THE ASH OF PLANTS. 135 
the sturgeon of the Caspian Sea. It is also an ingredient 
of guanos, and probably. of animal excrements in general. 
The tricalcic phosphate, or, as it is sometimes termed, 
the bone-phosphate, 3 CaO, P,O,, is a chief ingredient of 
the bones of animals, and constitutes 90 to 95 per cent of 
the ash or earth of bones. It may be formed by adding a 
solution of lime to one of phosphate of soda, and appears 
as a white precipitate. It is insoluble in pure water, but 
dissolves in acids and in solutions of many salts. In the 
mineral kingdom tricalcic phosphate is the chief ingredient 
of apatite and phosphorite.. These minerals are employed 
in the preparation of the so-called superphosphate of lime, 
which is consumed to an enormous extent as a turnip-fer- 
tilizer. The superphosphate of commerce, when genuine, 
is essentially a mixture of sulphate of lime with the three 
phosphates above noticed, of which the monocalcic phos- 
phate should ‘predominate. 
The Phosphates of Magnesia, Iron, and Manganese, 
are bodies insoluble in water, and require no particular 
notice. 
Tux Caiorwes are all characterized by their ready solu- 
bility in water. The chlorides of Lithium, Calcium, and 
Magnesium, are deliquescent, 1. e., they liquefy by absorb- 
ing moisture from the air. The chlorides of Potassium 
and Sodium alone need to be described. 
Chloride of Potassium, K Cl, 74.5.—This body may: be 
produced either by exposing metallic potassium to chlorine 
gas, in which case the two elements unite together direct- 
ly; or by dissolving caustic potash in chlorhydric acid. 
In the latter case water is also formed, as is expressed by 
the equation K HO +. HCl = KCl + H,0. 
Chloride of potassitim closely resembles common salt 
(chloride of sodium) in appearance, solubility in water, 
taste, etc. It is but rarely an article of commerce, but is 
present in the ash and in the juices of plants, especially of 
sea-weeds, and is likewise found in all fertile soils. 
