INDUSTRIAL FUMIGATION AGAINST INSECTS 



15 



neutralizing any small quantity of the acid-water mixture that may 

 leak out of the barrel. 



If three or four bricks are placed in the bottom of the washtubs 

 .for the barrels to rest on, the barrels will not become stuck in the 

 tubs. It is much better to have tubs large enough in diameter at the 

 bottom so that the barrels will not come in contact with the sides. 



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. 





pp 



# i 









tjfa& 





% 









mm : * 



■ 





I 



,.;'.5 .■.■;..' 



^ : :S:S|j;:!:.;&.,:;" : ' ; : 









■'■■■.: :-..■ > ... ■ ■ ^Wnp . 







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

 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 seven barrels generating enough 

 gas for 175,000 cubic feet of mill space. 



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 

 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 opera- 

 tor can lower six or eight 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 



