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



gations, when the vault is loaded to 25 percent of its capcity or 

 more, the dosage should be based on the weight of the flour to be 

 treated. A dosage of 12 ounces of liquid hydrocyanic acid or its 

 equivalent per ton of flour should be used for an exposure of from 

 24 to 48 hours if the temperature of the flour is 80° F. or above. 



VACUUM FUMIGATION OF FLOUR PRODUCTS 



For the vacuum fumigation of flour products at temperatures 

 above 70° F., it is recommended that 2 ounces of liquid hydrocyanic 

 acid per ton be used for an exposure of 3 hours with an absolute 

 pressure of 2 inches or less. The ethylene oxide-carbon dioxide 

 mixture can also be used successfully under the same conditions with 

 the following exposures and dosages : 3 hours, 10 pounds per ton ; 6 

 hours, 4 pounds per ton; 12 hours, 3 pounds per ton. In all cases 

 the gas should be circulated for 15 minutes after it is introduced. 



RICE 



Rice is grown and stored in the South, where it is subjected to the 

 attack of many of the worst insect pests of stored cereals. It can, 

 however, be successfully fumigated with a wide variety of materials. 



For atmospheric fumigation the following dosages of materials 

 can be used per 1,000 cubic feet of space : Liquid hydrocyanic acid 

 or its equivalent, 3 pounds; chloropicrin, 2 pounds; carbon disul- 

 phide, 5 pounds; ethylene dichloride-carbon tetrachloride mixture, 

 20 pounds; methyl bromide-carbon dioxide mixture, 15 pounds; or 

 ethylene oxide-carbon dioxide mixture, 20 pounds. These dosages 

 are based on an exposure of 24 hours with the temperature of the rice 

 70° F. or above. 



Vacuum fumigation is particularly useful in the treatment of 

 rice, and the following dosages are recommended per ton of rice: 

 Ethylene oxide-carbon dioxicle mixture, 2% pounds for 1 hour or 

 iy 2 pounds for 3 hours; methyl bromide-carbon dioxide mixture, 3 

 pounds for 1 hour or 1% pounds for 3 hours. 



These dosages should be used with an initial absolute pressure of 

 2 inches, and the fumigant circulated in the vault for 15 minutes. 

 If the vacuum vault is not equipped for circulating the gas, the 

 dosages should be increased by one-third. Liquid hydrocyanic acid 

 can also be used successfully with a dosage of 5 pounds per 1,000 

 cubic feet of space with an exposure period of 2 hours. 



COTTONSEED MEAL 



Cottonseed meal, stored in 100-pound sacks, if held in certain 

 storages during the summer following grinding, may become se- 

 riously infested with the cigarette beetle {Lasioderma serricorne 

 Fab.). The infestation by this insect in commercially valuable 

 meal is limited chiefly to the outer 2 or 3 inches, whether it is stored 

 in sacks or in bulk. If market conditions indicate that the meal 

 will be carried over the summer, losses resulting from rebates, re- 

 grinding, and resacking can be prevented by fumigation. If insects 

 are already very abundant in meal stored in reasonably tight ware- 

 houses, one thorough fumigation with hydrocyanic acid gas, at the 

 rate of 1 pound of sodium cyanide or its equivalent per 1,000 cubic 



