Determination Of Vapor Pressure Research Articles

The Example of the Development of Multimedia Courseware Simulating Physical Chemistry Experiments

The development process of software simulating physical chemistry experiments “The determination of saturated vapor pressure of liquid” as an example was shown based on Flash 8 software as a software developing platform and Photoshop as auxiliary software. The process of elements and instruments’ formation, the connection of instruments, the production of all kinds of scenes and their animation, the recording of sound, the simulation procedures were displayed. The courseware has been used in the physical chemistry experiment teaching. The good effect is obtained from the statistics of the student evaluations.

Determination and modelling of osmotic coefficients and vapour pressures of binary systems 1- and 2-propanol with C nMimNTf 2 ionic liquids ( n = 2, 3, and 4) at T = 323.15 K

The osmotic and activity coefficients and vapour pressures of binary mixtures containing 1-propanol, or 2-propanol and imidazolium-based ionic liquids with bis(trifluoromethylsulfonyl)imide as anion (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, C 2MimNTf 2, 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide, C 3MimNTf 2, and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, C 4MimNTf 2) were determined at T = 323.15 K using the vapour pressure osmometry technique. The experimental osmotic coefficients were correlated using the extended Pitzer model modified by Archer and the MNRTL model, obtaining standard deviations lower than 0.033 and 0.064, respectively. The mean molal activity coefficients and the excess Gibbs free energy for the mixtures studied were calculated from the parameters of the extended Pitzer model modified by Archer. Besides the effect of the alkyl-chain of the cation, the effect of the anion can be assessed comparing the experimental results with those previously obtained for imidazolium ionic liquids with sulphate anions.

Temperature Dependence of Vapor Pressures over Saturated Aqueous Solutions at Invariant Points of the NaCl + KNO3 + H2O, NaCl + Na2CO3 + H2O, and NaCl + Na2SO4 + H2O Systems

Vapor pressures of water over saturated solutions with regard to two salts, in the NaCl + KNO3 + H2O, NaCl + Na2CO3 + H2O, and NaCl + Na2SO4 + H2O systems are reported in the (278 to 323) K temperature range. The determined vapor pressures were used to obtain the water activities, the molar enthalpies of vaporization and the osmotic coefficients. Compositions of invariant points from the literature were correlated as a function of temperature with the aid of quadratic equations. These equations served to determine the molar enthalpies of solution.

Experimental Measurement of Vapor Pressures and Densities at Saturation of Pure Hexafluoropropylene Oxide: Modeling Using a Crossover Equation of State

Hydrofluoroalkenes, like hexafluoropropylene, can be considered as new working fluids for refrigeration systems and consequently volumetric and critical property data are required. In this study, a vibrating tube densitometer technique was used to determine densities at nine different temperatures between (263 and 358) K, and pressures between (0.04 and 15) MPa. The experimental uncertainties are ±0.0003 and ±0.0006 MPa for pressure, ± 0.02 K for temperature, ± 0.5% (relative) for vapor densities, and ±0.05% for liquid densities. A different equipment based on static method is used for the determination of pure component vapor pressures for temperatures between (231 and 359) K. The experimental uncertainties are ±0.0005 MPa for pressure and ±0.02 K for the temperature. Critical properties have been determined by direct measurement and also from utilization of experimental densities considering the asymptotic scaling law behavior. The Patel−Teja and crossover Patel−Teja equations of state are used to corre...

Experimental and theoretical determination of the saturation vapor pressure of silicon in a wide range of temperatures

Reference books and original studies devoted to the determination of the saturation vapor pressure of silicon in a wide range of temperatures have been analyzed. It has been established that no reliable experimental data in the range of high temperatures (above 2000 K) are available in the literature. It has been demonstrated that there is a need to perform additional theoretical and experimental investigations with the use of different methods. The total pressure and partial pressures of Si n (n = 1−6) molecules over liquid silicon are calculated in the temperature range 1700–3400 K. The calculation of the composition of the gas phase over the “Si(l)-container” systems is performed. Materials of the crucibles intended for the use in experimental investigations of the temperature dependence of the saturation vapor pressure of silicon over the liquid phase are recommended.

