44 
FUMIGATION FOR THE CITRUS WHITE FLY. 
Table VI. — Data concerning dosage in those experiments in which 100 per cent of white 
' Jties were destroyed. 
Experi- 
ment 
No. 
(series 
45). 
Measurements 
of tented tree. 
Approx- 
imate 
Approx- 
imate 
leakage 
surface 
Ratio of 
leakage 
surface 
to cubic 
contents. 
Rate: 
Number 
cubic feet 
per ounce 
cyanid. 
Amount 
cyanid 
Rate: 
Number 
Dis- 
tance 
over. 
Cir- 
cumfer- 
ence. 
capacity 
of in-" 
closed 
space. 
Amount 
cyanid 
recom- 
mended 
in table 
given in 
appendix 
cubic feet 
per ounce 
cyanid 
recom- 
mended. 
Feet. 
Feet. 
Cu. ft. 
Sq.ft. 
Ounces. 
Ounces. 
30 
m 
30 
735 
683 
1:1. (is 
6 
118 
9* 
77 
13 
31 
38 
1,149 
754 
1:1. 52 
11 1 
100 
11 
1(14 
19 
31| 
39 
1,219 
779 
1:1.56 
14* 
84 
11* 
106 
26 
33 
46 
1,656 
855 
1:1. 93 
13 
127 
14 
118 
33 
34* 
36 
1,224 
935 
1:1.31 
10 
122 
13 
94 
12 
:u T . 
43 
1,620 
935 
L: 1. 73 
I5f 
103 
14 
116 
24 
34* 
47 
1,855 
935 
1:1.98 
15* 
119 
15* 
119 
17 
364 
45* 
1,888 
1.043 
1:1.81 
21 
90 
17 
111 
9 
;;.;■. 
48 
2,049 
1,043 
1:1.96 
21 
98 
17 
120 
1 
37 
47 
2,075 
1,075 
1:1.93 
21 
99 
17 
122 
34 
40 
44 
2,092 
L.256 
1:1.66 
21 
100 
18* 
113 
35 
40 
47 
2,341 
1,256 
1:1.86 
20 
117 
20 
117 
6 
43i 
56 
3,412 
1,482 
1:2.35 
:: 
151 
26| 
129 
8 
44* 
58 
3.691 
1.554 
1:2.37 
27" 
136 
2'.t T , 
125 
4 
45" 
57* 
3,732 
1.589 
1:2.34 
23 
162 
28* 
131 
10 
45* 
67 
4,665 
1.625 
1:2.87 
35 
133 
344 
132 
23 
46* 
56 
3,556 • 
1.697 
1:2.15 
29i 
124 
30" 
118 
25 
48* 
57 
4,095 
1.846 
1:2.21 
33^ 
122 
33 
124 
7 
50* 
56 
4,275 
2,002 
1:2.13 
36 
119 
34 
125 
These tables show that with tents of 8-oimce duck and untreated 
with paint or sizing there is little or no advantage in exposures of 
more than 40 minutes. The results with exposures of 30 and 40 
minutes compare favorably with those ranging from 45 minutes to 
2 hours and 50 minutes. It is evident that the gas escapes rapidly 
and that in the course of a period of 30 to 40 minutes at the most 
the gas from a dosage of maximum utility is so diluted as to be 
practically ineffective. On the other hand, the table shows con- 
clusively that the experiments afford no justification for reducing the 
dosage on account of lengthening the exposure from 45 to 60 minutes 
or longer. Everything considered, the writer adopted the 40-minute 
period of exposure as probably affording the greatest benefit from a 
given amount of cyanid. 
As an aid in determining the rates of dosage which could be safely 
recommended for the various ratios of leakage surface to cubic eon- 
tents, the experiments referred to in Table V were arranged in accord- 
ance with the ratio, and in each case the writer estimated the amount 
of potassium cyanid which it seemed evident would have been ample 
for the destruction of all the insects. The degree of success obtained 
with the amount of potassium cyanid actually used was taken into 
consideration in estimating the amount needed. The data thus 
arranged, together with calculations of the rate, or number of cubic 
feet of space per ounce of potassium cyanid, are given in Table VII. 
