Unsaturated Vapor Research Articles

Moist convection and the injection of volcanic ash into the atmosphere

If unsaturated water vapor is carried upward by a volcanic eruption column, it may eventually become saturated owing to the decrease in temperature of the column as it expands through decompression and transfers heat to entrained air. Heat released as a result of the subsequent condensation of water vapor causes the air within the column to expand. We show that this increases the buoyancy and therefore the total height of rise of the column. The increase in height is significant in relatively small sub‐Plinian and Strombolian eruptions in which mass eruption rates lie in the range 103 to 106 kg/s. In such eruptions, the latent heat released as the entrained water vapor condenses may provide the main source of heat which drives the ash and clasts upward. The height of rise then becomes relatively insensitive to the mass flux erupted at the vent and depends primarily upon the vapor loading of the atmosphere. In a moist atmosphere, ash may rise several kilomtres higher than in an eruption of comparable strength in a dry environment. Moist convection leads to much wider ash dispersal, particularly from very small eruptions. Subsequently, rain flushing of ash from umbrella clouds may result from the water which forms through the condensation of entrained vapor; the ash provides natural condensation nuclei for some of this entrained vapor, whose mass may be much greater than that of the ash. In small columns (< 15km), the dominant source of water for the formation of accretionary lapilli may be derived from the entrained vapor. In larger Plinian eruptions (> 107 kg/s), the latent heat released by condensation of vapor is relatively small in comparison with the thermal energy provided by the hot clasts and therefore moisture has no significant effect upon the eruption column dynamics; furthermore, the mass of water vapor originating from the erupted volatiles is usually comparable to, or greater than, that entrained from the ambient air. Our model also shows that, if the erupting mixture becomes buoyant, then the eruption columns associated with phreatomagmatic eruptions ascend nearly as high as Plinian columns with the same mass eruption rate. This is because the water which is vaporized by the hot ash at the source, condenses higher in the column and thereby restores its latent heat to the ascending ash.

Si-C fiber prepared from polycarbosilane cured without oxygen

A new curing method for polycarbosilane was developed. In this method, halogenated hydrocarbon or unsaturated hydrocarbon vapor was used as curing agent. Si-C fiber with a small amount of oxygen was prepared from polycarbosilane fiber cured without introducing oxygen. The structure and the properties of the fiber are discussed in comparison with Si-C-O fiber obtained from thermal-oxidized polycarbosilane fiber. Using the new curing method, the thermal stability of the Si-C fiber was far improved with respect to that of conventional Si-C-O fiber.

Thermodynamic properties of unsaturated vapour and liquid states from a cubic equation of state: Supercritical and compressed liquid regions

The applicability of the Lielmezs—Merriman (LM) modification of the Peng—Robinson equation of state has been tested for supercritical and compressed liquid regions. The predicted thermodynamic properties (pressure, volume, temperature, departure functions: Δ H, Δ A, Δ S, Δ G, Δ U) and fugacity of the pure compounds have been compared with experimental data and with results calculated by the Soave—Redlich—Kwong (SRK) and Peng—Robinson (PR) equations of state.

Thermodynamic properties of unsaturated vapour and liquid states from a cubic equation of state: saturated and subcritical regions

The Lielmezs-Merriman (LM)-modification of the Peng-Robinson (PR) equation of state has been applied to the entire P- V- T surface except the critical iostherm. The applicability of this modification has been presently tested for the saturated and subcritical regions by comparing its predictions of thermodynamic properties (vapour pressure, liquid and vapour volumes, departure functions - Δ H, Δ A, Δ G, Δ S and Δ U, and fugacity) of pure compounds with the experimental data and calculations made by the Soave-Redlich-Kwong (SRK) and Peng-Robinson (PR) equations of state.

Mass-spectrometric study of gaseous (gallium + chlorine); molar enthalpies of formation of Ga 2Cl 4 and Ga 2Cl 2

A mass-spectrometric Knudsen-cell study was performed on unsaturated vapours from the vaporization of GaCl 3(s) and on saturated vapours from the vaporization of GaCl 2(s). Ga 2Cl 4(g) and Ga 2Cl 2(g) molecules were identified and their molar enthalpies of formation were determined as, respectively, −(570 ± 15) kJ·mol −1 and −(220 ± 19) kJ·mol −1. Attempts to measure the thermodynamic stability of GaCl 2(g) were not successful since this gaseous species appears as the less stable one in (gallium + chlorine).

