280 The Solubility of Calcium Phosphates in Citric Acid 



By calculation the lime and phosphoric acid exist as : 



Dicalcic phosphate (CaO)2H20P205 

 Tricaloic phosphate (CaO)3P205 ... 

 Water of crystallisation ... 



48-260 0-939 43-260 7-541 100-000 



If the water of crystallisation present be contained in the dicalcic 

 phosphate only and none with the tricalcic phosphate we would have 



Dicalcic phosphate 



(CaO)2H20P2058H20 ... 



CaHP04 . 4H2O 

 Tricalcic phosphate CagPjOg 



But as the tricalcic phosphate might also contain some water of crystal- 

 lisation, the first statement is probably more correct. 



The above sample therefore appears to be a mixture of 14-188 % 

 di- and 78-271 % tricalcic phosphate with water of crystallisation. 



No. 2. Calcii Phosphas B.P., purchased locally. 

 Upon analysis the following figures were obtained : 



Lime (CaO) 40-15 



Phosphoric acid (P.O.,) 47-52 



Wat'.M- 12-33 



100-00 



Per cent. 

 Loss in weight en drying in desiccator over sulphuric acid for 16 hours 1-184 

 Loss in weight on drying in desiccator over sulphuric acid for 112 hours 1-620 

 Loss on drying at 100" C. : 2 hours 3-46 %, 6 hours 3-51 %. 9 hours ... 3-60 

 Loss on ignition ... ... ... ... ... ... ... ... 12-35 



By calculation the lime and phosphoric acid arc found to exist in 

 the following combination : 



CaO HoO P2O5 Water 



Dicalcic phosphate (CaO)2H20P20s 32-142 5-166 40-751 — =78-059 



Tricalcic phosphate (CaO)3P205 ... 8-008 — 6-767 — = 14-777 



Water of crvstalhsation — — — 7-164 = 7-164 



40-150 5166 47-518 7-164 =100-000 



If all the water of crystallisation be contained in the dicalcic phosphate 

 only, the dicalcic phosphate present would conform to the formula 



