282 The Solubility of Calcitmi Phosphates in Citric Acid 



The method was followed and the product obtained was marked as 

 phosphate No. 4. 



On submitting this product (No. 4) to chemical analysis the follow- 

 ing data was obtained : 



Lime (CaO) 52-93 



Phosphoric Acid iV^O^) 41-44 



Water (combination and constitution) ... 5-68 



100-05 

 Per cent. 

 Loss on drying at 100° C. in 2 hoiu-s ... ... 1-91 



Loss on drying at 100° C. in 6 hours 1-95 



Loss on ignition ... ... ... ... .... 5-68 



By calculation the Ume and phosphoric acid probably exist as : 



CaO P2O5 



Dicalcic phosphate 4-590 5-819 



Tricaloic phosphate 42-142 35-621 



Lime (free) 6-198 — 



52-930 41-440 



Assuming that the water present is associated only with the dicalcic 

 phosphate and with the lime as hydrate, the formula of the dicalcic 

 phosphate present is (CaO)2H20Po054H20 or CaHP042H20. Thus : 



This preparation therefore is not pure tricalcic phosphate, but is a 

 mixture of 77-76 % tricalcic phosphate, 14-10 % dicalcic phosphate 

 and 8-19 % calcium hydrate. 



The method given in the British Pharmacopoeia^ for the preparation 

 of tricalcium phosphate, by dissolving bone ash in hydrochloric acid 

 and precipitating with ammonium hydrate was next tried. 



The preparation thus obtained was marked No. 5, and upon analysis 

 gave the following data : 



Lime (CaO) 53-05 



Phosphoric acid (PA) 41-17 



Water 5-78 



100-00 

 1 The British Pharmacojioeia (Spottiswoode and Co., London), 1891, p. 87. 



