Equilibrium Vapor Pressure Research Articles

Relating ΔHvap of Organic Liquids to Intermolecular Forces: Simple Modifications of a Classic General Chemistry Experiment

The concept of equilibrium vapor pressure plays a key role in the general chemistry curriculum; it is among the first and most easily demonstrated examples of equilibrium and frequently caps off the first semester of general chemistry where it illustrates the properties of liquids and intermolecular forces. We report here simple modifications of Levinson’s classic experiment that allow measurement of vapor pressures for organic samples at a variety of temperatures. Data analysis gives heats of vaporization which may be interpreted in terms of intermolecular attractive forces. Equipment needs are simple and readily available: a 10 mL graduated cylinder, a tall 1 L beaker, disposable graduated syringes, and a 10 in. needle or cannula bent into a “J” shape. The method uses 1 mL or less of organic sample per trial and works well for organic liquids that are immiscible with and are less dense than water. Student results are presented for the experiment conducted over three semesters as well as the impact on student learning as assessed by common exam results and end-of-semester student surveys.

Vapor Pressure of Aqueous HCOOK Solution as Working Fluids of an Absorption Heat Transformer at High Temperature

Aqueous potassium formate solution is regarded as a potential working fluid of an absorption heat transformer (AHT) because of its noncorrosive and biodegradable characteristics. The vapor pressure of working fluids is an important property for application in an absorption cycle. However, current experimental data are mostly limited to temperature and concentration ranges that are suitable for a dehumidification system. Thus, more accurate data of vapor pressure are anticipated. In this paper, the equilibrium vapor pressures of aqueous HCOOK solution were measured with a static method in the temperature range from 323.15 to 373.15 K. The mass concentration of HCOOK varied from 10 to 70%. The measured data were compared with the estimated values of a referenced chemical engineering property database (Aspen Plus). A relatively large mean absolute relative deviation (MARD) of 13.27% was found. The data were then correlated with a modified Antoine equation, and the MARD was reduced to 0.45%. The thermodynamic...

Distribution and energy balance of Pluto’s nitrogen ice, as seen by New Horizons in 2015

Pluto’s surface is geologically complex because of volatile ices that are mobile on seasonal and longer time scales. Here we analyzed New Horizons LEISA spectral data to globally map the nitrogen ice, including nitrogen with methane diluted in it. Our goal was to learn about the seasonal processes influencing ice redistribution, to calculate the globally averaged energy balance, and to place a lower limit on Pluto’s N2 inventory. We present the average latitudinal distribution of nitrogen and investigate the relationship between its distribution and topography on Pluto by using maps that include the shifted bands of methane in solid solution with nitrogen (which are much stronger than the 2.15-μm nitrogen band) to more completely map the distribution of the nitrogen ice. We find that the global average bolometric albedo is 0.83±0.11, similar to that inferred for Triton, and that a significant fraction of Pluto’s N2 is stored in Sputnik Planitia. We also used the encounter-hemisphere distribution of nitrogen ice to infer the latitudinal distribution of nitrogen over the rest of Pluto, allowing us to calculate the global energy balance. Under the assumption that Pluto’s nitrogen-dominated 11.5μbar atmosphere is in vapor pressure equilibrium with the nitrogen ice, the ice temperature is 36.93±0.10 K, as measured by New Horizons’ REX instrument. Combined with our global energy balance calculation, this implies that the average bolometric emissivity of Pluto’s nitrogen ice is probably in the range 0.47–0.72. This is consistent with the low emissivities estimated for Triton based on Voyager results, and may have implications for Pluto’s atmospheric seasonal variations, as discussed below. The global pattern of volatile transport at the time of the encounter was from north to south, and the transition between condensation and sublimation within Sputnik Planitia is correlated with changes in the grain size and CH4 concentration derived from the spectral maps. The low emissivity of Pluto’s N2 ice suggests that Pluto’s atmosphere may undergo an extended period of constant pressure even as Pluto recedes from the Sun in its orbit.

