76 
Fumigation should be done on a quiet day, as a high wind 
tends to blow the vapor thru such openings as may remain in the 
walls. A temperature of not less than 70° is to be preferred. 
Commonly two successive treatments three or four weeks apart 
are necessary to complete success. 
The operator must bear in mind, in his plans and procedure, 
that everything must be done in such a way that he shall not 
breathe the escaping gas. Milk, meats, and other moist or liquid 
food materials, should be removed before fumigating, as they are 
liable to become poisoned by absorption of the gas. Arrangements 
should be made to open the building from without for ventilation 
when the fumigation is completed, and it should not be entered 
until it is practically free from the gas. 
FUMIGATION WITH CARBON BISULFID 
This volatile and exceedingly ill-smelling chemical has been 
more or less used against stored grain insects for many years, but 
recent experiments, including some of those upon which this dis¬ 
cussion is based, have shown that the strengths at which it must 
be used and the best methods of its application, were but little un¬ 
derstood, and that it has often been recommended for too many 
purposes and for use under really impossible conditions. This 
has resulted in many failures which have discredited it more or 
less as an insecticide for granary and warehouse use. 
The commercial bisulfid is a heavy, oily fluid with a specific 
gravity of 1.29, boiling at 115 0 F., and igniting at about 300" F. 
It is cold to the touch, and because of its rapid evaporation it pro¬ 
duces a freezing sensation when applied to the skin. When 
handled in quantity one's feet are likely to become cold, especially 
if any of the fluid is spilled upon the shoes. The vapor is a little 
over two and a half times heavier than air, a point to be remem¬ 
bered in application, since it goes first to the bottom of the in¬ 
closure. When mixed with air it becomes inflammable and ex¬ 
plosive, especially when the mixture is in the ratio of about one 
part of the vapor to fourteen parts of air, equivalent to fifteen 
pounds of the fluid to a thousand cubic feet of space. Such a mix¬ 
ture of air and bisulfid vapor may be exploded by so small a cause 
as the spark made by hitting a nail or by turning an electric light 
on or off, instances of both of which have come within our own 
experience. The chemical leaves, on evaporation, a residue of im¬ 
purities which stain cloth and other substances, so that direct con¬ 
tact with it should be avoided. Its rate of evaporation is in pro¬ 
portion to the temperature and the area of its surface of exposure, 
being very rapid when exposed in shallow vessels and at a high 
temperature. Its efficiency is also the greater the more rapid the 
evaporation and the higher the temperature. One volume of the 
