A. A. Ramsay 283 



By calculation the lime and phosphoric acid would probably 

 exist as : 



53-050 41-170 



Assuming that the water present is associated only with the dicalcic 

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

 phosphate present would be (CaO)2H20P2054H20 or CaHP042H20. 



Thus: 



This preparation is not pure tricalcic phosphate, but is a mixture of 

 77-29 % tricalcium phosphate, 13-97 % bicalcium phosphate and 8-74 % 

 calcium hydrate. 



A second attempt was made to prepare pure tricalcium phosphate 

 by dissolving bone ash in hydrochloric acid and precipitating with 

 ammonium hydrate, following the method of the British Pharmacopoeia, 

 but washing the precipitate till free from chlorides with very dilute 

 ammonium hydrate as was done in the old analytical method of deter- 

 mining phosphoric acid as tricalcic phosphate. 



The product obtained after drying and igniting was marked No. 6. 

 Upon analysis the product was found to consist of : 



Lime (CaO) 56-15 



Phosphoric acid (P2O5) 43-85 



100-00 



Since the above is most probably a mixture of di- and tricalcic phos- 

 phate with free lime, it is impossible from the data given to calculate 

 the percentage of each, since several such mixtures could be calculated 

 having 56-15 % CaO and 43-85 % P2O5. 



Since 43-85 P2O5 requires 51-997 CaO to form tricalcic phosphate, 

 and 34-664 CaO to form dicalcic phosphate, the free lime may be any- 

 thing between 56-15 minus 51-997 = 4-153 and 56-15 minus 34-664 

 = 21-486. If however the free hme be 7-00 % (which is about that 