Thermo-physical behavior of borosilicate glasses in the presence of high-level radioactive liquid waste constituents

Elemental composition of high-level radioactive liquid waste (HLW) from samples of various batches was assessed by using side-on-view inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Under robust condition (Mg ratio, 10.2 ± 0.4 at RF power 1.3 kW), t he plasma excitation temperature (Texe, 9925 ± 1950 K) was calculated using the Boltzmann plot method. Thermal behavior of major constituents (> 1 g L−1) of HLW, such as nitrates of Na+, Fe3+, Cs+, Nd3+, and UO22+ , were studied using simultaneous thermal analyzer. Subsequently, the thermal stability of five and seven components borosilicate glasses was studied in detail with the above nitrates individually added as additives. Vapor pressure of sodium metaborate (NaBO2, one of the major vapor species from the glass melt in the off-gas system during vitrification of HLW) was estimated using transpiration thermogravimetry. Based on mass loss, the equilibrium vapor pressures (2.51–26.37 Pa) over a temperature span of 1233.15–1343.15 K were estimated. The molar enthalpy of vaporization (ΔvapH°) for sodium metaborate was calculated to be 287.84 ± 0.94 kJ mol−1 using the experimental data.

Humidity responsive single-layered film fabricated by hydrophilic titanium oxide nanotubes

We fabricated a humidity responsive film comprising a bundle of titanium oxide tubes, which changes its curvature corresponding to the relative humidity. The mechanism of changing the curvature of the film can be explained by adsorption, condensation, and evaporation of water molecules within the film. During adsorption, a liquid bridge is formed because of the growth of a water layer between tubes, thus contracting the tubes. When vapor pressure exceeds the equilibrium vapor pressure, condensation occurs at the meniscus of the liquid bridge, thus expanding the gap between tubes. We obtained the adsorption and desorption isotherms for the humidity responsive film by determining physical adsorption. Additionally, we demonstrated the varying motions of the humidity sensing film when a water droplet was applied on the surface. The sensor could distinguish between saturated and oversaturated humidity conditions, such as fog and rain, respectively, which is not possible using resistive humidity sensors. This humidity responsive film can be applied to environmental monitoring systems and possibly even to energy harvesting systems.

Experimental measurements of saturated vapor pressure and isothermal vapor-liquid equilibria for 1,1,1,2-Tetrafluoroethane (HFC-134a) + 3,3,3-trifluoropropene (HFO-1243zf) binary system

This work investigated saturated vapor pressure and isothermal vapor-liquid equilibrium (VLE) for 1,1,1,2-Tetrafluoroethane (HFC-134a) + 3,3,3-trifluoropropene (HFO-1243zf) binary system. The saturated vapor pressures of HFC-134a and HFO-1243zf ranging from (273.17–353.13) K, and VLE data at four temperatures (283.15, 293.15, 313.15, 323.14) K for the HFC-134a + HFO-1243zf system were measured by a static-analytical apparatus. The vapor pressure data of HFO-1243zf were regressed by a Wagner type equation and compared with existing literature data. The experimental VLE data of HFC-134a + HFO-1243zf system were correlated by Peng-Robinson (PR) equation of state (EOS) combined with van der Waals (vdW) mixing rules. The binary interaction parameters were obtained, and correlation deviation was acceptable. Azeotropic behavior can be found for the HFC-134a + HFO-1243zf system at measured temperatures. Our work provides fundamental thermodynamic properties of new mixed refrigerants which are crucial to evaluate their cycle performance and optimize the design of refrigeration system.

Fundamental study on the vaporization of cesium and iodine dissolved in LiF-NaF-KF molten salt

As a basic study related to a severe accident of Molten Salt Reactor (MSR), the equilibrium vapor pressures over LiF-NaF-KF eutectic salt (46.5–11.5–42.0 mol%, FLiNaK) containing Cs and I as volatile Fission Product(FP) were measured by a transpiration method under pure Ar gas flow at the temperature ranging from 900 to 1100 K. As the result, the vapor pressures of Cs and I in molten FLiNaK were evaluated to be higher than those of other elements in the salt, and the vapor pressure of the solvent salt elements such as Li and K also increased with addition of CsI and CsF. The activity coefficients of CsI and CsF were derived from the partial vapor pressure of CsI and CsF calculated by assuming the gas phase equilibrium. Activity coefficients of CsI, 6 to 13 in this temperature range, showed strongly positive deviation from ideal solution while those of CsF were around unity. This peculiar activity coefficients suggest instability of CsI in the FLiNaK salt as suggested for LiF-ThF4-CsI salt by literature. The vaporization behaviors measured for the FLiNaK with different Cs/I ratio indicated strong interaction between Cs and I in FLiNaK salt.