Determination of Urea Nitrate and Guanidine Nitrate Vapor Pressures by Isothermal Thermogravimetry

AbstractSince the bombing of Pan Am Flight 103 over Lockerbie, Scotland in 1988, detection of military explosives has received much attention. Only in the last few years has detection of improvised explosives become a priority. Many detection methods require that the particulate or vapor be available. Elsewhere we have reported the vapor pressures of peroxide explosives triacetone triperoxide (TATP), diacetone diperoxide (DADP), and 2,4,6‐trinitrotoluene (TNT). Herein we examine the vapor signatures of the nitrate salts of urea and guanidine (UN and GN, respectively), and compare them to ammonium nitrate (AN) and TATP using an isothermal thermo‐gravimetric method. The vapor signatures of the nitrate salts are assumed to be the vapor pressures of the neutral parent base and nitric acid. Studies were performed at elevated temperatures (80–120 °C for UN, 205–225 °C for GN, 100–160 °C for AN, and 40–59 °C for TATP), enthalpies of sublimation calculated and vapor pressures extrapolated to room temperature. Reported vapor pressure values (in Pa) are as follows: GN ≪UN <AN ≪TATP 2.66×10−18 3.94×10−5 5.98×10−4 24.8

Determination of saturated vapor pressure of organic substances from the triple to critical point

Methods are given of extrapolating the saturated vapor pressure of substances of “atmospheric range” to the entire liquid phase region from the triple to critical point. The extrapolation of the pT parameters from room temperature to the triple point is performed by simultaneous processing of vapor pressure and of differences between the heat capacities of ideal gas and liquid. The liquid-vapor equilibrium in the region from the normal boiling temperature to the critical point is predicted by the law of corresponding states of L.P. Filippov using the experimentally obtained pT data and values of density of liquids. Experimental facilities are described for determining the saturated vapor pressure by the comparison ebulliometric method and for determining the low-temperature heat capacity by the vacuum adiabatic calorimetry. The methods of extrapolating the vapor pressure are tested with standard substances for which reliable pT data are available for the entire liquid phase region.

Vapor Pressure Modeling for Fire Damage Assessment of HPC

High-performance concrete will undergo severe damage under fire conditions. It is well known that vapor pressure induced by high temperatures plays an important role in the damaging process. This paper presents a method of vapor pressure modeling, called equivalent expansion method, which can be implemented in FEM analysis. The modeling procedure consists of two parts, i.e. vapor pressure determination and vapor pressure modeling incorporated in FEM analysis. In order to make analysis more accurate, steam table is employed instead of ideal gas equation.

The mercury vapour pressure vs. temperature relation between (500 and 665) K

A gas-controlled heat-pipe is used at the Italian National Research Institute of Metrology (INRIM) to realise the mercury (liquid + vapour) equilibrium from (450 to 700) K. The pressure in the heat pipe is controlled between (5 and 200) kPa by means of an innovative computer-driven system having a pressure sensitivity of a few parts per million. The vapour pressure of 0.9999999 pure mercury has been measured between (500 and 665) K. A standard pressure balance and a standard platinum resistance thermometer (SPRT) calibrated at the ITS-90 fixed points, were used. The experimental data obtained are fitted to a semi-empirical relationship between vapour pressure and temperature. The basic features of gas-controlled heat pipes and the metrological quality of the temperature and pressure measurements available in the laboratory, allowed the determination of the mercury vapour pressure at the level of a few parts in 10 −5. The paper reports the acquired data and the evaluated relationship, together with the uncertainty budget of the associated measurements. A complete description of the mercury heat-pipe, the gas controlled system, the measuring instruments involved and the temperature and pressure data acquisition and processing is also presented. The relationship between temperature and pressure of the mercury liquid–vapour transition has then been derived and it is here reported together with the mathematical and experimental uncertainty budgets. An accurate comparison with the existing data is also reported.

