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Physico-chemical Methods for the Identification of 

 Microcrystalline Basic Calcium Phosphates Prepared in Vitro 



p. Lerch, C. Vuilleumier 



Institut fiir anorganische und physikalische Chemie der Universitat, Bern, Schweiz; 

 Institut de Radiophysique Appliquce, Universite de Lausanne, Lausanne, Suisse 



I. Introduction 



The method of synthesis of hydroxyapatite proposed by Hayek (1960), which 

 consists of the reaction of Ca(NO.j)2 in the presence of NH3 with Na2HP04 , 

 permitted us by changing the conditions of the proceedings to obtain two specific 

 kinds of phosphates: 

 hydroxyapatite (HA) Cai(,(P04)6(OH)o 

 hydrated tricalcium phosphate (TCPH) Ca9(P04)6- 1/2 H.O. 



For a better understanding of the synthesis mechanism of these components, and to 

 obtain a criterion which would permit the verification of the nature of the hydroxy- 

 apatite during synthesis, we thought that it would be interesting to measure the 

 variations of pH during this procedure; commonly, it seems that this operation takes 

 place as a simple neutralization. 



The conclusions of this method should make it possible to discuss the composition 

 and structure of other calciumorthophosphates analogous to those mentioned above, 

 which might play a part in the processes of calcification, such as octocalcium-ortho- 

 phosphate (OCP) Ca8Ho(P04)6-H,,0. 



For this purpose, we will use results already obtained (Lerch and Vuilleumier, 

 1964 a, b; Vuilleumier, 1965) in X-ray and electron diffractions, specific area 

 measurements and especially thermogravimetric (TG) and diiferential thermal analysis 

 (DTA). 



IL Experimental part and results 



The proportions of Ca"^"^ and PO4 were varied, thus giving excesses up to 

 200"/o of each ion. The reactives were permanently stirred at 25 C under N., during 



