INDUSTRIAL FUMIGATION AGAINST 1NSFCTS 



17 



Emptying the Generators 



When the fumigation is finished and the building has been thor- 

 oughly ventilated, the residue must be emptied from the generators. 

 Sometimes the chemical reaction is incomplete because some of the 

 sodium cyanide has not come in contact with the acid-water mixture 

 or because the wrong proportions of the materials have been used. 

 Therefore, when the generator is moved, the contents are shaken up 

 and additional small quantities of gas may be given off. For this 

 reason the operator 

 should breathe as lit- 

 tle as possible or use 

 a gas mask while 

 handling the barrels 

 and should not hold 

 his head over the 

 barrel. 



The residue, which 

 is poisonous, .can be 

 disposed of by dump- 

 ing it down a street 

 drain (fig. 17) or by 

 pouring it into a 

 hole in the ground 

 and covering it with 

 soil. 



THE LIQUID METHOD 



Liquid hydrocy- 

 anic acid is a vola- 

 tile, colorless liquid 

 which boils at 79° F. 

 It is marketed in 

 cylinders containing 

 30 or 75 pounds. On 

 exposure to air it gives off the same gas that is generated by mixing 

 sodium cyanide with sulphuric acid and water. In the hands of an 

 expert fumigator it is an almost ideal fumigant for use in large 

 enclosures. 



After a building has been prepared for fumigation, the gas is 

 applied entirely from the outside (figs. 18 and 19). The cylinders 

 containing the liquid hydrocyanic acid are lined up near the build- 

 ing, and the fumigant is forced in by compressed air. A proper 

 distribution of the gas within the building is obtained by means 

 of lines of pressure rubber tubing or metal piping equipped with 

 spray nozzles. A gas mask should be worn or kept close at hand. 



Figure 17. — Men carrying containers from a warehouse 

 to empty into a city drain the residue from a hydrocy- 

 anic acid gas fumigation. 



Piping the Building 



In small enclosures the gas can be distributed through rubber tub- 

 ing, but in large warehouses or mills it is desirable to install a per- 

 manent systein of piping. This may be constructed of iron, brass, or 

 copper. The iron piping is the least expensive, but, owing to its 



4964°— 37 3 



