Thermochemistry of double carbonates in the K2CO3-CaCO3 system

Alexandra Navrotsky, Robert L. Putnam, Camilla Winbo, Erik Rosén

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Enthalpies of formation, ΔHf, of the double carbonates K2Ca(CO3)2 (with two polymorphs, bütschliite and fairchildite) and K2Ca2(CO3)3 from the components K2CO3 and CaCO3 were determined at 298 K by drop solution calorimetry in molten 2PbO·B2O3 at 974 K. The enthalpies of formation were -38.7 ± 3.2 kJ/mol for bütschliite, -5.1 ± 3.3 kJ/mol for fairchildite and -7.2 ± 5.8 kJ/mol for K2Ca2(CO3)3. The entropy changes for the formation, ΔSf, were also evaluated for the double carbonates. Assuming ΔSf(bütschliite) = 0, because of its ordered structure, the entropy of formation of fairchildite is 40.9 ± 5.1 J/mol·K and of K2Ca2(CO3)3 is 39.4 ± 7.3 J/mol·K.

Original languageEnglish (US)
Pages (from-to)546-548
Number of pages3
JournalAmerican Mineralogist
Volume82
Issue number5-6
DOIs
StatePublished - 1997
Externally publishedYes

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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