Hydrofluoric acid solution calorimetric investigation of the effects of anorthite component on enthalpies of K-Na mixing in feldspars

Enthalpies of solution have been measured at 50 degrees C in 20.1 wt% hydrofluoric acid under isoperibolic conditions for a nine-member K-Na ion-exchange series based on a disordered oligoclase specimen containing 23.1 mol% anorthite (An) component. The series displays positive enthalpies of K-Na mixing, but magnitudes are substantially reduced relative to An-free analogs. Volumes of K-Na mixing for the series are similarly reduced; the asymmetry of these with respect to composition is the opposite of that for alkali feldspars. Lower magnitudes of the mixing properties are probably related to the shortened compositional range of this series, relative to normal alkali-feldspar series, and to a 23% An structural background against which the energetic effects of K-for-Na substitution are dampened.

Title	Hydrofluoric acid solution calorimetric investigation of the effects of anorthite component on enthalpies of K-Na mixing in feldspars
Creator	Hovis, Guy L.
Publisher	American Mineralogist
Academic Department	Geology & Environmental Geosciences
Division	Natural Sciences
Organization	Lafayette College
Date Issued	1997
Date Available	2013-02-06T20:21:36Z
Type	Article
Language	English
Bibliographic Citation	Hovis, G. L. (1997) "Hydrofluoric acid solution calorimetric investigation of the effects of anorthite component on enthalpies of K-Na mixing in feldspars." American Mineralogist 82 (1/2): 149-157.
Standard Identifier	Handle 10385/1088
Permalink	http://hdl.handle.net/10385/1088
Rights Statement	In Copyright
Rights Holders	Mineralogical Society of America