Solubility and vapor pressure data of bioactive 6-(acetylamino)-N-(5-ethyl-1,3,4-thiadiazol-2-yl) hexanamide

This paper presents new experimental data on some key physicochemical properties of original bioactive 6-(acetylamino)-N-(5-ethyl-1,3,4-thiadiazol-2-yl) hexanamide (AETH). Thermal analysis of the compound under study has been carried out using differential scanning calorimetry and thermogravimetric techniques. AETH solubility data in five pharmaceutically relevant solvents in the temperature range from 288.15 to 318.15 K have been obtained by the classic saturation shake-flask method. The bioactive compound has poor solubility in hexane and buffer solutions, while it is slightly soluble in selected alcohols. The experimental solubility results have been correlated by means of modified Apelblat and van’t Hoff equations. The selected thermodynamic models produced acceptable results. The Hansen solubility parameters and their components for AETH and solvents have been evaluated by using the van Krevelen–Hoftyzer atomic group contribution method. The ideal solubility and the solution activity coefficient at equilibrium in the selected solvents have been quantified based on experimental values of melting enthalpy and temperature. All the investigated solutions exhibit a positive deviation from ideality with the maximal solubility in alcohols. The equilibrium vapor pressure of the compound studied has been determined as a function of temperature in the range of 433.15–454.15 K by the transpiration method. The standard thermodynamic parameters of AETH sublimation have been calculated. It has been concluded that the high crystal lattice energy value equal to 131.5 kJ/mol is the dominant factor determining the poor solubility of the bioactive compound.

The potential role of methanesulfonic acid (MSA) in aerosol formation and growth and the associated radiative forcings

Abstract. Atmospheric marine aerosol particles impact Earth's albedo and climate. These particles can be primary or secondary and come from a variety of sources, including sea salt, dissolved organic matter, volatile organic compounds, and sulfur-containing compounds. Dimethylsulfide (DMS) marine emissions contribute greatly to the global biogenic sulfur budget, and its oxidation products can contribute to aerosol mass, specifically as sulfuric acid and methanesulfonic acid (MSA). Further, sulfuric acid is a known nucleating compound, and MSA may be able to participate in nucleation when bases are available. As DMS emissions, and thus MSA and sulfuric acid from DMS oxidation, may have changed since pre-industrial times and may change in a warming climate, it is important to characterize and constrain the climate impacts of both species. Currently, global models that simulate aerosol size distributions include contributions of sulfate and sulfuric acid from DMS oxidation, but to our knowledge, global models typically neglect the impact of MSA on size distributions. In this study, we use the GEOS-Chem-TOMAS (GC-TOMAS) global aerosol microphysics model to determine the impact on aerosol size distributions and subsequent aerosol radiative effects from including MSA in the size-resolved portion of the model. The effective equilibrium vapor pressure of MSA is currently uncertain, and we use the Extended Aerosol Inorganics Model (E-AIM) to build a parameterization for GC-TOMAS of MSA's effective volatility as a function of temperature, relative humidity, and available gas-phase bases, allowing MSA to condense as an ideally nonvolatile or semivolatile species or too volatile to condense. We also present two limiting cases for MSA's volatility, assuming that MSA is always ideally nonvolatile (irreversible condensation) or that MSA is always ideally semivolatile (quasi-equilibrium condensation but still irreversible condensation). We further present simulations in which MSA participates in binary and ternary nucleation with the same efficacy as sulfuric acid whenever MSA is treated as ideally nonvolatile. When using the volatility parameterization described above (both with and without nucleation), including MSA in the model changes the global annual averages at 900 hPa of submicron aerosol mass by 1.2 %, N3 (number concentration of particles greater than 3 nm in diameter) by −3.9 % (non-nucleating) or 112.5 % (nucleating), N80 by 0.8 % (non-nucleating) or 2.1 % (nucleating), the cloud-albedo aerosol indirect effect (AIE) by −8.6 mW m−2 (non-nucleating) or −26 mW m−2 (nucleating), and the direct radiative effect (DRE) by −15 mW m−2 (non-nucleating) or −14 mW m−2 (nucleating). The sulfate and sulfuric acid from DMS oxidation produces 4–6 times more submicron mass than MSA does, leading to an ∼10 times stronger cooling effect in the DRE. But the changes in N80 are comparable between the contributions from MSA and from DMS-derived sulfate/sulfuric acid, leading to comparable changes in the cloud-albedo AIE. Model–measurement comparisons with the Heintzenberg et al. (2000) dataset over the Southern Ocean indicate that the default model has a missing source or sources of ultrafine particles: the cases in which MSA participates in nucleation (thus increasing ultrafine number) most closely match the Heintzenberg distributions, but we cannot conclude nucleation from MSA is the correct reason for improvement. Model–measurement comparisons with particle-phase MSA observed with a customized Aerodyne high-resolution time-of-flight aerosol mass spectrometer (AMS) from the ATom campaign show that cases with the MSA volatility parameterizations (both with and without nucleation) tend to fit the measurements the best (as this is the first use of MSA measurements from ATom, we provide a detailed description of these measurements and their calibration). However, no one model sensitivity case shows the best model–measurement agreement for both Heintzenberg and the ATom campaigns. As there are uncertainties in both MSA's behavior (nucleation and condensation) and the DMS emissions inventory, further studies on both fronts are needed to better constrain MSA's past, current, and future impacts upon the global aerosol size distribution and radiative forcing.

