Showing papers in "Journal of Physical and Chemical Reference Data in 1996"

A New Equation of State for Carbon Dioxide Covering the Fluid Region from the Triple‐Point Temperature to 1100 K at Pressures up to 800 MPa

Abstract: This work reviews the available data on thermodynamic properties of carbon dioxide and presents a new equation of state in the form of a fundamental equation explicit in the Helmholtz free energy. The function for the residual part of the Helmholtz free energy was fitted to selected data of the following properties: (a) thermal properties of the single‐phase region (pρT) and (b) of the liquid‐vapor saturation curve (p s, ρ′, ρ″) including the Maxwell criterion, (c) speed of soundw and (d) specific isobaric heat capacityc p of the single phase region and of the saturation curve, (e) specific isochoric heat capacityc v , (f) specific enthalpyh, (g) specific internal energyu, and (h) Joule–Thomson coefficient μ. By applying modern strategies for the optimization of the mathematical form of the equation of state and for the simultaneous nonlinear fit to the data of all these properties, the resulting formulation is able to represent even the most accurate data to within their experimental uncertainty. In the technically most important region up to pressures of 30 MPa and up to temperatures of 523 K, the estimated uncertainty of the equation ranges from ±0.03% to ±0.05% in the density, ±0.03% to ±1% in the speed of sound, and ±0.15% to ±1.5% in the isobaric heat capacity. Special interest has been focused on the description of the critical region and the extrapolation behavior of the formulation. Without a complex coupling to a scaled equation of state, the new formulation yields a reasonable description even of the caloric properties in the immediate vicinity of the critical point. At least for the basic properties such as pressure, fugacity, and enthalpy, the equation can be extrapolated up to the limits of the chemical stability of carbon dioxide. Independent equations for the vapor pressure and for the pressure on the sublimation and melting curve, for the saturated liquid and vapor densities, and for the isobaric ideal gas heat capacity are also included. Property tables calculated from the equation of state are given in the appendix.

NIST–JANAF Thermochemical Tables for the Bromine Oxides

Abstract: The thermodynamic and spectroscopic properties of the bromine oxide species have been reviewed. Recommended NIST–JANAF Thermochemical Tables are given for six gaseous bromine oxides: BrO, OBrO, BrOO, BrOBr, BrBrO, and BrO3. Sufficient information is not available to generate thermochemical tables for any condensed phase species. Annotated bibliographies (over 280 references) are provided for all neutral bromine oxides which have been reported in the literature. There are needs for additional experimental and theoretical data to reduce the uncertainties in the recommended values for these six species. Of all the species mentioned in the literature, many have not been isolated and characterized. In fact some do not exist. Throughout this paper, uncertainties attached to recommended values correspond to the uncertainty interval, equal to twice the standard deviation of the mean.

Electron Interactions with CF4

Abstract: Carbon tetrafluoride (CF4) is one of the most widely used components of feed gas mixtures employed for a variety of plasma‐assisted material‐processing applications. It has no stable excited states and, in a plasma environment, is an ideal source of reactive species, especially F atoms. To assess the behavior of CF4 in its use in manufacturing semiconductor devices and other applications, it is necessary to have accurate information about its fundamental properties and reactions, particularly its electronic and ionic interactions and its electron collision processes at low energies (<100 eV). In this article we assess and synthesize the available information on the cross sections and/or the rate coefficients for collisional interactions of CF4 with electrons. Assessed information is presented on: (i) cross sections for electron scattering (total, momentum, elastic differential, elastic integral, inelastic), electron‐impact ionization (total, partial, multiple, dissociative), electron‐impact dissociation (...

Revised Group Additivity Values for Enthalpies of Formation (at 298 K) of Carbon–Hydrogen and Carbon–Hydrogen–Oxygen Compounds

Abstract: A program has been undertaken for the evaluation and revision of group additivity values (GAVs) necessary for predicting, by means of Benson’s group additivity method, thermochemical properties of organic molecules. This review reports on the portion of that program dealing with GAVs for enthalpies of formation at 298.15 K (hereinafter abbreviated as 298 K) for carbon–hydrogen and carbon–hydrogen–oxygen compounds. A complete database of experimental data for gas, liquid, and crystal (solid) phase enthalpies of formation is presented. The GAVs, ring strain corrections, and non‐nearest neighbor interactions derived from the database are presented in tabular form, together with a description of their evaluation and comments on reliability, uncertainties, and missing or questionable data.

