94 
Journal of Agricultural Research 
Vol. XXIV, No. I 
Tabi<^ IV .—Analysis of o.i gm. dry insoluble residue from treatment of lead arsenate 
with soap solution 
No, 
Soap. 
read arsenate. 
Weight of 
Weight of 
Ratio of 
AS2O3 to 
PbO. 
Quantity. 
Kind. 
Quantity. 
Brand. 
AS2O3. 
PbO. 
I 
Gm. 
0.6 
Sodium stearate.... 
Gm. 
2.00 
-M’' 
Gm. 
O.OIOI 
Gm. 
0.0437 
I • 4-3 
2 
1.8 
2.00 
“M” 
.0065 
.0274 
I : 4.2 
3 
.6 
.do. 
2.00 
.0122 
.0460 
I : 3.8 
4 
1.8 
.do.. 
2.00 
“M” 
,0065 
.0283 
I : 4-3 
5 
.6 
.do. 
2.15 
< ( > > 
.0132 
•0475 
I : 3.6 
6 
1.8 
.do. 
2.15 
< < ^ f ) 
.0092 
.0310 
I : 3-4 
7 
.6 
.do. 
2.15 
<< /jp) j 
.0140 
.0468 
I • 3-3 
8 
1.8 
2.15 
.0086 
.0257 
I ; 3.0 
9 
.6 
Sodium oleate. 
2.00 
-M” 
.0256 
•0538 
1:2.1 
10 
1.8 
.do. 
2 . 00 
“M” 
.0211 
.0482 
I : 2.3 
II 
.6 
2.00 
“M” 
.0322 
•0552 
I : 1.7 
12 
1.8 
.do.. 
2.00 
“M” 
.0204 
.0470 
I : 2.3 
13 
.6 
.do. 
2.15 
<( fjyy y 
. 0244 
• 0635 
1:2.6 
14 
1.8 
2.15 
<( y^y y 
. 0242 
.0610 
I : 2.5 
15 
.6 
. do . 
2.15 
i( fij^y y 
.0221 
.0564 
I : 2.5 
16 
1.8 
..... do . 
2.15 
(1 yj^y y 
.0185 
.0482 
1:2.6 
Theoretical for diplumbic ortho arsenate (PbHAs04) i : 1.94. 
Theoretical for triplumbic ortho arsenate (Pb 3 (As 04 ) 2 ) i : 2.91. 
Theoretical for lead hydroxy arsenate (Pb50H,(As04)3) i : 3.23. 
SUMMARY 
The data exhibited make the following conclusions plain: 
(1) That pure soaps dissolve arsenic from both samples of lead arsenate 
and therefore might cause injury to foliage. 
(2) That sodium stearate is much more effective in dissolving arsenic 
from both “M” and “T” than is sodium oleate, from two to six or even 
seven times as much soluble arsenic being found in the solution of the for¬ 
mer as in the latter. 
(3) That, as Tartar and Robinson point out (4, 7), the arsenic of 
diplumbic arsenate is much more acted upon than the more basic com¬ 
pound. 
(4a) Increasing the concentration of the stearic soap solution increased 
the amount of arsenic made soluble. 
(4b) Increasing the concentration of the oleic soap made more arsenic 
soluble from the acid lead arsenate “M’' but did not increase the 
amount made soluble from the basic lead arsenate “T.” 
(5) The extent of the action was sometimes greater when the lead 
arsenate was ground in water than in the soap, sometimes less. No 
definite statement can be made as to which is most effective. 
(6) Sodium stearate dissolves far too much arsenic from diplumbic 
arsenate to confirm the supposition that its action stops with the con¬ 
version of diplumbic into lead hydroxy arsenate. 
(7) Both sodium stearate and sodium oleate dissolve arsenic from 
basic lead arsenate, the stearic soap in large quantities (as much as 25 
percent). 
(8) Numbers 6 and 7 together indicate that the action of soaps upon 
lead arsenates is of the double decomposition sort. 
