12 
Effect of the potassium sulphate solution upon the solubility of lime and magnesia in the 
soils. 
[Expressed in parts per million in the percolate.] 
Percolates of 100 cc. 
each. 
Lime. 
Magnesia. 
Soil 
No. 292. 
Soil 
No. 448. 
SoU 
No. 428. 
SoU 
No. 474. 
SoU 
No. 292. 
SoU 
No. 448. 
SoU 
No. 428. 
SoU 
No. 474. 
100 
104 
56 
66 
50 
68 
36 
26 
44 
28 
22 
20 
36 
24 
14 
40 
10 
24 
24 
24 
12 
8' 
514 
146 
150 
158 
164 
70 
48 
102 
70 
94 
72 
68 
32 
54 
24 
34 
32 
32 
26 
24 
26 
34 
28 
26 
18 
22 
22 
34 
82 
300 
46 
500 
40 
700 
38 
900 
38 
2,700 
24 
3,300 
34 
The data presented in the preceding tables throw considerable light 
upon the retaining power which Hawaiian soils possess for potash. 
In the absorption of potash the salts undergo a decomposition, the 
result of which is a replacement of calcium or magnesium by potassium. 
The two former elements combine with the acid constituent of the 
potash salt and pass off in the drainage water. It has been found 
that potassium sulphate is more firmly fixed than the chlorid. In 
general the reaction taking place is a replacement of the calcium in 
the zeolitic silicates, but humus and the iron and aluminum hydrates 
also fix potash to a certain extent. 
It may be seen from the above tables that the soil highest in lime 
and magnesia had the highest fixing power for potash, and the other 
three soils in proportion. This is in agreement with the findings 
of other investigators. Crawley * found that Hawaiian soils fixed 
potash quite firmly, but the fixation was not nearly so lasting as that 
of phosphoric acid. The results given herewith indicate this to be 
true and also the saturation point for potash to be far below that of 
phosphoric acid, even in the soils high in lime and magnesia. In the 
preceding table there are some very striking results showing the 
decrease in concentration of lime and magnesia in the filtrate, with 
decrease in amount of potash fixed by the soil. The fixation of this 
element in the soils highest in lime and magnesia is almost constant 
for the first liter of solution passing through the soil column. On the 
other hand, the fixing power of the other soils decreases more rapidly 
and they are more easily saturated, while the soil containing 8 per 
cent of magnesia had not reached a state of saturation at the close of 
the experiments. 
ABSORPTION OF NITROGEN. 
AMMONIUM SULPHATE. 
This series was carried out in a manner similar to the previous 
one — namely, 100 grams of soil was placed in glass tubes, with percola- 
tion at the rate of 100 cubic centimeters per 24 hours. The percolate 
1 Jour. Amer. Chem. Soc, 25 (1903), p. 47. 
