Volume 28, Issue 6, November 1999
Index of content:
28(1999); http://dx.doi.org/10.1063/1.556047View Description Hide Description
This article updates a 14 yr old review on this subject [J. Phys. Chem. Ref. Data 14, 731 (1985)]. A survey of the electron affinity determinations for the elements up to is presented, and based upon these data, a set of recommended electron affinities is established. New developments in the experimental methods which yield accurate electron binding energies are described. Fine structure splittings and excited state energies of negative ions as well as lifetimes of metastable states are given. Progress in theoretical calculations of atomic electron affinities is documented by comparison with reliable experimental data.
28(1999); http://dx.doi.org/10.1063/1.556045View Description Hide Description
A group additivity method based on molecular structure is described that can be used to estimate solid–liquid total phase changeentropy and enthalpy of organic molecules. The estimation of these phase changes is described and numerous examples are provided to guide the user in evaluating these properties for a broad range of organic structures. A total of 1858 compounds were used in deriving the group values and these values are tested on a database of 260 additional compounds. The absolute average and relative errors between experimental and calculated values for these 1858 compounds are 9.9 J⋅mol−1⋅K−1 and 3.52 kJ⋅mol−1, and 0.154 and 0.17 for and respectively. For the 260 test compounds, standard deviations of and between experimental and calculated values were obtained. Estimations are provided for both databases. Fusion enthalpies for some additional compounds not included in the statistics are also included in the tabulation.
Properties of Materials and Systems of Importance to Environmental Fates and Remediation. III. Review of Previous Thermodynamic Property Values for Chromium and Some of its Compounds28(1999); http://dx.doi.org/10.1063/1.556053View Description Hide Description
Twenty-seven (27) crystalline and aqueous chromium species from the NBS Tables of Chemical Thermodynamic Properties were selected based upon their possible importance to environmental fate and remediation processes. Their NBS files were studied to determine the sources of information and the methodology used to determine the NBS selected thermodynamic values. The NBS tables for chromium were compiled in 1966. A literature search was performed to determine the existence of additional data for these species. Documentary data are presented for the thermodynamic properties of these twenty-seven (27) species.
Revised Thermochemical Properties of Phosphinidene (PH), Phosphine Phosphorus Nitride (PN), and Magnesium Phosphate28(1999); http://dx.doi.org/10.1063/1.556046View Description Hide Description
Revised thermochemical tables for phosphinidene (PH), phosphine phosphorus nitride (PN), and magnesium orthophosphate are computed. These computations were done because the P reference state was not adjusted to the white P reference state and/or because the tables of these compounds are printed erroneously in the 4th edition of the NIST-JANAF Thermochemical Tables.
28(1999); http://dx.doi.org/10.1063/1.556049View Description Hide Description
This paper gives the 1998 self-consistent set of values of the basic constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for international use. Further, it describes in detail the adjustment of the values of the subset of constants on which the complete 1998 set of recommended values is based. The 1998 set replaces its immediate predecessor recommended by CODATA in 1986. The new adjustment, which takes into account all of the data available through 31 December 1998, is a significant advance over its 1986 counterpart. The standard uncertainties (i.e., estimated standard deviations) of the new recommended values are in most cases about 1/5 to 1/12 and in some cases 1/160 times the standard uncertainties of the corresponding 1986 value. Moreover, in almost all cases the absolute values of the differences between the 1998 values and the corresponding 1986 values are less than twice the standard uncertainties of the 1986 values. The new set of recommended values is available on the World Wide Web at physics.nist.gov/constants.