Insecticides and Related Substances. 313 



odor by the odor they themselves produce Charcoal is a 

 deodorant by virtue of its great absorptive capacity for gases. 

 It acts by mechanical absorption of offensive gases into its pores. 

 Incidental materials. Use is often made of arsenite of soda, 

 common salt, carbolic acid, sulphuric acid and other compounds, 

 as weed destroyers. Iron sulphate solution, prepared by dissolv- 

 ing 100 pounds of the granulated salt in 50 gallons of water for 

 each acre of land has been successfully used in eradicating wild 

 mustard. Untoward effects of these substances on the soil can 

 be corrected in many cases by applications of lime. Copper sul- 

 phate applied to reservoirs at the rate of one part of salt to from 

 one million to ten million parts of water has been extensively 

 used in destroying algae growth. 



