8 BULLETIN 143, U. S. DEPARTMENT OE AGRICULTURE. 
Table IV. — Solubility of feldspar in water and in water saturated with C0 2 , as 
determined by various investigators. 
Investigator. 
Amount 
of feld- 
spar used. 
Amount 
of water 
used. 
Time of 
contact. 
Method of treatment. 
Amount 
of K 2 dis- 
solved from 
feldspar. 
Amount 
of K 2 in 
solutions. 
Grams. 
3,000 
2,000 
2 
2 
25 
25 
Grams. 
5,000 
(COs) 3,000 
1,000 
(COj) 1,000 
100 
100 
192 hours.. 
240 hours 
Triturated in re- 
volving cylinder. 
do 
Per cent. 
0.420 
.013 
.085 
.125 
» .100 
i 1.280 
P. p. m. 
2,520.0 
90.0 
Do 
Cameron and Bell. . . 
Do.. .. 
14 months. 
...do 
Allowed to stand in 
contact with water. 
1.7 
2.5 
Cushman and Hub- 
bard. 
Do 
Not given. 
...do 
Mineral ground while 
dry. 
Mineral ground wet. 
1250.0 
1 3,200.0 
1 Total residue. 
In the experiments for comparing the solubility of the potash in 
33SB with that of feldspar, a large quantity of the slag product was 
first prepared and ground to pass a 200-mesh screen. On analysis 
this material showed the following composition : 
Per cent. 
K 2 citric soluble 5. 14 
K 2 total 5.43 
P 2 5 citric soluble 6. 32 
P 2 5 total 6.31 
Two samples of this slag of 25 grams and 0.25 gram, respectively, 
and the same quantities in weight of feldspar (ground equally fine) 
were placed in platinum-lined brass cylinders, 100 cubic centimeters 
of water were added to each and carbon dioxide under an average 
pressure of 1J atmospheres was passed through the solutions for one 
week. At the end of that time the amount of potash dissolved from 
each sample was determined by analysis of the* solutions. The re- 
sults of these analyses are given in Table V. 
Table V. — Solubility of the potash in the slag product (33SB) in water 
saturated with carbon dioxide, compared with that of the potash in 
feldspar. 
Amount of 
material 
used. 
Amount of 
water 
employed. 
Potash dissolved. 
Material used. 
Potash in 
solution. 
Percentage 
of total 
potash in 
sample. 
Grams. 
25.00 
.25 
25.00 
.25 
C.c. 
100 
100 
100 
100 
P. p. 771. 
127.5 
4.7 
150.0 
11.9 
i 0.36 
Do 
1.37 
Slag (33SB ) . 
1.11 
Do 
8.76 
