INDUSTRIAL FUMIGATION AGAINST INSECTS 



15 



should be cleaned and allowed to stand full of water overnight previ- 

 ous to the day of fumigation. Each barrel will hold a maximum 

 charge of 30 pounds of sodium cyanide, or enough to fumigate about 

 30,000 cubic feet of space. When it is necessary to fumigate small 

 rooms of a few thousand cubic feet as separate units, earthenware 

 or stone crocks (fig. 13) of appropriate size can be used. Oil barrels 

 sawed in half are used less often. 



Each barrel generator should be set in a galvanized-iron wash tub 

 in which has been placed a pailful of water containing several hand- 

 fuls of washing soda. This precaution provides for catching and 

 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 



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Figure 14. — Seven 50-gallon oil barrels, in tubs, arranged in line near the door 

 of a woolen 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. 



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 in 

 small galvanized tubs. 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, 