Use of modified martin equation for unsaturated vapour and liquid states

The Chakma-Lielmezs-Islam modification of the Martin equation of state ▪ where a( T)= a( P c, T c)α( T ∗) in which ▪ α( T ∗) = 1+ pT ∗q has been extended to unsaturated liquid and vapour states by means of a correcting function C f, such that the α( T ∗) term becomes α( T ∗) = 1+ pC f T ∗q The proposed extension has been successfully compared with the results obtained by means of the original Martin equation of state, the Chakma-Lielmezs-Islam modification of the Martin equation for the saturated states, and the Soave-1972 modification of the Redlich-Kwong equation of state.

Application of modified redlich-kwong equation for unsaturated vapour and liquid states

The Lielmezs-Howell-Campbell modification of the Redlich-Kwong equation of state ▪ where a( T)=a( T c, P c)α( T ∗) and α( T*)=1+ p( T ∗) q has been extended to include unsaturated states in terms of a correcting function C f such that the a( T*) term becomes α( T ∗)=1+ pC f( T ∗) q A comparison has been made for pure substances in the vapour state (14 compounds, 1330 data point pairs) and in the liquid state (12 compounds, 827 data point pairs) with the results obtained by means of this work and the Soave 1972 modification of the Redlich-Kwong equation and Lee-Kesler equation of state.

ChemInform Abstract: Equilibrium Measurements in the System Se/O/Cl.

AbstractInvestigation of the evaporation and thermal decomposition behaviour by total pressure measurements over the condensed phases and in the unsaturated vapour show the composition Cl/Se = 2 to have the lowest and Cl/Se = 4 to have the highest total pressure of the system Se/Cl.

Application of the modified van der waals equation for unsaturated vapour and liquid states

The Law-Lielmezs (L-L) modification of the Van der Waals equation of state: P = RT/( V-b)- a( T)/ V 2 where: a( T) = a( T c)· a( T c·a(T ∗) and: a( T ∗) = 1 + pT ∗ q has been extended to include unsaturated states in terms of a correcting function C f(such that the α( T ∗) term becomes: a( T ∗) = 1 + p C f T ∗ q The proposed extension has been compared with the results obtained by the use of the original Van der Waals equation of state.

A compositional multiphase model for groundwater contamination by petroleum products: 1. Theoretical considerations

A mathematical model is developed to describe the fate of hydrocarbon constituents of petroleum products introduced to soils as an immiscible liquid from sources such as leaking underground storage tanks and ruptured pipelines. The problem is one of multiphase transport (oil (immiscible), air, and water phases) of a reactive contaminant with constituents such as benzene, toluene, and xylene found in refined petroleum products like gasoline. In the unsaturated zone, transport of each constituent can occur as a solute in the water phase, vapor in the air phase, and as an unaltered constituent in the oil phase. Additionally, the model allows for adsorption. Molecular transformations, microbially mediated or abiotic, are incorporated as sink terms in the conservation of mass equations. An equilibrium approximation, applicable to any immiscible organic contaminant is applied to partition constituent mass between the air, oil, water, and adsorbed phases for points in the region where the oil phase exists. Outside the oil plume the equilibrium approximation takes on a simpler form to partition constituent mass between the air, water, and adsorbed phases only. Microbial degradation of petroleum products is first discussed in a general model, then the conservation of mass equation for oxygen is incorporated into the analysis which takes advantage of the key role played by oxygen in the metabolism of hydrocarbon utilizing microbes in soil environments. Approximations to two subproblems, oil plume establishment in the unsaturated zone, and solute and vapor transport subsequent to immiscible plume establishment are then developed from the general model.

