Sulfur isotope effects in volcanic gas mixtures

1970 ◽  
Vol 7 (6) ◽  
pp. 1402-1409 ◽  
Author(s):  
V. A. Grinenko ◽  
H. G. Thode
Keyword(s):  
Isotope Exchange ◽  
Sulfur Isotope ◽  
Chemical Reduction ◽  
Isotope Effects ◽  
Exchange Constant ◽  
Exchange Reactions ◽  
Volcanic Gas ◽  
Temperature Changes ◽  
Kinetic Isotope ◽  
Exchange Constants

Sulfur isotope effects in the exchange systems (1) [Formula: see text] and (2) [Formula: see text] have been studied at various temperatures. It has been shown that in the presence of water vapor sulfur isotope exchange proceeds at an appreciable rate in (1) above 150 °C and in (2) above 300 °C.The isotopic exchange constant for (1) approaches unity in the temperature range from 200 to 400 °C and the exchange constants for (2) at 400 °C and 450 °C equal 1.0095 and 1.0090 respectively favoring 34S in the SO2.The kinetic isotope effect in the chemical reduction of SO2 to S0 in consequence of its interaction with H2S has been determined at 25 °C, 200 °C, and 280 °C. At these temperatures the 32SO2 molecules react 1.6% faster than the 34SO2 molecules.It is concluded that the spread in isotopic composition of various forms of sulfur in volcanic gases is caused not only by isotope exchange reactions between oxidized and reduced forms of sulfur but also by kinetic isotope effects in unidirectional reactions which result from major temperature changes at the outflow.

FRACTIONATION OF GERMANIUM ISOTOPES IN CHEMICAL REACTIONS

1964 ◽  
Vol 42 (8) ◽  
pp. 1971-1978 ◽  
Author(s):  
H. M. Brown ◽  
H. R. Krouse
Keyword(s):  
Partition Function ◽  
Isotope Exchange ◽  
Isotope Fractionation ◽  
Kinetic Isotope Effect ◽  
Chemical Reduction ◽  
Isotope Effects ◽  
Equilibrium Constants ◽  
Kinetic Isotope Effects ◽  
Exchange Reactions ◽  
Kinetic Isotope

Isotopic vibrational frequencies and the corresponding partition-function ratios for several compounds containing Ge70 and Ge76 have been calculated at various temperatures. The theoretical equilibrium constants for germanium isotope-exchange reactions derived from these partition-function ratios indicate that noticeable germanium isotope fractionation might be effected with laboratory reactions. Calculated kinetic isotope effects in the breaking of diatomic bonds also predict observable alterations of the Ge70/Ge76 ratio.A kinetic isotope effect of 1.0% observed in the chemical reduction of GeO2 to GeO is discussed.

Tellurium isotope fractionation study

1968 ◽  
Vol 46 (4) ◽  
pp. 583-591 ◽  
Author(s):  
R. M. Smithers ◽  
H. R. Krouse
Keyword(s):  
Normal Vibration ◽  
Isotope Fractionation ◽  
Sulfur Isotope ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Abundance Ratio ◽  
Isotopic Equilibrium ◽  
Kinetic Isotope ◽  
Equilibrium Exchange ◽  
Exchange Constants

"Normal vibration equations" have been solved to yield vibrational frequencies for isotopic compounds of tellurium. These frequencies were used to evaluate "partition function ratios" for 122Te- and 130Te-containing compounds. Theoretical "isotopic equilibrium exchange constants" and estimates of "kinetic isotope effects" were derived from these ratios. The results suggest that the 122Te/130Te abundance may be altered significantly in laboratory reactions and terrestrial processes.Preliminary experiments have realized kinetic isotope effects of 0.7 and 0.6% in inorganic and microbiological reductions respectively of tellurite to elemental tellurium. These results are interpreted in terms of the isotope effect in Te—O bond breakage.The maximum variation in the 130Te/122Te abundance ratio of six natural tellurides and two commercial preparations of TeO32− was found to be 0.4%.The results are compared with those found in analogous selenium and sulfur isotope investigations.

THERMODYNAMIC PROPERTIES AND GEOCHEMISTRY OF ISOTOPIC COMPOUNDS OF SELENIUM

1962 ◽  
Vol 40 (2) ◽  
pp. 367-375 ◽  
Author(s):  
H. R. Krouse ◽  
H. G. Thode
Keyword(s):  
Partition Function ◽  
Kinetic Isotope Effect ◽  
Chemical Reduction ◽  
Equilibrium Constants ◽  
Elemental Selenium ◽  
Exchange Reactions ◽  
Kinetic Isotope ◽  
Naturally Occurring ◽  
Selenium Isotope ◽  
Selenium Isotopes

Using "normal vibration equations" and statistical mechanics, the isotopic vibrational frequencies and the partition function ratios for various Se76- and Se82-containing compounds have been calculated. The equilibrium constants for selenium isotope exchange reactions derived from these partition function ratios indicate that noticeable fractionation of selenium isotopes can be expected in the laboratory and in naturally occurring processes.The Se82/Se76 ratios for 16 natural samples have been compared mass spectrometrically. Variations of up to 1.5% found in this ratio are discussed.A kinetic isotope effect of 1.5% found in a chemical reduction of selenite ion to elemental selenium is also discussed.

NMR Stratagems for the Study of Multiple Kinetic Hydrogen/Deuterium Isotope Effectsof Proton Exchange. Example: Di-p-fluorophenylformamidine/THF

1989 ◽  
Vol 44 (5) ◽  
pp. 459-472
Author(s):  
Hans-Heinrich Limbach ◽  
Ludger Meschede ◽  
Gerd Scherer
Keyword(s):  
Nmr Spectroscopy ◽  
Magnetization Transfer ◽  
Isotope Effects ◽  
Geometric Mean ◽  
Kinetic Isotope Effects ◽  
Proton Exchange ◽  
Exchange Reactions ◽  
H Nmr ◽  
Kinetic Isotope ◽  
Hydrogen Deuterium

Stratagems are presented for the determination of kinetic isotope effects of proton exchange reactions by dynamic NMR spectroscopy. In such experiments, lineshape analyses and/or polarization transfer experiments are performed on the exchanging protons or deuterons as well as on remote spins, as a function of the deuterium fraction in the mobile proton sites. These methods are NMR analogs of previous proton inventory techniques involving classical kinetic methods. A theory is developed in order to derive the kinetic isotope effects as well as the number of transferred protons from the experimental NMR spectra. The technique is then applied to the problem of proton exchange in the system 15N,15N′-di-p-fluorophenylibrmamidine, a nitrogen analog of formic acid, dissolved in tetrahydrofuran-d8 (THF). DFFA forms two conformers in THF to which s-trans and s-cis structures have been assigned. Only the s-trans conformer is able to dimerize and exchange protons. Lineshape simulations and magnetization transfer experiments were carried out at 189,2 K, at a concentration of 0.02 mol l-1, as a function of the deuterium fraction D in the 1H-15N sites. Using 1H NMR spectroscopy, a linear dependence of the inverse proton lifetimes on D was observed. From this it was concluded that two protons are transported in the rate limiting step of the proton exchange. This result is expected for a double proton transfer in an s-trans dimer with a cyclic structure. The full kinetic HH/HD/DD isotope effects of 233:11:1 at 189 K were determined through 19F NMR experiments on the same samples. The deviation from the rule of geometric mean, although substantial, is much smaller than found in previous studies of intramolecular HH transfer reactions. Possible causes of this effect are discussed.

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