... is analogous to that developed for sulfides ( Deore and Navrotsky 2006 ). Complete dissolution of selenides is documented by furnace tests and visual inspection, and supported by consistent results for enthalpy. Enthalpies of formation (Δ f H °, kJ/mol) from the elements were determined for zinc selenide (ZnSe...

... and complete conversion of sulfide to dissolved sulfate. Complete dissolution of sulfides and retention of sulfur in the solvent is documented by furnace tests and visual observation, consistent determination of enthalpy of drop solution, and comparison with previous data for the heat of formation of ZnS, PbS...

..., magnesite, quartz, tremolite and talc were measured under identical conditions in the same calorimeter. Our refined value for the enthalpy of formation from the elements at 298.15 K for Mg-Al disordered, end-member pargasite with X F = 0 lies between - 12651.4 ± 12.7 and - 12659.4 ± 14.0 kJ/mol, depending...

... . The enthalpy of drop solution of the bulk samples (as well as the calculated values for the enthalpy of formation from the elements of Mg-staurolite) are strongly correlated to the H content of the samples. The enthalpy of formation from the elements is best described by the linear relation Δ f H 0 298 (Mg...

... exchanged into CHA. The enthalpies of formation were determined for all samples, and the partial molar enthalpy of hydration was measured by varying the water content of one Ca-CHA. The enthalpy of formation depends strongly on the exchanged cation, becoming more exothermic in the order Ca, Li, Na, K...

...Mirko Schoenitz; Alexandra Navrotsky Abstract The silicon-free end member of the hydrogrossular solid solution series, katoite Ca 3 Al 2 [(OH) 4 ] 3 , was synthesized in a solid-media, piston-cylinder apparatus. The enthalpy of formation from the component oxides was measured by high-temperature...

... solvent at 702 °C. The enthalpy of formation of stoichiometric, end-member (CaTiSiO 5 ) titanite is redetermined to be –119.59 ± 2.24 kJ/mol from the oxides and –2610.13 ± 2.90 kJ/mol from the elements at 25 °C. The new value is either 8.725 or 13.525 kJ/mol more negative than the currently accepted...

...Liang Chai; Alexandra Navrotsky Abstract The enthalpy of formation of siderite at 298 K has been determined from transposed temperature drop calorimetric measurements of enthalpies of decomposition of siderite at both 978 and 1075 K in an O 2 atmosphere. Synthetic siderite was used...

... Δ G R .298 0 is 41.78 ± 0.18 kJ. Using the accurately measured dissociation pressures of calcite in this temperature range and the available high-precision thermal data for calcite and wollastonite and their component oxides, a molar enthalpy of formation of wollastonite of Δ H f .298 0 = − 89.61...

... vessel. The metastable equilibrium andalusite + corundum + quartz was reversed at 700 °C and 7.75 ± 0.25 kbar in the piston-cylinder apparatus. The reversals yield enthalpy of formation values from the oxides of −8.563 ± 0.189 kJ/mol for kyanite and −4.499 ± 0.125 kJ/mol for andalusite at 298 K...

...Sophie Billon; Philippe Vieillard Abstract A method for the prediction of the enthalpies of formation Δ H ° f for minerals of hydrous sulfates is proposed and is decomposed in the following two steps: (1) an evaluation of Δ H ° f for anhydrous sulfates based on the differences in the empirical...

...Alexandra Navrotsky; Christopher Capobianco Abstract (Ca,Mg) carbonates have been studied by solution calorimetry at 85°C in an acid solvent (1 M HC1) that was saturated at room temperature with NaCl and contained 0.75 M CaCl 2 and 0.25 M MgCl 2 . The enthalpy of formation of ordered dolomite from...

...Amir H. Tavakoli; Alexandra Navrotsky Abstract Binary and ternary sulfides in the Fe-Ni-S system are of major fundamental and practical interest in environmental, geological, and planetary science. Despite extensive thermodynamic modeling of phase equilibria, the enthalpies of formation of solid...

...James R. Rustad Abstract Electronic structure calculations are carried out to estimate the enthalpies of formation of rare-earth orthophosphates from their oxides. The calculated enthalpies of formation are systematically less exothermic than the measured values. The discrepancy is almost entirely...

...Karrie-Ann Kubatko; Katheryn Helean; Alexandra Navrotsky; Peter C. Burns Abstract The enthalpies of formation of seven uranyl oxide hydrate phases and one uranate have been determined using high-temperature oxide melt solution calorimetry: [(UO 2 ) 4 O(OH) 6 ](H 2 O) 5 , metaschoepite; β-UO 2 (OH...

... of formation from oxides becomes more exothermic as the size of the RE cation increases, a trend seen previously in other RE compounds including pyrochlores, perovskites, and phosphates. For smaller RE cations the enthalpy of exchange of RE between niobates and titanates is close to zero, whereas larger RE...

..., respectively. The enthalpy of dehydroxylation of sepiolite was found as 145 ± 14 kJ/(mol H 2 O). Obtained data point at different binding strengths of water in the structure of sepiolite. The enthalpies of formation from the elements Δ H 0 f (298.15 K) were derived by melt solution calorimetry for sepiolite...

...Wolf-Achim Kahl; Walter V. Maresch Abstract Molar enthalpies of formation of natural, near end-member tremolite and talc have been calculated from high temperature lead borate drop-solution calorimetry. Using three mutually consistent reaction cycles for each phase, the critical volatile component...

... with the help of a high-temperature heat-flux Tian-Calvet microcalorimeter. The samples were characterized by X-ray spectroscopy analysis, X-ray powder diffraction, thermal analysis, and FTIR spectroscopy. The enthalpies of formation of clinochlores were found using the melt solution calorimetry method...

... solution calorimetric data from this laboratory for sanidine, albite, muscovite, paragonite, halite, sylvite, salammoniac, gibbsite, and water, along with enthalpies of formation from Robie and Hemingway (1995) for the same phases, the heats of formation at 298.15 K of buddingtonite and tobelite have been...