収穫後のキュウリ果実における果肉の呼吸と気体蓄積の関係

Cucumber fruits were stored for 9 days at 20°C under unsaturated vapour conditions. The rate of respiration in the pericarp tissue, as measured by O2 uptake, showed a rise following an initial decrease. The rise was associated with an increase in gas pressure and the formation of gas spaces. Respiration rate reached a peak earlier and then decreased faster than the gas pressure did. Gas spaces developed steadily in spite of a decline in respiration rate and gas pressure. Itsuggested that a decrease in membrane permeability might be involved in the development of gas spaces.In fruits stored at 7.5°C, gas pressure in the tissue did not rise and the respiration rate was constantly low when measured at 7.5°C. However, when measured at 20°C, the respiration rate changed in almost the same way as in fruits stored at 20°C.

Effect of hexane of the radiothermoluminescence of polyethylene

The authors have investigated the change in the curve of radiothermoluminescence of PE as a function of the time of holding of the polymer in liquid hexane or its unsaturated vapours at room temperature and different pressures. With increase in the content of hexane in the polymer the intensity of radiothermoluminescence diminishes and the temperature of the high temperature maximum falls. These changes are reversible and associated respectively with change in the conditions of radiolysis in the amorphous regions of the polymer and with its plasticizing action on the amorphous regions. Removal of hexane from the polymer restores the intensity and position of the maximum. The holding of PE in liquid hexane leads to irreversible changes in the curve of radiothermoluminescence. The irreversible action of hexane is connected with washing out of impurities from the polymer.

Volume and specific gravity of cucumber fruits as affected by moisture condition after harvest

When cucumber fruits were stored at temperatures of 10, 20 and 30°C, in conditions that were so wet that they were able to absorb water freely through the skin, they maintained a constant specific gravity which was a hhigh as it had been at the time of picking, with a hyperbolic increase in volume. After removal to unsaturated vapour conditions at 20°C, their volume and specific gravity changed in a similar way to these of fruit which had not been in wet storage. Storage in humid conditions at 10°C resulted in almost constant specific gravity and volume, but storage at 20 or 30°C produced a gradual increase in volume as well as a decrease in specific gravity of fruits, in spite of the fresh weight showing little change. After removal of these fruits to unsaturated vapour conditions, the volume and specific gravity changed at a much faster rate with their specific rates having a peak. The shorter the humid storage, the higher the peak. The decrease in the specific gravity of picked cucumber fruits was discussed in relation to the presence of water stress.

Effect of parthenocarpy, peeling and fruit age on the changes in volume and specific gravity of cucumber fruits during storage at 20°C

Either parthenocarpically grown, peeled or at any stage of picking, cucumber fruits showed a tendency to increase in volume and decrease in specific gravity while they were stored under unsaturated vapour pressure at 20°C. The amount of change varied according to the treatment. Recovery from a flaccid appearance occurred in all fruit except very young ones. In those fruits the incipient recovery from wilting, an increase in volume and a decrease in specific gravity, coincided. Parthenocarpic fruits showed an increase in volume at almost the same rate in any transverse quarter of a fruit, in contrast to the pollinated ones in which the most distal quarter enlarged more than the other parts. Pithy appearance of the fruit wall was evenly distributed through a parthenocarpic fruit to a moderate degree, but at the proximal half of a pollinated one it was severe.

Vaporization of magnetite and wüstite in ultra-high neutral vacuum with mass-spectrometric analysis of gaseous phase

The vaporization of magnetite at 1373 to 1673 K, and of wüstite of various compositions at 1543 to 1573 K was investigated with the help of an omegatron type mass-spectrometer, the method having been modified to carry out quantitative measurements of oxygen partial pressures greatly diminished due to by-pumping taking place in vacuum systems. In accord with theoretical considerations, magnetite in high neutral vacuum at temperatures lower than about 1630 K dissociates congruently with the evolution of oxygen and unsaturated iron vapor, without the formation of wüstite. Wüstite of almost any composition decomposes in these conditions with the preferential loss of iron and converts spontaneously into magnetite. The single-phase magnetite dissociation pressure proper p′(O 2) is therefore greater than the equilibrium one p″(O 2) for the two-phase system magnetite + wüstite at T less than about 1630 K. Standard Gibbs free energy changes of the processes investigated and the iron activity in magnetite are computed.

