Solution calorimetric investigation of fluor-chlorapatite crystalline solutions

Solution calorimetric measurements have been made on 17 synthetic fluorapatite-chlorapatite crystalline solutions at 50 degrees C in 20.0 wt% HCl under isoperibolic conditions. Analysis of the calorimetric data indicates that heats of mixing across the series may reach values as high as 8.3 kJ/mol. Normally such a high degree of thermodynamic nonideality would be associated with immiscibility, yet no such miscibility gap is indicated by either synthetic or natural fluor-chlorapatite specimens. Based on full chemical analyses, all Cl-rich samples (X(Cl) > 0.65) of this study have halogen deficiencies that imply the presence of 4-11 mol% vacancies in the anion sites, which are interpreted to be associated with oxyapatite substitution. Separate analysis of data for the vacancy-free samples produces a linear fit for enthalpy of solution vs. composition, which yields an alternative interpretation of thermodynamic ideality. Together these models define the limits of enthalpy behavior for the fluor-chlorapatite system.

Title	Solution calorimetric investigation of fluor-chlorapatite crystalline solutions
Creator	Harlov, D. E.
Creator	Hovis, Guy L.
Publisher	American Mineralogist
Academic Department	Geology & Environmental Geosciences
Division	Natural Sciences
Organization	Lafayette College
Date Issued	2010
Date Available	2012-01-13T18:59:08Z
Type	Article
Language	English
Keyword	fluorapatite
	thermodynamics
	chlorapatite
	enthalpies of mixing
Bibliographic Citation	Hovis, G. L. and D. E. Harlov. (2010) "Solution calorimetric investigation of fluor-chlorapatite crystalline solutions." American Mineralogist 95 (7): 946-952.
Standard Identifier	Handle 10385/884
Standard Identifier	DOI 10.2138/am.2010.3485
Permalink	http://hdl.handle.net/10385/884
Rights Statement	In Copyright
Rights Holders	Mineralogical Society of America