Showing papers in "Journal of Physical and Chemical Reference Data in 1998"

Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update

Abstract: The available data on gas-phase basicities and proton affinities of approximately 1700 molecular, radical and atomic neutral species are evaluated and compiled. Tables of the data are sorted (1) according to empirical formula and (2) according to evaluated gas basicity. This publication constitutes an update of a similar evaluation published in 1984.

The Viscosity of Carbon Dioxide

Abstract: When representative equations for the viscosity of carbon dioxide were published in 1990, it was recognized that, owing to inconsistencies among the available experimental liquid viscosity data which could not be resolved, new measurements were necessary. Since then, two new sets of measurements have been performed and it is appropriate to revise the published equations in order to improve their performance in the liquid region. In the previous work, the excess viscosity was represented by two separate equations, one for the gas phase and the other, a provisional one, for the liquid phase. Both equations were joined by a blending function. In the present work, the excess viscosity for the whole thermodynamic surface is represented by one equation. The resulting overall viscosity representation for carbon dioxide covers the temperature range 200 K⩽T⩽1500 K and densities up to 1400 kg m−3. In terms of pressure, the viscosity representation is valid up to 300 MPa for temperatures below 1000 K, whereas for higher temperatures and owing to the limitation of the equation of state used, the upper pressure limit is restricted to 30 MPa. The uncertainties associated with the proposed representation vary from ±0.3% for the viscosity of the dilute gas near room temperature to ±5.0% at the highest pressures. Tables of viscosity generated by the representative equations are included for easy reference and to assist validation of computer coding.

Data on Internal Rarefied Gas Flows

Abstract: The present review, containing 178 references, is dedicated to one of the largest and most important branches of the rarefied gas dynamics, namely internal flows. A critical analysis of the corresponding numerical data and analytical results available in the literature was made. The most reliable data were selected and tabulated. The review will be useful as a reference for mathematicians, physicists and aerodynamicists interested in rarefied gas flows. In this paper the complete ranges of the main parameters, determining rarefied gas flows through a capillary, are covered. The capillary length varies from zero, when the capillary degenerates into a thin orifice, to infinity when the end effects can be neglected. The Knudsen number, characterizing the gas rarefaction, varies from zero when the gas is considered as a continuous medium to infinity when the intermolecular collisions can be discounted. The pressure and temperature drops on the capillary ends vary from the small values when the linear theory i...

The observed properties of liquid helium at the saturated vapor pressure

Abstract: The equilibrium and transport properties of liquid 4He are deduced from experimental observations at the saturated vapor pressure. In each case, the bibliography lists all known measurements. Quantities reported here include density, thermal expansion coefficient, dielectric constant, superfluid and normal fluid densities, first, second, third, and fourth sound velocities, specific heat, enthalpy, entropy, surface tension, ion mobilities, mutual friction, viscosity and kinematic viscosity, dispersion curve, structure factor, thermal conductivity, latent heat, saturated vapor pressure, thermal diffusivity and Prandtl number of helium I, and displacement length and vortex core parameter in helium II.

Revised Formulation for the Refractive Index of Water and Steam as a Function of Wavelength, Temperature and Density

Abstract: Schiebener et al. published a formulation for the refractive index of water and steam in 1990 [J. Phys. Chem. Ref. Data 19, 677 (1990)]. It covered the ranges 0.2 to 2.5 μm in wavelength, −12 to 500 °C in temperature, and 0 to 1045 kg m−3 in density. The formulation was adopted by the International Association for the Properties of Water and Steam (IAPWS) in 1991. In the present article, the data, after conversion to ITS-90, have been refitted to the same functional form, but based on an improved equation of state for water adopted by IAPWS in 1995. The revised coefficients are reported, and some tabular material is provided. The revised refractive-index formulation was adopted by IAPWS in 1997 and is available as part of a National Institute of Standards and Technology Standard Reference Database. For most conditions, the revised formulation does not differ significantly from the previous one. A substantial improvement has been obtained in supercooled water at ambient pressure, where the previous formula...

Isotopic Compositions of the Elements 1997

Abstract: The Commission’s Subcommittee for the Isotopic Composition of the Elements has carried out its biennial review of isotopic compositions, as determined by mass spectrometry and other relevant methods. This involves a critical evaluation of the published literature, element by element, and forms the basis of the Table of Isotopic Compositions of the Elements as Determined by Mass Spectrometry presented here. New guidelines have been used to arrive at the uncertainties on the isotopic abundances and there are numerous changes to the table since it was last published in 1991. Atomic Weights calculated from this table are consistent with Ar(E) values listed in the Table of Standard Atomic Weights 1997.

