Oxygen isotope salt effect

Figure 11. (A) Hydrogen isotope salt effects in NaCl solntions to 450°C. Plotted points represent data obtained from liqnid-vapor eqnilibration, H2-water eqnilibration, and mineral-water exchange experiments. (B) Oxygen isotope salt effects in NaCl solntions to 400°C. Plotted points represent data from liqnid-vapor eqnilibration, C02-water eqnilibration, and mineral-water exchange experiments. Solid enrves are based on the liqnid-vapor eqnilibration experiments of Horita et al. (1995a).

As already treated in the hydrogen section, isotope fractionations, the hydration of ions may play a significant role in hydrothermal solutions and volcanic vapors (Driesner and Seward 2000). Such isotope salt effects may change the oxygen isotope fractionation between water and other phases by several permil. 

Kawabe 1 (1978) Calculation of oxygen isotope fractionation in quartz-water system with special reference to the low temperatirre fractionatioa Geochim Cosmochim Acta 42 613-621 Kendall C, Chou. 1-M, Coplen TB (1983) Salt effect on oxygen isotope equilibria. EOS Trans Am Geophys Union 64 334-335... 

Additionally, in order to accurately calculate F values from exchange data we need to account for the salt effect on the oxygen and hydrogen equilibrium isotope fractionation between minerals and fluids, based on results reported by Horita et al. (1993a,b 1995) and Chacko et al. (this volume). These results indicate the mineral - salt fractionation may be 0.6 to 1 per mil smaller than the mineral-pure water fractionation at 300°C for a 5 m NaCl solution (Horita et al. 1995). This type of data will play an important role in the ultimate accuracy of the rate constants calculated from partial exchange experiments involving minerals and salt solutions. 

Traesdell AH (1974) Oxygen isotope activities and concentration in aqueous salt solutions at elevated temperatures Consequences for isotope geothermometry. Earth Planet Sci Lett 23 387-396 Tsuchiyama A, Kawamura K, Nakao T, Uyeda C (1994) Isotopic effects on diffusion in MgO melt simulated by the molecular dynamics (MD) method and implications for isotopic mass fractionation in magmatic systems. Geochim Cosmochim Acta 58 3013-3021 Tsuneyuki S, Matsui Y (1995) Molecular dynamic study of pressure enhancement of ion mobilities in liquid silica. Phys Rev Lett 74 3197-3200... 

Fractional distillation of NO provides another effective route and, as the heavier isotope of oxygen is simultaneously enriched, the product has a high concentration of N 0. Many key nitrogen compounds are now commercially available with N enriched to 5%, 30% or 95%, e.g. N2, no, NO2, NH3, HNO3 and several ammonium salts and nitrates. Fortunately the use of these compounds in tracer experiments is simplified by the absence of exchange with atmospheric N2 under normal conditions, in marked contrast with labelled H, C and O compounds where contract with atmospheric moisture and CO2 must be avoided. 

Sofer Z (1978) Isotopic composition hytotion water in gypsum. Geochim Cosmochim Acta 42 1141-1149 Sofer Z, Gat JR (1972) Activities and concentrations of oxygen-18 in concentrated aqueous salt solutions Analytical and geophysical implications. Earth Planet Sci Lett 15 232-238 Sofer Z, Gat JR (1975) The isotope composition of evaporating brines Effects of the isotopic activity ratio in saline solutions. Earth Planet Sci Lett 26 179-186... 

Quaternary salts, isolation of, 10 Quaternization, by alkyl halides, 2-7 by aryl halides, 7-9 on carbon, 53 definition of, 2 by dimethyl sulfate, 9 electronic effects in, 11 in JV-heterocycles, 16, 38 by heterocyclyl halides, 7—9 isotope effect on, 55 mechanism of, 53-56 by methyl euyl-sulfonates, 9, 10 on oxygen, 52 rates of, 55 reagents for, 2-10 by self-condensation, 8 solvent effect on, 10, 55 solvents for, 10 steric effects on, 12, 13 substituents, influence on, 11, 19, 23 on sulfur, 51 Quinaldine, 4-amino-, 4 Quinazolines, 2-alkyl-, salt formation of, 6... 

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