Solubility characteristics of synthetic silicate sulphate apatites

✍ Scribed by K. S. Leshkivich; E. A. Monroe

• Book ID: 104734042
• Publisher: Springer
• Year: 1993
• Tongue: English
• Weight: 526 KB
• Volume: 28
• Category: Article
• ISSN: 0022-2461
• DOI: 10.1007/bf00349026

✦ Synopsis

Isomorphic substitution of (Si, S) for phosphorus in apatite (Cas(PO)aF) was investigated in the solid solution series from P-apatite to (Si, S)-apatite utilizing compositions of Cas(P04 )3 x (Si04)x/2(SO4)x/2 F with x = O,0.75,1.5,2,2.25,3. Study of the solubility characteristics of these apatites showed an increased weight loss in water with progression from the P-apatite end member to the (Si, S)-apatite end member. Experimentally determined pKsp decreased from 60.62 for the fluorapatite (Ca5(P04)3 F) to 31.65 for fluorellestadite (Ca~(Si04)l .~(S04)1.5 F). The free energy of formation calculated from the solubility product became less negative from -6755 kJ mol-1 for fluorapatite to -5760 kJ mol-1 for fluorellestadite.