Thermochemistry of selected trivalent lanthanide and americium compounds: orthorhombic and hexagonal hydroxycarbonates
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Fabian Rorif
Abstract
The molar enthalpies of dissolution of a number of well-characterized hexagonal hydroxycarbonates Ln(OH)CO3(hex) (Ln = La, Nd, Sm, Eu) in 6.00 mol dm-3 HCl were measured at 298.15 K. A new sealed solution micro-calorimeter was developed for this purpose. It was made of an 18-carat gold alloy in order to improve the performances of a calorimeter previously built in our laboratory. The following standard molar enthalpies of formation, ΔfH°m [Ln(OH)CO3, hex], in kJ mol-1, were calculated: -(1627.8±1.6), -(1614.8±1.9), -(1613.4±1.6), and -(1523.0±3.0), for the La, Nd, Sm, and Eu compounds, respectively. These results allowed an extrapolation to ΔfH°m [Eu(OH)CO3·0.5H2O, orth]=-(1653.4±3.6)kJ mol-1 and to ΔfH°m [Am(OH)CO3, hex]=-(1552.5±3.3)kJ mol-1. Using auxiliary data and estimated entropies, the solubility products of the hexagonal hydroxycarbonates were calculated. They are compared here with values deduced from solubility and calorimetric measurements for the corresponding orthorhombic hydroxycarbonates. Our approach generally leads to values similar to those deduced from solubility studies. The orthorhombic form is found to be metastable with respect to the hexagonal form.
© 2005 Oldenbourg Wissenschaftsverlag GmbH
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- Thermochemistry of selected trivalent lanthanide and americium compounds: orthorhombic and hexagonal hydroxycarbonates
- Simple and safe production of yttrium-90 from a new type of 90Sr/90Y generator
- Radiometric method for the study of the corrosion reactions of steel samples in strongly acidic media
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Articles in the same Issue
- Transmutation experiments on 129I, 139La and 237Np using the Nuclotron accelerator
- Electrochemical redox reactions of uranium(VI) complexes with multidentate ligands in dimethyl sulfoxide
- Solubility of ThO2·xH2O(am) in carbonate solution and the formation of ternary Th(IV) hydroxide-carbonate complexes
- Eu(III), Sm(III), Np(V), Pu(V), and Pu(IV) sorption to calcite
- Thermochemistry of selected trivalent lanthanide and americium compounds: orthorhombic and hexagonal hydroxycarbonates
- Simple and safe production of yttrium-90 from a new type of 90Sr/90Y generator
- Radiometric method for the study of the corrosion reactions of steel samples in strongly acidic media
- Comparison of techniques for measuring ion exchange selectivities in zeolites
