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R. A. Robie

Publications and source records attributed to R. A. Robie.

30 records · Page 2Linked to original sources
USGS1984

Heat capacity and thermodynamic functions for gehlenite and staurolite: with comments on the Schootky anomaly in the heat capacity of staurolite.

The heat capacities of a synthetic gehlenite and a natural staurolite were measured from 12 and 5 K, respectively, to 370 K by adiabatic calorimetry, and the heat capacities of staurolite were measured to 900 K by differential scanning calorimetry. At 298.15 K and 1 bar the entropy of gehlenite is 210.1 + or - 0.6 J/(mol.K) and that of staurolite is 1019.6 + or - 12.0 for H2Al2Fe4Al16Si8O48 and 1101.0 + or - 12.0 for 103(H3Al1.15Fe2+0.60)- 324(Fe2+2.07Fe3+0.54 Ti0.08Mn0.02Al1.19)(Mg0.44Al15.26)Si8O48. -J.A.Z.

American Mineralogist↗
USGS1978

Revised values for the Gibbs free energy of formation of [Al(OH)4 aq-], diaspore, boehmite and bayerite at 298.15 K and 1 bar, the thermodynamic properties of kaolinite to 800 K and 1 bar, and the heats of solution of several gibbsite samples

Solution calorimetric measurements compared with solubility determinations from the literature for the same samples of gibbsite have provided a direct thermochemical cycle through which the Gibbs free energy of formation of [Al(OH) 4 aq − ] can be determined. The Gibbs free energy of formation of [Al(OH) 4 aq − ] at 298.15 K is −1305 ± 1 kJ/mol. These heat-of-solution results show no significant difference in the thermodynamic properties of gibbsite particles in the range from 50 to 0.05 μm. The Gibbs free energies of formation at 298.15 K and 1 bar pressure of diaspore, boehmite and bayerite are −9210 ± 5.0, −918.4 ± 2.1 and −1153 ± 2 kJ/mol based upon the Gibbs free energy of [A1(OH) 4 aq − ] calculated in this paper and the acceptance of −1582.2 ± 1.3 and −1154.9 ± 1.2 kJ/mol for the Gibbs free energy of formation of corundum and gibbsite, respectively. Values for the Gibbs free energy formation of [Al(OH) 2 aq + ] and [AlO 2 aq − ] were also calculated as −914.2 ± 2.1 and −830.9 ± 2.1 kJ/mol, respectively. The use of [AlC 2 aq − ] as a chemical species is discouraged. A revised Gibbs free energy of formation for [H 4 SiO 4aq 0 ] was recalculated from calorimetric data yielding a value of −1307.5 ± 1.7 kJ/mol which is in good agreement with the results obtained from several solubility studies. Smoothed values for the thermodynamic functions C P 0 , ( H T 0 - H 298 0 ) T "> HT0- H2980)T , ( G T 0 - H 298 0 ) T "> (GT0- H2980)T , S T 0 - S 0 0 , ΔH ƒ,298 0 ">ƒ ΔHƒ,2980 kaolinite are listed at integral temperatures between 298.15 and 800 K. The heat capacity of kaolinite at temperatures between 250 and 800 K may be calculated from the following equation: C P 0 = 1430.26 − 0.78850 T + 3.0340 × 10 −4 T 2 −1.85158 × 10 −4 T 2 1 2 + 8.3341 × 10 6 T −2 "> 12+ 8.3341 × 106T−2 . The thermodynamic properties of most of the geologically important Al-bearing phases have been referenced to the same reference state for Al, namely gibbsite.

Geochimica et Cosmochimica Acta↗
USGS1970

Specific heats of lunar surface materials from 90 to 350 degrees Kelvin

The specific heats of lunar samples 10057 and 10084 returned by the Apollo 11 mission have been measured between 90 and 350 degrees Kelvin by use of an adiabatic calorimeter. The samples are representative of type A vesicular basalt-like rocks and of finely divided lunar soil. The specific heat of these materials changes smoothly from about 0.06 calorie per gram per degree at 90 degrees Kelvin to about 0.2 calorie per gram per degree at 350 degrees Kelvin. The thermal parameter γ = (kρC) -½ for the lunar surface will accordingly vary by a factor of about 2 between lunar noon and midnight.

Science↗
USGS1966

Some Debye temperatures from single-crystal elastic constant data

The mean velocity of sound has been calculated for 14 crystalline solids by using the best recent values of their single‐crystal elastic stiffness constants. These mean sound velocities have been used to obtain the elastic Debye temperatures θ D e for these materials. Models of the three wave velocity surfaces for calcite are illustrated.

Journal of Applied Physics↗
USGS1965

Vacuum-jacketed hydrofluoric acid solution calorimeter

A vacuum‐jacketed metal calorimeter for determining heats of solution in aqueous HF was constructed. The reaction vessel was made of copper and was heavily gold plated. The calorimeter has a cooling constant of 0.6 cal‐deg −1 ‐min −1 , approximately ¼ that of the air‐jacketed calorimeters most commonly used with HF. It reaches equilibrium within 10 min after turning off the heater current. Measurements of the heat of solution of reagent grade KCl(−100 mesh dried 2 h at 200°C) at a mole ratio of 1 KCl to 200 H 2 O gave Δ H = 4198±11 cal at 25°C.

Review of Scientific Instruments↗
USGS1964

Equilibrium of talc with enstatite and quartz

A thermodynamic calculation of the vapor pressure of H 2 0 in equilibrium with talc gives p H 2 O of one atmosphere at 718° ± 15°K in contradiction to the results of Mueller.

Science↗
USGS1962

Elastic constants of calcite

The recent measurements of the elastic constants of calcite by Reddy and Subrahmanyam (1960) disagree with the values obtained independently by Voigt (1910) and Bhimasenachar (1945). The present authors, using an ultrasonic pulse technique at 3 Mc and 25°C, determined the elastic constants of calcite using the exact equations governing the wave velocities in the single crystal. The results are C 11 =13.7, C 33 =8.11, C 44 =3.50, C 12 =4.82, C 13 =5.68, and C 14 =−2.00, in units of 10 11 dyn/cm 2 . Independent checks of several of the elastic constants were made employing other directions and polarizations of the wave velocities. With the exception of C 13 , these values substantially agree with the data of Voigt and Bhimasenachar.

Journal of Applied Physics↗