362 MILL AND ELEVATOR INSECTS 



liquid at a temperature of 140 degrees P. to 180 degrees F. This 

 will be approximately the temperature of the liquid up to one- 

 half hour after mixing the acid and water, with the mill at ordinary 

 temperature. 



6. Experiments in the laboratory and practical work in many 

 mills indicate that eggs of the flour moth are killed by this gas, 

 and that other stages of the insect are reached and killed even 

 when covered by an inch or more of webbing. 



Precautions. 1. Calculations as to the cubical contents of 

 each floor to be fumigated must be absolutely accurate. 



2. Get only the best material; a poor grade of cyanide or acid 

 can not be relied upon. 



FIG. 364. Pieces of cyanide should be from two to four inches in diameter. 



3. Put on the work only a few picked men, selecting them 

 from among the most intelligent of your employes. 



4. Take every measure possible to prevent the cyanide from 

 coming in contact with the acid until the critical moment when 

 such contact is desired. Be sure that each step of the process 

 has been carefully studied beforehand. Do not hang bags as shown 

 in figure 363. 



5. Provide for thorough ventilation from the outside. Do not 

 enter the mill until it has been well aired for at least two hours. 



6. Removal of the jars from the building after the operation 

 and the disposing of the residue in a safe place, call for care, and 

 should not be intrusted to men who are careless or ignorant as 

 to the nature of the gas. They should be cautioned to avoid a 

 jar which bubbles, and should at all times keep their faces away 



