16 A MANUAL OF WEEDS 



must be exercised in its use. Do not inhale the powdered drug 

 when making the solution, or the spray as it is delivered ; keep to 

 the windward side while working with it. The formula for the 

 solution is one pound of the drug in three to nine gallons of water. 

 White arsenic is cheaper than Arsenite of soda, but needs to be 

 combined with twice its weight of Sal soda in order to be readily 

 soluble in water ; the formula being, one pound of White arsenic, 

 two pounds of Sal soda, three to nine gallons of water. These 

 arsenical compounds are the chief ingredients of all commercial 

 weed-killers, and are used on walks, roadways, tennis courts, and all 

 places where the complete and lasting extirpation of all plant 

 growth is required. 



