Peter J. Dunlop

On obtaining interatomic potentials from multiproperty fits to experimental data

High‐resolution differential cross section (DCS) and accurate new limiting diffusion measurements for all the unlike‐pair He+rare‐gas systems are combined in constructing new multiproperty interatomic potentials. The new potentials predict most properties available for these systems, including independent high‐resolution DCS measurements. Remaining discrepancies with earlier multiproperty potentials for HeKr and HeXe are attributed to incompatibilities among data sets used in the multiproperty fitting procedure. It is also shown that the 5% difference in well depths between two recently proposed potentials for HeXe is due to some of the data used in constructing these potentials, and that the DCS measurements of those studies are mutually consistent. Finally, the present potentials are refined slightly for agreement with high‐energy cross section measurements. At the present level of reliability for DCS and dilute‐gas data, it seems likely that high‐resolution DCS and accurate (limiting) diffusion measure...

Diffusion coefficients and thermal diffusion factors for five binary systems of nitrogen and a noble gas

Diffusion coefficients, D12, and thermal diffusion factors, αT, are reported for the systems He-N2, Ne-N2, Ar-N2, Kr-N2 and Xe-N2; the D12 values were measured over the temperature range 275–323 K and the αT values at 300 K. The diffusion coefficients were combined with accurate second virial coefficient data to obtain (m, 6, 8) potential parameters and these values, together with existing potential parameters, were used to calculate αT values for comparison with experiment.

Use of accurate diffusion and second virial coefficients to determine (m, 6, 8) potential parameters for nine binary noble gas systems

Using accurate binary diffusion coefficients obtained over a temperature range of 275 to 323 K, together with some excellent second virial coefficients in the literature, (m, 6, 8) potential parameters have been obtained for the systems He-Ne, He-Ar, He-Kr, He-Xe, Ne-Ar, Ne-Kr, Ne-Xe, Ar-Kr and Ar-Xe. These parameters accurately predict all the precise binary transport properties which have been reported for these systems, some over a range of 1400 K. The present analysis indicates that these mixtures are not conformal with any one of the assumed (m, 6, 8) group of potentials.

Thermal diffusion factors at 300 K for seven binary noble gas systems containing helium or neon

Thermal diffusion factors, αT, have been measured as a function of concentration at 300 K for seven binary noble gas systems containing helium or neon. The results, obtained with a two-bulb cell, are in agreement with those of Saviron et al. who used a thermal diffusion column, and in general greater than those of Taylor et al. who used a 20-tube trennschaukel. The experimental results agree well with values predicted by the Chapmen-Cowling theory and the recent potential functions reported in the literature.

Vapour pressures and excess Gibbs energies of mixtures of benzene with chlorobenzene, n-hexane, and n-heptane at 25°C

Excess Gibbs energies, which were calculated from static vapour pressure measurements, are reported for benzene + chlorobenzene, benzene + n-hexane, and benzene + n-heptane at 25°C. The excess Gibbs energy per unit volume is found to be a symmetrical function of the volume fraction for the benzene + alkane systems.

Volatile leaf oils of some south-western and southern Australian species of the genus Eucalyptus (Series 1). Part XIX