Volumetric Properties of Single Aqueous Electrolytes from Zero to Saturation Concentration at 298.15 °K Represented by Pitzer’s Ion‐Interaction Equations

Abstract: The ion interaction approach developed by Pitzer allows the prediction of various thermodynamic characteristics of multiple‐solute electrolyte solutions, if the respective parameters for each type of single‐solute electrolyte solution are known. The present paper discusses the Pitzer approach to the calculations of the volumetric properties of single‐solute electrolyte solutions. The databases for the densities and the apparent molal volumes versus concentrations were created at 298.15 °K using essentially all published relevant data for each single‐solute electrolyte solution. Poor experimental data were discarded by a statistical treatment applied to these databases. Proper treatment of all good quality density and apparent molal volume data, in a wide range of concentrations from infinite dilution through saturation, allowed us to evaluate the volumetric ion interaction parameters (V0MX, βMX(0)V, βMX(1)V, βMX(2)V, and CMXV) at 298.15 °K for 102 electrolytes. Strong linear relationships between the βMX...

NIST‐JANAF Thermochemical Tables for Oxygen Fluorides

Abstract: The thermodynamic and spectroscopic properties of the oxygen fluoride species have been reviewed. Recommended thermochemical tables are given for five gaseous oxygen fluorides: OF, OFO, FOO, FOF, and O2F2. Sufficient information is not available to generate thermochemical tables for any condensed phase species. Annotated bibliographies (over 600 references) are provided for all neutral oxygen fluorides which have been reported in the literature. There are needs for additional experimental and theoretical data to reduce the uncertainties in the recommended values for these five species. Of all the species mentioned in the literature, many have not been isolated and characterized. In fact, some do not exist. Throughout this paper, uncertainties attached to recommended values correspond to the uncertainty interval, equal to twice the standard deviation of the mean.

A Modified Benedict-Webb-Rubin Equation of State for the Thermodynamic Properties of R152a (1,1-difluoroethane)

Abstract: A modified Benedict–Webb–Rubin (MBWR) equation of state has been developed for R152a (1,1‐difluoroethane). The correlation is based on a selection of available experimental thermodynamic property data. Single‐phase pressure–volume–temperature (PVT), heat capacity, and sound speed data, as well as second virial coefficient, vapor pressure, and saturated liquid and saturated vapor density data, were used with multi‐property linear least‐squares fitting to determine the 32 adjustable coefficients of the MBWR equation. Ancillary equations representing the vapor pressure, saturated liquid and saturated vapor densities, and the ideal gas heat capacity were determined. Coefficients for the equation of state and the ancillary equations are given. Experimental data used in this work covered temperatures from 162 K to 453 K and pressures to 35 MPa. The MBWR equation established in this work may be used to predict thermodynamic properties of R152a from the triple‐point temperature of 154.56 K to 500 K and for pressures up to 60 MPa except in the immediate vicinity of the critical point.

NIST{endash}JANAF Thermochemical Tables for the Iodine Oxides

Abstract: The thermodynamic and spectroscopic properties of the iodine oxide species have been reviewed. Recommended NIST{endash}JANAF Thermochemical Tables are given for six gaseous iodine oxides: IO, OIO, IOO, IOI, IIO, and IO{sub 3}. Sufficient information is not available to generate thermochemical tables for any condensed phase species. Annotated bibliographies (over 400 references) are provided for all neutral iodine oxides which have been reported in the literature. There is a lack of experimental thermodynamic and spectroscopic information for all iodine oxide species, except IO(g) and OIO(g). The recommended thermochemical tables are based on estimates for the structure, vibrational frequencies, and enthalpy of formation based in part on the spectroscopic and thermodynamic data for the other halogen oxides [J. Phys. Chem. Ref. Data {bold 25}, 551 (1996); {bold 25}, 1061 (1996)]. Although there is a definite lack of information in comparison with the other halides, this information is provided for the iodine oxides for the following reasons: (1) to complete the study of the halogen oxide family and (2) to stress the need for additional experimental measurements. Of all the species mentioned in the literature, many have not been isolated or characterized. In fact, some do not exist. Throughout this paper, uncertainties attachedmore » to recommended values correspond to the uncertainty interval, equal to twice the standard deviation of the mean. {copyright} {ital 1996 American Institute of Physics and American Chemical Society.}« less

