40 CIRCULAR 369, U. S. DEPT. OF AGRICULTURE 



feet is sufficient for this purpose. An exposure of 24 hours is 

 desirable. 



Where nut meats in the shell are stored without cold storage, it 

 sometimes becomes necessary to fumigate the warehouses also. Hy- 

 drocyanic acid is the best fumigant for this purpose and should be 

 applied at the rate of 16 ounces of liquid hydrocyanic acid or its 

 equivalent per 1,000 cubic feet. Excellent results can be obtained 

 in tightly constructed warehouses, even though the bagged nuts are 

 piled in large stacks. If possible, a 48-hour exposure should be 

 given. 



Nuts absorb considerable hydrocyanic acid gas, and therefore a 

 warehouse that has been fumigated cannot be aired out very quickly. 

 Large stacks of bagged nuts hold the gas and give it off slowly over 

 a period of several days. In one fumigation conducted by the writ- 

 ers in an exceptionally tight warehouse, bagged peanuts retained 

 so much of the gas that it was unsafe for workmen to enter the ware- 

 house until it had been aired for 5 days. When ventilation is ample, 

 however, workmen can usually enter the following morning, after 

 the gas escaping from the sacked nuts during the night while the 

 warehouse is closed has been blown out of the main aisles. 



VAULT FUMIGATION FOR NUTS 



Nuts are usually fumigated in atmospheric vaults or vacuum tanks 

 before they leave the factory or go from the storage warehouse to the 

 factory. A 1,000-cubic-foot atmospheric vault will hold about half 

 a carload of bagged nuts, such as peanuts — about two hundred and 

 fifty 100-pound bags of shelled peanuts or 125 such bags of peanuts 

 in the shell. 



A dosage of 3 pounds of ethylene oxide or 25 pounds of the ethy- 

 lene oxide-carbon dioxide mixture per 1,000 cubic feet of space, with 

 an exposure of from 20 to 24 hours, will give excellent results at 

 a cost of from 1 to 3 cents per 100-pound bag, including labor 

 charges. 



The mixtures of carbon dioxide with methyl formate or methyl 

 bromide may be used at dosages of 30 pounds and 20 pounds, respec- 

 tively, per 1,000 cubic feet of space. 



Hydrocyanic acid can also be used for fumigating nuts in atmos- 

 pheric vaults, although it is not so popular for this purpose as 

 ethylene oxide. A dosage of one-half pound of liquid hydrocyanic 

 acid or its equivalent is required for each 1,000 cubic feet of space. 



VACUUM FUMIGATION FOR NUT MEATS 



For the vacuum fumigation of nuts the ethylene oxide-carbon 

 dioxide mixture is excellent. A dosage of 30 pounds per 1,000 cubic 

 feet for a period of from 1 to 2 hours gives satisfactory results at a 

 cost of from 3y 2 to 4 cents per 100 pounds of nuts. The methyl 

 bromide-carbon dioxide mixture can be used at the same dosage. 

 A mixture of carbon disuphide and carbon dioxide has been used in 

 the vacuum treatment of nuts, but owing to the need for special 

 equipment for applying it safely and to the fact that it is unsuitable 

 for the treament of pecans, Brazil nuts, and cashews, it is not recom- 

 mended. 



