PHOSPHATES. 429 



(c.) Decompose the latter by just so much sulphuric acid, as pre- 

 cipitates the earth. 



(d.) An acid solution remains, which, after evaporation, is viscous, 

 tenacious, and uncrystallizable. 



(e.) By a stronger heat, phosphuretted hydrogen gas is expelled 

 phosphorus sublimed and phosphoric acid remains. 



3. PROPERTIES. 



(a.) Forms with alkaline and earthy bases, salts of extreme solu- 

 bility. 



(b.) Those of baryta and strontia, crystallize with great diffi- 

 culty. 



(c.) Those of the alkalies are soluble in all proportions, in highly 

 rectified alcohol. 



(d.) That of potassa is more deliquescent than muriate of lime. 



(e.) Absorb oxygen slowly from the air, and by heat applied in a 

 retort, give the same products as the acid itself. 



4. COMPOSITION. Phosphorus, 72.75 100. 



Oxygen, 27.25 37.44 



100. 



Calculated by Dulong, upon the supposition that it is a binary 

 compound of oxygen and phosphorus, but it may be a triple com- 

 pound of these two, and hydrogen forming an hydracid ; in which 

 case, its proper name would be hydro-phosphorous acid. Sir H. 

 Davy thinks that the oxygen of this acid is just half that of phospho- 

 rous acid, and of course that 100 of phosphorus are combined with 

 33.75 oxygen. If, as above stated, phosphorous acid consists of an 

 equivalent of each element, it is probable that this acid contains two 

 equivalents of phosphorus, 12 x2=24-f- 1 of oxygen, 8=32, its rep- 

 resentative number.* It is not certain that we are yet accurately 

 acquainted with the proportions of the elements in the acids of phos- 

 phorus. 



PHOSPHATES. 



General Characters. 



(a.) Phosphates of alkalies partially decomposed by ignition with 

 charcoal ; phosphate of ammonia is decomposed by heat alone. 



(b.) Phosphates of the alkaline earths not decomposed when heat- 

 ed with charcoal, nor is phosphorus obtained. 



(c.) Before the blowpipe, both alkaline and earthy phosphates, 

 melt into a vitreous globule, sometimes transparent and sometimes 

 opake ; that of ammonia is dissipated entirely. 



* Henry, Vol. I, p. 374, 10th Ed. 



