INSECTICIDES 55 



vision for opening some doors or windows on each floor from the 

 outside should have been made. 



Needless to say, the building can not be entered during the 

 fumigation. When all is in readiness the operator or operators 

 should start on the upper floor, in the rooms farthest removed 

 from the stairway and drop the bags of cyanide quickly into the 

 jars of liquid, go quickly to the next floor below and repeat the 

 operation and so on to the ground floor and from there outside, 

 closing and locking the last door. The building should be locked 

 and placarded and it is well to have a watchman to warn people 

 from the vicinity. After 12 to 24 hours the windows and doors 

 should be opened from the outside and the building allowed to 

 air for one to three hours when it will be safe to enter. Inside 

 doors should be left open. A thick newspaper should be placed 

 under each jar to protect the floor from splashing of the liquid 

 which may occur during the generation of the gas, which may be 

 violent. The cyanide used must be 98 to 99 per cent pure and the 

 acid of specific gravity 1.83, commercial. This treatment will 

 kill all stages of insects, also rats and mice but will not injure the 

 contents of the house in any way excepting that moist foods 

 should not be exposed to the gas. Let us repeat, however, that 

 the gas is ONE OF THE MOST VIOLENT POISONS KNOWN. 



Cyanide fumigation is extensively used on the Pacific Coast 

 for the control of insects on fruit trees, these being fumigated 

 under specially constructed tents. Dosage tables and other in- 

 formation concerning this practice should be secured through the 

 California Experiment Station at Berkeley where Dr. C. W. 

 Wood worth has largely perfected the methods used. 



Sulfur Dioxid. The fumes of burning sulfur, mostly sulfur 

 dioxid, have long been recognized as a standard remedy for the 

 fumigation of dwellings and barracks for insect pests. Successful 

 fumigation for the bedbug has been reported when stick sulfur has 

 been burned at the rate of 2 pounds per 1000 cubic feet of space. 

 The chief objection is the strong bleaching effect of the fumes in 

 presence of moisture and their destructive action on vegetation. 

 Recently this gas has been extensively used under the name of 

 " Clayton gas," for the fumigation of ships and ships' cargoes, par- 

 ticularly grain. It is forced into the tight hold of a ship by special 

 apparatus and is exceedingly penetrating and effective. The 



