4 BULLETIN 1149, TJ. S. DEPARTMENT OF AGRICULTURE. 
Investigators in the United States Public Health Service (1) fumi- 
gated bread and milk with hydrocyanic acid and then fed them to 
white mice. They found that "when exposed to the cyanide gas in 
the concentration usually advised for fumigating tight compart- 
ments" they "did not absorb or adsorb sufficient cyanide to cause 
symptoms when fed to white mice." With double the amount of 
hydrocyanic acid, "prolonged" exposure, and no aeration after 
fumigation, death of the mice resulted, but "after one or two hours 
exposure of the food to the air no symptoms were produced.'' They 
summarize, "The conclusion from these experiments is that the pos- 
sibility of food poisoning occurring from food materials exposed to 
cyanide gas is extremely remote." 
Lubsen, Saltet, and Wolff (15) state that hydrocyanic acid can be 
used for the destruction of insects in flour and other foodstuffs, since 
it does not affect foods, except milk and other liquids. 
Marchadier, Goujon, and de Laroche (16) advise against the use of 
hydrocyanic acid fumigation for flour. They recognize its value for 
clothes and things of that type, but think that flour may hold enough 
of the gas to cause injury to health. They found a hydrocyanic 
acid content of 82 parts per million in one flour and say that the 
foods prepared from it (cakes, sauces, etc.) still had the taste of 
cherry laurel, even after cooking. They do not describe the treat- 
ment which the flour had received. 
PURPOSE OF PRESENT INVESTIGATION. 
There are no analytical data on the quantity of hydrocyanic acid 
absorbed under the usual conditions of fumigation, except those of 
Guthrie and of Bail, who give some results on five products, but none 
which indicate the rate of loss of hydrocyanic acid on aeration. 
Schmidt worked with excessive concentrations of the fumigant. 
Experimental work was therefore undertaken in the United States 
Department of Agriculture to find how much hydrocyanic acid is 
absorbed under ordinary conditions of fumigation on a large number 
of fruits, vegetables, and seeds, and at what rate it is given off when 
the products are exposed to the air. 
EXPERIMENTAL WORK. 
FRUITS AND VEGETABLES. 
Fruits and vegetables were bought in season in the open market? 
and in a condition as nearly perfect as possible. They were divided 
into three lots. 
One lot was analyzed without being fumigated, to guard against 
reporting as absorbed hydrocyanic acid any which might be present 
in the fruit naturally. 
The second lot was fumigated at normal atmospheric pressure 
(NAP) by the "pot" method. The fumigant in this method was 
prepared by adding sodium cyanide to diluted sulphuric acid in the 
proportion of 1 : 1£ : 2. That is, for every avoirdupois ounce of sodium 
cyanide 1J fluid ounces of sulphuric acid and 2 ounces of water 
are used. 
The third lot was fumigated by a modification of the vacuum 
method described by Sasscer and Hawkins (20). The fumigant in 
this method was prepared from sodium cyanide, sulphuric acid, and. 
