THE ASH OF PLANTS. 117 



flcially, and the liquids may be thrown about by the sudden ijrmation 

 of steam at the points of contact, when subsequently stirred. 



Sulphuric acid forms with the bases an important class 

 of salts the sulphates to be presently noticed, some of 

 which exist in the ash, as well as in the sap of plants. 

 When organic matters containing sulphur, as hair, album 

 in, etc., are burned with full access of air, this element re 

 mains in the ash as sulphates, or is partially dissipated as 

 sulphurous acid. 



PHOSPHOKFS AND ITS COMPOUNDS. 



Phosphorus, Sym. P, at. wt. 31, has been sufficiently 

 described, (p. 43.) Of its numerous compounds but two 

 require additional notice. 



Anhydrous Phosphoric Acid, Sym. P Q O 6 , mo. wt. 142, 

 does not occur as such in nature. When phosphorus is 

 burned in dry air or oxygen, anhydrous phosphoric acid 

 is the snow-like product, (Exp. 18.) It has no sensible 

 acid properties until it has united to water, which it com 

 bines with so energetically as to produce a hissing noise 

 from the heat developed. On boiling it with water for 

 some time, it completely dissolves, and the solution con 

 tains 



Hydrated Phosphoric Acid, Sym. P 2 O 5 , 3 H 2 O, 196, 

 or H 3 PO 4 , 98. The chief interest which this compound 

 has for the agriculturist lies in the fact that the com 

 binations which are formed between it and various bases 

 phosphates are among the most important ingredients 

 of plants and their ashes. 



When bodies containing phosphorus in other forms than 

 phosphoric acid, as protagon, (p. 93,) and, perhaps, some 

 of the albuminoids, are disorganized by heat or decay the 

 phosphorus appears in the ashes or residue, in the con 

 dition of phosphoric acid or phosphates. 



The formation of several phosphates has been shown in 



