INDUSTRIAL FUMIGATION AGAINST INSECTS 15 



If earthenware crocks are used, these also should be set each in a 

 small galvanized tub. It is seldom practical to use crocks of more 

 than 4-gallon capacity. A 3-pound charge of cyanide is the most 

 that can be safely used in a crock of this size without danger of 

 spattering during the evolution of the gas. 



Handling Cyanide for the Generator 



The weighing of cyanide should be delayed as late as possible be- 

 fore the fumigation is begun. The cyanide absorbs moisture, and if 

 it remains in a paper package for a long time before fumigation, 

 the moisture gathering on the lumps of cyanide will moisten the 

 paper so that when the sack is picked up it may break and dis- 

 charge the cyanide. Where small charges of cyanide are used, 

 as in 4-gallon crocks, it is best to use two paper sacks, one of which 



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Figure 16. — Seven 50-gallon oil barrels, in tubs, arranged in line near the door of ;i 

 woollen factory- The sodium cyanide has been dropped into the acid-water mixture. 

 Note gas mixed with steam rising from the barrels. Each of these barrels had a 

 charge of 25 pounds of sodium cyanide, the battery of 7 barrels generating enough gas 

 for 175,000 cubic feet of mill space. 



will fit easily inside the other. By wrapping the unoccupied por- 

 tion of the sacks tightly about the cyanide and tying with a string, 

 a compact package is obtained, which can easily be lowered into the 

 acid-water mixture with one hand. If two bags are used, the 

 operator can lower 6 or 8 charges of cyanide into the containers before 

 the acid eats through the paper of the charge first dropped, and 

 often he can be out of the building before any gas is evolved. If 

 the sacks are merely tied close above the cyanide, or twisted, without 

 wrapping, during the reaction the acid-water mixture may be forced 

 up along the neck of the bag and over the edge of the container. 

 If the cyanide is properly packaged, however, there will be no 

 overflow. 



When large dosages are used in barrels, sometimes as large as 30 

 pounds, it is safer to place the cyanide in gunny sacks. When charges 

 in such sacks are lowered into the barrels, gas j s evolved at once 



