PHOSPHATES. 439 



2. PROPERTIES. 



(a.) They are compressed prisms; speedily effloresce and re- 

 quire 1 5 parts of cold water for solution ; hot water dissolves so much 

 that crystals form as the solution cools. 



(b.) Lose water of crystallization by heat; melt by a still higher 

 heat into a glass. 



(c.) Decomposed entirely by sulphuric, nitric, and muriatic acids, 

 and by fixed alkalies and alkaline earths. Ammonia forms a triple 

 salt, which exists in urine. 



(d.) Composed of acid, 1 equivalent, 20; base 1, 28=48, and 

 when crystallized, water 7 = 63 = 111. Thomson. 



PHOSPHATE OF AMMONIA AND MAGNESIA. 



1 . DISCOVERY. Found by Fourcroy, in the calculus of a horse; ex- 

 ists in the bones of most animals, and is common in the human subject. 



2. PREPARATION. 



(a.) Formed by adding phosphate of ammonia, or ammonia, or its 

 carbonate to phosphate of magnesia; or carbonate of ammonia and 

 afterwards phosphate of soda to solution of sulphate of magnesia, 

 when the double phosphate subsides in the form of minute grains. 



(b.) Magnesia is detected when in solution in an acid, with or 

 without other earths, in the following manner. 



(c.) Add to the solution bi-carbonate of ammonia, (formed by ex- 

 posing common carbonate to the air, till it has lost its smell ;) the 

 other earths will be precipitated, but not the magnesia. 



(d.) Add a cold saturated solution of phosphate of soda ; a white 

 powder precipitates which is the ammoniaco-magnesian phosphate. 



(e.) Ammoniacal phosphate of magnesia is a white powder which 

 lines the cavities of some calculi in the form of crystals^ and is fre- 

 quently deposited in crystals. 



(f.) Tasteless, insoluble in water, soluble in acids, even in the 

 acetic, and is precipitated unchanged when the acid is saturated by 

 ammonia ; decomposed by heat, the ammonia and water flying away,, 

 and leaving the phosphate of magnesia ; composed of equal weights 

 of phosphate of ammonia, phosphate of magnesia, and water.* 



PHOSPHATE OF ALUMINA. 



Phosphoric acid combines with alumina, to saturation, forms a 

 white insipid powder which melts before the blowpipe into a transpa- 

 rent globule. 



& & * # & * 



The phosphates of the other earths are comparatively unimportant. 



* Its composition is said to be otherwise not accurately determined. Stromeyer 

 states the magnesia at .37. Turner. 



But Thomson states it at 1 equiv. phosphate of magnesia, 48, 1 equiv. phosphate of 

 ammonia, 45, 4 of water, 36 ; its equivalent being 129, the salt being dried without 

 heat. 



