Search results for "Liquid gas"
showing 6 items of 6 documents
Liquid gas techniques for GC trace analysis
1990
Liquid gases (LG), i.e. low boiling compounds with vapor pressures below 5 bar at room temperature, are introduced as solvents for trace analyses. A system for preparin, diluting and handling LG solutions safely and conveniently in 5 to 500 μl amounts was developed as well as a syringe for direct injection of μl-LG samples into capillary GC. Even technical grade LG are of high purity. GC/FID of LG solutions (starting at −60°C) allows the separation of volatile traces from the solvent peak: e.g., dichloromethane can be measured in the picogram range.
Liquid/Gas and Liquid/Liquid Phase Equilibria of the System Water/Bovine Serum Albumin
2013
The thermodynamic behavior of the system H2O/BSA was studied at 25 °C within the entire composition range: vapor pressure measurements via head space sampling gas chromatography demonstrate that the attainment of equilibria takes more than one week. A miscibility gap was detected via turbidity and the coexisting phases were analyzed. At 6 °C the two phase region extends from ca. 34 to 40 wt % BSA; it shrinks upon heating. The polymer rich phase is locally ordered, as can be seen under the optical microscope using crossed polarizers. The Flory-Huggins theory turns out to be inappropriate for the modeling of experimental results. A phenomenological expression is employed which uses three adju…
Cellulose/Water: Liquid/Gas and Liquid/Liquid Phase Equilibria and Their Consistent Modeling
2007
Liquid/liquid and liquid/gas equilibria were measured for the water/cellulose system at 80 °C using three different polymer samples. For these experiments we prepared cellulose films of approximately 20−25 μm in thickness and determined their equilibrium swelling in water. Thereafter the polymer concentration in the mixed phase was increased by means of a stepwise removal of the volatile component, and the equilibrium vapor pressures were measured using an automated combination of head space sampling and gas chromatography. Contrary to the usual behavior of polymers, the swelling of cellulose increases as its molar mass becomes larger. The Flory−Huggins interaction parameters calculated fro…
Nuclear liquid-gas phase transition and supernovae evolution
2004
It is shown that the large density fluctuations appearing at the onset of the first order nuclear liquid-gas phase transition can play an important role in the supernovae evolution. Due to these fluctuations, the neutrino gas may be trapped inside a thin layer of matter near the proto-neutron star surface. The resulting increase of pressure may induce strong particle ejection a few hundred milliseconds after the bounce of the collapse, contributing to the revival of the shock wave. The Hartree-Fock+RPA scheme, with a finite-range nucleon-nucleon effective interaction, is employed to estimate the effects of the neutrino trapping due to the strong density fluctuations, and to discuss qualitat…
Interfacial tension between coexisting polymer solutions in mixed solvents and its correlation with bulk thermodynamics: phase equilibria (liquid/gas…
2002
Abstract Vapor pressures, phase equilibria and interfacial tensions σ were measured for solutions of poly(dimethylsiloxane) (PDMS, M w [equals]75 kg/mol and M n [equals]50 kg/mol) in mixed solvents of toluene (TL) and ethanol (EtOH) at 30, 40, 50 and 60 °C. The experimental ternary phase diagrams can be modeled quantitatively from the determined concentration and temperature dependent binary interaction parameters χ ij if the experimentally inaccessible composition dependence of χ EtOH/PDMS is adjusted. The relations between σ and the equation of state of the system differ from that applying to single solvents. The exponents as well as the amplitude prefactors of the corresponding scaling l…
A liquid gas target system for medium energy electron scattering
1972
Abstract A liquid gas target system is described, which is suitable for high resolution electron scattering experiments at medium energies. The liquid gas chamber of the target system has, for ease of comparison with solid targets, the form of a thin-walled flat box 2 mm in thickness. The position of the target assembly can be changed by remote control.