LEA K \>,i « >i GAS im RING I 'I'l l; \ I [0N6. 17 
GENERAL CONSIDERATIONS. 
LEAKAGE OF GAS Dl RING OPERATIONS. 
One of the most important questions relating to the proper dosage 
in fumigation is that of the leakage of gas through the tent; in fact, 
the dosage depends directly upon the leakage. To measure with 
accuracy the amount of gas which escapes through tenting fabrics 
of various grades during a given length of time, or the rapidity with 
which the gas within the tent is diluted under different condition-, 
is a difficult problem. In this work, as far as we have progressed, no 
attempt has been made to measure directly with instruments the 
rapidity with which the gas is diluted, but rather to measure it indi- 
rectly and roughly through determining the effect on insects by using 
different durations of exposure. The easiest and most practical 
method of determining the influence of leakage is by fumigating 
trees of the same size, in which all factors affecting the results arc 
identical with the exception of t lie length of exposure. 
There is, however, one consideration of value relative to the leak- 
age of gas, which it is quite necessary to understand in successfully 
fumigating an orchard containing trees of a wide range of size. In 
geometrical figures which approximate in shape a citrus tree, the 
volume decreases at a more rapid rate than does the surface area. 
In order to bring out the relation of this fact to orchard fumigation, 
the following table has been prepared: 
Tablk VI I.— Leakage of gas from t> nts covering trees of different dimt nsions. 
Dimensions of tree. 
( ontents 
oi volume 
of tented 
lice. 
Exposed 
surface of 
tent. 
Leakage 
surface as 
per cent of 
volume.** 
Around. 
Over. 
Feel. 
12 
id 
28 
36 
44 
54 
Feet. 
20 
30 
40 
50 
60 
70 
( ubic U t. 
MM 
364 
1,040 
2.147 
.,.(,1!.-, 
S quart in I. 
85 
205 
420 
675 
995 
1 . 1 15 
/ '< r rent. 
86 
56 
40 
31 
26 
22 
a The comparison here and in the discussion which follows is between square feci of surface and cubic 
feet of volume. 
Taking the first tree, 20 feet around by 12 feet over, representing a 
volume of 1)9 cubic feet and an exposed surface area of 85 square 
feet, the ratio of leakage surface to volume is Mi: loo. For each cubic 
foot of volume within that 20 by 12 tree there i^ 0.86 square loot 
of leakage surf ace in the tent. The tree lo by 28 feel has 0.4 square 
foot of leakage surface for each cubic fool in the tent, while a tree 
70 by 54 has but 0.22 square foot of leakage surface to each cubic 
foot within. Suppose that these tented trees were charged with 
gas and that all the gas were to ocape through the tent. In the 
