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Abstract  

The stability constants, β1, of monochloride complex of Am(III) have been determined in a mixed system of dimethyl sulfoxide (DMSO) and water at 1.00 mol·dm−3 ionic strength using solvent extraction. The values of β1 in mixed DMSO+H2O solutions decrease rapidly with an increase in the mole fraction of DMSO (X s) in mixed solvents and become negative ones, which is not in a definition of stability constant, inX s>0.04. The variation of β1 inX s≦0.02 was accounted for by the size-variation of the primary solvation sphere around Am(III), which was present as a solventshared ion-pair, and by a little effect due to an invasion (coordination) of ClO4 into the secondary solvation sphere of Am3+. On the other hand, it was concluded that the β1 obtained by solvent extraction inX s>0.02 was an apparent value, because of a large effect due to an invasion (coordination) of ClO4 into the secondary solvation sphere of Am(III).

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Abstract  

The stability constants , of monochloride complex of Eu(III) in the tracer concentrations have been determined in the mixed system of dimethyl sulfoxide (DMSO) and water with 1.0 mol·dm−3 ionic strength using a solvent extraction technique. The values of decrease up to about 0.2 mole fraction of DMSO (X s) in the mixed solvent system and then increase. Calculation of Eu3+−Cl distance using a Born-type equation of the Gibbs' free energy derived from the revealed that the estimated distance between Eu3+ and Cl (d Eu−Cl) increases linearly withX s in 0≤X s<0.043 and 0.043<X s<0.172, but their slopes are different. The line in the first region means a linear enlargement of the thickness of the primary solvation sphere of Eu3+ with increasingX s. The larger slope againstX s in 0.043<X s<0.172 is attributable to lowering of , based on the increase in the solvation number of the primary solvation sphere of Eu3+. The considerably large value ofd Eu−Cl atX s=0.202 might result from lowering of by a coordination of ClO 4 into the secondary solvation sphere of Eu3+ and the extremely drop ofd Eu−Cl atX s=0.276 might reflect on a conversion of the ion-pair type, i.e., the coexistence of two kinds of a solvent-shared ion-pair and a contact one by the appearance of the contact one.

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Abstract  

The stability constants (b1) of the monofluoro complex of Cm(III) have been determined in mixed solvents of methanol and water using the solvent extraction technique. The values of lnb1 increase as the molar fraction of methanol (Xs) in the mixed solvent increases. The variation in the stability constants mainly depends on the solvation of F- and slightly depends on both (1) the solvation of cations in connection with the complexation of CmF2+ and (2) the electrostatic attraction of Cm3+-F-. The variation in lnb1 for Cm(III) due to the effect of both (1) and (2) is similar to that for Sm(III). By variation of lnb1 the coordination number in the primary hydration sphere (CN) of Cm(III) decreased from a value between CN = 9 and CN = 8 to CN = 8, at about Xs = 0.02. The Xs value of the inflection point of the CN for Cm is slightly lower than Xs = 0.06 for Sm(III) and Xs = 0.03 for Eu(III), previously obtained.

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Abstract  

We observed the interference effect of electron-capture X-rays emitted by the nuclear transformations in radioisotopes. This interference is between the direct monochromatic emission from the radioactive atoms and the emission totally reflected by the substrate surface. Nanometer-level structural information about the radioactive atoms can be obtained by analyzing the measured interference fringes because the period of these fringes depends on the position of the radioactive atoms relative to the substrate surface. In this work, we used the functional protein molecules (myosin subfragment 1 (S1)) which were radioiodinated with no carrier added125I to observe the conformational changes in aqueous solutions.

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Abstract  

The stability constants, β1, of each monochloride complex of Am(III) have been determined in a mixed system of methanol and water at 1.0 mol·dm−3 ionic strength using a solvent extraction technique. The values of β1 of Am(III) decrease up to about 0.1 mole fraction of methanol (X s) in the bulk solutions and then increase with increasingX s when 0.1<X s≤0.4. The distance of Am3+−Cl in the mixed system was estimated using a Born-type equation. From the estimated distance of Am3+−Cl (d Am−Cl), it is concluded that AmCl2+ in the aqueous solution is present as a solvent-shared ion-pair. Further, based on the variation of dAm−Cl with increasingX s, the variations of β1 in the system are accounted for by the size-variation of the primary solvation sphere around Am(III) and by an effect due to the presence of a slight covalency in the solvation of Am(III).

