Some water-soluble organic iodine compounds (aqueous solution) can be analyzed for iodine by isotopically exchanging with labelled elementary iodine (organic solution). The method is applicable to exchange systems in which the rate of the exchange is rather small but measurable, before the exchange equilibrium is attained. The iodine content of iodoaromatic amino acids such as 5-iodouracil and 3,5-diiodotyrosine can be determined within an error of ±4%.
In torsional braid analysis (TBA) the thermocouple junction is not in contact with the specimen, and therefore temperature standards are necessary. However TBA is devised only for application to high polymers, which are not appropriate for standards. The transition and fusion temperatures of several substances of low molecular weight, such as water,o-terphenyl, potassium nitrate andn-azoxyanisole, have been studied by TBA, and their applicability as standards to TBA is discussed. It is found that water,o-terphenyl and potassium nitrate can be used as standards.
A new type of the isotope exchange method of analysis is proposed. The method can be applied to the exchange system in which
the rate of the exchange reaction is rather slow but measurable, before the exchange equilibrium is attained. The validity
of the principle of the method is verified experimentally with several exchange systems of RyI+KI*⇌RyI*+KI (RyI stands for alkyl, alkylene or benzyl iodide) type. The iodine content of the organic iodine compounds can be determined
with an error of ±4%.
Authors:Y. Takahashi, Y. Minai, Y. Meguro, S. Toyoda, and T. Tominaga
Binding constants of Eu(III)- and Am(III)-complexes with soil-derived humic acid were determined by solvent extraction at various pH and ionic strength. Based on the dependence of binding constants on pH and ionic strength, stabilities of the humate complexes in land water and seawater were estimated. Speciation calculation based on the binding constants indicated that Am(III) could combine with humic substances in natural water system.
Authors:Y. Takahashi, T. Kimura, Y. Kato, Y. Minai, and T. Tominaga
Luminescence lifetime of Eu(III) in polyacrylate and polymaleate complexes has been measured to evaluate the number of water molecules bound to the ion. The number of residual water molecules hydrated to Eu(III) in the polyacrylate and polymaleate complexes ranged from 3.5 to 4.5 when the supporting electrolyte concentration was 0.01. The residual hydration number decreased with the addition of supporting electrolyte. These results indicate that Eu(III) is surrounded by polymolecular ligands in these complexes.
Speciation and solubility of neptunium were studied using paper electrophoresis, ion exchange and ultrafiltration. Among these methods, the paper electrophoresis was found to be suitable for measuring speciation and solubility of neptunium of low concentration, if chemical species had opposite charge each other or dissolved species had a charge. Using paper electrophoresis, hydrolysis constants of NpO2OH0 and NpO
and solubility product of NpO2 were obtained and ionic-strength dependence of speciation was observed.
Authors:T. Nishida, Y. Yoshida, Y. Takahashi, S. Okada, and J. Yamaki
The Mössbauer spectrum of LiFeVPOx, LiFeV0.5POx and LiFePOx glasses prepared by conventional melt-quenching method for cathode active material is composed of a doublet due to distorted
FeIIIO4 tetrahedra. The Mössbauer spectrum of LiFePOx glass has an additional doublet due to distorted FeIIO6 octahedra. Heat treatment of LiFeVPOx and LiFeV0.5POx glasses at a given temperature close to each crystallization temperature causes a marked decrease in the value of Δ, reflecting a decrease in the distortion or an increase in the local symmetry of distorted FeIIIO4 tetrahedra. Heat treatment of LiFeVPOx glass causes an increase in the electric conductivity from the order of 10−7 to 10−3 S·cm−1, together with an increase in the specific discharge-and charge-capacity of a coin-type Li-ion cell from 50 to 150 mAh·g−1. These results prove that structural relaxation of the glass network causes an increase in the electric conductivity and
an increase in the energy density of the Li-ion cell.
Authors:Y. Takahashi, Y. Minai, T. Kimura, and T. Tominaga
Distribution of trace amount of Eu(III), or Am(III), in the aqueous/solid system containing humic acid and kaolinite, or montmorillonite,
was studied by batch experiments. Humic acid was also adsorbed on the clay minerals and its adsorption isotherm can be regarded
as a Langmuir type. It is shown that Eu(III), or Am(III), exists as humate complex either in the aqueous or on solid phase
in the system including kaolinite, or montmorillonite. These results suggest that the organic-inorganic complex like clay
minerals coated with humic substances is important as metal reservoir in the environment.
Authors:Y. Takahashi, T. Kimura, Y. Kato, Y. Minai, Y. Makide, and T. Tominaga
Laser-induced fluorescence spectroscopy was applied to obtaining hydration structure of Eu(III) complexes with synthetic polycarboxylates
of poly(acrylic acid), poly(maleic acid), poly(methacrylic acid), and poly(a-hydroxyacrylic acid). Dependence of
(the number of water molecules in the first coordination sphere of Eu(III) ion) on pH and supporting electrolyte concentration
was obtained for these complexes. The spectroscopic results show that Eu(III) is surrounded by the “cage” of polycarboxylate
ligands. The pH-induced transition in conformation of poly(methacrylic acid) ligand was clearly observed in the
Authors:T. Shibasaki, T. Furuya, J. Kuwahara, Y. Takahashi, H. Takahashi, and T. Hashimoto
Summary Structural phase transitions upon the application of high pressure in LaGaO3 and LaCrO3, which were prospected from diffraction and thermal analyses of phase transition under ambient pressure, were discovered by using high-pressure X-ray diffraction. It was revealed that the crystal structures of LaCrO3 and LaGaO3 changed completely from that of orthorhombic distorted perovskite to that of a rhombohedral distorted one upon the application of pressure higher than 5.4 and 3.0 GPa, respectively, at room temperature. The variation of lattice constants with pressure was investigated for the high-pressure rhombohedral phases of LaCrO3 and LaGaO3 and isothermal compressibility was estimated. The variation of lattice constants with pressure at room temperature in the high-pressure rhombohedral phase was compared with that with temperature at ambient pressure in high-temperature rhombohedral phase. It was found that the application of pressure decreased the crystal symmetry, which was opposite to the result in the case of increasing the temperature.