CHAPTER IX 
ESTIMATING GAS FOR ORCHARD WORK 
MOUNTS OF CHEMICALS.—The foreman or super- 
intendent should be responsible for the chem- 
icals used for making the gas. Asa rule, 
where the sheet tents are used, different 
amounts are necessary for individual trees, espe- 
cially where they vary in size. The superintendent 
judges the size of the tree as soon as it is tented, 
and estimates and weighs the chemicals accord- 
ingly. It is difficult to estimate the cubic contents 
of a tented tree, and as a result some unsatisfac- 
tory work is done. Indeed, it is surprising that the 
results are as uniform as they are. In California the 
trees to be fumigated are usually inspected in advance, 
so that the superintendent can, in a general way, esti- 
mate the amount of gas necessary. A little more gas 
than the tree will stand without injury is usually pro- 
duced. ‘This is somewhat misleading, for the larger 
the tree the greater theinjury. If the dose is properly 
proportional to the cubic content, there is a slower 
diffusion of the gas, in which case care must be taken 
when large trees are fumigated. 
The usual method is to measure the tree and find 
the amount of chemicals necessary by reference to a 
table prepared for that purpose. If the tables are cor- 
rectly calculated and the measurement accurately done 
this is perhaps the safest method. As already indi- 
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