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Abstract  

The stability constants, β1, of each monochloride complex of Ln(III) (Ln=Nd or Tm) have been determined in the mixed system of dimethyl sulfoxide (DMSO) and water with 1.0 mol·dm−3 ionic strength using a solvent extraction technique. The values of β1 of Ln(III) decrease to about 0.2 mole fraction of DMSO (X s) in the mixed solvent system and then increase withX s (>about 0.2). However, the variation mode of β1 of Nd(III) withX s somewhat differs from that of Tm(III). Calculation of Ln3+−Cl distance using a Born-type equation of the Gibbs' free energy derived from the β1 evealed the followings: (1) For Tm3+ with coordination number 8, the estimated distance between Tm3+ and Cl (d Tm-Cl) increases linearly withX s in 0.00≤X s≤0.17. This means an enlargement of the primary solvation sphere size of Tm3+ withX s. On the other hand, thed Tm-Cl shows a decrease withX s in 0.17<X s<0.28. (2) The estimatedd Nd-Cl increases linearly withX s in 0.00≤X s<0.06 and 0.06<X s≤0.17, but their slopes are different. The larger slope againstX s in 0.06<X s≤0.17 is attributable to a lowering of the β1 by a coordination of ClO4 into the secondary solvation sphere of Nd3+ and/or by an increase in the solvation number of the primary solvation sphere of Nd3+.

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Abstract  

The stability constants, 1, of each monochloride complex of Nd(III) and Tm(III) have been determined in the mixed system of methanol and water with 1.0 mol·dm–1 ionic strength using a solvent extraction technique. The values of 1 of Nd(III) and Tm(III) increase as the mole fraction of methanol in the mixed solvent system (X s) increases. However, the variation mode of 1 againstX s in the region of 0.00 X s 0.40 differs from each other, a concave curve for the Nd(III) and a convex curve for the Tm(III). The LnCl2+ formed is present as a solvent-shared ion-pair. Since Cl is a structure breaking ion, it was assumed that the primary solvation sphere of Ln3+ directly contacted with Cl. Calculation of Ln3+–Cl distance using Bom-type equation revealed the followings: (1) for Tm3+ with coordination number 8, the estimated distance between Tm3+ and Cl increases linearly withX s in 0.00 X s 0.40. The results mean an increase of the primary solvation sphere size of Tm3+ withX s. (2) For Nd3+, the distance between Nd3+ and Cl decreases linearly withX s in 0.00 X s<0.13, where both coordination numbers of 9 and 8 coexist, while it increases withX s in 0.13<X s 0.40. The results mean a decrease of the primary solvation-sphere size of Nd3+ withX s in 0.00 X s<0.13 and an increase of that withX s in 0.13<X s 0.40.

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Abstract  

The stability constans, 1, of each monochloride complex of Eu(III) have been determined in the methanol and water mixed system with 1.0 mol·dm–3 ionic strength using a solvent extraction technique. The values of 1 increase with an increase in the mole fraction of methanol (X S) in the mixed solvent system when 0 X S 0.40. The, distance of Eu3+–Cl in the mixed solvent system was calculated using the Born-type equation and the Gibbs' free energy derived from 1. Calculation of the Eu3+–Cl distance and the preferential solvation, of Eu3+ by water proposed the variation of the outersphere complex of EuCl2+ as follows: (1) [Eu(H2O)9]3+Cl, [Eu(H2O)8]3+Cl and [Eu(H2O)7(CH3OH)3+Cl inX S 0.014, (2) [Eu(H2O)8]3–Cl and [Eu(H2O)7(CH3OH)]3+Cl in 0.014<X S<0.25 and (3) [Eu(H2O)7(CH3OH)]3–Cl and [Eu(H2O)6(CH3OH)[2 3+Cl in 0.25<X S 0.40.

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Abstract  

The stability constants (β 1) of iodide ion-pairs of trivalent f-block element ions (lanthanoids Ce, Eu, Gd, Tb and Tm, and actinoid Am) were determined in the vicinity of pH 2.5 of mixed methanol/water solvent solutions of an ionic strength of 1.00 mol·dm−3 at 298±1 K. The values were less than 2. From the variation in distance between Eu3+ and I, which was calculated using a Born-type equation for Gibbs’ free energy derived from β 1(Eu), the Eu3+-I interaction was shown to be solvent-shared ion-pair formation when the mole fraction of methanol (X MeOH)≤0.40. In contrast, it was suggested that the interaction of Am3+-I changed from solvent-separated ion-pair to solvent-shared ion-pair with increasing X MeOH when X MeOH≤0.10, but remained as solvent-shared ion-pair in the range 0.16≤X MeOH≤0.40. Furthermore, β 2(Am) was measured in the range 0.31≤X MeOH≤0.40. It was also shown that the β 1 values of lanthanoids at X MeOH = 0.40, except for that of Gd(III), decreased with increasing atomic number.

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Abstract  

The formation constants of thiocyanate complexes of Eu(III) and Am(III) in trace concentrations were investigated in mixed solvent (CH3OH+H2O) solutions of different ionic strength. Furthermore, in paper electrophoresis, the moving velocities of the species of Eu(III) and Am(III) were investigated in 1.1M (H, Na)(SCN, ClO4) mixed solvent (CH3OH-H2O) solutions. The results showed that the difference between the velocities of Eu(III) and Am(III) is explained by the difference of the mean charges calculated by the formation constants of thiocyanate complexes of Eu(III) and Am(III) in the solution.

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