Uranyl aqueous solutions

The larger cations of Group 1 (K, Rb, Cs) can be precipitated from aqueous solution as white solids by addition of the reagent sodium tetraphenylborate, NaB(C( H5)4. Sodium can be precipitated as the yellow sodium zinc uranium oxide ethanoate (sodium zinc uranyl acetate). NaZn(U02)3(CH3C00)y. 9H2O. by adding a clear solution of zinc uranyl acetate in dilute ethanoic acid to a solution of a sodium salt. 

The elucidation of actinide chemistry in solution is important for understanding actinide separation and for predicting actinide transport in the environment, particularly with respect to the safety of nuclear waste disposal.72,73 The uranyl CO + ion, for example, has received considerable interest because of its importance for environmental issues and its role as a computational benchmark system for higher actinides. Direct structural information on the coordination of uranyl in aqueous solution has been obtained mainly by extended X-ray absorption fine structure (EXAFS) measurements,74-76 whereas X-ray scattering studies of uranium and actinide solutions are more rare.77 Various ab initio studies of uranyl and related molecules, with a polarizable continuum model to mimic the solvent environment and/or a number of explicit water molecules, have been performed.78-82 We have performed a structural investigation of the carbonate system of dioxouranyl (VI) and (V), [U02(C03)3]4- and [U02(C03)3]5- in water.83 This study showed that only minor geometrical rearrangements occur upon the one-electron reduction of [U02(C03)3]4- to [U02(C03)3]5-, which supports the reversibility of this reduction. 

Experimental Coordination Environment of Uranyl(VI) in Aqueous Solution. 

TEM has been used to determine the shape and particle size of nanoparticles [27, 33]. Samples are prepared by placing a drop of preparation on copper grids, followed by negative staining with an aqueous solution of sodium phosphotungstate, phosphotungstic acid, or uranyl acetate [27, 163, 164]. Freeze fracturing with TEM has been... 

Inorganic extractions seem to have come into practical use without any great notice. Although Peligot in 1842 reported that uranyl nitrate could be recrystalhzed from ether, he never mentioned extraction of this salt from aqueous solutions. In textbooks after 1870, however, it is stated briefly that ether can even withdraw sublimate (HgCy from aqueous solution. It was also reported, for example, that cobalt thiocyanate is weakly extracted by ether, better by amyl alcohol, and even better by a mixture of both. 

The uranyl dicarbonate species is extremely stable in aqueous solutions but by evaporation can become sufficiently concentrated by evaporation to generate the low solubility mineral carnotite in the pH range 6 to 8, the natural range of pH values in the Namibian groundwaters. 

The extraction of uranyl nitrate from 1 M aqueous solution into 30% tributylphosphate in oil is accompanied by an initial interfacial turbulence (41), with more transfer than calculated, even though re-solvation of each uranyl ion at the interface must be a relatively complex process. If the turbulence is suppressed with sorbitan mono-oleate, transfer proceeds at a rate in excellent agreement with theory. 

In aqueous solution, uranium exists in four oxidation states Us+(red), U4+(green) and its oxide ion U02 which is unstable, and the yellow uranyl ion, U02 +. In sohd compounds the metal exhibits several oxidation states. 

The general electrochemical behavior of uranium in aqueous solutions is dominated by the reduction of the hexava-lent uranyl moiety, 1102. As shown in Table 1, the potential for the UO2 /UO2 couple is 0.089 0.002 V versus SHE, as determined from formal potential data in C104 solutions (0.5-3.0 M) [49, 50aj. The electrochemical reduction of uranyl compounds has been a thoroughly studied... 

Morris studied the aqueous solution voltammetric behavior of some uranyl coordination complexes to learn how changes in the ligand environment influence the redox potentials and heterogeneous electron-transfer kinetic parameters for the single-electron transfer... 

Solubility in Aqueous Solutions of Ammonium Sulfate, Ammonium Acid Sulfate, Sodium Chloride, Sodium Nitrate, Lead Nitrate, Uranyl Nitrate and Ammonium Thiocyanate... 

Glutaraldehyde (2%) in phosphate-buffered saline is used to fix the sections. Sections are stained with a 4% aqueous solution of uranyl acetate. 

The U(IV) chemistry is similar to that of Th4+, except for the difference in the charge/radius ratio of the ions. U4+ solutions are green in color, stable, and slowly oxidized by air to U02+. Solutions of U4+ are generally prepared by reduction of solutions of the uranyl (U02+) ion. U(IV) forms complexes with many anions (C204-,C2H302, C03-, Cl-, and NO3"). The chlorides and bromides of U(IV) are soluble while the fluorides and hydroxides are insoluble. In aqueous solution, U(IV) hydrolyzes via the reaction,... 

There are always preferences as to which stain to use for any given virus. An aqueous solution of uranyl acetate (UA) at 2% is a good general stain but others should be tried if this does not give the results required (2). UA is incompatible with some buffers, especially phosphate, which is the buffer of preference in this chapter. To avoid precipitation, treated grids must be washed with distilled water before UA is used (1,4). In addition UA is toxic, so users should refer to the Hazard Data Sheet produced by the manufacturer before use. 

Stoichiometrical quantities of the HDBM (l,3-diphenyl-l,3-pentanedione) and U02 (CH3COO)2 were dissolved in tepid ethanol. The solution was concentrated and left at room temperature until crystallization. The product was washed with ether and dried at 130°C and a pressure of I0 7 mm Hg in an Abderhalden drying apparatus provided with P4O]0. Uranyl bis-(2-hydroxybenzaldehyde) [79] was synthesized from stoichiometric quantities of an alcoholic solution of 2-hydroxybenzaldehyde and an aqueous solution of uranyl nitrate trihydrate, U02(N03)2 3H20. It is noted [79] that, for uranyl P-diketonates his-(2-hydroxybenzaldehyde) and b is-(2 - h ydroxy-1 -naphtli a I d e h y de), their crystals do not exhibit the appropriate size and crystalline shape to perform polarization measurement in the solid state. 

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