TY - JOUR
T1 - Thermochemistry of double carbonates in the K2CO3-CaCO3 system
AU - Navrotsky, Alexandra
AU - Putnam, Robert L.
AU - Winbo, Camilla
AU - Rosén, Erik
PY - 1997
Y1 - 1997
N2 - 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.
AB - 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.
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U2 - 10.2138/am-1997-5-614
DO - 10.2138/am-1997-5-614
M3 - Article
AN - SCOPUS:0031463862
SN - 0003-004X
VL - 82
SP - 546
EP - 548
JO - American Mineralogist
JF - American Mineralogist
IS - 5-6
ER -