INDUSTRIAL FUMIGATION AGAINST INSECTS 



11 



provide cross ventilation. The men can then go outside and wait 

 until the building is partially aired before completing the work. It 

 is important that the watchmen be instructed to prevent anyone 

 from entering the building while it is being ventilated. A large 

 proportion of the fatalities connected with fumigation have been 

 due to criminal neglect on the part of watchmen. 



FUMIGATION WITH HYDROCYANIC ACID GAS 



For the fumigation of large buildings there is no more efficient gas 

 than hydrocyanic acid. It is relatively inexpensive, kills with great 

 rapidity, and, al- 

 though deadly pois- 

 onous, can be han- 

 dled with reasonable 

 safety by experienced 

 men. It can be used 

 in nearly ail types of 

 buildings and will 

 not injure most arti- 

 cles of commerce. 



Hydrocyanic acid 

 gas is commonly pro- 

 duced in one of four 

 ways: (1) By gener- 

 ating it in a barrel, 

 earthenware crock, 

 or other container 

 from a mixture of 

 sodium cyanide, sul- 

 phuric acid, and 

 water — the so-called 

 barrel or pot meth- 

 od; (2) by pumping 

 it into the building 

 or machinery in liq- 

 uid form from cylin- 

 ders — the liquid 

 method; (3) by 

 spreading on the 

 floor of the building 

 an absorbent mate- 

 rial saturated with 

 liquid hydrocyanic 

 acid — the discoid 

 method; (4) by 

 spreading on the 

 floor of the building 



a powder consisting of calcium cyanide, which combines with mois- 

 ture from the air to form hydrocyanic acid gas — the powder method. 



THE BARREL OR POT METHOD 



The barrel or pot method of generating hydrocyanic acid gas is so 

 called because the chemicals used are placed together in a barrel (figs. 



Figure 12. — Man wearing- gas mask about to lower bag of 

 sodium cyanide into a barrel containing sulphuric acid 

 and water. If the cyanide is put in a gunny sack, there 

 is no danger of the bottom of the bag breaking and spill- 

 ing the cyanide. The cyanide should not be dropped into 

 the acid-water mixture ; it should be lowered carefully. 



