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Isidor Kirshenbaum

Bio: Isidor Kirshenbaum is an academic researcher from Columbia University. The author has contributed to research in topics: Boiling point & Vapor pressure. The author has an hindex of 5, co-authored 7 publications receiving 1031 citations.

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TL;DR: In this paper, the fractionation factor for the exchange reaction between ammonia and ammonium nitrate was determined as a function of the dissolved ammonia content, and the equilibrium constant for N14H4+N15H3+N14H3(gas) was calculated to be 1.034.
Abstract: The fractionation factor for the exchange reaction between ammonia and ammonium nitrate was determined as a function of the dissolved ammonia content. It was found that for a stock solution containing 59.3–59.6 percent ammonium nitrate α=−0.029 M+1.034, where α is the fractionation factor at 25°C and M the fraction (Moles NH3)/(Moles NH3+Moles NH4NO3), in solution. From these data, the equilibrium constant for the exchange reaction N14H4+(sol)+N15H3(gas)⇌N15H4+(sol)+N14H3(gas) was calculated to be 1.034, while that for the reaction N14H3(sol)+N15H3(gas)⇌N15H3(sol)+N14H3(gas) was found to be 1.005. Vapor pressure and density data were determined for the ammonia‐ammonium nitrate solutions as a function of the ammonia concentration.

64 citations

Journal ArticleDOI
TL;DR: In this article, the differences in the vapor pressures of natural nitrogen and samples containing 34.6 percent nitrogen were measured by a differential method and were found to be given by log P1/P2=(0.2474/T)−0.001994 where 1 refers to the natural nitrogen, and 2 refers to heavy sample.
Abstract: The differences in the vapor pressures of natural nitrogen and samples containing 34.6 percent nitrogen‐15 were measured by a differential method and were found to be given by log P1/P2=(0.2474/T)−0.001994 where 1 refers to the natural nitrogen and 2 refers to the heavy sample. The difference in the heats of vaporization of the two samples was calculated to be 1.14 calories, that of the heavy sample being higher. The triple point pressures were measured and found to be 9.386 cm of Hg and 9.378 cm of Hg, respectively. From this the difference in the triple points was calculated to be 0.020°K. Assuming that Raoult's law may be used, the ratio of the vapor pressures and the difference in the heats of vaporization of the two pure isotopes, nitrogen‐14 and nitrogen‐15, were found to be log(P14/P15)=(0.7230/T)−0.005822ΔHvap 15−ΔHvap 14=3.33 calories. The triple point of the pure nitrogen‐15 was found to be 0.058° higher than that of nitrogen‐14 and the boiling point 0.052° higher. The differences in the vapor p...

23 citations


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Journal ArticleDOI
26 May 1961-Science
TL;DR: The relationship between deuterium and oxygen-18 concentrations in natural meteoric waters from many parts of the world has been determined with a mass spectrometer and shows a linear correlation over the entire range for waters which have not undergone excessive evaporation.
Abstract: The relationship between deuterium and oxygen-18 concentrations in natural meteoric waters from many parts of the world has been determined with a mass spectrometer. The isotopic enrichments, relative to ocean water, display a linear correlation over the entire range for waters which have not undergone excessive evaporation.

6,721 citations

Journal ArticleDOI
TL;DR: In this paper, a fundamental equation of state has been formulated for heavy water in the form Ψ = Ψ(p,T) in which Ω = Helmholtz free energyp = density T = thermodynamic temperature.
Abstract: A fundamental equation of state has been formulated for heavy water in the form Ψ = Ψ(p,T) in which Ψ = Helmholtz free energyp = density T = thermodynamic temperature. The complete range of single phase states in the range up to 100 MPa and 600 °C is covered by a single equation which is fitted both to P v T values, for saturated and unsaturated states, and to enthalpy values for saturation states only. The equation is constrained to fit the critical point conditions determined by Blank. It represents all thermodynamic properties of D2O, in the above range of states, within what is believed to be the accuracy of the experimental data.

1,776 citations

Journal ArticleDOI
09 Jun 1961-Science
TL;DR: A standard, based on the set of ocean water samples used by Epstein and Mayeda to obtain a reference standard for oxygen-18 data, but defined relative to the National Bureau of Standards isotopic reference water sample, is proposed for reporting both deuterium and oxygen- 18 variations in natural watersrelative to the same water.
Abstract: A standard, based on the set of ocean water samples used by Epstein and Mayeda to obtain a reference standard for oxygen-18 data, but defined relative to the National Bureau of Standards isotopic reference water sample, is proposed for reporting both deuterium and oxygen-18 variations in natural waters relative to the same water. The range of absolute concentrations of both isotopes in meteoric-waters is discussed.

