THE ASH OF PLANTS. 117 
ficially, and the liquids may be thrown about by the sudden formation 
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. 
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, O,, 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 héat developed. On boiling it with water ‘for 
some time, it completely dissolves, and the solution con- 
tains— : 
Hydrated Phosphoric Acid, Sym. P, O,, 3 H, O, 196, 
or H, PO,, 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. 2 
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 
