THE PLANT. 33 



NEUTRALS . 

 CHLORINE. 



Chlorine is an important ingredient of vegetable 

 ashes. It is not found alone in nature, but is always 

 in combination with other substances. Its most im- 

 portant compound is with sodium, forming chloride 

 of sodium (or common salt). Sodium is the base 

 of soda, and common salt is usually the cheapest 

 source from which to obtain both soda and chlorine. 

 Chlorine unites with lime in the formation of chloride 

 of lime, which is much used to absorb or destroy the 

 unpleasant odors of decaying matters, and in this 

 character it is of use in the treatment of manures. 



OXID EOF IRON. 



Oxide of iron, one of the constituents of ashes, is 

 common iron rust. Iron itself is naturally of a 

 greyish color, but when exposed to the atmosphere, 

 it readily absorbs oxygen and forms a reddish com- 

 pound. It is in this form that it usually exists in 

 the soil, and many soils as well as the red sandstones 

 are colored by -it. It is seldom, if ever, necessary to 

 apply this as a manure, there being usually enough 

 of it in the soil. 



This red oxide of iron, of which we have been 

 speaking, is called by chemists the peroxide. There 

 is another compound which contains less oxygen than 

 this, and is called the protoxide of iron, which is 



2* 



