Titre du document / Document title

Thermodynamic properties of two iron silicates. Heat capacities of deerite from the temperature 10 K to 700 K and of grunerite from 10 K to 1000 K

Auteur(s) / Author(s)

KOMADA N. ⁽¹⁾ ; WESTRUM E. F. ⁽¹⁾ ; HEMINGWAY B. S. ; ANOVITZ L. M. ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Univ. Michigan, dep. chemistry, Ann Arbor MI 48109, ETATS-UNIS

Résumé / Abstract

Heat-capacity measurements were made on deerite and on grunerite with an adiabatic calorimetric system from the temperature 10 K to 350 K and by d.s.c. in the super-ambient region. Slight Schottky-like and bell-shaped anomalies appear near T = 16 K and 34 K in the deerite heat-capacity curve. The smaller than expected magnetic susceptibility and Mössbauer spectral changes at T > 210 K were interpreted as a thermally activated electron-delocalization mechanism in the deerite sample and yet another deerite sample by adjusting for anharmonicity and resolving the small excess heat capacities by the Komada-Westrum approach. A sharp anomaly centered at T = 35.5 K was observed in the heat capacity of grunerite curve. Measured values of C_p,m/R, x{S^o_m(T') - S^o_m(10 K)}/R, and - (Φ^o_m(T') - Φ^o_m(10 K}/R at T' = 298.15 K for deerite are 94.55, 95.21, and -43.50, respectively, where C_p,m denotes molar heat capacity, S^o_m standard molar entropy, H^o_m standard molar enthalpy, and where Φ^o_m = Δ^T₀S^o_m- Δ^T₀H^o_mT. The corresponding values for grunerite are 82.38, 83.98, and -39.69, respectively.

Revue / Journal Title

Journal of chemical thermodynamics   ISSN 0021-9614   CODEN JCTDAF 

Source / Source

1995, vol. 27, n^o10, pp. 1097-1118 (56 ref.)

Langue / Language

Anglais

Editeur / Publisher

Elsevier, Kidlington, ROYAUME-UNI  (1969) (Revue)

Mots-clés anglais / English Keywords

Thermodynamic properties ; Specific heat ; Experimental study ; Iron Silicates ; Adiabatic calorimeter ; Inorganic compounds ;

Mots-clés français / French Keywords

Propriété thermodynamique ; Chaleur massique ; Etude expérimentale ; Fer Silicate ; Calorimètre adiabatique ; Fe O Si ; Composé minéral ;

Mots-clés espagnols / Spanish Keywords

Estudio experimental ; Calorímetro adiabático ;

Localisation / Location

INIST-CNRS, Cote INIST : 14300, 35400005014437.0050