Microwave spectra of molecules of astrophysical interest: XXIII : Acetaldehyde

Abstract: The microwave spectrum of acetaldehyde is critically reviewed and supplemented with spectral frequency calculations derived from the rotation‐internal rotation analysis. A simultaneous analysis of the torsional ground state, vt=0, and first and second torsionally excited states, vt=1 and 2, was carried out. The primary objective of this review is to provide radio astronomers with complete spectral coverage over the range of 900 MHz to 500 GHz for the ground state and covering rotational quantum number, J, from 0 to 26.

Liquid-Liquid Demixing from Solutions of Polystyrene. 1. A Review. 2. Improved Correlation with Solvent Properties

Abstract: Low pressure liquid–liquid demixing data for polystyrene dissolved in 76 different one‐component solvent systems are reviewed and correlated. The phase diagrams are discussed. With only one exception the molecular weight of each solvent is less than that of two polystyrene monomer units. A new relation is developed which quantitatively correlates the area of solubility lying between the UCS and LCS demixing curves in the (Tc, Mw−1/2) projection with solvent solubility parameters.

Thermodynamic Properties of Alkali Metal Hydroxides. Part 1. Lithium and Sodium Hydroxides

Abstract: The data on thermodynamic and molecular properties of the lithium and sodium hydroxides have been collected, critically reviewed, analyzed, and evaluated. Tables of thermodynamic properties (C°p,Φ°=−(G°−H°(0)/T, S°, H°−H°(0), ΔfH°, ΔfG°) of these hydroxides in the condensed and gaseous states have been calculated using the results of the analysis and some estimated values. The recommendations are compared with earlier evaluations given in the JANAF Thermochemical Tables and Thermodynamic Properties of Individual Substances. The properties considered are: the temperature and enthalpy of phase transitions and fusion, heat capacities, spectroscopic data, structures, bond energies, and enthalpies of formation at 298.15 K. The thermodynamic functions in solid, liquid, and gaseous states are calculated from T=0 to 2000 K for substances in condensed phase and up to 6000 K for gases.

Extended Additivity Model of Parameter log(L16)

Abstract: An additivity model of the apolar solute‐solvent parameter log(L16) was verified using sets of 939 nonaromatic and 1075 aromatic compounds. Unbiased distributions of errors and of the contribution significance level were statistically tested. An analysis of the CH2 group contribution in 34 homologous series indicates that the differences among the homologous series are statistically insignificant and related to interactional contributions rather than to the nature of the CH2 group.

Standard Thermodynamic Functions of Some Isolated Ions at 100–1000 K

Abstract: The standard thermodynamic functions (Cp°, S°, H° and (G°−H0°)/T) at 100 to 1000 K of 24 polyatomic gaseous ions are reported, based on structural and spectroscopic data from the literature. These ions supplement the 130 ions previously studied and are: zirconyl, hydrotelluride, amide, selenocyanate, tellurocyanate, orthoborate, metaphosphate, arsenite, orthosilicate, tetrachloropalladate(II), tetrabromopalladate(II), tetrachloroplatinate(II), tetrabromoplatinate(II), hexafluorophosphate, hexafluoroarsenate, hexafluoroantimonate, hexabromoplatinate(IV), tetracyanonickelate, tetracyanomercurate, octacyanomolybdate(IV), sulfamate, benzoate, guanidinium, and glycine as cation, zwitterion, and anion.