62 ELEMENTS OF PLANTS. 



phorus matches, commonly called lucifer or friction 

 matches, which a little rubbing produces heat enough to 

 set on fire. 



Phosphate of lime is found not only in the seeds of 

 very many plants, especially those of which bread is 

 made, but in all plants, and in the bones of men and 

 other animals, whence it is called bone-earth. 



216. The ashes of all kinds of straw and grass, of the 

 bamboo cane, and of the scouring rush, consist, in a very 

 large degree, of silex or silica; and all these plants owe 

 the stiifness and hardness of their stems to the silica 

 contained in them. 



Silica is oxygen combined with a metal-like substance 

 called silicon. When perfectly pure, silica is a white, 

 gritty powder, without taste or smell. It is the substance 

 of which quartz, rock-crystal and flint are composed. 

 Though wholly unlike, in appearance, to the other acids, 

 it is yet an acid, and combines with the oxides of many 

 of the metals to form silicates, and, in these forms, 

 constitutes a very large portion of all rocks and soils. 



217. In the ashes of trees and other woody plants, as 

 well as in most other ashes, potash is found. If wood 

 ashes be leached, that is, if hot water be poured upon 

 them, it will, in a short time, dissolve the potash in the 

 ashes. The dark-colorqd, strong lye, thus obtained, boiled 

 with oil or fat, forms common soft soap. 



Lye, boiled away, in a pot, without fat, leaves a dirty 

 looking substance called potash. This, when somewhat 

 pimMi d, is called pcarlash. 



218. This common Potash is the carbonate of potassa, 

 ii compound of carbonic acid and potassa, which is, itself, 

 a compound of oxyjren with a metal called potassium. 

 This metal has the lustre of silver, but is soft, and so light 