Partially (resp. fully) reversible adsorption of monoterpenes (resp. alkanes and cycloalkanes) to fused silica.

This work compares the extent of reversibility and the thermodynamics of adsorption (Kads, ΔG°ads) of room-temperature vapors of common environmentally relevant monoterpenes (α-pinene, β-pinene, limonene, and 3-carene) and industrially relevant cyclic and acyclic non-terpene hydrocarbons (cyclohexane, hexane, octane, and cyclooctane) to fused silica surfaces. Vibrational sum frequency generation spectroscopy carried out in the C-H stretching region shows negligible surface coverage-dependent changes in the molecular orientation of all species surveyed except for cyclohexane. The group of monoterpenes studied here distinctly exhibits partially reversible adsorption to fused silica surfaces compared to the group of non-terpene hydrocarbons, demonstrating a link between molecular structure and adsorption thermodynamics. The standard Gibbs free energy of adsorption is nonlinearly correlated with the equilibrium vapor pressure of the compounds surveyed.

Vapor pressure of methylammonium halides. Part II: Vapor pressure and standard entropy of methylammonium bromide

The equilibrium vapor pressure of methylammonium bromide was measured as a function of temperature in the range of 433–503 K. Standard enthalpy and entropy of sublimation of CH3NH3Br at 298.15 K and 1 atm were determined as (196.7 ± 2.8) kJ·mol−1 and (280.0 ± 5.6) J·mol−1 K−1, respectively. The measured value of sublimation enthalpy was found to be in agreement with that directly calculated from the available thermodynamic data. Standard entropy of the crystalline CH3NH3Br at 298.15 K was determined for the first time as (160.2 ± 5.6) J·mol−1 K−1.

Ongoing resurfacing of KBO Eris by volatile transport in local, collisional, sublimation atmosphere regime

Kuiper belt object (KBO) Eris is exceptionally bright with a greater visible geometric albedo than any other known KBO. Its infrared reflectance spectrum is dominated by methane, which should form tholins that darken the surface on timescales much shorter than the age of the Solar System. Thus one or more ongoing processes probably maintain its brightness. Eris is predicted to have a primarily nitrogen atmosphere that is in vapor pressure equilibrium with nitrogen-ice and is collisional (not ballistic). Eris’s eccentric orbit is expected to result in two atmospheric regimes: (1) a period near perihelion when the atmosphere is global (analogous to the atmospheres of Mars, Triton, and Pluto) and (2) a period near aphelion when only a local atmosphere exists near the warmest region (analogous to the atmosphere of Io). A numerical model developed to simulate Eris’s thermal and volatile evolution in the local atmosphere regime is presented. The model conserves energy, mass, and momentum while maintaining vapor pressure equilibrium. It is adaptable to other local, collisional, sublimation atmospheres, which in addition to Io and Eris, may occur on several volatile-bearing KBOs. The model was applied for a limiting case where Eris is fixed at aphelion and has an initial nitrogen-ice mass everywhere equal to the precipitable column of nitrogen in Pluto's atmosphere during the New Horizons encounter (the resultant mass if the Pluto atmosphere collapsed uniformly onto the surface). The model results indicate that (1) transport of nitrogen in the local, collisional, sublimation atmosphere regime is significant, (2) changes of Eris’s albedo or color from nitrogen transport may be observable, and (3) uniform collapse of a global, nitrogen atmosphere likely cannot explain Eris’s anomalous albedo in the present epoch. Seasonal volatile transport remains a plausible hypothesis to explain Eris’s anomalous albedo and geologic processes that renew Pluto’s brightest surfaces, such as convection and glaciation, may also be operating on Eris.