1,773 citations

Journal ArticleDOI
TL;DR: Measurements of δ15 N might offer the advantage of giving insights into the N cycle without disturbing the system by adding 15 N tracer, as well as giving information on N source effects, which can give insights into N cycle rates.
Abstract: Equilibrium and kinetic isotope fractionations during incomplete reactions result in minute differences in the ratio between the two stable N isotopes, 15N and 14N, in various N pools. In ecosystems such variations (usually expressed in per mil [δ15N] deviations from the standard atmospheric N2) depend on isotopic signatures of inputs and outputs, the input–output balance, N transformations and their specific isotope effects, and compartmentation of N within the system. Products along a sequence of reactions, e.g. the N mineralization–N uptake pathway, should, if fractionation factors were equal for the different reactions, become progressively depleted. However, fractionation factors vary. For example, because nitrification discriminates against 15N in the substrate more than does N mineralization, NH4+ can become isotopically heavier than the organic N from which it is derived.Levels of isotopic enrichment depend dynamically on the stoichiometry of reactions, as well as on specific abiotic and biotic conditions. Thus, the δ15N of a specific N pool is not a constant, and δ15N of a N compound added to the system is not a conservative, unchanging tracer. This fact, together with analytical problems of measuring δ15N in small and dynamic pools of N in the soil–plant system, and the complexity of the N cycle itself (for instance the abundance of reversible reactions), limit the possibilities of making inferences based on observations of 15N abundance in one or a few pools of N in a system. Nevertheless, measurements of δ15N might offer the advantage of giving insights into the N cycle without disturbing the system by adding 15N tracer.Such attempts require, however, that the complex factors affecting δ15N in plants be taken into account, viz. (i) the source(s) of N (soil, precipitation, NOx, NH3, N2-fixation), (ii) the depth(s) in soil from which N is taken up, (iii) the form(s) of soil-N used (organic N, NH4+, NO3−), (iv) influences of mycorrhizal symbioses and fractionations during and after N uptake by plants, and (v) interactions between these factors and plant phenology. Because of this complexity, data on δ15N can only be used alone when certain requirements are met, e.g. when a clearly discrete N source in terms of amount and isotopic signature is studied. For example, it is recommended that N in non-N2-fixing species should differ more than 5‰ from N derived by N2-fixation, and that several non-N2-fixing references are used, when data on δ15N are used to estimate N2-fixation in poorly described ecosystems.As well as giving information on N source effects, δ15N can give insights into N cycle rates. For example, high levels of N deposition onto previously N-limited systems leads to increased nitrification, which produces 15N-enriched NH4+ and 15N-depleted NO3−. As many forest plants prefer NH4+ they become enriched in 15N in such circumstances. This change in plant δ15N will subsequently also occur in the soil surface horizon after litter-fall, and might be a useful indicator of N saturation, especially since there is usually an increase in δ15N with depth in soils of N-limited forests.Generally, interpretation of 15N measurements requires additional independent data and modelling, and benefits from a controlled experimental setting. Modelling will be greatly assisted by the development of methods to measure the δ15N of small dynamic pools of N in soils. Direct comparisons with parallel low tracer level 15N studies will be necessary to further develop the interpretation of variations in δ15N in soil–plant systems. Another promising approach is to study ratios of 15N[ratio ]14N together with other pairs of stable isotopes, e.g. 13C[ratio ]12C or 18O[ratio ]16O, in the same ion or molecules. This approach can help to tackle the challenge of distinguishing isotopic source effects from fractionations within the system studied.

1,518 citations

Journal ArticleDOI
TL;DR: A review of nonsolvent induced phase separation membrane preparation and characterization for many commonly used membrane polymers is presented in this article, which includes membrane porosity and pore size distribution characterization, membrane physical and chemical properties characterization, and thermodynamic and kinetic evaluation of phase inversion process.
Abstract: The methods and mechanisms of nonsolvent induced phase separation have been studied for more than fifty years. Today, phase inversion membranes are widely used in numerous chemical industries, biotechnology, and environmental separation processes. The body of knowledge has grown exponentially in the past fifty years, which suggests the need for a critical review of the literature. Here we present a review of nonsolvent induced phase separation membrane preparation and characterization for many commonly used membrane polymers. The key factors in membrane preparation discussed include the solvent type, polymer type and concentration, nonsolvent system type and composition, additives to the polymer solution, and film casting conditions. A brief introduction to membrane characterization is also given, which includes membrane porosity and pore size distribution characterization, membrane physical and chemical properties characterization, and thermodynamic and kinetic evaluation of the phase inversion process. ...

1,063 citations