CALCIUM PHOSPHATES 



125 



108. The Calcium Phosphates. 



{a) Tricalcium Phosphate. — The amorphous salt is 

 precipitated by adding sodium phosphate solution 

 (NagHPOJ in excess to a solution of calcium chloride 

 which has been made distinctly alkaline with ammonia. 

 The Ca3(P04)2 is obtained as an earthy white powder 

 by filtering off the gelatinous precipitate, washing 

 thoroughly, and drying in the oven. 



(Jj) Dicalcium Phosphate. — This salt, Ca2H2(P04)2. 

 is precipitated by the addition of a solution of calcium 

 chloride to one of ordinary sodium phosphate. The 

 precipitate is filtered off, washed, and dried. 



{c) Monocalcium Phosphate. — CaH4(P04)2 may be 

 obtained by dissolving the dicalcium phosphate {U) in 

 phosphoric acid solution and allowing the liquid 

 spontaneously to evaporate. The salt forms rhombic 

 tables, which are very readily soluble in water. 



109. Solubilities of the Calcium Phosphates, 



(a) The tricalcium and dicalcium phosphates should 

 be tested with regard to their solubilities in water, 2 per 

 cent, citric acid solution and 5 per cent, ammonium 

 citrate solution. A good idea of the solubility may. be 



