31 
nitric acid were used as solvents. One hundred grams of soil was 
shaken with 500 cubic centimeters of water for 1 week and 250 cubic 
centimeters used for analysis by the colorimetric method. Fifty 
grams of soil was shaken with 500 cubic centimeters of 1 per cent 
citric acid, and 20 grams of soil was digested and shaken with 200 
cubic centimeters of fifth-normal nitric acid at 40° C. for 5 hours. 
An analysis was made of 100 cubic centimeters of the nitric acid 
extract, from which no precipitate could be obtained with molybdate 
solution. Only a trace of phosphate could be detected by colorimetric 
determination in 50 cubic centimeters of this solution. The results 
obtained with water and citric acid are given in Table VIII. 
Table VIII. — Solubility of -phosphoric acid in the soils in pots of Experiment I. 
Pot Xos. 
Fertilizer added. 
Soluble 
in water. 
Soluble 
in citric 
acid. 
Parts per 
million. 
Per cent. 
4.8 
0. 00280 
4.8 
.00310 
4.4 
.00335 
8.0 
.00350 
3.8 
.00444 
9.4 
.00508 
7.4 
.00584 
5.4 
.00537 
4.6 
. 00537 
3.0 
.00814 
3.0 
.00663 
6.4 
.00612 
7.6 
.00795 
4.8 
.00558 
6.8 
.00493 
4.8 
.00698 
5.2 
.00652 
6.0 
. 00730 
6.0 
.00809 
4.0 
.00665 
3.4 
.00557 
3.4 
.00649 
3.4 
.00493 
2.6 
.00728 
2.8 
.00255 
3.0 
.00270 
3.4 
.00255 
3.2 
.00303 
2.2 
.00222 
2.6 
.00255 
2.8 
.00715 
2.8 
.00525 
4.0 
.00780 
3.2 
.00413 
5.4 
.00255 
3.2 
.00431 
2.4 
.0127.-. 
3.2 
.00828 
2.4 
.00619 
4.8 
.00716 
2.6 
.00619 
2.6 
.00652 
6.8 
.00731 
5.8 
.00717 
1.2 
5,6 
9,10 
13.14 
17.1- 
21.22 
25.2>3 
29.30 
33,34 
41.42 
45.46 
49.50 
53.54 
57.58 
61.02 
65.1 i 
69.70 
73.71 
77.7s 
81.-2 
89,90 
93.94 
97,98 
99,102.... 
105,106... 
109.110... 
113,111... 
117.11-... 
121.122... 
125.126... 
129.130... 
133.134... 
137.13-... 
141.142... 
145.146... 
149,150... 
153.154... 
157.15-... 
161.162... 
166 166... 
i::;.i74... 
K-Ca-L-Pi/2 (slag A) 
K-Ca-Pi/2 (slagA) 
K-Ca-L-P^ (slag B) 
K-Ca-Pj/2 (slag B) 
K-Ca-L-Pj/2 (slag C) 
K-Ca-Pi/ 2 (slag C) 
K-Ca-L-Pi/2 (slag D) 
K-Ca-Pi/2 (slagD) 
K-Ca-L-Px/2 (acid phosphate) . . . 
K-Ca-Pi/2 (acid phosphate) 
K-Ca-L-P i/j (phosphate rock) . . . 
K-Ca-Pi/2 (phosphate rock) 
K-Ca-L-Pi/2 (sodium phosphate) 
K-Ca-Pi/2 (sodium phosphate) . . . 
K-Ca-L-P! (slag A) 
K-Ca-Pi (slag A) 
K-Ca-L-P! (slag B 
K-Ca-Pi (slag B) 
K-Ca-L-Px (slag C) 
K-Ca-Pi (slag C) 
K-Ca-L-P! (slag D) 
K-Ca-Pi (slag D) 
K-Ca-L-P! (acid phosphate) 
K-Ca-Pi (acid phosphate) 
K-Ca-L-Pi (phosphate rock) 
K-Ca-Pi (phosphate rock). 
Pi (sodium phosphate) . 
K-Ca-L-I 
K-Ca-Pi (sodium phosphate). 
K-Cax-L-Pi (sodium phosphate) 
K-Cax-Pi (sodium phosphate) 
1/2-K1 1/2-Ca-Iy-Pi (sodium phosphate). 
1/2-K1 1/2-Ca-Pi (sodium phosphate) . . . 
K-Ca-L-Pi 1/2 (sodium phosphate) 
K-Ca-Pi 1/2 (sodium phosphate) . 
P2 (phosphate rock) 
K-Ca-L- 
K-Ca-P2 (phosphate rock) 
K-Ca-L-Pi/2 (superphosphate) 
K-Ca-Pi/2 (superphosphate) . . 
K-Ca-L-Pi (superphosphate).. 
K-Ca-Pi (superphosphate) 
Owing to the high fixing power of this type of soil, the analysis of 
the water extracts would not be expected to show any great varia- 
tion in solubility. Such proved to be the case, and it is probable 
