6 4 
Journal of Agricultural Research 
Vol. XIV, No. i 
intervals for eight hours the contents of the bottles were thoroughly 
mixed by vigorous shaking. In the case of the pair of soils from each 
area the two bottles, the one with the treated and the other with the 
untreated soil, were placed side by side and shaken at the same time, 
thus insuring the same degree of agitation and extraction. Then they 
were allowed to stand for 48 hours, or longer if the most of the clay 
particles had not settled within that time. Then 3,000 c. c. of the 
supernatant liquid from each was decanted and filtered. Owing to the 
presence of colloidal day in the filtered solutions, especially those from 
the untreated soils, it was necessary to remove this, which was easily 
accomplished by bringing the solution to the boiling point, adding 0.5 
gm. of aluminium chlorid and 5 c. c. of ammonium-hydroxid solution. 
The flocculated precipitate of aluminium hydroxid on settling removed 
from suspension the day particles. After the solutions had been allowed 
to stand for several minutes, they were passed through ordinary filter 
papers, giving dear filtrates. The filtrate thus prepared from each soil 
and representing a definite quantity of this was then analyzed for potash 
according to the well-known chloroplatinate method, in which the potas¬ 
sium is weighed as potassium chloroplatinate. 
Table II .—Effect of gypsum upon amount of water-soluble potash 
Soil. 
Weight 
of soil 
corre¬ 
sponding 
to soil 
extract 
used for 
determi¬ 
nation. 
Deter¬ 
mina¬ 
tion. 
Untreated soil. 
Weight 
of potas¬ 
sium 
chloro- 
platinate. 
Percentage 
of potash. 
Treated soil. 
Weight 
of potas¬ 
sium 
chloro- 
platinate. 
Percentage 
of potash. 
Increase 
in potash 
due to 
gypsum. 
Average 
Average 
Average 
Average 
Average 
Gm. 
ISO 
i$o 
80 
80 
150 
ISO 
80 
80 
80 
80 
Gm. 
O. 0262 
. 0269 
0266 
0160 
0149 
0155 
0x98 
0196 
OI97 
0098 
OII2 
0105 
. 0180 
. 0200 
0 X 90 
o. 00338 
. 00347 
Gm. 
O. 0327 
• 0311 
Per cent. 
o. 00422 
. 00401 
OO343 
0319 
OO413 
00387 
00361 
0260 
0257 
. 00629 
. 00621 
00374 
OO255 
OO252 
02 59 
0309 
0297 
. 00626 
00399 
00383 
00254 
0303 
00391 
00237 
00271 
0208 
0178 
00254 
0193 
00436 
00489 
0362 
0336 
00462 
0349 
00503 
00431 
00467 
00876 
00813 
00845 
o. 00070 
00252 
00137 
00213 
00383 
