18 
oxids. Then, apparently the more soluble oxid, Mn 3 4 , is formed in 
greater amounts when the soil is heated to 250° C. 
LIME AND MAGNESIA. 
The two tables below show the effects of heat upon the solubility 
of lime and magnesia : 
Solubility of lime in water and fifth-normal nitric acid. 
[Calculated on basis of dry soiL] 
Soil No. 
Soluble in water (parts per million). 
Soluble in fifth-normal nitric acid (per 
cent). 
Air dry. 
Dried at 
100° C. 
Dried at 
250° C. 
Ignited. 
Air dry. 
Dried at 
100° C. 
Dried at 
250° C. 
Ignited. 
74 
176.8 
28.1 
224. 9 
112.6 
183.0 
296.9 
82.2 
26.5 
57.1 
184.4 
16.1 
59.2 
330.6 
44.2 
302.9 
86.9 
232.1 
133.3 
107.3 
98.5 
93.9 
1, 455. 6 
33.8 
67.1 
2,801.1 
64.3 
910.9 
242.3 
195.6 
363.0 
270.6 
330.5 
697.5 
1,509.3 
225.8 
763.6 
1,039.5 
38.1 
766.8 
207.1 
206.3 
261.9 
232.6 
332. 9 
547.7 
220.6 
106.1 
708.6 
2.312 
.026 
.448 
.147 
.378 
.344 
.159 
.174 
.388 
.466 
.056 
.248 
2.332 
.030 
.909 
.856 
.406 
.362 
.158 
.174 
.409 
.479 
.083 
.252 
2.131 
.024 
.511 
.986 
.318 
.330 
.124 
.167 
.329 
.395 
.056 
.226 
1.427 
.024 
.323 
.674 
.876 
.316 
.108 
.136 
.191 
.368 
.058 
.162 
L64 
9 
292 
290 
405 
416 
417 
406 
428 
426 
448 
Solubility of magnesia in water and fifth-normal nitric acid. 
[Calculated on basis of dry soil.] 
Soil No. 
Soluble in water (parts per 
million). 
Soluble in fifth-normal nitric acid (per 
cent). 
Air dry. 
Dried at 
100° C. 
Dried at 
250° C 
Ignited. 
Air dry. 
Dried at 
100° C. 
Dried at 
250° C. 
Ignited. 
74 
75.1 
50.2 
96.4 
83.4 
285.2 
209.7 
105.1 
67.5 
82.2 
152.6 
34.6 
57.8 
73.9 
42.2 
99.5 
91.1 
385.2 
130.9 
127.5 
126.6 
87.2 
366.8 
47.4 
77.8 
182.7 
60.2 
167.3 
136.7 
230.3 
151.6 
140.9 
189.8 
234.7 
268.4 
158.1 
297.9 
63.1 
44.2 
150.4 
130.5 
192.6 
147.0 
127.5 
157.1 
245.9 
134.2 
108.4 
303.3 
0.121 
.019 
.071 
.150 
.500 
.206 
.073 
.071 
.204 
.114 
.047 
.074 
0.123 
.020 
.066 
.359 
.522 
.204 
.062 
.073 
.226 
.107 
.040 
.064 
0.138 
.021 
.081 
.344 
.301 
.140 
.042 
.049 
.115 
.082 
.041 
.048 
0.096 
164 
.019 
3 
.049 
292 
.197 
290 
.283 
405 
.060 
416 
.046 
417 
.062 
406 
.098 
428 
.079 
426 
.044 
448 
.048 
The series of lime determinations shows that this constituent is 
most soluble in water in the soils which were heated to 250° C. 
and least soluble in the air-dried soils. This is true of every sample 
except one (No. 290), this latter being a peculiar adobe type of 
soil from the experiment station grounds. In dilute nitric acid it 
will be observed that lime is most soluble in those soils heated to 
100° C, and, unlike the water extractions, the least concentration 
is obtained from the ignited soils. Thus it is shown that the action 
of nitric acid in no way correlates with that of distilled water. How- 
ever, the results show the more highly organic soil to contain lime 
