THE CHEMICAL COMPOSITION OF SOIL COLLOIDS 
11 
CHEMICAL COMPOSITION 
Chemical analyses were made of the samples of soils just described, 
and these analyses are given in Table 2. 
The method of analysis is that sketched in a previous publication 
(Robinson, 3Jf). It is the sodium carbonate fusion method es- 
sentially as outlined by Hillebrand (23). 
The figures o-iven for phosphoric acid and manganese are averages 
of duplicates ; the same is true for the sulphur, chlorine, and or- 
ganic matter in about one-third of the cases. All unusual results 
were repeated, and if the summation was between 99.50 and 101 
per cent it was considered satisfactory. This somewhat higher 
limit than the usual 100.75 per cent was taken, because in many 
seemingly good analyses of soils and of colloids high in organic 
matter, iron, and aluminum, the totals run high. This is probably 
due to a partial reduction of the ferric oxide during ignition and in 
some measure to the presence of ferrous iron in the soil. 
Table 
-Chemical composition of soils from which colloids were extracted 
No. 
Soil type 
Carrington loam, Iowa 
Carrington loam, Iowa 
Cecil clay loam, Maryland 
Cecil clay loam, Georgia 
Cecil clay loam, Georgia 
Chester loam, Virginia 
Chester loam, Maryland 
Chester loam. Maryland 
Clarksville silt loam, Kentucky.. 
Clarksville silt loam, Kentucky.. 
Hagerstown loam, Maryland 
Hagersfown loam, Maryland 
Houston black clay, Texas 
Huntington loam, Alaryland 
Huntington loam, Maryland 
Lufkin clay, Mississippi 
Manor loam, Maryland 
Manor loam, Maryland 
Marshall silt loam, Nebraska 
Marshall silt loam, Nebraska 
Miami silty clay loam, Indiana.. 
Miami silty clay loam, Indiana.. 
Norfolk fine sandy loam, North 
C ar olina 
Norfolk fine sandy loam, North 
C ar olina 
Ontario loam, New York 
Ontario loam, New York 
Orangeburg fine sandy loam, 
Mississippi 
Orangeburg fine sandy loam, 
Mississippi 
Sassafras silt loam, Maryland 
Sassafras silt loam, Maryland 
Stockton clay adobe, California.. 
Stockton clay adobe, California.. 
Susquehanna clay, Mississippi. _ 
Vega Baja clay loam, Porto Rico. 
Wabash silt loam, Nebraska 
Wabash silt loam, Nebraska 
Depth Si0 2 
- 7" 
- 9" 
-18" 
-32" 
-10" 
-36" 
-8"j 
-30" I 
i 1 ! 
-30" [ 
-36" | 
-20"! 
-14"! 
-18"! 
-10"| 
-24" 
P.ct. 
77.28 
82.22 
50.59 
83.81 
75. 68, 
77.53 
84.37 
74.73 
81.85 
77.66 
82.73 
72.29 
58. 29 
72.62 
72.12 
75.93 
71.94 
67. 69 
72.06 
70.22 
77.79 
60.36 
T1O2 
0"- 8" 90. 34 
12"-36'' 
0"-12" 
12"-22'' 
0"-10" 
10"-36' ; 
0"- 8" 
8"-22" 
0"-38" 
38"-50" 
4"-36" 
0"-12" 
0"-15" 
15"-36" 
85 
74.92 
73. 45 
87.61 
82.88 
75. 45 
63.52 
62.46 
62.07 
51.32 
72.37 
73.24 
AI2O3 
P.ct. 
0.53 
.40 
.39 
.80 
.87 
1.17 
1.37 
.92 
.63 
.63 
.79 
.78 
1.20' 
1.07 
.55 
.55] 
.67 
.71 
.91 
.82! 
Fe2 0s 
P.ct. 
8.93 
8.78J 
18. 67 
7.70 1 
12. 95 
9.62 
6.971 
13. 43 
7.35 
10. 03 
7.30 
12. 86l 
12. 70j 
11.85 
13.32! 
12.08 
14.68 
17.25 
11.18 
12.91 
9.74 
18. 24 
P.ct 
2.89 
2.54 
13.82 
2.97 
4.21 
4.21 
2.28 
4.45 
2.79 
3.83 
3.03 
. 94 2. 89 
1. 06 7. 62 
.72 10.47 
.71 10.81 
.50: 2.57 
.52 
1.09 
1.05 
1.21 
MnO 
2.67 
3.48 
6.19 
P.ct. 
0.056 
.016 
.080 
.204 
.165 
.1 
.049 
.085 
.150 
.129 
.142 
.040 
( 3 ) 
.185 
.139 
.023 
.212 
.075 
.050 
.100 
.075 
.060 
.001 
.005 
.094 
.052 
.93] .641 
6.30 
7.49 
11.89 
14.341 
15. 861 
18. 45i 
1.16 22.92! 11.71| 
.58 12.23 3.35 
.62 11.89 3.58i 
1.00 
2.41! 
2.25 
4.45 
7.98 
7.09 
8.42 
.043 
.030 
.159 
.097 
.013 
( 3 ) 
.107 
.079 
CaO 
MgO 
P.ct. 
P.ct. 
0.84 
0.56 
.86 
.55 
4.55 
3.55 
.28 
.15 
.43 
.14 
.07 
.49 
.37 
.32 
.33 
.4] 
.29 
.23 
.38 
.55 
.46 
.79 
.48 
.81 
7.77 
2.08 
.47 
. 72 
.45 
.69 
.52 
.83 
.36 
.89 
.25 
1.22 
.90 
.66 
1.03 
1.12 
.61 
.62 
1.69 
2.01 
.10 
.08 
.31 
.07 
1.23 
.98 
1.22 
1.33 
.16 
.06 
.26 
.14 
.41 
.36 
.40 
.55 
2.34 
1.81 
2.46 
2.84 
.37 
.67 
.30 
.15 
1.07 
.93 
1.06 
.92 
K20 
P.ct. 
1.35 
. 16 
1.55 
2.04 
1.55 
1.36 
1.82 
1.52 
2.84 
( 3 ) 
Na 2 
2.85 
.40 
1.25 
1.40 
.45 
.37 
1.87 
2.06 
.78 
1.24 
.76 
( 3 ) 
2.35 
2.38 
P.ct. 
1.15 
1.25 
.11 
.43 
.24 
.19 
.74 
.22 
.95 
1.04 
.36 
.45 
( 3 ) 
.93 
.54 
.73 
.40 
.75 
1.02 
1.14 
1.09 
1.11 
.04 
.21 
2.15 
2.31 
.15 
.35 
.90 
1.09 
1.68 
2.51 
.02 
( 3 ) 
1.20 
1.14. 
3 Not determined. 
