The Vapor Pressures of the Isotopic Forms of Water

Wahl, M. H.; Urey, Harold C.

doi:10.1063/1.1749690

Cited by 39 publications

(5 citation statements)

References 7 publications

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“…The equilibrium separation effect, which occurs as water changes phase to a gaseous state, is due to the different vapor pressures of the H2180 and H2180 molecules. The H2180-water has a lower vapor pressure (Wahl and Urey, 1935;Szapiro and Steckel, 1967), and therefore has a greater tendency to remain in the liquid phase. Thus, at any water/atmosphere interface under two-phase equilibrium conditions, there occurs a specific temperature dependent fractionation which accumulates the heavier water in the liquid state -at 25 ° C the enrichment is 9%01.…”

Section: A Basic Modelmentioning

confidence: 99%

“…It was already known that heavy water (HDO or H2180) has a lower vapor pressure than H2160 (Wahl and Urey, 1935), and therefore the liquid phase is enriched isotopically in a batch distillation process (Baertschi and Th/irkauf, 1960;Merlivat et al, 1963); however, the dynamics of evaporation under natural conditions (i.e. in air of non-zero humidities) was poorly understood.…”

Section: Introductionmentioning

confidence: 99%

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The effects of water-stress on leaf H2 18O enrichment

Farris

Strain

1978

Radiat Environ Biophys

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Water-stress experiments with Phaseolus vulgaris L. were undertaken to determine the transpiration rate dependency of the naturally occuring leaf H2(18O) fractionation process. Water-stress leaf H2(18O) levels were observed to be unexpectedly higher than controls. Speculations on the cause of this phenomenon are discussed. Since transpiration rate variations should theoretically affect only the rate and not the extent of leaf H2(18O) fractionation, the respective time courses for water-stressed and control leaf H2(18O) accumulations were compared. Water-stressed leaves displayed a slower rate of isotopic enrichment relative to controls, as was predicted from their reduced transpiration rate. In an absolute sense, however, both control and water-stress leaf H2(18O) fractionation rates were markedly greater than projected values from the existing model. Consequently, transpiration rates cannot be derived accurately at present from the observed rates of leaf H2(18O) discrimination. Several modifications of the theory are also considered.

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Section: A Basic Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The effects of water-stress on leaf H2 18O enrichment

Farris

Strain

1978

Radiat Environ Biophys

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“…In the Earth's atmosphere, the heavy isotopomers of water are condensed preferentially because they have a lower equilibrium vapor pressure than does H 2 O. Many studies have measured fractionation factors − and equilibrium vapor pressures − of the various isotopomers. The effect of isotope on vapor pressure has been summarized for water and ice .…”

Section: Introductionmentioning

confidence: 99%

Isothermal Desorption Kinetics of Crystalline H₂O, H₂¹⁸O, and D₂O Ice Multilayers

2003

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The isothermal desorption rates of crystalline H 2 O, H 2 18 O, and D 2 O ice multilayers were measured over a temperature range from 175 to 190 K. The desorption rates were measured with optical interferometry using ice multilayers grown epitaxially on a Ru(001) surface in an ultrahigh vacuum chamber. The Arrhenius parameters for the desorption of H 2 O and H 2 18 O were identical within experimental error. For H 2 O, the preexponential was ν ) 10 32.6(0.3 cm -2 s -1 and the activation energy was E ) 13.9 ( 0.2 kcal mol -1 . For H 2 18 O, the preexponential was ν 18 ) 10 32.4(0.3 cm -2 s -1 and the activation energy was E 18 ) 13.8 ( 0.2 kcal mol -1 . Despite the near equivalence in the Arrhenius parameters, H 2 18 O desorbed at a rate that was slower by ∼9% throughout the range of temperatures. In contrast, the desorption rate of D 2 O was slower by 49-62% compared with H 2 O over the measured temperature range. The Arrhenius parameters for the desorption of D 2 O were ν D ) 10 33.4(0.5 cm -2 s -1 and E D ) 14.8 ( 0.4 kcal mol -1 . A transition state model was developed to explain the measured desorption kinetics. The transition state model predicts that total molecular mass has only a small effect on the desorption kinetics because the mass differences among the isotopomers are small. On the other hand, the principal moments of inertia of the desorbing molecules have a large effect on the desorption rate. About each of the three axes, D 2 O has roughly twice the moment of inertia of H 2 O or H 2 18 O. This larger moment of inertia affects the desorption rate in two ways. First, surface bound D 2 O molecules have lower frequencies for hindered rotations. These lower frequencies result in less zero-point energy for the surface bound molecule and a larger desorption activation energy. Second, a transition state D 2 O molecule has a larger rotational partition function. This larger rotational partition function yields a larger preexponential for desorption.

