224 WEEDS 



here listed. A pint of crude carbolic acid will do better service than 

 two gallons of kerosene, and costs much less. 



Carbolic acid. This is one of the quickest and most valuable herbi- 

 cides. The crude acid is relatively cheap. It is not quite equal to the 

 arsenical poisons for penetrating the soil, or in lasting effects, but it is 

 often preferable because of cost or convenience. It does not corrode 

 metals, and therefore may be applied with any spray-can or pump. 

 An effective method is to squirt the strong acid from an ordinary oil 

 can on the roots or crown of individual weeds. If it is to be sprayed or 

 sprinkled broadcast on the foliage or ground, it should be diluted with 

 15 to 30 parts of water, and this mixture agitated frequently during use. 



Sulfuric acid (oil of vitriol). This is destructive to everything it- 

 touches. It can be applied in the crown or about the roots of coarse or 

 especially hardy plants, provided the user is willing to kill the adjacent 

 vegetation also. In general, carbolic acid will be preferred, partly 

 because sulfuric acid can be handled only in glass vessels. 



Caustic soda. A strong solution of this material makes a cheap 

 and effective herbicide, commended especially for pouring on soil 

 where it is desired to destroy poison ivy or other deep-rooted or woody 

 plants. Soil so treated will be rendered sterile for some time, but the 

 soda will gradually leach away. Like salt, this is most effective if 

 applied in hot, dry weather. 



Arsenical compounds. One or another of the soluble arsenical com- 

 pounds form the most effective herbicides known, to use on roadways 

 and other plain surfaces. These form the basis of all, or nearly all, of 

 the various proprietary " herbicides " or " weed-killers." The sim- 

 plest to employ is arsenite of soda. This needs only to be dissolved in 

 water for use, the rate of 1 pound in 3 to 9 gallons of water. White 

 arsenic is still cheaper, but according to Schutt's formula it must be 

 combined with sal soda, which is somewhat bothersome. (White 

 arsenic, 1 pound ; washing soda, 2 pounds ; water, 3 to 9 gallons.) An 

 important characteristic of these arsenical poisons is that they endure 

 for a long time and do not readily wash or leach away. 



Application of Herbicides 



Gravel roadways, gutters, tennis courts, walks, and like surfaces can be 

 kept free from weedy growths by the application of any of the above. 



