Relation to Deleterious Chemical Agents 457 



of water. Waste formalin at the rate of 1 pound to 10 gal- 

 lons of water may be used under similar circumstances. 



Copper sulfate and iron sulfate are, however, the two 

 compounds which may be commercially employed with 

 hand or power sprayers for the suppression of certain weeds 

 in fields of grain or flax, and in large lawns. Copper 



FIQ. 132. Wild mustard of size effectively reached and readily injured 

 by the spray. 



sulfate is commonly used as a solution containing from 3 

 to 5 per cent of the salt, 12 to 20 pounds to 50 gallons of 

 water. It is usually recommended to employ iron sulfate at 

 a strength of 1^ to 2 pounds of the salt per gallon of water. 

 280. Practicability of the chemical method. The 

 chemical method may be wisely employed under certain 

 circumstances, as follows : 



