24 
The results herewith shown are not very consistent, but the average 
ndicates the maximum solubility of carbonic acid to be in the samples 
treated to 100° and 250° C, indicating that drying has the effect of 
increasing the amounts of bicarbonates in the soil and thus increasing 
the solubility of the bases with which carbonic acid combines. One' 
reason suggested in the above table for a decrease in water soluble 
constituents upon ignition is that ignition would cause a transforma- 
tion of the bicarbonates into normal carbonates, therefore temporarily 
reducing their solubility in water. 
At the beginning of this work . some determinations of titanium 
were made, but these were not carried through the series. This 
element was not present in the water extract in large enough quantities 
to be determined. In the dilute nitric acid extracts it was present in 
very small amounts in the samples dried, in air and at 100° C, but in 
much larger quantities in the extracts from samples heated to 250° C. 
and ignition, the maximum solubility being obtained upon the ignited, 
samples. 
EFFECT OF HEAT UPON RICE AND TARO SOILS. 
In the following table is shown the effect of heat upon the soils used 
in aquatic agriculture, comparing this with the solubility of the 
elements in the wet and soggy condition: 
Effect of heat upon soils used in aquatic agriculture. 
[Parts per million of dry soil water extract.] 
Condition of 
sample. 
Silica 
(Si0 2 ). 
Alu- 
mina 
(A1 2 3 ). 
Iron 
oxid 
(Fe 2 3 ). 
Manga- 
nese 
oxid 
(Mn 3 0<). 
Lime 
(CaO). 
Mag- 
nesia 
(MgO). 
Potash 
(K 2 0). 
Phos- 
phoric 
acid 
(P2O5). 
Sul- 
phuric 
acid 
(S0 3 ). 
Bicar- 
bonates 
(HCO3). 
Rice soil, No. 405: 
Wet 
6.9 
2.3 
.6.9 
5.7 
16.1 
36.6 
4.6 
4.5 
31.2 
33.5 
5.6 
7.6 
13.8 
17.6 
12.2 
62.4 
10.3 
19.6 
28.5 
38.0 
12.2 
6.4 
9.2 
■ 5.4 
5.1 
86.1 
4.6 
2.7 
4.0 
2.1 
64.7 
5.9 
10.3 
14.9 
18.4 
34.4 
9.1 
4.4 
6.0 
9.6 
664.8 
296.9 
133.3 
363.0 
261.9 
318.6 
57.1 
93.9 
697.5 
547.7 
458.7 
209.7 
130.9 
151.6 
147.0 
310.0 
82.2 
87.2 
234.7 
245.9 
111.9 
96.6 
55.1 
45.9 
43.6 
31.8 
36.5 
49.2 
19.4 
78.2 
43.7 
27.1 
31.0 
33.0 
25.3 
38.7 
23.4 
35.7 
21.2 
23.4 
153.9 
129.6 
149.3 
942.0 
583.6 
137.8 
260.3 
326.4 
1,555.9 
1,479.9 
328 9 
Air dry 
Dried at 100° 
c 
161.4 
297.5 
Dried at 250° 
c 
157.3 
Ignited 
Tarosoil,No. 406: 
Wet 
174.6 
294.9 
Air dry 
Dried at 100° 
c 
52.5 
136.4 
Dried at 250° 
c 
68.2 
Ignited 
118.5 
When the types of soil were chosen for use in this series, two were 
selected with a view to obtaining some information upon the soils 
in use for rice and taro culture. It would be expected that heat and 
its accompanying oxidation would have a marked effect upon this 
type of soil for the reason that for the most part it exists in a reduc- 
ing environment. The above table shows solubility in water only. 
The samples were taken from the field in wet condition and extrac- 
tions were made upon weighed samples immediately upon receipt 
in the laboratory, the moisture content in this state being about 
