Showing papers in "Journal of Physical and Chemical Reference Data in 1980"

Evaluated kinetic and photochemical data for atmospheric chemistry

Abstract: This paper contains a critical evaluation of the kinetics and photochemistry of gas phase chemical reactions of neutral species involved in middle atmosphere chemistry (10–55 km altitude). The work has been carried out by the authors under the auspices of the CODATA Task Group on Chemical Kinetics. Data sheets have been prepared for 148 thermal and photochemical reactions, containing summaries of the available experimental data with notes giving details of the experimental procedures. For each reaction a preferred value of the rate coefficient at 298 K is given together with a temperature dependency where possible. The selection of the preferred value is discussed, and estimates of the accuracies of the rate coefficients and temperature coefficients have been made for each reaction. The data sheets are intended to provide the basic physical chemical data needed as input for calculations which model atmospheric chemistry. A table summarizing the preferred rate data is provided, together with an Appendix listing the available data on enthalpies of formation of the reactant and product species.

Static Dielectric Constant of Water and Steam

Abstract: This paper reviews and evaluates the experimental works of the static dielectric constant (permittivity) of water and steam over the century. The critically evaluated experimental data are represented by a function of temperature and density. This representation was carefully examined in the light of the criteria for smoothness and physical plausibility. As a result of this work, which was largely stimulated by the activities of the International Association for the Properties of Steam, a new International formulation for the static dielectric constant of water and steam was adopted. This formulation covers a temperature range from 0 to 550 °C and a pressure range up to 500 MPa.

Refractive index of silicon and germanium and its wavelength and temperature derivatives

Abstract: Refractive index data for silicon and germanium were searched, compiled, and analyzed. Recommended values of refractive index for the transparent spectral region were generated in the ranges 1.2 to 14 μm and 100–740 K for silicon, and 1.9 to 16 μm and 100–550 K for germanium. Generation of these values was based on a dispersion equation which best fits selected data sets covering wide temperature and wavelength ranges. Temperature derivative of refractive index was simply calculated from the first derivative of the equation with respect to temperature. The results are in concordance with the existing dn/dT data.

Energy levels of magnesium, Mg I through Mg XII

Abstract: Energy level data are given for the atom and all positive ions of magnesium (Z=12). These data have been critically compiled, mainly from published material on measurements and analyses of the optical spectra. We have derived or recalculated the levels for a number of the ions. In addition to the level value in cm−1 and the parity, the J value and the configuration and term assignments are listed if known. Leading percentages from the calculated eigenvectors are tabulated wherever available. Ionization energies are given for all spectra.

Pair, Triplet, and Total Atomic Cross Sections (and Mass Attenuation Coefficients) for 1 MeV-100 GeV Photons in Elements Z=1 to 100,

Abstract: Tables of photon cross sections and mass attenuation coefficients for all elements Z=1 to 100 are given for photo energies in the range 1 MeV to 100 GeV. The pair and triplet production cross sections take into account recent theoretical work, including atomic form factor and incoherent scattering function data, as well as extensive new total attenuation coefficient measurements at Mainz. Cross section values for the atomic photoeffect and coherent and incoherent (Compton) scattering are explicitly listed and are included in the total cross sections (excluding photonuclear) and mass attenuation coefficients.

A compilation of kinetic parameters for the thermal degradation of n‐alkane molecules

Abstract: A list of several hundred free‐radical reactions which occur during the low temperature (700–850 K) pyrolysis of small n‐alkane molecules has been assembled and a set of reliable, self‐consistent Arrhenius rate parameters has been assigned on the basis of experiment, theory, thermochemical estimates and structural analogy. Rate parameters have been recommended for the following types of reactions, with the number of each type in parentheses: initiation (32), recombination (135), disproportionation (108), H‐transfer (112), decomposition (41), addition (58), and isomerization (11), givin a total of 505 reactions. This compilation is intended for use in assembling reaction matrices in computational modeling studies of the thermal reactions of hydrocarbon molecules.

An Improved Representative Equation for the Dynamic Viscosity of Water Substance

Abstract: Experimental evidence for steam and other fluids has demonstrated the existence of an anomalous enhancement of the dynamic viscosity in the close vicinity of the critical point. A re‐analysis of the experimental evidence for the viscosity of steam indicates that the observed behavior of the critical viscosity enhancement is consistent with current theoretical predictions. An interpolating equation for the dynamic viscosity of water substance is presented which is in good agreement with the experimental viscosity data in a large range of temperatures and pressures. The equation contains a smaller number of coefficients than the current international equation for the viscosity of water substance and incorporates the enhancement of the viscosity in the close vicinity of the critical point.

The solubility of some sparingly soluble lead salts: An evaluation of the solubility in water and aqueous electrolyte solution

Abstract: The literature on the solubility of sparingly soluble lead salts in water and in aqueous electrolyte solution was reviewed. Solubility data were compiled and evaluated. Recommended and tentative values of the solubilities are presented. A partial compilation of solubility products and of complex ion formation constants are given. Where possible the solubility product values have been checked for consistency against thermodynamic data from sources other than solubility measurements.

