Thermodynamic properties of minerals and related substances at 298.15 K (25.0 C) and one atmosphere (1.013 bars) pressure and at higher temperatures

Critically selected values for the entropy (S°288.«), molar volume (VWw), and for the heat and Gibbs free energy of formation (AH 0 f,z98.i5 and AG°f.288.is) are given for 50 reference elements and 285 minerals and related substances. For 211 materials for which high-temperature heat-capacity or heat-content data are available AH°f,T , AG°f,T , S°T, logKf/r and (G°T H°298.i5/T) are tabulated at 100°K intervals for temperatures up to 2,000°K. For substances having solid-state phase changes or whose melting or boiling point is less than 2,000°K, we also have tabulated the properties listed above at the temperature of the phase change so that the heat or entropy changes associated with the transformation form an integral part of the high-temperature tables. INTRODUCTION The purpose of these tables is to present a critical summary of the available thermodynamic data for minerals and related substances in a convenient form for the use of earth scientists. To make the tables as useful as possible we have tried to include as much of the necessary auxiliary data as possible so that a single set of tables would suffice for most calculations, to insure internal consistency and to provide for the means of rapid revision and expansion as new data become available. This compilation is divided into two sections. In the first section we give values for the entropy (S°288.i 5 ), molar volume (V°298 . K ), the heat (enthalpy, AH°f.298.i 5 ) and Gibbs free energy (AG0 f,288. 15 ), and the logarithm of the equilibrium constant of formation (log Kf, 298.15) for the reference elements, minerals, a number of oxides, and other substances of geological interest. The data have been critically evaluated and uncertainties assigned to the 298.15°K properties. The sources of data are indicated numerically in the tables and listed in complete form following the tables. 2 THERMODYNAMIC PROPERTIES OF MINERALS The data are arranged in order of their conventional mineralogical groups. Within each group (for example the oxides) the listing is by alphabetical order of the chemical symbol of the principal cation. The tables in the second section contain values for the high-temperature thermodynamic properties, H°T H°ns.u, (G°T -H°298.iS )/T, S°T, AG°f,T, AH°,,T, and log Kf,T at 100°K intervals up to 2000°K. Heat-capacity data, as such, have been omitted from these tables in favor of the function H°T H 0 298.i 5 which is the quantity actually measured in most high-temperature experiments. Heat capacities, C P , derived from H°T H°298.i 5 data are at best only approximate and their use should be avoided when possible. Approximate values for C P are readily obtained from the first differences of the tabulated H° T H 0 298.i5 function. Thermodynamic properties of gases at high pressures have not been included in these tables. High pressure-high temperature functions of the geologically important gases H20 and C02 are given by Bain (1964), Hilsenrath and others (1955), and Robie (1966). These tables entirely supersede two earlier reports on the same subject matter by Robie (1959,1966)! ACKNOWLEDGMENTS Professor E. F. Westrum, Jr., University of Michigan, Professor 0. J. Kleppa, University of Chicago, and P. B. Barton, Jr., Priestley Toulmin, and D. R. Wones, U.S. Geological Survey, have kindly permitted us to use some of their unpublished data. We are particularly grateful to Keith Beardsley of the U.S. Geological Survey who wrote the computer routines for processing the 298.15°K tables and the bibliography. E-an Zen of the U.S. Geological Survey and Professor J. B. Thompson, Jr., of Harvard University offered many helpful suggestions for improving the clarity and usefulness of these tables. Computer facilities at the Massachusetts Institute of Technology were used initially to develop the program for compiling hightemperature thermodynamic functions. More recent revisions of the program and the present set of tables were prepared at the Harvard Computing Center, with computer costs supported by the Higgins Fund and the Committee on Experimental Geology and Geophysics of Harvard University. THERMODYNAMIC PROPERTIES OF MINERALS 3 PHYSICAL CONSTANTS AND ATOMIC WEIGHTS The symbols and constants adopted for this report are listed in table 1. Values for the physical constants used in the calculations were those recommended by the National Academy of ScienceNational Research Council (U.S. Natl. Bur. Standards Tech. News Bull., v. 47, p. 175-177, 1963). For convenience we also give values of the international atomic weights for 1963 (scale C12 = 12.0000) in alphabetical order by their chemical symbol in table 2. Elements for which no atomic weight is listed have no stable isotope. TABLE 1. Symbols and constants T Temperature in degrees Kelvin, (°K) gfw Gram formula weight H° -H° Enthalpy at temperature T relative to 298.15°K in cal gfw 1 , T S° Entropy at temperature T in cal deg-gfw" 1 G° -H° T SM.15 m Gibbs free energy function in cal deg-gfw" 1 A^f° Heat of formation from reference state in cal gfw" 1 AG° Gibbs free energy of formation from reference state in cal gfw"1 Kr Equilibrium constant of formation Cp Heat capacity at constant pressure in cal deg-gfw" 1 0 Superscript indicates the substance is in its standard state » TTO meit Heat of melting at one atmosphere in cal gfw" 1 AH° Heat of vaporization to ideal gas at one atmosphere at the "p normal boiling point in cal gfw" 1 V° Volume of one gram formula weight at one atmosphere and "* " 298.15°K in cm8 R Gas constant, 1.98717 ±.00030 cal deg-gfw 1 , 8.31469 joules deg-gfw" 1 cal Calorie, unit of energy, 4.1840 absolute joules, 41.2929 cm* atmosphere A Avogadro's number, (6.02252 ±. 00028) xlO23 formula ' units gfw1 P Pressure, either in atmosphere or bars atm Atmosphere, 1,013,260 dynes cm"* bar Bar, 1,000,000 dynes cm"2 log Common logarithm, base 10 In Natural logarithm, base e= 2.71828. . . THERMODYNAMIC PROPERTIES OF MINERALS TABLE 2. Atomic weights for 1963