A Helmholtz Free Energy Formulation of the Thermodynamic Properties of the Mixture {Water + Ammonia}

Abstract: A thermodynamic model incorporating a fundamental equation of state for the Helmholtz free energy of the mixture {water+ammonia} is presented which covers the thermodynamic space between the solid–liquid–vapor boundary and the critical locus. It is also valid in the vapor and liquid phases for pressures up to 40 MPa. It represents vapor–liquid equilibrium properties with an uncertainty of ±0.01 in liquid and vapor mole fractions. Typical uncertainties in the single-phase regions are ±0.3% for the density and ±200 J mol−1 for enthalpies. Details of the data selection and the optimization process are given. The behavior of the fundamental equation of state is discussed in all parts of the thermodynamic space.

Energetics of the O–H Bond in Phenol and Substituted Phenols: A Critical Evaluation of Literature Data

Abstract: This review presents a critical assessment of the available experimental information (contained in ∼90 literature references) on the thermochemistry of the O–H bond in phenol and substituted phenols. The analysis led to a set of recommended values for the O–H bond dissociation enthalpies, which in turn allowed us to discuss several empirical and theoretical methodologies used to estimate these data.

Reference Correlation of the Viscosity of Propane

Abstract: A new representation of the viscosity of propane includes a zero-density correlation and an initial-density dependence correlation based on the kinetic theory of dilute gases and on the Rainwater–Friend theory. The higher density contributions of the residual viscosity in the representation are formed by a combination of double polynomials in density and reciprocal temperature, and a free-volume term with a temperature-dependent close-packed density. The full surface correlation is based on a set of primary experimental data selected as a result of a critical assessment of the available information from 37 original viscosity studies. The review refers to 96 citations altogether. The validity of the representation extends from the triple point to 600 K and 100 MPa in accordance with the modified Benedict–Webb–Rubin equation of state. The uncertainty of the representation varies from ±0.4% for the viscosity of the dilute gas phase between room temperature and 600 K, to about ±2.5% for the range 100–475 K up to about 30 MPa, and to about ±4% for points outside this range. Tables of the viscosity according to the representative equations at selected temperatures and pressures and along the saturation line provide easy reference as well as the validation of computer codes.

Electron Interactions with C2F6

Abstract: Perfluoroethane (C2F6, hexafluoroethane) is a man-made gas with many important applications (eg, in the aluminum industry, the semiconductor industry, plasma chemistry and etching technologies, and pulsed power switching) In these and other uses, knowledge of the interactions of slow electrons (kinetic energies less than about 100 eV) is fundamental in optimizing performance parameters involved in the particular application We, therefore, have critically evaluated and synthesized existing knowledge on electron interactions with C2F6 The following cross sections and their intercomparison are presented and discussed: total electron scattering, momentum transfer, integral elastic, differential elastic, differential vibrational, vibrational inelastic, total ionization, partial ionization, total dissociation, and electron attachment Information is presented also on the coefficients for electron impact ionization, effective ionization, electron attachment, and electron transport (lateral diffusion coeffic

Survey and Assessment of Available Measurements on Thermodynamic Properties of the Mixture {Water+Ammonia}

Abstract: Mixtures of water and ammonia play an important role in absorption refrigeration cycles and have received attention as working fluids in modern power generation cycles. For design and simulations during the development of any application, the thermodynamic properties have to be known accurately. Measurements of available thermodynamic data are compiled and summarized. The data sets are compared, using a Helmholtz free energy formulation. Recommendations are given for which data sets are suited to serve as a basis for an equation of state formulation of the thermodynamic properties of {water+ammonia}. Gaps in the database are shown to give experimenters orientation for future research.

Electron Interactions With C3F8

Abstract: To aid the many and diverse applications for which perfluoropropane (C3F8) is suited, we critically evaluate and synthesize existing knowledge on electron scattering and electron energy-loss processes for the C3F8 molecule, and provide recommendations for the most reliable data. We also draw attention to electron-interaction data that are not presently available, but are needed for modeling the behavior of C3F8 in practical uses, especially plasma processing.

