Synthesis and Crystal Structure of Rubidium Uranyltricarbonate

A procedure for the synthesis of uranyltricarbonatetetrarubidium Rb₄UO₂(CO₃)₃ was developed. Its crystal structure was determined by X-ray diffraction analysis: space group C2/c; a=10.778(5) , b=9.381(2) , c=12.509(3) . =94.42(3)°, Z=4; 1178 independent reflections, R=0.0662.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 5, 2005, pp. 387–390.Original Russian Text Copyright © 2005 by Chernorukov, Mikhailov, Knyazev, Kanishcheva, Zamkovaya.     

Crystal Structure of HAsUO6 4H2O

The crystal structure of HAsUO₆ 4H₂O was solved at 295 K by X-ray analysis. Reasons for structural changes due to temperature variation are analyzed.     

Crystal structure and thermodynamic properties of dipotassium diiron(III) hexatitanium oxide

In the present work, the temperature dependence of heat capacity of dipotassium diiron(III) hexatitanium oxide has been measured for the first time in the range from 10 to 300 K by means of precision adiabatic vacuum calorimetry. The experimental data were used to calculate standard thermodynamic functions, namely the heat capacity $ C_{p}^{ \circ } (T) $ , enthalpy $ H^{ \circ } (T) - H^{ \circ } (0) $ , entropy $ S^{ \circ } (T) - S^{ \circ } (0), $ and Gibbs function $ G^{ \circ } (T) - H^{ \circ } (0) $ for the range from T → 0 to 300 K. The structure of K₂Fe₂Ti₆O₁₆ is refined by the Rietveld method: space group I4/m, Z = 1, a = 10.1344(2) Å, c = 2.97567(4) Å, V = 305.618(7) Å³. The high-temperature X-ray diffraction was used for the determination of coefficients of thermal expansion.     

Synthesis and characterization of MIIU3O10 · nH2O (MII = Mg, Mn, Co, Ni, Cu, Zn, Cd) triuranates

Individual crystalline phases of composition M^IIU₃O₁₀ · nH₂O were prepared by reacting schoepite UO₃ · 2.25H₂O with aqueous solutions of Mg, Mn, Co, Ni, Cu, Zn, or Cd nitrates under hydrothermal conditions at 200°C. The composition and structure of the resultant compounds were determined by hightemperature X-ray diffraction, IR spectroscopy, scanning calorimetry, and chemical analysis; the dehydration and thermal destruction of the compounds were studied.     

State of uranyl silicates MII(HSiUO6)2 ·6H2O (MII=Mn, Co, Ni, Cu, Zn) in aqueous solutions

Uranyl silicates with formula M^II(HSiUO₆)₂·6H₂O (M^II=Mn, Co, Ni, Cu, Zn) were investigated in aqueous solutions in the pH range of 0÷14. The pH interval was established where compounds preserve their composition and structure. It varies in the pH range of (3.5–4.0)÷(10.8–11.4) and depends on M^II type. Out of this pH interval investigated uranyl silicates convert to the compounds of other composition and structure, such as amorphous silica, polyuranates and hydroxides of 3d-transition elements. The solubility of M^II(HSiUO₆)₂·6H₂O was determined, it’s value changes on the several orders of magnitude from 10^?6 M in subalkali solutions to 10^?3 M in acid and strongly alkaline media. Using obtained experimental data the solubility products and solubility curves of uranyl silicates were calculated by mathematical modeling. Also the speciation diagrams of uranium (VI), silicon (IV) and M (II) in solutions and solids were plotted.     

Synthesis,Structure, and Properties of Cesium Polyuranate [Cs2(H2O)3][(UO2)6O3(OH)8]·2H2O

Russian Journal of General Chemistry - Cesium uranate [Cs2(Н2О)3][(UO2)6O3(OH)8]·2H2O was obtained by reacting hydrated uranium(VI) oxide UO3·2.25H2O with a cesium nitrate...     

Crystal structure of M<Superscript>I</Superscript>VWO<Subscript>6</Subscript> (M = Li,Na) compounds

Compounds of the composition M^IVWO₆ (M = Li, Na) were prepared by solid-phase synthesis at 600°C. The compounds crystallize in the mineral brannerite structure type. The sodium derivative was prepared and identified for the first time. The crystal structures of the compounds were refined by the Rietveld method (space group C2/m).     

Thermochemistry of Compounds of the MI I(PUO6)2·nH2O Series

The standard enthalpies of formation of uranophosphates M^{I I}(PUO₆)₂·nH₂O (M^{I I} = Mn, Fe, Co, Ni, Cu, Zn, Cd) are determined. The standard enthalpies of the synthesis and dehydration of these compounds are calculated and analyzed.     

Synthesis and study of sodium triuranate Na<Subscript>2</Subscript>(UO<Subscript>2</Subscript>)<Subscript>3</Subscript>O<Subscript>3</Subscript>(OH)<Subscript>2</Subscript>

Sodium triuranate Na₂(UO₂)₃O₃(OH)₂ was synthesized by the reaction between aqueous uranyl acetate solution and aqueous sodium nitrate solution under hydrothermal conditions at 200°C. The composition and structure of the synthesized compound were determined, and its dehydration and thermal decomposition were studied, by chemical analysis, X-ray diffraction, IR spectroscopy, and thermal analysis.     

Synthesis and Properties of Uranosilicates M[HSiUO6] · nH2O (M = NH4+, Li,Na, K,Rb, Cs)

A complete set of uranosilicates M[HSiUO₆] · nH₂O of alkali metals and ammonium was obtained under hydrothermal conditions. The functional and phase similarity of the compounds was proved by X-ray phase analysis and IR spectroscopy. The effect of water molecules on the structures of hydrated and anhydrous uranosilicates and the nature of water in these compounds were elucidated by studying hydration-dehydration processes. The dependence of the X-ray and thermal properties of the compounds on the nature of interlayer atoms was considered.