Ethanol and Methanol Burn Risks in the Home Environment.

Biofuel heaters and fireplaces have in recent years been introduced for indoor and outdoor use. Due to their simplicity, they are usually equipped with few or no safety features. Worldwide, incidents resulting in major skin burn injury and long hospitalization periods have occurred when using such biofuel units. The present study analyses the characteristics of the liquids ethanol and methanol to get a scientific background for understanding related accidents. The comparably heavy vapors, especially from ethanol, may generate a pillow of combustible gas in the vicinity of the unit, particularly in quiescent indoor air conditions. It is also revealed that these fuels represent a potential severe risk, since the equilibrium vapor pressures are close to the stoichiometric fuel–air composition at normal room temperatures. Selected incidents were reviewed to understand the mechanisms involved when severe burns were received by the users. It turns out that the most severe incidents were related to refilling operations and included ignition of the fuel container vapor phase. When ignited, the container gas phase expansion propelled burning fuel from the bottle or container onto the user or other persons in the vicinity. Similar incidents involving refilling methanol for chemistry demonstrations and ethanol for endodontic (dentistry) treatment were also studied and it was shown that these accidents followed similar accident mechanisms. It may be concluded that the main contributors to burn risk are the near-stoichiometric vapor pressure of these liquids at room temperature and the close proximity of the fuel container to burning fuel. Research needs and possible technical barriers are suggested to reduce this risk for the future.

The changes of brain activity associated with postoperative cognitive dysfunction after coronary bypass surgery

This chapter deals with atmospheric water and stone weathering. The first topic is the formation of acid rain in clouds (rainout) and the acidification of drops while they fall through the atmosphere (washout). The synergism between wet and dry deposition determines the formation of black and grey crusts or white areas on the monument's surface. The next topic concerns how rainwater penetrates the capillary fringe and internal porosity of stones and, in particular, the capillary suction and the physical and chemical remedies. The effects of salts and contaminants, the equilibrium vapour pressure over a solution, and the effects of sea spray on monument weathering are also considered. A list of popular errors and misunderstandings that should be avoided is discussed.

Structure and hydrogen absorption properties of Ti53Zr27Ni20(Pd,V) quasicrystals

The structure and hydrogen absorption properties of Pd and V doped TiZrNi quasicrystals were investigated in terms of the equilibrium vapor pressure of hydrogen, and the results were compared with those of undoped samples. Rapidly quenched Ti53Zr27Ni20 alloys formed quasicrystals and absorbed hydrogen H/M (hydrogen to host metal atom ratio) value of 1.79 at room temperature. This was attributed to their structure, which contains mostly tetrahedral interstitial sites that are chemically formed by atoms having a high affinity with hydrogen. However, the relatively low equilibrium vapor pressure of hydrogen, 0.14 Torr at 300 °C, prevents TiZrNi quasicrystals for the practical application on energy storage materials. To overcome this limitation, we replaced Ti with Pd and V to increase the vapor pressure of hydrogen and investigated the properties of hydrogen absorption behaviors. Results of XRD measurements revealed that the quasicrystal structure was maintained by the replacement of Ti with a maximum of 8 at. % of Pd and V. Total amounts of the absorbed hydrogen decreased from 1.33 to 1.06 and to 1.12 of the H/M values when the Ti was replaced by 8 at. % of Pd and V, respectively, at 300 °C. The pressure-composition-temperature data measured using an automatic gas-handling system revealed that the equilibrium vapor pressure increased from 0.14 to 0.21 and to 0.56 Torr at H/M value of 0.5 when Ti atoms were replaced by 8 at. % Pd, and V, respectively, without the appearance of an impurity phase. Our results demonstrate that the replacement of Ti with Pd and V is an effective method to increase the equilibrium vapor pressure of hydrogen without a phase transformation in a TiZrNi quasicrystal system.

Enhanced Solar Thermal Evaporation of Ethanol-Water Mixtures, through the Use of Porous Media.

A significant enhancement of solar irradiation induced evaporation of water, and ethanol-water mixtures, through the use of carbon foam based porous media, is demonstrated. A relationship between the consequent rate of mass loss, with respect to the equilibrium vapor pressure, dynamic viscosity, surface tension, and density, was developed to explain experimental observations. The evaporative heat loss was parametrized through two convective heat transfer coefficients-one related to the surface and another related to the vapor external to the surface. The work promotes a better understanding of thermal processes in binary liquid mixtures with applications ranging from phase separation to distillation and desalination.