Temperature Dependence of Vapor Pressures over Saturated Aqueous Solutions at Invariant Points of the NaCl + KCl + H2O, NaCl + NaNO3 + H2O, KCl + KBr + H2O, KCl + KI + H2O, KCl + KNO3 + H2O, and KCl + K2SO4 + H2O Systems

Vapor pressures of water over saturated solutions with regard to two salts, in the NaCl + KCl + H2O, NaCl + NaNO3 + H2O, KCl + KBr + H2O, KCl + KI + H2O, KCl + KNO3 + H2O, and KCl + K2SO4 + H2O systems, are reported in the (278 to 323) K temperature range. The determined vapor pressures served to obtain the water activities, the osmotic coefficients, and the molar enthalpies of vaporization.

Solid Vapor Pressure and Enthalpy of Sublimation for Ammonium Perfluorooctanoate

A modified gas saturation method was used to directly determine the solid vapor pressure of ammonium perfluorooctanoate (APFO). Measurements were made over the temperature range from (45 to 60) °C. Pressures ranged from (0.04 ± 0.007) Pa to (0.17 ± 0.028) Pa. A relationship was developed for determining vapor pressure as a function of temperature for conditions near the test range, and an environmentally relevant vapor pressure of (0.003 ± 0.0005) Pa was calculated at 25 °C. This ambient vapor pressure for the ammonium salt of perfluorooctanoate (PFO) is 3 orders of magnitude lower than the ambient vapor pressure of the acid form, perfluorooctanoic acid (PFOA), which is approximately 4.1 Pa at 25 °C. This finding underscores the importance of knowing what compound is present in the environment and using the appropriate properties to be able to predict environmental fate and transport behavior. The enthalpy of sublimation was calculated as 90.9 kJ·mol−1. It is hypothesized that APFO may undergo a multistage sublimation process.

Vapor pressure determination for solid and liquid La2S3 using boiling points

A high-temperature technique was developed for vapor pressure determination of solid and liquid γ-La2S3 (we called it the boiling point technique). Melting temperatures and total vapor pressures were measured for incongruently vaporizing γ-La2S3 at 1853–2210 K and 0.3–3.0 atm pressures. Having compared the slopes of the log p(S2) versus 1/T plots measured by various techniques, we recommend the equation log p(S2) [atm] = (6.31 ± 0.15) − (12720±310)T −1 for T = 1021–2013 K as the most reliable for practical use.

Vapour-phase Dyeing of Synthetic-polymer Fibres

Absorption isotherms at high temperatures for some disperse dye vapours and secondary cellulose acetate film have been determined and found to be linear. In order to calculate dye vapour concentrations, two methods have been used for the determination of vapour pressures, and from the results it is shown that disperse dye molecules can associate in the vapour phase. The absorption of dye vapour by polyester fibre in the form of small packages over the range 180–220°C, as well as a laboratory machine that can be used for this purpose, are described. Package dyeing on a larger scale with dye vapour is considered to be possible.

Construction of gas saturation curve

A method is proposed for determining saturation pressure as a function of saturation temperature without using computers and handbooks, which is of particular interest for checking pump efficiency, appraising saturation pressure variation in the system, and designing complicated high-vacuum systems. A table is provided for construction of saturation curves, upon use of which the error in the determination of saturated vapor pressure as a function of temperature does not exceed one-half order of magnitude for all the investigated gases. An ordered relationship of critical points of noble gases is presented in saturation pressure-temperature coordinates.