Molten Salts Data as Reference Standards for Density, Surface Tension, Viscosity, and Electrical Conductance: KNO3 and NaCl

Abstract: Accuracy estimates for physical property measurements are usually based on somewhat subjective quality judgements and the difficulties encountered in interpreting accuracy statements in the literature are frequently compounded through lack of details on the methods of measurements, chemical purity, and related experimental aspects. In the present communication we report the results of a Standards Program initiated in 1973 with participating laboratories in Czechosloskia, German Democratic Republic‐DDR, Japan, Norway, Poland, Rumania, and U.S.A. Potassium nitrate (m.335 °C) and sodium chloride (m 800 °C) were selected as the two reference salts for the properties: density, surface tension, viscosity, and electrical conductance. The results of the measurements have been critically examined, and are reported herewith. It has been possible to resolve some of the difficulties encountered in accuracy estimates through this ’’round‐robin’’ series of measurements, and to up‐grade some of the data‐sets to calibrat...

Microwave spectra of molecules of astrophysical interest. XVIII. Formic acid

Abstract: The available data on the microwave spectrum of formic acid are critically reviewed for information applicable to radioastronomy. Molecular data such as the derived rotational constants, centrifugal distortion constants and electric dipole moment are tabulated. The observed rotational transitions are presented for the astronomically interesting isotopic forms. Calculated rotational transitions up to 300 GHz are presented for the ground vibrational state of H12C16O16OH, H12C16O16OD, D12C16O16OH and H13C16O16OH. Some observed transitions are also listed for H12C16O18OH and H12C18O16OH. Estimated error limits have been reported for all measured transitions.

Microwave spectra of molecules of astrophysical interest. XIX. methyl cyanide

Abstract: The microwave spectrum of methyl cyanide is critically reviewed for information applicable to radio‐astronomy. Molecular data such as the derived rotational constants, centrifugal distortion parameters, hyperfine coupling constants, electric dipole moment and molecular structure are tabulated. The observed rotational transitions are presented for the astronomically interesting isotopic forms and the lowest lying vibrational state of methyl cyanide. Calculated rotational transitions are presented for the ground vibrational state of 12CH312C14N, 13CH312C14N, 12CH313C14N, 12CH312C15N, and for the vibrationally excited state ν8 of 12CH312C14N.

Molten Salts: Volume 5, Part 2. Additional Single and Multi-Component Salt Systems. Electrical Conductance, Density, Viscosity and Surface Tension Data

Abstract: Data on the electrical conductance, density, and surface tension of more than ninety additional multi‐component salt systems have been systematically collected and evaluated. Results are given for mixtures over a range of compositions and temperatures. Values of the above properties for some sixty single salt systems are also reported.

Tables of Molecular Vibrational Frequencies Part 10

Abstract: Fundamental vibrational frequencies of 94 molecular forms of 23 polyatomic chain molecules of halogenoalkanes and halogenoalkyl ethers consisting of the CH3, CH2, O, F, Cl, Br, and I groups are given as an extension of tables of molecular vibrational frequencies published in the NSRDS‐NBS publication series and in this journal. On preparing the tables in this part, an approach, similar to that in Part 9 but different from that in earlier parts, based on the calculations of normal vibration frequencies was adopted. A set of force constants which explains all the frequencies of small molecules for which the assignments had been established was obtained and then the frequencies of larger molecules were calculated and compared with the frequencies observed in the infrared and Raman spectra. The tables provide a convenient source of information for those who require vibrational energy levels and related properties in molecular spectroscopy, thermodynamics, analytical chemistry, and other fields of physics and chemistry.

Energy levels of scandium, Sc i through Sc xxi

Abstract: The energy levels of the scandium atom in all of its stages of ionization, as derived from the analyses of atomic spectra, have been critically compiled. In cases where only line classifications are reported in the literature, level values have been derived. Electron configurations, term designations, J‐values, experimental g‐values, and ionization energies are included. Calculated percentages of the two leading components of the eigenvectors of the levels are given, where available.

Saturation states of heavy water

Abstract: A study has been made of the saturation properties of D2O from the triple point temperature to 325 °C, in the light of information on the saturation properties of H2O. Saturated liquid volumes have been determined by extrapolation to saturation pressure of relatively abundant liquid phase data (corrected to 100% D2O). Saturated liquid enthalpy has been determined by extrapolation of liquid phase specific heat data, and integration along the saturation line, allowing for the compressibility effect. Saturated vapor volumes have been determined by use of an extended virial equation formulated for H2O and corrected for D2O. Saturated vapor enthalpies have been determined by use of the Clapeyron equation, and compared to vapor enthalpies calculated from the extended virial equation. Saturated liquid and vapor volumes have been extrapolated to the critical temperature to allow an inference of the critical density.

Compilation and Evaluation of Solubility Data in the Mercury (I) Chloride-Water System

Abstract: The more than one dozen papers dealing with the solubility of mercury (1) chloride in water or in aqueous chloride solutions have been compiled in the format set by the IUPAC Solubility Data Project, and have been evaluated. Mercury (I) chloride dissolves in water, forming the following species: He(OH)2, HgCl2, HgOH+, HgOH+, HgCl+, Hg2+2, and Hg2OH− in addition to H+ and Cl−. In excess chloride solutions it dissolves to give, mainly, HgCl−3 and HgCl2−4. Thus, many homogeneous equilibria have to be considered beside the two heterogeneous ones; Hg2Cl2(s)=Hg2+2(aq)+2Cl−(aq) and Hg2+2(aq)=Hg2+(aq)+ Hg(l), of which K°s0 and (K°r)−1, respectively, are the equilibrium constants. The papers in which the total solubility (sum of all the mercury containing aqueous species) and the solubility product (derived from e.m.f. data) are reported do not give as accurate and reliable quantities as are obtained from the appropriate standard electrode potentials. The following values are recommended as valid at 298.15 K: log ...