F. G. Brickwedde

Thermodynamic Properties of Gaseous 1,3‐Butadiene and the Normal Butenes above 25°C Equilibria in the System 1,3‐Butadiene, n‐Butenes, and n‐Butane

Tables of the thermodynamic functions Cp0, H0, S0, and F0 are given for 1,3‐butadiene and the normal butenes for temperatures from 298.16°K to 1500°K for the substances in the ideal gas states at one atmosphere pressure. These have been prepared using reliable spectroscopic and molecular data, together with calorimetric entropies, gaseous specific heats, and heats of formation. Equilibrium constants are given for reactions in the system 1,3‐butadiene, n‐butenes, and n‐butane. Available experimental data are compared with the calculations. The calorimetric data for 1,3‐butadiene furnish strong evidence for the existence of two geometric (cis‐trans) isomeric forms of 1,3‐butadiene in appreciable concentrations at room temperatures. The two forms differ in energy by 2.3 kcal. mole−1, and are separated by a C–C rotational barrier 2.6 kcal. mole−1 above the lowest energy level of the cis, or higher, energy form.

The Low Temperature Heat Capacities, Enthalpies, and Entropies of UF4 and UF6

The heat capacity of UF4 has been measured from 20° to 350°K and that of UF6 from 14° to 370°K. Molar heat capacities have been tabulated at 5‐degree intervals and extrapolated to 0°K. From them the entropies and enthalpies of the compounds have been found by integration and tabulated. The triple point temperature of UF6 was found to be 337.212°K (64.052°C) and the heat of fusion was found to be 19,193 j mole−1.

The Vapor Pressures and Derived Thermal Properties of Hydrogen and Deuterium

(1) The vapor pressure equations of liquid and solid, normal deuterium were determined by comparison of the vapor pressure of deuterium with that of liquid, normal hydrogen between 13.9° and 20.40°K. The triple and boiling points of deuterium were found to be 18.58° and 23.5°K, respectively. (2) The changes with time in the vapor pressures of liquid hydrogen and liquid deuterium at 20.4°K, resulting from ortho‐para conversions, were investigated. The rate of change of the vapor pressure of liquid deuterium resulting from its natural, self‐conversion was found to be less than 1/40th of the natural rate of conversion for liquid hydrogen. (3) From the vapor pressure equations of deuterium and an equation of state, its latent heats were deduced by the use of the Clausius‐Clapeyron equation. Two equations of state for deuterium were used: (a) the empirically determined equation for hydrogen, and (b) an equation deduced from an equation of state of hydrogen of a form required by the Bose‐Einstein statistics by ...

Thermodynamic Properties of Ethylbenzene Vapor from 300° to 1500°K

In this paper are presented tables of the more important thermodynamic functions of ethylbenzene in the ideal gas state from 300° to 1500°K. These functions were calculated using spectroscopic, structural, and calorimetric data. Six investigations of the Raman spectrum of ethylbenzene and three of the infra‐red absorption spectrum were available for an assignment of frequencies to the intramolecular vibrations. Included in the paper is a calculation from calorimetric data of the enthalpy and entropy of saturated vapor at 294°K relative to the solid at 0°K. This paper completes a report on a determination of the thermodynamic properties of ethylbenzene covering the solid, liquid, and vapor phases, extending from 0° to 1500°K. All the experimental results are presented in detail in preceding papers.

The Difference in Vapor Pressures of Ortho and Para Deuterium

The difference between the vapor pressures, ΔP(e — n), of the 20.4°K equilibrium mixture and the normal mixture of the ortho and para varieties of D2 were determined from 15° to 20.4°K. ΔP(e — n) varied from 0.3 mm of Hg at 15°K to 3.8 mm at 20.4°. ΔP(e — n) for deuterium is small as compared with ΔP(e — n) hydrogen, but [ΔP(orthopara)/P(n)] for deuterium is approximately equal to [ΔP(para‐ortho)/P(n)] for hydrogen at the same temperature. Further measurements were made on the uncatalyzed change with time of the vapor pressure of liquid normal deuterium. The change for deuterium is less than one mm of Hg in 200 hours, whereas the vapor pressure of liquid normal hydrogen increases one mm in 4 hours. This large difference in rates is attributable to the difference in magnetic moments of the proton and deuteron. If Wigners theory of the ortho‐para conversion by paramagnetic molecules in the gaseous phase is extended to the liquid phase to calculate the relative rates of change of the vapor pressures of liqu...