INSECTICIDES AND FUNGICIDES 



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has a rather pleasant odor, be used in its stead. This also is a fluid, and is 

 used in the same way as carbon bisulphide, namely, by pouring it into open 

 dishes or crocks and allowing it to evaporate in a box, bin or room. 



It is not nearly as effective in small quantities as either cyanide of 

 potassium or carbon bisulphide, and the large quantities that must be 

 used increase the cost of treatment. 



Para-dichlorobenzene. — This is a recently proposed fumigant and is 

 not yet in general use, because of its cost. It is not evil-smelling like 



Making Preparations to Fumigate with Hydrocyanic Gas. 1 

 Front edge of sheet tent and top of derrick ready to be pulled over tree. 



carbon bisulphide, and appears to be quite effective in destroying weevils 

 in grain and clothes moth. Since it is not inflammable, it can be more 

 safely used about dwellings, though its fumes have wonderful penetrating 

 power and escape in some quantity even from tightly stoppered bottles. 

 From a limited experience with it the writer is disposed to regard it very 

 favorably for fumigating seeds and fabrics, though more extended tests 

 may show it to have defects that are not now apparent. 



Hydrocyanic Acid Gas. — This gas is made from cyanide of potassium 

 (98 per cent), commercial sulphuric acid of good grade and water. The 



i Courtesy of C. S. Dept. of Agriculture. 



