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'Isotope effects' in keywords Facet   Publication Year 1997  [X]
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1Author    Masahisa KakiuchiRequires cookie*
 Title    Hydrogen Isotope Fractionation in Aqueous Alkali Halide Solutions  
 Abstract    The D/H ratios of hydrogen gas in equilibrium with aqueous alkali halide solutions were deter-mined at 25 °C, using a hydrophobic platinum catalyst. The hydrogen isotope effect between the solution and pure water changes linearly with the molality of the solution at low concentrations, but deviates from this linearity at higher concentration for all alkali halide solutions. The magnitude of the hydrogen isotope effect is in the order; Kl > Nal > KBr > CsCl ^ NaBr > KCl > NaCl > LiCl, at concentrations up to a molality of 4 m. The sign and trend of the hydrogen isotope effect is different from that of oxygen. In aqueous alkali halide solutions, the hydrogen isotope effect is influenced by both the cation and the anion species, while the oxygen isotope effect is mainly caused by the cation species. This suggests that the mechanism of hydrogen isotope fractionation between the water molecules in the hydration spheres and the free water molecules differs from the mechanism of the oxygen isotope fractionation. The hydrogen and oxygen isotope effects for alkali halides, except LiCl and NaCl, may be influenced by changes in energy of the hydrogen bonding in free water molecules. 
  Reference    Z. Naturforsch. 52a, 811—820 (1997); received April 15 1997 
  Published    1997 
  Keywords    Hydrogen Isotope, Alkali halide, D/H fractionation, Thermodynamics, Isotope effect 
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 TEI-XML for    default:Reihe_A/52/ZNA-1997-52a-0811.pdf 
 Identifier    ZNA-1997-52a-0811 
 Volume    52 
2Author    A. Kondoh, T. OiRequires cookie*
 Title    Interaction of Alkaline Earth Metal Ions with Acetic and Lactic Acid in Aqueous Solutions Studied by 13 C NMR Spectroscopy  
 Abstract    Interaction of alkaline earth metal (magnesium, calcium, strontium and barium) ions with acetic and lactic acid in aqueous media was investigated by 13 C NMR spectroscopy. In the acetate systems, signals whose chemical shifts were the averages of those of the free and bound acetate ions were observed. Downfield shifts of the carboxylate carbon signals with increasing metal ion concentration indicated that the acetate ion acted as a monodentate ligand coordinating to the metal ion using the carboxylate group. The metal ion concentration dependence of the peak positions of the methine and carboxylate carbon signals of the lactate ion in the lactate systems suggested that the lactate ion coordinated to a metal ion using the carboxylate and hydroxyl groups. Unique upfield shifts upon complexation in the magnesium lactate systems suggested that the lactate ion coordinated to the magnesium ion from outside the primary hydration sphere. The present results were consistent with the isotope effects of the alkaline earth metals observed in cation exchange chromatography. 
  Reference    Z. Naturforsch. 52a, 351—357 (1997); received December 4 1996 
  Published    1997 
  Keywords    13 C NMR, Alkaline Earth Metals, Acetic Acid, Lactic Acid, Isotope Effects 
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 TEI-XML for    default:Reihe_A/52/ZNA-1997-52a-0351.pdf 
 Identifier    ZNA-1997-52a-0351 
 Volume    52