Volume 18, Issue 4, October 1989
Index of content:
A Fundamental Equation for Water Covering the Range from the Melting Line to 1273 K at Pressures up to 25 000 MPa18(1989); http://dx.doi.org/10.1063/1.555836View Description Hide Description
In order to represent the thermodynamic properties of water (H2O) over an extremely large range of temperature and pressure that is not covered by existing equations of state, a new fundamental equation has been developed. The Helmholtz function was fitted to the following kinds of experimental data: (a) pρT data, (b) thermal properties of the saturation curve (p s ,ρ’,ρ‘), (c) speed of soundw, (d) isobaric heat capacityc p , (e) isochoric heat capacityc v , (f) differences of the internal energy u, (g) differences of the enthalpyh, (h) Joule–Thomson coefficient μ, and (i) the isothermal throttling coefficient δ T . A new statistical selection method was used to determine the final form of the equation from a ‘‘bank’’ of 630 terms which also contained functional forms that have not been previously used. This 58‐coefficient equation covers the entire fluid region from the melting line to 1273 K at pressures up to 25 000 MPa, and represents the data within their experimental accuracy also in the ‘‘difficult’’ regions below 0 °C, on the entire saturation curve, in the critical region and at very high pressures. The equation was constrained at the critical point as defined by the parameters internationally recommended by the International Association for the Properties of Steam (IAPS). Besides the 58‐coefficient equation for the entire pressure range, a 38‐coefficient equation is presented for providing a ‘‘fast’’ equation for practical and scientific calculations in the pressure range below 1000 MPa. This equation has, with the exception of the critical region, nearly the same accuracy as the 58‐coefficient equation. The quality of the new equations will be illustrated by comparing the values calculated from them with selected experimental data and with the IAPS‐84 formulation and the Scaling‐Law equation.
18(1989); http://dx.doi.org/10.1063/1.555837View Description Hide Description
The thermodynamic data for toluene have been evaluated and fit to a highly constrained, nonanalytic equation of state. Comparisons of the equation with the selected P V T and derived property data are given. Extensive tables are presented providing tabular values for coexisting liquid and vapor as well as for the single phase along isobars. The equation of state and tables cover the range from the triple point (178.15 K) to 800 K, with pressures to 1000 bar.
18(1989); http://dx.doi.org/10.1063/1.555843View Description Hide Description
Reduction of an electron acceptor (oxidant), A, or oxidation of an electron donor (reductant), A2 −, is often achieved stepwise v i a one‐electron processes involving the couples A/A⋅− or A⋅−/A2 − (or corresponding prototropic conjugates such as A/AH⋅ or AH⋅/AH2). The intermediate A⋅−(AH⋅) is a free radical. The reduction potentials of such one‐electron couples are of value in predicting the direction or feasibility, and in some instances the rate constants, of many free‐radical reactions.Electrochemical methods have limited applicability in measuring these properties of frequently unstable species, but fast, kinetic spectrophotometry (especially pulse radiolysis) has widespread application in this area. Tables of c a. 1200 values of reduction potentials of c a. 700 one‐electron couples in aqueous solution are presented. The majority of organic oxidants listed are quinones, nitroaryl and bipyridinium compounds. Reductants include phenols, aromatic amines, indoles and pyrimidines, thiols and phenothiazines. Inorganic couples largely involve compounds of oxygen, sulfur, nitrogen and the halogens. Proteins, enzymes and metals and their complexes are excluded.
Photoemission Cross Sections for Atomic Transitions in the Extreme Ultraviolet due to Electron Collisions with Atoms and Molecules18(1989); http://dx.doi.org/10.1063/1.555844View Description Hide Description
This article reviews experimental photoemission cross sections in the extreme ultraviolet, for transitions in excited atoms and atomic ions formed in electron collisions with atoms and molecules. A survey of the available experimental data for each investigated target gas reveals severe inconsistencies between cross sections reported by different laboratories. As almost all reported cross sections are based on relative measurements, a detailed discussion is given of the methods used for normalization of the cross sections.