Thermodynamic properties of Aqueous Magnesium Chloride Solutions from 250 to 600 K and to 100 MPa

Abstract: A new general model that describes the thermodynamic properties of MgCl2(aq) has been developed from a global fit to experimental results, including isopiestic molalities, vapor pressure measurements, freezing-point depressions, enthalpies of dilution, heat capacities, and densities, for this system. The model is based on a recent ion-interaction treatment with extended higher-order virial terms, and on experimental results from 240 to 627 K at pressures to 100 MPa and molalities to 25 mol⋅kg−1.

Tables of Elastic Scattering Cross Sections of Photons in the Energy Range 50–1500 keV for All Elements in the Range 13⩽Z⩽104

Abstract: Tables of differential and total elastic scattering cross sections for 92 elements in the atomic number range 13⩽Z⩽104 and for selected photon energies in the range 50–1500 keV have been presented. The energies are chosen to cover the most commonly used photon energies and in a suitable grid so as to enable one to use the usual interpolation methods to determine cross sections for any other energies in this energy range. The available experimental results are also compared with the tabulated values and the difference is presented graphically.

Thermochemistry of the Boranes

Abstract: A compilation is presented of published experimental and computational reports (191 references) on the structures, vibrational frequencies, molar enthalpies of formation and standard entropies for 26 gas phase boranes for the temperature range from 0 to 1500 K. The thermochemical properties have been collated via standard programs and are listed in a convenient tabular format. Levels of uncertainties in the thermodynamic functions have not been assessed, because of the limited experimental and computational data. The tabulated values were fitted to standard seven-parameter (NASA) polynomials to facilitate the computation of enthalpies of formation, entropies, and heat capacities for modeling purposes. Within the context of intrinsic uncertainties, the equilibrium compositions of the gas phase were calculated, constrained to constant temperature and volume, for several boron–hydrogen (B/H) ratios, at various temperatures and pressures. The (unexpected) results indicate that in none of the reported gas-phas...

An International Standard Equation of State for the Thermodynamic Properties of HFC-125 (Pentafluoroethane)

Abstract: An 18-coefficient modified Benedict–Webb–Rubin equation of state for HFC-125 (pentafluoroethane) has been developed. Correlations of vapor pressure and saturated liquid density are also presented. This equation of state has been developed using experimental data for the relationship of pressure-volume-temperature of fluid, saturation properties, isochoric heat capacity data, and speed of sound data. The equation of state is valid in the superheated gaseous phase and the compressed liquid phase at pressures up to 68 MPa, densities to 1700 kg/m3, and temperatures from the triple point (172.52 K) to 475 K. This equation of state has been selected as an international standard formulation for HFC-125 based on an evaluation of the available equations of state by Annex 18 of the International Energy Agency.

Thermodynamic Properties of Import to Environmental Processes and Remediation. I. Previous Thermodynamic Property Values for Cadmium and Some of Its Compounds

Abstract: The sources of previous thermodynamic property values are detailed for cadmium and some compounds of cadmium that might be expected as derivative from anthropogenic introduction of cadmium into the environment or are required for calculation of thermodynamic properties of cadmium-containing systems. Included are descriptions of the sources of information and methodology used to obtain the values for these compounds reported in the NBS series of publications loosely and collectively referred to as the NBS Thermodynamics Tables.

Simultaneous Assessment of the YBa2Cu3O6+z Thermodynamics Under the Linear Error Model

Abstract: About 3000 experimental points obtained in 220 miscellaneous experiments published in 57 papers have been processed simultaneously in order to obtain the most reliable Gibbs energy of the YBa2Cu3O6+z solid solution in the temperature range from 250 to 1300 K. A part of this solution is well-known as the “Hi-Tc Y123” phase. All other thermodynamic properties of the solution including the conditions for the tetragonal-orthorhombic phase transition and the miscibility gap at lower temperatures, are derived from the assessed Gibbs energy. The linear error model introduced recently by one of the authors has been employed for the simultaneous assessment. The results obtained are compared with those of the conventional weighted least squares method and the benefit of the new approach is discussed. Another problem in simultaneous assessment that is also considered is visualizing the quality of the fit. New types of graphs (partly based on the linear error model) that facilitate visualizing the quality of the fit ...

IUPAC - NIST Solubility Data Series 66. Ammonium Phosphates

Abstract: The solubility of ammonium phosphate is reviewed. Many ammonium phosphates can be described in terms of the ternary system: NH3–PO5–H2O. However, this system differs from systems like the sulfates and halates in that it has a marked tendency to form condensed oligophosphate ions. The literature survey covers the period up to 1988.