Search results for "Vapor pressure"
showing 10 items of 69 documents
Persistence of orographic mixed‐phase clouds
2016
Mixed-phase clouds (MPCs) consist of ice crystals and supercooled water droplets at temperatures between 0 and approximately −38°C. They are thermodynamically unstable because the saturation vapor pressure over ice is lower than that over supercooled liquid water. Nevertheless, long-lived MPCs are ubiquitous in the Arctic. Here we show that persistent MPCs are also frequently found in orographic terrain, especially in the Swiss Alps, when the updraft velocities are high enough to exceed saturation with respect to liquid water allowing simultaneous growth of supercooled liquid droplets and ice crystals. Their existence is characterized by holographic measurements of cloud particles obtained …
Isobaric Vapor−Liquid Equilibria of the Water + 1-Propanol System at 30, 60, and 100 kPa
1996
Isobaric vapor−liquid equilibria for the water + 1-propanol system are reported at 30, 60, and 100 kPa. The results were found to be thermodynamically consistent according to Van Ness−Byer−Gibbs, Kojima, and Wisniak methods. The system shows a minimum boiling azeotrope, and the azeotropic composition is scarcely shifted with pressure. Results were compared with literature values. The data were correlated with Margules, Van Laar, Wilson, NRTL, and UNIQUAC liquid-phase activity coefficient models.
Vapor–liquid equilibria in the systems 3-methylpentane+methyl 1,1-dimethylethyl ether and 3-methylpentane+methyl 1,1-dimethylpropyl ether at 101.3 kPa
1999
Abstract Pure-component vapor pressure of 3-methylpentane and vapor–liquid equilibrium (VLE) for the binary systems of 3-methylpentane with methyl 1,1-dimethylethyl ether (MTBE) and with methyl 1,1-dimethylpropyl ether (TAME) at 101.3 kPa have been measured. Both systems exhibit small positive deviations from ideality. They can be described as regular solutions and do not present azeotrope. The activity coefficients and boiling points of the solutions were correlated with its composition by Wilson, UNIQUAC, NRTL, and Wisniak–Tamir equations.
Vapor−Liquid Equilibria for the Binary Systems tert-Butyl Alcohol + Toluene, + Isooctane, and + Methylcyclohexane at 101.3 kPa
1998
Vapor-liquid equilibria were measured for binary systems of tert-butyl alcohol with toluene, isooctane, and methylcyclohexane at 101.3 kPa using a recirculating still. Experimental values of the vapor pressure of non-oxygenated pure components have been obtained. The accuracy of experimental measurements was ±0.01 K in temperature, ±0.01 kPa in pressure, and ±0.001 in mole fractions. The results are thermodynamically consistent according to the point-to-point consistency test. The data were correlated with five liquid-phase activity coefficients models (Margules, Van Laar, Wilson, NRTL, UNIQUAC).
Temperature dependent properties of environmentally important synthetic musks.
2002
Environmental fate determining physical properties including their temperature dependence for five nitro musks and for seven polycyclic musks were estimated. The properties evaluated were vapor pressure in a solid and liquid state (PS and PL), solubility in water (S), Henry's law coefficient (H = PL/S) and log octanol-water partition coefficient (log KOW). Gas chromatography for starting values of vapor pressure estimation and HPLC experiments at 5-20 degrees C for comparison of the theoretical versus experimental solubilities in water were performed. The values of temperature (T) dependence coefficients (Ai and Bi) in equations: log (Property)i = Ai - Bi/T were determined. Values of proper…
Isobaric Vapor−Liquid Equilibrium in the Systems 2,3-Dimethylpentane + Methyl 1,1-Dimethylethyl Ether, + Diisopropyl Ether and + Methyl 1,1-Dimethylp…
1999
New, consistent vapor−liquid equilibrium data for the binary systems 2,3-dimethylpentane + methyl 1,1-dimethylethyl ether, + diisopropyl ether, and + methyl 1,1-dimethylpropyl ether are reported at 101.3 kPa. The measured systems deviate slightly from ideal behavior, and only the system methyl 1,1-dimethylpropyl ether + 2,3-dimethylpentane presents an azeotrope. The activity coefficients for the solutions were correlated with their compositions by the Wilson, UNIQUAC, and NRTL models. Wisniak−Tamir equations were used to correlate the boiling points of the solutions with their compositions.
Organic solvent desorption from two tegafur polymorphs.
2013
Desorption behavior of 8 different solvents from α and β tegafur (5-fluoro-1-(tetrahydro-2-furyl)uracil) has been studied in this work. Solvent desorption from samples stored at 95% and 50% relative solvent vapor pressure was studied in isothermal conditions at 30 °C. The results of this study demonstrated that: solvent desorption rate did not differ significantly for both phases; solvent desorption in all cases occurred faster from samples with the largest particle size; and solvent desorption in most cases occurred in two steps. Structure differences and their surface properties were not of great importance on the solvent desorption rates because the main factor affecting desorption rate …
A Simple method for estimating the latent heat flux over grass from radiative bowen ratio
1998
Abstract The evaluation of crop evapotranspiration from infrared temperature is usually calculated as the residual component of the surface energy balance. This method has given good results over a full grass canopy cover with unstressed transpiration, in spite of the not well understood meaning of the aerodynamic resistance needed. A simple and more accurate method, which determines the Bowen ratio (β) and the latent heat flux (λE) over a reference grass area without knowledge of surface resistances, is proposed. The proportionality between β and a radiative Bowen ratio βs is shown. The radiative Bowen ratio is derived from surface and air temperatures and vapor pressure. This relationship…
A predictive model for salt nanoparticle formation using heterodimer stability calculations
2021
Acid–base clusters and stable salt formation are critical drivers of new particle formation events in the atmosphere. In this study, we explore salt heterodimer (a cluster of one acid and one base) stability as a function of gas-phase acidity, aqueous-phase acidity, heterodimer proton transference, vapor pressure, dipole moment and polarizability for salts comprised of sulfuric acid, methanesulfonic acid and nitric acid with nine bases. The best predictor of heterodimer stability was found to be gas-phase acidity. We then analyzed the relationship between heterodimer stability and J4×4, the theoretically predicted formation rate of a four-acid, four-base cluster, for sulfuric acid salts ove…
Efficient prediction of thermodynamic properties of quadrupolar fluids from simulation of a coarse-grained model: the case of carbon dioxide.
2008
Monte Carlo simulations are presented for a coarse-grained model of real quadrupolar fluids. Molecules are represented by particles interacting with Lennard-Jones forces plus the thermally averaged quadrupole-quadrupole interaction. The properties discussed include the vapor-liquid coexistence curve, the vapor pressure along coexistence, and the surface tension. The full isotherms are also accessible over a wide range of temperatures and densities. It is shown that the critical parameters (critical temperature, density, and pressure) depend almost linearly on a quadrupolar parameter q=Q(*4)T*, where Q* is the reduced quadrupole moment of the molecule and T* the reduced temperature. The mode…