Measurements of saturated-liquid densities for isobutane at T = (280 to 407) K

Ten measurements of the saturated-liquid density for isobutane were obtained by means of a metal-bellows variable volumometer at T = (280 to 407) K. The mole fraction purity of the isobutane used in the measurements was 0.9999. For the determination of the saturation boundary at each temperature for isobutane, we measured the density data at intervals of about 12 kPa very close to the saturation boundary. The expanded uncertainties ( k = 2) in temperature, pressure, and density measurements have been estimated to be less than 3 mK, less than 0.8 kPa, and 0.08%, respectively. After such measurements had been completed, the saturated-liquid density results for each temperature were determined as the point of intersect between the isotherm and our previously determined vapour pressure value. The expanded uncertainties ( k = 2) in the present saturated-liquid density data have also been estimated to be less than 0.08%, except the uncertainty of the saturated-liquid density data at T = 400 K being 0.09% (0.31 kg · m −3). Based on the present measurements as input data, the saturated-liquid density correlation were also provided for the systematic comparisons between the present measurements and the literature data.

The vapour pressures over saturated aqueous solutions of dl-2-aminobutyric acid, 4-aminobutyric acid, sodium- d-gluconate, sodium hippurate, and potassium magnesium- l-aspartate

Vapour pressures of water over saturated solutions of dl-2-aminobutyric acid, 4-aminobutyric acid, sodium- d-gluconate, sodium hippurate, and potassium magnesium- l-aspartate were determined over the (278 to 322) K temperature range. The determined vapour pressures were used to obtain the water activities, the molar enthalpies of vaporization, and the osmotic coefficients of sodium- d-gluconate.

Freezing of Lennard-Jones fluid in cylindrical nanopores under tensile conditions

We have shown the Lennard-Jones (LJ) phase diagram for a slit-shaped nanopore by molecular simulations and thermodynamically predicted the results with no adjustable parameter. With this success, LJ phase diagrams are predictable. In this study, the freezing of an LJ CH4 capillary condensate under a tensile condition in a nonstructural carbon nanopore with a cylindrical geometry was examined using molecular dynamics (MD) simulation. We employ a unit cell in contact with a bulk vapor phase, which is useful for the determination of the bulk vapor pressure in equilibrium with the molecules in a pore. The MD simulation results show liquid-solid (amorphous) phase transitions with a variation in the bulk vapor pressure. The frozen particles are arranged in concentric circular regions along the wall similar to those reported by Maddox and Gubbins. The freezing points are determined from the variations in density, enthalpy, arrangement, and structural functions. The obtained liquid-solid coexistence points are found to exhibit a significant dependence of the freezing point on the equilibrium bulk vapor pressure, forming an extraordinarily skewed curve on the p-T diagram, in contrast to the bulk phase coexistence that is represented by an almost vertical line. The origin of the significant dependence is considered to be the Laplace effect on the capillary condensate similar to the case with a slit-shaped pore. A simple model, which the authors earlier presented for slit-shaped nanopores, successfully predicted the p-T relation of the freezing point for cylindrical nanopores as well.

The vapour pressures over saturated aqueous solutions of sodium and potassium acetates, chlorates, and perchlorates

Vapour pressures of water over saturated solutions of sodium acetate, potassium acetate, sodium perchlorate, and potassium perchlorate were determined over the (278 to 318) K temperature range and compared with available in the literature data. The cases of saturated solutions of sodium chlorate and potassium chlorate are also considered. The determined vapour pressures were used to obtain the water activities, the osmotic coefficients, and the molar enthalpies of vaporization in considered systems.

The thermodynamic stability of inclusion compounds of Zinc(II) and Nickel(II) coordination polymers with chlorobenzene as a guest: The determination of guest vapor pressure by the tensimetric method

The static membrane method was used to study the temperature dependences of equilibrium guest vapor pressure over inclusion compounds of two coordination polymers with chlorobenzene, [M(bipy)(DBM)2] · 2C6H5Cl, where M = M(II) = Zn and Ni, bipy = 4,4′-dipyridyl, and DBM = C6H5COCHCOC6H 5 − is the dibenzoylmethanate anion. The data obtained were used to calculate the thermodynamic parameters of dissociation of these compounds. The regions of their existence and the stoichiometry and character of phase transitions were determined by thermogravimetric and differential thermal analyses.

Static headspace--gas chromatography: theory and practice

Static headspace--gas chromatography: theory and practice