10 
* 
and this solidifying or ‘‘freezing” of the residue may prevent com- 
plete development of the gas, as has been demonstrated. 
Much recent work by experts and agents of this Bureau has dem- 
onstrated that for ordinary well-constructed mills or granaries good 
results may be anticipated by the use of 10 ounces of cyanid of pot- 
ash and corresponding amounts of the other ingredients to 1,000 
cubic feet of air space. This strength, therefore, may be daken as 
the standard for mill and granary fumigation. 
If mills could be made practically air-tight, and some are nearly 
so, undoubtedly a considerably smaller amount of cyanid to each 
1,000 cubic feet would give equally good results,* but the miller will 
hardly be willing to risk success by a slight economy in cyanid and 
acid, in view of the money loss due to “shut downs” incidental to 
any fumigation. 
In very loosely constructed or more or less open frame buildings, 
or where only a short exposure is permissible, it is practically impos- 
sible to successfully fumigate for most insects affecting stored prod- 
ucts; but sometimes, by increasing the amount of cyanid to double 
the quantity normally employed, fair results may be obtained. 
Good results can not be expected with an exposure of less than 
16 or 18 hours, while a period of from 24 to 36 hours is preferable. 
ESTIMATING AMOUNTS OF CHEMICALS FOR FUMIGATION OF MILLS. 
The first preliminary to the fumigation of a mill or granary is the 
making of an accurate estimate of the amount of chemicals required 
for the different stories of the building. It is desirable to make the 
computation of space for each floor separately and to prepare a table 
for the guidance of the operators indicating the number of generators 
and the amount of chemicals to be distributed on each floor. Inside 
measurements should be taken, and the height of each story should 
be carefully measured as well as the floor space. 
Under ordinary conditions it is best to generate the gas at the 
standard rate on each floor of the building. The first table which 
follows illustrates the normal proportions for each floor. These 
tables are submitted as indications of a convenient method to be 
followed in making the computations and tabular statement. In 
view of the fact, however, that the gas is lighter than air and rises, 
it may be desirable in the case of buildings which have many open- 
ings from one floor to another, which can not be easily sealed or 
stopped up, to develop the greatest amount of gas in the basement, 
a Mr. C. H. Popenoe, working under the instructions of the writer in the vicinity 
of the District of Columbia, and Mr. D. K. McMillan, fumigating under the writer’s 
directions in Kansas, have met with success with lower strengths in fumigating nearly 
air-tight mills and other structures. 
[Cire >} 