The Hot Corrosion of CoCrAlY Turbine Blade Coatings by Na2 SO 4 and Vaporous NaCl

To investigate whether unsaturated vapor can have effects in hot corrosion, experiments have been conducted wherein specimens cut from turbine blades were sprayed with , and then exposed in a tube furnace at 1625°F under an air stream containing (1/20 the saturation pressure at 1625°F) with inspection and sulfate recoating every 24 hr. Several chloride effects were evident within 100–200 hr under this test regime. These included: (i) increasing the vaporization rate; (ii) causing formation of a spalling surface oxide; (iii) removing Cr by the formation of volatile complexes which apparently contain S and Na as well as Cr and Cl; (iv) interacting with Ti at the coatingblade interface; and (v) accelerating sulfidation‐oxidation attack upon the coating. This latter attack occurs when both blade metal and coating are exposed simultaneously to the sulfate, as at a cut edge. It is confined to the layer, and consists of a sulfidation front and oxidation front which traverse the coating successively, effectively stripping the coating from the supposedly less resistant blade alloy. Sodium chloride increases the kinetics of attack and appears to promote the formation of over as the predominate sulfide phase. A search for chloride was made by energy‐dispersive x‐ray analysis in the SEM, but despite the obvious influences, no trace of chloride was found except possibly in the Ti interaction. The individual effects are discussed in relation to earlier research results and as they may pertain to shipboard hot corrosion.

Solvent vapor pressure effects in a supported liquid phase catalyst system. Oxidation of ethylene to acetaldehyde.

The performances of a supported liquid phase catalyst are investigated under unsaturated vapor pressures of the solvent, in contrast with the conditions of previous studies where the presaturated reacting gas mixtures were applied for preventing vaporization of the solvent. In the present work, oxidation of ethylene to produce acetaldehyde is carried out by the catalyst system of aqueous solution of PdCI2 and CuCl2 supported on porous particles. It is found that the reaction takes place at much higher rates when the reactant gas is not saturated with the water solvent than when it is saturated. The increase in activity of the reaction is considered to be brought about by the dual features of mass transfer and chemical reaction. The effectiveness factor of the catalyst is, in the case of unsaturated gas, increased by rapid gas diffusion through the empty space in the pore volume which otherwise is filled with liquid. The activity for the unsaturated gas becomes sometimes about two orders of magnitude greater than even the mass transfer free activity for the saturated gas. An attempt is made to propose a reaction model which explains both qualitatively and quantitatively the kinetic data obtained experimentally under the unsaturated conditions.

Method for the computer calculation of the thermodynamic parameters of complexation reactions from tensimetric data

1. A method has been proposed for the computer calculation of the thermodynamic parameters of complexation reactions based on tensimetric measurements in unsaturated vapors. The method makes it possible to reveal reactions taking place in the gaseous phase and their stoichiometry and to determine the corresponding parameters ΔH t o and ΔS T o . 2. The method considered may be used in investigations not only of complexation reactions but also of other types of gas-phase reactions in which one product forms during an interaction between two substances.

Observation of the nu-squared band of PH3 in the atmosphere of Saturn

Observation of the $nu$$sub 2$ band of PH$sub 3$ in the Saturnian atmosphere represents the first positive identification of this compound in the planet. The observed spectrum is consistent with line formation in the planet's troposphere where the dominant sources of opacity are molecular hydrogen and unsaturated phosphine vapor. (AIP)

The accelerated ageing of plastic encapsulated semiconductor devices in environments containing a high vapour pressure of water

Early indications that water vapour accelerates the degradation of plastic encapsulated semiconductor devices have been pursued further with tests at high, unsaturated vapour-pressures. Equipment has been developed to apply unsaturated water vapour at pressures greater than one atmosphere to the devices and the results have shown a well ordered relationship between vapour pressure and time to failure, which may be extrapolated to the environmental conditions pertaining to use. The validity of an accelerated test using the vapour pressure of water is supported by experimental observations and provides the basis for a simple, short-term test for assessing the reliability of plastic encapsulated semiconductor devices intended for long-life applications.