, 
are to be drawn from these calculations as from those given in the 
previous table. In practically all cases the process of extraction ap- 
pears to have rendered the colloidal material slightly more adsorptive 
of dye, slightly less adsorptive of water, and considerably less ad- 
sorptive of ammonia. 
It is conceivable that apparently unimportant variations in the 
process of extracting the colloidal material, such as in the volume of 
water used, might affect the adsorptive capacity of the extracted col- 
loid. However, this should not affect the calculated values for the 
adsorptive capacity of the colloid when in the soil. As a matter 
of fact, the calculated values for the adsorptive capacity of colloid 
"when in the soil" show a fair agreement in the case of the two 
samples of Cecil soil. In the case of the two samples of Sharkey soil 
the calculated values for the adsorptive capacities of the colloids when 
in the soil should not agree, since the two colloids are different. The 
colloidal material of the first sample of Sharkey soil given in the table 
contains particles up to 1 micron in diameter and the colloidal mate- 
rial of the second sample contains only particles that would pass 
through the supercentrifuge, i. e., particles up to probably 0.3 micron 
in diameter. As might be expected, the second sample with the 
smaller particles shows the higher adsorptive capacity. 
