R. Guillaumont

Thermodynamic properties of 5f elements

Abstract The function P(M) defined by Nugent, Burnett and Morss ( J. Chem. Therm. 5 , 665 (1973)) has been reexamined utilizing new experimental data. This function now appears to be linear with Z for the actinide series. New values for ΔH ° S and ΔH ° f for each element of the actinide series are derived. The entropy of formation ΔS ° f of the M aq 3+ ions was estimated which allowed the determination of the free energy change ΔG ° and redox potential E ° for the couple M aq 3+ /M. The redox potentials for E °(M( X )/M) for all known redox states of the actinide series were estimated.

Fonctions thermodynamiques de complexes halogénés de Sm, Eu, Gd, Tb et Dy

Abstract Coherent values of s1, ΔH° and δS° for complexing of Maq3+ ions (M = Sm, Eu, Gd, Tb and Dy) by L− (L = Cl, Br, I, NO3, F) (μ = 1) have been obtained by solvent extraction method, using aqueous phases containing all the elements. ΔH° values vs Z, shows the “gadolinium break”.

Citric complexes and neodymium citrate: NdCit, 3H2O

Abstract After determination by a potentiometric method of the formation constants of different neodymium citric acid complexes in aqueous solution as a function of pH (1–13), we succeeded in obtaining crystallized neodymium citrate Nd cit, 3H2O by a rigorously defined process. The crystals are monoclinic, space group P P 2 1 c cell dimensions a = 6.295 A , b = 9.794 A , c = 18.346 A , and β = 111.41° , with four formulae funits per unit cell.

Radiopolarography of barium and radium

Abstract The amalgamation reaction of aqueous ions Ra 2+ and Ba 2+ has been investigated by mean of radiopolarography using tracers of 226 Ra (α-emitter) and 131 Ba (γ-emitter) in aqueous solution. The slope of the logarithmic transformed waves is close to 1/0.03 V −1 . The apparent reversibility of the systems has been observed in different conditions of the supporting electrolyte. The variation of the reversible half wave potential with the square root of the ionic strength μ is obtained and discussed. The extrapolation to μ = 0 provides (E 1 2 ) rev [ Ba 2+ / Ba(Hg) ]=−1.916 V vs S.C.E. and (E 1 2 ) rev [ Ra 2+ / Ra(Hg) ]=−1.852 V vs S.C.E. A discontinuity on the radiopolarographic waves has been systematically observed, which is explained by a “screen” effect related to the ionic structure in the vicinity of the dropping mercury electrode.

Extraction par solvant des lanthanides a l'etat de thenoyltrifluoroacetonates a partir de l'eutectique KNO3LiNO3

Abstract Solvent extraction (150°C) of lanthanides with TTA dissolved in polyphenyl eutectic from a molten salt (LiNO3z.sbnd;KNO3) has been studied in closed systems as a function of CTTA, pNO2 and pO2. Distribution data and other measurements are consistent with mechanisms which go through dimerisation of TTA in the organic phase. Influence of the composition of gaseous phase could be quite important as shown on neodymium.