354 MILL AND ELEVATOR INSECTS 



but also that one good "whiff" of the gas generated by the contact 

 of acid and cyanide might produce fatal results. Drinking water 

 should not be exposed to the fumes. Bright steel, if not covered, 

 may be slightly tarnished by fumigation. 



Advantages of the Treatment. Summing up the advantages 

 of the hydrocyanic acid gas treatment, it may be said: 



1. It is always available and not expensive. 



2. It is a method of relief for mills outside of the "freezing" 

 zone, and freezing is by no means an absolute cure. 



3. Its use at the strength indicated is absolutely safe as regards 

 fire or explosiveness. 



4. It is absolute death, at strength used, to eggs, as well as 

 the other stages in the life of the flour moth. 



J 5. Its deadly qualities of themselves call for such extreme 

 care in its use as to insure safety. In other words, in the hands of 

 those acquainted with its nature and its use, it is a safe agent. 



The Method Briefly Described. Certain conditions are neces- 

 sary to insure successful fumigation. In the first place, the 

 environment of the building to be treated is of importance. Mani- 

 festly, if it is one of a block of buildings, or if there is another 

 building owned by a different party directly contiguous, into 

 which the gas might penetrate where it is not desired, the permis- 

 sion of the owners of such property should be obtained, and pre- 

 cautions taken to prevent accident. When a mill stands by itself 

 at a distance from other buildings with which it is in no way 

 connected, no such preliminary precautions are necessary. 



Secondly, the building to be fumigated must be fairly tight. 

 If windows are very loose, paper should be pasted over the cracks. 

 Further, when possible, if the stories to be fumigated are not 

 separated from each other, some temporary inclosure should be 

 made, thus insuring each story getting the maximum amount of gas. 



Find accurately the number of cubic feet in each story to be 

 treated, making no allowance for machinery or empty bins. Allow 

 0.25 of a gram of cyanide for every cubic foot of space. After 

 multiplying the number of cubic feet by 0.25, divide by 28.35 to 

 reduce to ounces, and divide this result by 16; the final quotient 

 is the number of pounds (avoirdupois) of cyanide needed. But 

 experience has taught the writer that it is well to use two or three 

 jars more on each floor than the above specifications call for, to 

 insure thorough work; hence it is wise to add nine or ten pounds 

 more for each story, when making up your order. The amount 



