ARSENICALS. 21 
Table 10. — Arsenic on potato and apple leaves sprayed with lead or calcium arsenates. 
Spray used. 
Average 
number 
of 
samples. 
Arsenic (As) found. 
Year and locality. 
Per 
square 
meter 
of leaf 
surface. 
On dry 
leaves. 
1917. 
Washington, D. C 
POTATO LEAVES. 
Acid lead arsenate 
7 
8 
2 
2 
2 
2 
3 
3 
2 
2 
5 
5 
2 
2 
4 
4 
Milli- 
grams. 
5 
3 
80 
56 
16 
19 
Parts per 
million. 
140 
Do... 
50 
Acid lead arsenate 
1,460 
Do... 
1,270 
Acid lead arsenate 
50 
Do 
70 
1918. 
Acid lead arsenate 
170 
Do 
Calcium arsenate 
60 
180 
Do 
Calcium arsenate 
270 
1919. 
Acid lead arsenate 
260 
Do. 
210 
1917. 
Greenwood, Va 
APPLE LEAVES. 
Acid lead arsenate 
40 
9 
510 
Do .. 
120 
191S. 
130 
Do 
260 
The results of the tests for all three years show an average of 286 
parts per million of arsenic on the dry leaves receiving the lead 
arsenate spray and an average of 219 parts per million of arsenic on 
the dry leaves receiving the calcium arsenate spray. The 1917 and 
1919 results show that a larger percentage of arsenic of acid lead 
arsenate adhered to the leaves than of the arsenic of the calcium 
arsenate. The 1918 results are practically the same for the two 
arsenates. 
Lime was used with certain of the arsenates in some of the 1918 
tests (Table 11). Potato vines were sprayed with a commercial 
calcium arsenate and a commercial acid lead arsenate alone and w^th 
the addition of lime to each. Zinc arsenite and calcium meta- 
arsenate w^ere used without the addition of lime. Two calcium 
arsenates, one with a molecular ratio of 3 CaO to 1 As 2 5 and the 
other with one of 4 to 1, were tested, with and without the addition 
of lime. In these two cases both 2 ounces and 4 ounces of lime per 
10 gallons of spray were used. The arsenious or arsenic oxid con- 
tents of the sprays were made the same in all cases, with the exception 
of calcium meta-arsenate. From the data in Table 11 it is evident 
that the lime was of no advantage in increasing the amount of arsenic 
adhering to the leaves. 
