THE ASH OF PLANTS. 117 



ficialty, and the liquids may be thrown about by the sudden formation 

 of steam at the points of contact, when subsequeutly 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. 



PHOSPHORUS 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 2 O 5 , 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 



Hydratcd 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 ofhcr 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 



