The heat capacities of osumilite from 298.15 to 1000K, the thermodynamic properties of two natural chlorites to 500 K, and the thermodynamic properties of petalite to 1800 K Entity Journal Article uri icon

DCO ID 11121/9505-8925-5034-2227-CC

year of publication

  • 1984


  • We report results obtained with our recently automated low-temperature adiabatic calorimeter. A brief description of the change is in the instrument are provided.

    The heat capacities of natural osumilite (K0.93Na0.09Ca0.02Ba0.01Mg1.88Fe0.38Ti0.01Al4.62Si10.12O30) were measured from 340 to 1000 K by differential scanning calorimetry. The following polynomial fits the specific heat (J/g · K) of the natural sample with an average deviation of 0.5 percent between 298 and 1000 K.

    (eq. abbrev'd)

    The heat capacities of two natural chlorites have been measured between 0 and 500 K. For the chlorite composition (Si2.99Al1.01)(Al1.39Fe3+0.21Fe2+0.57Mg3.52)O10(OH)8, the measured molar heat capacities, C°p, between 200 and 500 K are consistent with the equation:

    (eq. abbrev'd)

    For the chlorite composition (Si2.47Al1.53)(Al1.60Fe2+3.29Mg1.05)O10(OH)8 the polynomial

    (eq. abbrev'd)

    fits the measured molar heat capacities with an average deviation of ±0.36 percent. The heat-capacity values were not corrected for deviations from end member compositions. The entropy of the former phase is 431.7 ± 5.0 J/(mol·K) and that of the latter is 495.7 ± 10 J/(mol·K), both at 298.15 K. The reported entropy values do not contain a configurational entropy term and thus represent S298 - S0.

publication date

  • 1984


  • 69