Thermodynamic Properties of Aegirine Entity Journal Article uri icon

DCO ID 11121/6673-9992-1783-1204-CC

year of publication

  • 1984

abstract

  • The thermodynamic properties of aegirine, of composition [(Na 0.869 Fe3+0.7362 Fe2+0.16 Mn0.03 Ca0.1121)(Al0.14Si1.9738)(O6)], were experimentally determined at the Bureau of Mines as part of its efforts to advance minerals technology. The standard enthalpy of formation determined by hydrofluoric acid solution calorimetry is

     ΔHf°298 = -641.12 ± 0.73 kcal/mol. 

    The standard enthalpy of formation from the oxides is

     ΔH°298 = -37.136 ± 0.509 kcal/mol. 

    Low-temper.ature heat capacities were determined by adiabatic calorimetry from 19.1 to 304.6 K. The derived standard entropy is S°298 = 38.03±0.14 cal/mol•K. The heat capacity was measured over the range 348 to 1,198 K by differential scan­ning calorimetry. 

    These experimentally determined data were combined with data from the litera­ture to calculate the Gibbs energies of formation and equilibrium constants of form­ation over the temperature range of the measurements. Standard enthalpies of forma­tion are given as functions of temperature. The standard Gibbs energy of formation at 298.15 K is 

    ΔGf°298 = -600.36 kcal/mol. 

publication date

  • 1984

issue

  • 8912