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“…175 cm.-l is ascribed to hindered translation, and if the poorly resolved absorption in the range 320 -1000 cm.-l is ascribed to hindered rotation with characteristic frequencies of 475, 590 and 755 cm.-l, the isotope fractionation of water on distillation can be accounted for. If the changes in frequency with tem perature of some of the modes as indicated by infrared and Raman data are allowed for, and for others are estimated with these as guides, the fractiona tion data (30,31) as function of temperature are also accounted for over the whole range. The external modes in response to interactions in the liquid favor H2018 being bound more strongly than H2015 in the liquid, but the change in frequency for the internal modes on condensing the vapor offsets their effect to some extent.…”

Section: Nature Of the Solventmentioning

confidence: 99%

Applications of Oxygen Isotopes in Chemical Studies

Taube¹

1956

Annu. Rev. Nucl. Sci.

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The choice of the general subject of this article requires no apology, but the choice of the specific material to fit to the space allotted does. The limita tions and research interests of the reviewer were a governing factor in mak ing the selection, but also the consideration entered that the effects of the major omissions are tempered by other recent reviews in which much of the material omitted is discussed. Thus the important work in geochemistry involving oxygen isotopes is discussed in excellent reviews by Dole (I), and more recently by Craig & Boata (2). The work on heterogenous systems is discussed more completely in the article by Dole. It is hoped in this connec tion that a general article on the application of isotopes in the study of heterogeneous catalysis, induding work with oxygen isotopes, will be forth coming. In the subjects chosen for review, an effort has been made to be com plete ; and earlier literature as well as the more recent has been referred to. When work which is within the scope of the subject matter is not cited, it is because of oversight or because the work is dealt with in a more general article by the same author.The present article stresses the application of oxygen isotopes to the study of chemical phenomena in homogeneous solution. Much of the work exploiting oxygen isotope effects has been done for such systems. For reac tions of oxygen-containing substances in an oxide-labile solvent such as water, isotope studies can answer important questions which no other method can answer as directly; and they have been of great help in defining the nature of the solvent and of the substances dissolved in it, and in exposing the mechanisms of reactions in solution. TECHNIQUESIn the work reviewed, mainly the oxygen isotopes of mass 18 and 16 come into question. The mass spectrometric method of measuring isotope ratios has almost completely supplanted that depending on the determination of density differences in water. With care, commercial instruments can measure differences to a precision of 1 part in 1000 in O2 or CO2 of normal oxygen isotopic composition. With specially designed instruments (3), a precision of one part in approximately 10,000 on CO2 can be attained.When the oxygen is available as water, an accurate method (4) of isotopic assay is equilibration of CO2 with the H20, followed by measurement of the isotopic ratio in the CO2• Dostrovsky & Klein (5) have described the high temperature equilibration of CO2 and H20, and have derived an equation 1 The survey of literature pertaining to this review was completed in January, 1956.

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The Vapor Pressures of the Isotopic Forms of Water

Cited by 39 publications

References 7 publications

The effects of water-stress on leaf H2 18O enrichment

The effects of water-stress on leaf H2 18O enrichment

Isothermal Desorption Kinetics of Crystalline H₂O, H₂¹⁸O, and D₂O Ice Multilayers

Applications of Oxygen Isotopes in Chemical Studies

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The Vapor Pressures of the Isotopic Forms of Water

Cited by 39 publications

References 7 publications

The effects of water-stress on leaf H2 18O enrichment

The effects of water-stress on leaf H2 18O enrichment

Isothermal Desorption Kinetics of Crystalline H2O, H218O, and D2O Ice Multilayers

Applications of Oxygen Isotopes in Chemical Studies

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Isothermal Desorption Kinetics of Crystalline H₂O, H₂¹⁸O, and D₂O Ice Multilayers