ARSENICALS. 37 
Table 17. — Relative toxicity of arsenates and arsenites on 4 species of insects, 1920. 
Arsenicals and control. 
Percentage of insects dead within— 
3 days. 
6 days. 
6 
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CQ 
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39 
25 
23 
64 
Commercial acid lead arsenate. . . 
Laboratory sodium arsenate 
Average for arsenates '. 
Commercial zinc arsenite 
Commercial Paris green 
91.0 
99.0 
95.0 
96.0 
100.0 
100.0 
98.0 
9S.5 
9S.0 
0.0 
11.0 
2S.8 
19.9 
12.5 
30.7 
38.9 
IS. 5 
22.7 
24.1 
0.0 
18.1 
36.6 
27.3 
6S.9 
65. 7 
59. 3 
53.9 
61.9 
34. 7 
0.6 
21.0 
33.0 
27.0 
25.0 
15.0 
25.0 
22.0 
21.8 
11.0 
0.0 
35.3 
49.3 
42.3 
50.6 
52.8 
55.8 
48.1 
51.8 
42.0 
100.0 
100.0 
100.0 
100.0 
*i66."6" 
100.0 
100.0 
0.0 
72.8 
72.2 
72.5 
37.5 
85.2 
S6.7 
72.3 
70.4 
57.1 
0.0 
82.2 
91.4 
86.8 
96.9 
99.0 
97.5 
97.6 
97.7 
92.0 
8.8 
58.0 
62.0 
60.0 
44.0 
62.0 
55.0 
57.0 
54.5 
33.0 
12.0 
78.3 
81.4 
79.9 
69.6 
86.6 
88 
89 
90 
do 
do 
Average for arsenites 
Commercial London purple 
Control with food 
84.8 
81.7 
80.7 
70.5 
Arsenicals and control. 
Percentage of insects 
dead within— 
Toxicity for— 
10 days. 
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Commercial acid lead arsenate 
99.3 
96.6 
98.0 
60.9 
100.0 
100.0 
96.6 
89.4 
94.7 
2.6 
100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
23.1 
99.8 
98.9 
99.3 
87.0 
100.0 
100.0 
98.9 
96.5 
98.2 
97.0 
99.7 
98.3 
98.7 
100.0 
100.0 
99.3 
99.5 
99.3 
61.0 
65.9 
63.5 
37.0 
72.0 
75.2 
62.5 
60.8 
58.6 
66.8 
76.0 
71.4 
88.6 
88. 2 
85.6 
83.8 
86.5 
75.6 
39.5 
47.5 
43.5 
34.5 
38.5 
40.0 
39.5 
38.1 
22.0 
66.1 
25 
Laboratory sodium arsenate 
72.3 
Average for arsenates 
100.0 
69.2 
23 
Commercial zinc arsenite 
64.7 
64 
Commercial Paris green 
74.7 
88 
89 
do 
do.... 
75.2 
71.2 
100.0 
71.5 
90 
Commercial London purple 
63.9 
Control with food 
0.0 

1 Based on mortalities for third and sixth days only. 
In 1920 experiments similar to the preceding ones were performed, 
using one lead arsenate, one sodium arsenate, one zinc arsenite, 
three Paris greens, and one London purple (an arsenate and an 
arsenite combined). The following data, which are not given in 
Table 17, were obtained: Silkworms, 2 sets (each of 50); webworms 
(H. cunea), 1 set (variation 90-136, average 120); tent caterpillars, 
3 sets (207-507, average 288); and honeybees, 2 sets (each of 50). 
Table 17 shows that the average percentage of toxicity of the arsenates 
was 69.2, while that of the four arsenites was 71.5. The toxicity of 
the arsenites should be 16.2 per cent more than that of the arsenates, 
providing the toxicity is due to the arsenic, irrespective of its form 
of combination. According to the preceding figures, the toxicity 
of the four arsenites is only 3.3 per cent more than that of 
the two arsenates. Comparing the toxicity of the four arsenites 
with that of the lead arsenate, however, it is 7.8 per cent more, 