The volatile leaf oils of Eucalyptus miniata Cunn. ex Schauer, E. canaliculata Maiden, E. pumila Cambage, E. vergrandis L. A. S. Johnson & K. D. Hill, E. suggrandis L. A. S. Johnson & K. D. Hill, E. tenera L. A. S. Johnson & K. D. Hill, E. incerata Brooker & Hopper ined., E. recta L. A. S. Johnson & K. D. Hill, E. balladoniensis Brooker subsp. sedens L. A. S. Johnson & K. D. Hill, E. ‘species P subsp. P’ L. A. S. Johnson & K. D. Hill, E. ‘species T’ L. A. S. Johnson & K. D. Hill, E. ovata Labill. var. ovata, E. yarraensis Maiden & Cambage, E. nova-anglica H. Deane & Maiden, E. smithii R.T. Baker, E. dawsonii R.T. Baker, E. agglomerata Maiden, E. radiata Sieber ex DC. subsp. radiata, E. radiata Sieber ex DC. subsp. robertsonii (Blakely) L. A. S. Johnson & D. F. Blaxell, E. dives Schauer, E. pauciflora Sieber ex Spreng. subsp. pauciflora and E. pauciflora Sieber ex Spreng. subsp. niphophila (Maiden & Blakely) L. A. S. Johnson & D. F. Blaxell, isolated by vacuum distillation, were analysed by GC and GC–MS. Many species contained α-pinene (0–84.3%), limonene (0–6.3%), α-phellandrene (0–16.9%), 1,8-cineole (0–77.5%), p-cymene (0–27.2%), β-caryophyllene (0–10.8%), terpinen-4-ol (0–28.2%), piperitone (0–54.5%), aromadendrene (0–21.9%), bicyclogermacrene (0–65.6%) and torquatone (tr.–3.6%) as principal leaf oil components.

Diffusion and thermal diffusion in some dilute binary gaseous systems between 195 and 400 K: Tests of several asymmetric potentials using the infinite order sudden approximation

Limiting binary diffusion coefficients, D012, for mixtures of He with Ar, O2, N2, CO2 and SF6 and of Ar with N2 and O2, determined by the two-bulb method, are reported for the temperature range 195–400 K. The apparatus, calibrated with absolute data obtained at 300 K with a Loschmidt cell, greatly extends the temperature range covered in this Laboratory, previously limited to 275–325 K. Thermal diffusion factors, αT, have been measured for the systems He-Ar at 350 K with He-O2, He-CO2 and Ar-O2 at 255.3 K. These results together with others previously reported have been used to test several asymmetric potential functions recently published in the literature.

Volatile leaf oils of some south-western and southern Australian species of the genus Eucalyptus. Part VII. Subgenus Symphyomyrtus, section Exsertaria

The volatile leaf oils of Eucalyptus seeana Maiden, E. bancroftii (Maiden) Maiden, E. parramattensis C. Hall, E. amplifilia Naudin, E. tereticornis J. Smith, E. blakelyi Maiden, E. dealbata A. Cunn. ex. Schauer, E. dwyeri Maiden & Blakely, E. vicina L. A. S. Johnson & K. D. Hill, E. flindersii Boomsma, E. camaldulensis Dehnh. var camaldulensis, E. camaldulensis Dehnh. var. obtusa Blakely, E. rudis Endl., E. exserta F. Muell. and E. gillenii Ewart & L. R. Kerr, isolated by vacuum distillation, were analysed by GC-MS. Most species contained α-pinene (1.5–14%), 1,8-cineole (0–81%), p-cymene (0.6–28%) and aromadendrene/terpinen-4-ol (0.6–24%) as principal leaf oil components.

Precise Method for Measuring Absolute Values of Diffusion Coefficients of Binary Gas Mixtures

An apparatus is described for determining binary diffusion coefficients of gases as a function of temperature, pressure, and concentration. Binary diffusion coefficients are reported for the systems H2−N2 and He−Ar at 300°K and 1 atm. The data are believed to be precise to approximately 0.2%, and show a linear dependence on concentration for the system H2−N2.

Anisotropic intermolecular potentials for HeC2H2, HeC2H4, and HeC2H6, and an effective spherical potential for HeCHF3 from multiproperty fits

Differential cross section (DCS) measurements are reported for scattering of a He atomic beam by crossed beams of C2H2, C2H4, C2H6, and CHF3. In addition, interaction virial measurements and accurate limiting diffusion measurements are presented for these systems. Damping of the DCS diffraction oscillations is used to extract anisotropic intermolecular potentials, which are constrained in multiproperty fits to accurately reproduce the dilute gas data. The radial anisotropies determined are in the sequence C2H6>C2H4∼C2H2>CHF3, as sampled by the He probe.