24 
BULLETIN" 1452, U. S. DEPARTMENT OF AGRICULTURE 
tion (column 3) was much less in each case than the adsorption of 
NH 3 from the gas, 18 although the two series of values stand in about 
the same order. There is of course no reason wiry there should be any 
fixed proportion between these two values, since the exact quantity of 
NH 3 adsorbed from NH 4 C1 or from ammonia gas is governed largely 
by the conditions of the determinations. 
If the adsorption of NH 3 from NH 4 C1 is primarily a chemical 
phenomenon and the adsorption of NH 3 gas is chiefly governed by 
the structure of the colloid, the relation between the two adsorptions 
might be taken as indicating that structure and chemical activity 
usually vary in the same direction in the soil colloids, the structure 
varying less widely than the chemical properties. 
Some investigators who worked with the whole soil apparently 
believed that all the monovalent and divalent bases in the colloidal 
material are replaceable. Others believed that calcium is replaced 
to a greater extent than the other bases. Quantitative data bearing 
on this question are given in Table 13. This table shows the total 
quantities of the monovalent and divalent bases in the colloid, the 
quantities removed by the NH 4 C1 solution, and the proportion of 
each base which was removed. 
Table 13. — Monovalent and divalent base* present in soil coHoids and quantities 
removed by normal NH^Cl solution 
CaO 
MgO 
K 2 
Na 3 
Kind of colloid 
Pres- 
ent in 
colloid 
Quan- 
tity 
re- 
moved 
Pro- 
por- 
tion of 
total 
re- 
moved 
Pres- 
ent in 
colloid 
Quan- 
tity 
re- 
moved 
Pro- 
por- 
tion of 
total 
re- 
moved 
Pres- 
ent in 
colloid 
Quan- 
tity 
re- 
moved 
Pro- 
por- 
tion of 
total 
re- 
moved 
Pres- 
ent in 
colloid 
Quan- 
tity 
re- 
moved 
Pro- 
por- 
tion of 
total 
re- 
moved 
Fallon 
Per ct. 
2.36 
1.48 
1.12 
.37 
.28 
.18 
Per ct. 
2.13 
1.33 
1.00 
.39 
17 
.13 
Per ct. 
90 
90 
89 
100 
61 
72 
Per ct. 
5.32 
2.54 
1.95 
1.37 
.46 
.39 
Per ct. 
0.34 
.36 
.29 
.13 
.06 
.06 
Per ct. 
6 
14 
15 
9 
13 
15 
Per ct. 
2.24 
1.86 
2.07 
1.04 
.55 
.92 
Perct. 
0.34 
.10 
.13 
.04 
Trace. 
.02 
Per ct. 
15 
5 
6 
4 
2 
Per ct. 
0.54 
.24 
.19 
.31 
.31 
.29 
Per ct. 
0.25 
.04 
Per ct. 
4.6 
Sharkey 
Marshall 
17 
Sass-frrtS 
Norfolk 
.05 
Trace. 
.02 
16 
Susquehanna... 
7 
None of the monovalent or divalent bases appear to be completely 
removable by NH 4 C1. However, there is a wide difference between 
the bases with regard to the proportion removable. Calcium is 
nearly all removed from most colloids, whereas only a small part of 
the magnesium, potassium, or sodium is attacked. The proportion 
of the total quantity of a base which is removable does not appear 
to be the same for the different colloids, nor does the absolute quan- 
tity of any base which is removable appear to be constant for all 
colloids, nor does the proportion of a base which is removable appear 
to vary with the total content of that base. 
The quantity of a base which is removable by a neutral salt solu- 
tion varies somewhat with the nature and concentration of the salt. 
18 In the case of the acid colloids — Norfolk, Sassafras, and Susquehanna — the differ- 
ence between NH 3 adsorbed from NILC1 and from NH :! gas is somewhat less than is 
shown in Table 12. Treatment of these colloids with NH 4 C1 doubtless exchanged some 
II or Fe and Al, besides the Ca, Ms, etc., from which the absorption of the NH 3 was 
calculated. Determinations of the Norfolk colloid, for instance, showed the adsorption 
of NH y from NH 4 C1 was approximately 0.0080 gram instead of 0.0015 gram. 
