10 FUMIGATION METHODS 



and sizzling similar to that produced by a piece of red- 

 hot iron in cold water. Xhere is also a dense cloud of 

 so-called steam given off. This bubbling is due to the 

 action of the acid on the cyanide, and the so-called 

 steam is the gas being produced. The result of this 

 chemical action is the production of hydrocyanic acid 

 gas (HCN), known in the liquid form as prussic acid, 

 according to the following equation : 2KCN + H 2 SO 4 

 = 2 HCN H- K 2 SO 4 . The gas has an odor somewhat 

 similar to that of peach pits, but do not stick your 

 nose over a vessel in a house or under a tent to test it. 

 These fumes, if inhaled, would prove fatal, and thus 

 the necessity of great care. 



The vessel. Various kinds of vessels can be used 

 for the acid and water. Usually an ordinary earthen 

 jar, china dish, or bowl is used. In some cases a 

 wooden pail or tub can be used to good advantage. 

 As a rule, earthenware vessels are employed in orchard 

 and nursery fumigation. The size of the vessel will 

 depend upon the amount of material to be used for 

 generating the gas. Sometimes in mills, warehouses, 

 elevators, and other enclosures large jars or wooden 

 pails containing from two to three gallons are necessary. 

 Under no circumstances should tin or iron vessels of 

 any kind be used, as the acid would quickly corrode 

 and ruin them. For small boxes a china bowl or tea- 

 cup can be used. 



Residue in the jar. After a charge of gas has been 

 liberated there will be a residue left in the jar. At 

 first, and while still warm, it is a whitish liquid, with 

 a bluish cast, but as it cools it becomes thick like paste 



