A method for controlling alkali-metal oxide activities in one-atmosphere experiments and its application to measuring the relative activity coefficients of NaO0.5 in silicate melts

Hugh St C. O'Neill

doi:10.2138/am.2005.1792

A method for controlling alkali-metal oxide activities in one-atmosphere experiments and its application to measuring the relative activity coefficients of NaO_0.5 in silicate melts

Hugh St C. O'Neill^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

32 Citations (Scopus)

Abstract

The activity of alkali metal oxides can be controlled in one-atmosphere wire-loop experiments at high temperature by suspending a crucible containing alkali silicate melt beneath the samples. The method has been applied to measuring the activity coefficient of NaO_0.5 in a series of CMAS-NaO_0.5 melts relative to that in the anorthite-diopside eutectic composition at 1400 °C, using a reservoir of NaO_0.5-SiO₂ melt. The results show that this relative activity coefficient decreases strongly with SiO ₂, increases with CaO and MgO, but is insensitive to AlO_0.5. This latter behavior is inconsistent with " quasi-crystalline" models of melt thermodynamics that hypothesize Na-Al species.

Original language	English
Pages (from-to)	497-501
Number of pages	5
Journal	American Mineralogist
Volume	90
Issue number	2-3
DOIs	https://doi.org/10.2138/am.2005.1792
Publication status	Published - 2005

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N2 - The activity of alkali metal oxides can be controlled in one-atmosphere wire-loop experiments at high temperature by suspending a crucible containing alkali silicate melt beneath the samples. The method has been applied to measuring the activity coefficient of NaO0.5 in a series of CMAS-NaO0.5 melts relative to that in the anorthite-diopside eutectic composition at 1400 °C, using a reservoir of NaO0.5-SiO2 melt. The results show that this relative activity coefficient decreases strongly with SiO 2, increases with CaO and MgO, but is insensitive to AlO0.5. This latter behavior is inconsistent with " quasi-crystalline" models of melt thermodynamics that hypothesize Na-Al species.

AB - The activity of alkali metal oxides can be controlled in one-atmosphere wire-loop experiments at high temperature by suspending a crucible containing alkali silicate melt beneath the samples. The method has been applied to measuring the activity coefficient of NaO0.5 in a series of CMAS-NaO0.5 melts relative to that in the anorthite-diopside eutectic composition at 1400 °C, using a reservoir of NaO0.5-SiO2 melt. The results show that this relative activity coefficient decreases strongly with SiO 2, increases with CaO and MgO, but is insensitive to AlO0.5. This latter behavior is inconsistent with " quasi-crystalline" models of melt thermodynamics that hypothesize Na-Al species.

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JF - American Mineralogist

IS - 2-3

ER -

A method for controlling alkali-metal oxide activities in one-atmosphere experiments and its application to measuring the relative activity coefficients of NaO_0.5 in silicate melts

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