Thermodynamic properties of scapolites at temperatures ranging from 10 K to 1000 K
| Autor: | Yury V. Semenov, Norikazu Komada, Edgar F. Westrum, I. L. Khodakovsky, David P. Moecher, Bruce S. Hemingway, Mikhail Yu. Zolotov |
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| Rok vydání: | 1996 |
| Předmět: |
Chemistry
Enthalpy Analytical chemistry Scapolite Thermodynamics Calorimetry Meionite engineering.material Heat capacity Atomic and Molecular Physics and Optics Differential scanning calorimetry Marialite engineering General Materials Science Physical and Theoretical Chemistry Intermediate composition |
| Zdroj: | The Journal of Chemical Thermodynamics. 28:941-973 |
| ISSN: | 0021-9614 |
| DOI: | 10.1006/jcht.1996.0083 |
| Popis: | The heat capacities of five mineral samples from the scapolite solid-solution series, Na 1 Al 3 Si 9 O 24 Cl (marialite) to Ca 4 Al 6 Si 6 O 24 CO 3 (meionite), were measured by the adiabatic method from T = 8 K to T = 350 K and by the differential scanning calorimetry (d.s.c.) method from T = 300 K to T = 1000 K. The meionite (Me) content in per cent {Me = 100 Ca*/(Ca* + Na*)} (where the asterisk indicates that possible substituents are included) and molar heat capacity ( C p.m / R ) at T = 298.15 K for each sample is: Me 28 , 82.07; Me 44 , 82.09; Me 55 , 83.95; Me 69 , 85.80; Me 88 , 84.54. The standard molar entropies, { S m o (298.15 K) - S m o (0K)} R ?1 ( R = 8.31451 J·K -1 ·mol -1 ), at T = 298.15 K for the respective compositions are : 85.05 ± 0.26, 83.78 ± 0.50, 85.22 ± 0.24, 85.76 ± 0.21, and 84.17 ± 0.59. The calculated standard molar entropies (as above) at T = 298.15 K for the end-members marialite and meionite, and for an intermediate composition (mizzonite=Me 75 ) are 84.85, 83.94 and 86.15, respectively. Values of the coefficients in the equation C p.m / R = a + bT + cT 2 + dT ?1/2 + eT -2 (valid from T = 300 K to T = 1000 K) are: (Me x , a , b /K, c /K 2 , d /K ?1/2 , e /K -2 ) Me 88 , 315.580, −0.0795676, 1.52825·10 -5 , −3954·83, 1808460; Me 69 , 261.285, −0.0415017, 8.73053·10 -7 , −3028.28, 1083666; Me 55 , 232.236, −0.0352222, 6.49875·10 -6 , 2505.99, 601750; Me 44 , 276.696, −0.0756614, 2.39722·10 -5 , -3210.40, 1044363; Me 28 , 149.917, 0.0229399, -1.23180·10 -5 , 1208.87; -318470. Smoothed thermodynamic functions for the five samples are also presented. The enthalpies of solution for five natural scapolites were measured in 2PbO·B 2 O 3 melts at T = 973 K by Calvet-type calorimetry. |
| Databáze: | OpenAIRE |
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