INDUSTRIAL FUMIGATION AGAINST INSECTS 



11 



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, although deadly poisonous, can be handled with 

 reasonable safety by 

 experienced men. It 

 can be used in nearly 

 all types of build- 

 ings and will not in- 

 jure most articles of 

 commerce. 



Hydrocyanic acid 

 gas is commonly pro- 

 duced in 1 of 4 

 ways: (1) By gen- 

 erating it in a 



rel, 



crock, or 



bar- 

 ea-rthe n ware 

 other con- 

 tainer from a mix- 

 ture of sodium cyan- 

 ide, sulphuric acid, 

 and water — the so- 

 called " barrel or 

 pot" method: (2) 

 by pumping it into 

 the building in 

 liquid form from 

 cylinders — 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 moisture 

 acid gas — the powder method. 



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

 sodium cyanide into a barrel containing sulpburic acid 

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

 is no danger of the bottom of the bag breaking and 

 spilling the cyanide. The cyanide should not be 

 (Lopped into the acid-water mixture; it should be 

 lowered carefully. 



from the air to form hydrocyanic 



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. 

 1 and 12) or some similar container (fig. 13). This method, while 

 more laborious than others, gives excellent results and is the safest 

 for the use of other than professional fumigators. It can be made 

 thj cheapest method of fumigation. 