High purity and crystalline thin films of methylammonium lead iodide perovskites by a vapor deposition approach

A procedure for the physical vapor deposition (PVD), in high-vacuum conditions, for high purity and crystalline methylammonium lead halide perovskite thin films is described. This procedure and methodology can be used to fabricate high-performance hybrid organic-inorganic materials that have recently emerged as the next-generation photovoltaic technology. PVD of methylammonium iodide and lead iodide to produce lead halide perovskite thin films was optimized according to the equilibrium vapor pressures of corresponding precursors evaporated from Knudsen effusion cells. Optical properties of perovskite thin films were characterized by UV-Vis-NIR and fluorescence spectroscopy. The high crystallinity of vapor-deposited thin films on glass, indium tin oxide, fluorine-doped tin oxide, and TiO2 surfaces was proved by scanning electron microscopy and X-ray diffraction. This vapor deposition approach leads to the production of very pure, crystalline and high stable perovskite thin films.

Bigleaf-An R package for the calculation of physical and physiological ecosystem properties from eddy covariance data.

We present the R package bigleaf (version 0.6.5), an open source toolset for the derivation of meteorological, aerodynamic, and physiological ecosystem properties from eddy covariance (EC) flux observations and concurrent meteorological measurements. A ‘big-leaf’ framework, in which vegetation is represented as a single, uniform layer, is employed to infer bulk ecosystem characteristics top-down from the measured fluxes. Central to the package is the calculation of a bulk surface/canopy conductance (Gs/Gc) and a bulk aerodynamic conductance (Ga), with the latter including formulations for the turbulent and canopy boundary layer components. The derivation of physical land surface characteristics such as surface roughness parameters, wind profile, aerodynamic and radiometric surface temperature, surface vapor pressure deficit (VPD), potential evapotranspiration (ET), imposed and equilibrium ET, as well as vegetation-atmosphere decoupling coefficients, is described. The package further provides calculation routines for physiological ecosytem properties (stomatal slope parameters, stomatal sensitivity to VPD, bulk intercellular CO2 concentration, canopy photosynthetic capacity), energy balance characteristics (closure, biochemical energy), ancillary meteorological variables (psychrometric constant, saturation vapor pressure, air density, etc.), customary unit interconversions and data filtering. The target variables can be calculated with a different degree of complexity, depending on the amount of available site-specific information. The utilities of the package are demonstrated for three single-level (above-canopy) eddy covariance sites representing a temperate grassland, a temperate needle-leaf forest, and a Mediterranean evergreen broadleaf forest. The routines are further tested for a two-level EC site (tree and grass layer) located in a Mediterranean oak savanna. The limitations and the ecophysiological interpretation of the derived ecosystem properties are discussed and practical guidelines are given. The package provides the basis for a consistent, physically sound, and reproducible characterization of biometeorological conditions and ecosystem physiology, and is applicable to EC sites across vegetation types and climatic conditions with minimal ancillary data requirements.

Experimental measurement of equilibrium vapour pressure of H2O/KCOOH (potassium formate) solution at high concentration

This paper presents the measurement of the equilibrium vapour pressure of H2O/KCOOH solution with a concentration in salt from 60 to 80% in the temperature range from 5 to 75 °C typical for desiccant application. The experimental measurements were performed in a VLE apparatus instrumented with a pressure gauge having a maximum uncertainty (k = 2) within ±35 Pa and a platinum resistance thermometer having a maximum uncertainty (k = 2) within ±0.05 K. A set of 40 experimental data points on H2O/KCOOH equilibrium vapour pressure was fully reported and compared with the unique other set of experimental data (Beyer and Steiger, 2010) available in the open literature and also with the estimation of a referenced chemical engineering property database (Aspen Plus®): a reasonable agreement was found in both the cases. A best-fitting regression model based on present set of data was also reported: the mean absolute percentage deviation between experimental and calculated data is 1.1%.

Vaporization behavior of an alkyl diphenyl ether and a commercial lubricant

The equilibrium vapor pressure as a function of temperature for an alkyl diphenyl ether with a vaporization coefficient significantly smaller than unity was characterized using the combined Langmuir free evaporation and mass loss Knudsen effusion technique. Results are compared using different cell designs and discrepancies, difficulties, and complications are discussed. The enthalpy and entropy of vaporization are estimated using the average temperature of the measurements.