2 BULLETIN 1149, U. S. DEPARTMENT OP AGRICULTURE. 
has been employed at ports of entry (9, 17) to prevent the intro- 
duction from foreign countries of many injurious insect pests that 
have not yet gained a foothold here. Among the most important 
of these pests are the pink boll worm and the citrus black fly. Fumi- 
gation with hydrocyanic acid gas is also a means for the prevention 
of epidemics of yellow fever (5) and bubonic plague (6, 13, 19). 
Ships coming from ports where these diseases exist are fumigated 
on arrival in order to kill mosquitoes and rats which carry the 
causative organisms. 
Food products fumigated to destroy the insects with which they 
are infested come into contact with hydrocyanic acid. This is true 
in the fumigation of imported fruits and vegetables at ports of entry 
and in the fumigation of flour and grains in mills and warehouses. 
In destroying insects and rats in dwellings and ships, foodstuffs 
may not be removed during exposure to the gas. In any case there 
is the possibility of exposure to the fumigant of products intended 
for food. 
Since hydrocyanic acid is extremely poisonous to man, it is impor- 
tant to know how much of it is absorbed and retained by foods. Very 
little work on this subject seems to have been done, although appar- 
ently the opinion that there is no danger in the fumigation oi dry 
foods 5 is fairly general. 
REVIEW OF LITERATURE. 
Guthrie (10) was unable to find a trace of residual gas in oranges 
that had been fumigated with hydrocyanic acid gas, in the propor- 
tions recommended for actual practice, for three hours and then 
allowed to remain in the open air for a half hour. He states that 
"similar experiments were made on samples of apples and lemons 
* * * with the same result." 
Townsend (22) reports that seeds, whether dry or moist, are 
capable of absorbing nydrocyanic acid, even when its concentration 
in the atmosphere is very low. He fed fumigated seeds (corn and 
wheat) to mice and concludes from his experiments that "dry grains 
and other seeds treated for several days with hydrocyanic acid gas 
of any strength will not be injured for food. * * * Damp 
grains and other seeds treated with hydrocyanic acid gas of any 
strength, even for short periods of time, should not be used for food 
until several hours after removing from the gas." 
Schmidt (21) fumigated peaches, plums, pears, lemons, and apples 
with hydrocyanic acid gas, apparently in rather high concentration. 
He placed his material in a chamber of 9.4 liters capacity and, in the 
course of a half hour, carried over into it by means of a stream of air 
the acid freed from 20 grams of potassium cyanide. He gives no 
values for the rate at which the air entered. If the stream of ah' 
was just strong enough to get all the hydrocyanic acid over into the 
chamber, without carrying any out, the atmosphere surrounding 
the fruit would contain about 78 per cent of the fumigant. This is 
equivalent to treatment with the gas from 213 ounces of potassium 
cyanide or 160 ounces of sodium cyanide per hundred cubic feet, 
which would be from 50 to 150^times as concentrated as that used 
* H. D. Young reports that the workmen engaged in citrus fruit- fumigation in California often hang 
their lunches in the trees which they expect to finish about lunch rime. Immediately after fumigatioa 
the lunches are removed and eaten with no ill effects. 
