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Hydrolysis of Plutonium(VI) at Variable Temperatures (283-343 K)
No full textThe hydrolysis of Pu(VI) was studied at variable temperatures (283-343 K) by potentiometry, microcalorimetry, and spectrophotometry. Three hydrolysis reactions, mPuO(2)(2+) + nH(2)O = (PuO(2))(m)(OH)(n)((2m-n)+) + nH(+)), in which (n,m) = (1,1), (2,2), and (5,3), were invoked to describe the potentiometric and calorimetric data. The equilibrium constants (*beta(n,m)) were determined by potentiometry at 283, 298, 313, 328, and 343 K. As the temperature was increased from 283 to 343 K, *beta(1,1), *beta(2,2), and *beta(5,3), increased by 1, 1.5, and 4 orders of magnitude, respectively. The enhancement of hydrolysis at elevated temperatures is mainly due to the significant increase of the degree of ionization of water as the temperature increases. Measurements by microcalorimetry indicate that the three hydrolysis reactions are all endothermic at 298.15 K, with enthalpies of (35.0 +/- 3.4) kJ mol(-1), (65.4 +/- 1.0) kJ mol(-1), and (127.7 +/- 1.7) kJ mol(-1) for Delta H(1,1), Delta H(2,2), and Delta H(5,3), respectively. The hydrolysis constants at infinite dilution have been obtained with the Specific Ion Interaction approach. The applicability of three approaches for estimating the equilibrium constants at different temperatures, including the constant enthalpy approach, the DQUANT equation, and the Ryzhenko-Bryzgalin model, were evaluated with the data from this work
The thermodynamics of 1,4,7,10,13 - pentaazatridecane complexes of silver(I) in dimethyl sulfoxide.
No full textThe thermodynamic parameters Delta G degrees, Delta H degrees and Delta S degrees for the formation of silver(I) mononuclear (AgL(+)) and polynuclear ([Ag(2)L](2+), [Ag(3)L(2)](3+)) complexes with 1,4,7,10,13-pentaazatridecane (L = tetren) have been obtained in dimethyl sulfoxide (dmso) at 25 degrees C and in an ionic medium of 0.1 mol dm(-3). The complexes are enthalpy stabilized while the entropy contributions oppose their formation. Tetren, differently from other linear polyamines which have only aminoethylenic subunits and less than Eve nitrogens, is able to form polynuclear species in dmso. Structures and stabilities of the complexes are discussed in relation to the characteristics of the ligan
Fotochimica degli attinoidi. IV. Meccanismo di fotoriduzione dello ione uranile in alcooli alifatici.
No full textThe photochemical reaction of aliphatic alcohols with uranyl(VI) ion was studied
Thermodynamic Properties of Actinide Complexes. IV. Thorium(IV)- and Uranyl(VI) - Malonate Systems.
No full textThe stability consts. and thermodn. of formation of Th4+ and UO22+ malonate complexes were detd. by potentiometric and calorimetric titrns. in 1.00 M NaClO4 at 25°. All complexes formed were stabilized by a large entropy gain. Stability const. values agreed with an ionic bonding model in which the malonate behaved as a bidentate ligand forming only chelate complexes
Actinide Complexes in Aqueous Solution.
No full textStability consts. and thermodn. of coordination of actinides in aq. soln. are reviewed with 25 refs
Reactions of 5-Sulphosalicylic acid with lanthanides(III) and thorium(IV) in aqueous solution.
No full textThe complex formation equilibria of 5-sulphosalicylic acid with lanthanide(III) and thorium(IV) ions have been studied by means of potentiometric [H+] measurements in aqueous solution at 20 °C in a 1M (Na,H)ClO4 medium. The analysis of the potentiometric data referring to pH ranges where the hydrolytic reactions of metal ions are negligible indicates the formation of chelate complexes of the type LnL and LnL23- for the rare earth ions and ThL+ for the thorium ion. The ligand behaves as chelating agent through both the deprotonated carboxylate and phenolate groups. The stability constants of the complexes are reported and discussed
Thermodynamic Properties of Actinide Complexes. Part VI. Thorium(IV) - Monochloroacetate System.
No full textmonochloroacetic acid were detd. in 1.00 M NaClO4 at 25 °C. Comparison is given with literature data for the Th(IV)-acetate system. The thermodn. values for the two systems indicate a lower stability for the Th-monochloroacetate complexes as compared to the Th-acetate complexes. The lower ligand basicity results in both a weaker metal-ligand interaction and a more extensive hydration of the complexes forme
Polarographic Investigations on Uranyl(VI) Complexes in Dimethylsulfoxide. 1. Monocarboxylic Ligands.
No full textThe formation of acetate, glycolate, chloroacetate and β-chloropropionate complexes of uranium(VI) in dimethylsulfoxide has been investigated by the polarographic method. 0.1M tetrabutylammonium perchlorate was used as supporting electrolyte. The 3:1 acetate and the 1:1 glycolate complexes give distinct cathodic waves; the polarographic behaviour allows to evidentiate also the 1:1 and 2:1 acetate, the 1:1 chloroacetate and β-chloropropionate complex formation. The formed complexes are stronger in DMSO than in water and the more so the harder the ligand. The (a)-character of uranyl ion is more marked in DMSO than in aqueous media
Yield of Magnesium Isotopes by Intermediate-energy, Photon-induced, Spallation in Natural Chlorine.
No full textTargets of LiCl (natural Cl) were irradiated with bremsstrahlung beams in the energy range 0.3-1 GeV and the mean cross-sections per photon were deduced for the prodn. of 27Mg and 28Mg from 35,37Cl. Comptete agreement was found between the experimentally determined yields and those calculaied by using a modified CDMD Rudstam formula
Vanadyl(IV) - Acetate Complexes in Aqueous Solution.
No full textThe formation of vanadyl(IV) complexes with acetates were studied by potentiometric titrn. methods; the stepwise formation consts. of mononuclear complexes, [VO(CH3COO)]+ and [VO(CH3COO)2], were calcd. to be 72.2 and 12.6 M-1, resp., in 1 M aq. perchlorate at 25 °C. A comparison was made with the literature values for the corresponding neptunyl(IV) complexes
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