Temperature Dependent Vapor Pressures of Chlorinated Catechols, Syringols, and Syringaldehydes

1999 ◽  
Vol 44 (2) ◽  
pp. 200-202 ◽  
Author(s):  
Ying Duan Lei ◽  
Frank Wania ◽  
Wan Ying Shiu ◽  
David G. B. Boocock
Keyword(s):  
Vapor Pressures ◽  
Temperature Dependent ◽  
Chlorinated Catechols

THE EFFECT OF WATER VAPOR UPON THE DEHYDRATION OF CaSO4•2H2O

1964 ◽  
Vol 42 (4) ◽  
pp. 792-801 ◽  
Author(s):  
H. G. McAdie
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Water Vapor Pressure ◽  
Vapor Pressures ◽  
Heat Of Solution ◽  
Temperature Dependent ◽  
Exponential Factor ◽  
Fixed Composition ◽  
Kinetics Of ◽  
Partial Water

Kinetics of the two-stage dehydration of CaSO4•2H2O have been examined under controlled water vapor pressures up to one atmosphere. For both stages water vapor initially accelerated the rate of dehydration and subsequently retarded it. Separate, temperature-dependent water vapor pressures were noted above which each stage could be suppressed.The hemihydrate was clearly defined either as a change in the rate of weight loss during dehydration or, at higher water vapor pressures, as a fixed composition. The heat of solution of the hemihydrate increased linearly with the partial water vapor pressure present during its formation, but was independent of the formation temperature over the range studied. Activation energy and pre-exponential factor for the dihydrate → hemihydrate process also increased linearly with water vapor pressure. Hemihydrates produced at the extremes of water vapor pressure corresponded to the α- and β-modifications, as defined thermodynamically, and the production of a hemihydrate series with properties varying linearly from one extreme to the other is discussed.

scholarly journals No anomalous supersaturation in ultracold cirrus laboratory experiments

2020 ◽  
Vol 20 (2) ◽  
pp. 1089-1103 ◽  
Author(s):  
Benjamin W. Clouser ◽  
Kara D. Lamb ◽  
Laszlo C. Sarkozy ◽  
Jan Habig ◽  
Volker Ebert ◽  
...  
Keyword(s):  
Vapor Pressure ◽  
Cirrus Clouds ◽  
Vapor Pressures ◽  
Saturation Vapor Pressure ◽  
Temperature Dependent ◽  
Hexagonal Ice ◽  
Radiative Impact ◽  
Aerosol Chamber ◽  
Saturation Vapor

Abstract. High-altitude cirrus clouds are climatically important: their formation freeze-dries air ascending to the stratosphere to its final value, and their radiative impact is disproportionately large. However, their formation and growth are not fully understood, and multiple in situ aircraft campaigns have observed frequent and persistent apparent water vapor supersaturations of 5 %–25 % in ultracold cirrus (T<205 K), even in the presence of ice particles. A variety of explanations for these observations have been put forth, including that ultracold cirrus are dominated by metastable ice whose vapor pressure exceeds that of hexagonal ice. The 2013 IsoCloud campaign at the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud and aerosol chamber allowed explicit testing of cirrus formation dynamics at these low temperatures. A series of 28 experiments allows robust estimation of the saturation vapor pressure over ice for temperatures between 189 and 235 K, with a variety of ice nucleating particles. Experiments are rapid enough (∼10 min) to allow detection of any metastable ice that may form, as the timescale for annealing to hexagonal ice is hours or longer over the whole experimental temperature range. We show that in all experiments, saturation vapor pressures are fully consistent with expected values for hexagonal ice and inconsistent with the highest values postulated for metastable ice, with no temperature-dependent deviations from expected saturation vapor pressure. If metastable ice forms in ultracold cirrus clouds, it appears to have a vapor pressure indistinguishable from that of hexagonal ice to within about 4.5 %.

New system for temperature dependent measurements of vapor pressures of substances in the range below 1 pascal

1985 ◽  
Vol 93 ◽  
pp. 295-298 ◽  
Author(s):  
W.-D. Emmerich ◽  
H. Pfaffenberger
Keyword(s):  
Vapor Pressures ◽  
Temperature Dependent ◽  
New System

scholarly journals Vapor Pressure Mapping of Ionic Liquids and Low-Volatility Fluids Using Graded Isothermal Thermogravimetric Analysis

2019 ◽  
Vol 3 (2) ◽  
pp. 42 ◽  
Author(s):  
Sudhir Ravula ◽  
Nathaniel E. Larm ◽  
Mohammad A. Mottaleb ◽  
Mark P. Heitz ◽  
Gary A. Baker
Keyword(s):  
Ionic Liquids ◽  
Vapor Pressure ◽  
Critical Evaluation ◽  
Deep Eutectic Solvents ◽  
Vapor Pressures ◽  
Temperature Dependent ◽  
Pressure Mapping ◽  
Sustainable Implementation ◽  
Alkane Chain ◽  
T Values

One of the hallmarks of ionic liquids (ILs) and a critical part of their sustainable implementation is their low volatility, although statements in this regard are frequently made in the absence of a critical evaluation. Although it is generally accepted that conventional ILs exhibit significantly reduced vapor pressures relative to common organic solvents, glib statements about ILs having zero volatility can no longer be abided, even if a concrete temperature-dependent vapor pressure, Pvap(T), framework for placement of IL performance has not yet been established. In this communication, Pvap(T) values of 30 illustrative low-volatility fluids—including representative imidazolium-, ammonium-, and pyrrolidinium-based aprotic ILs; examples of protic, polymeric, and di-cationic ILs; as well as deep eutectic solvents (DESs) and glycols—were determined using a simple, convenient, and reproducible isothermal thermogravimetric method. Guided by this “vapor pressure map”, observed trends can be discussed in terms of anion basicity, cation geometry, alkane chain length, hydrogen bonding strength, and van der Waals forces, providing a context for the placement of theoretical and experimental vapor pressures gleaned in future IL and DES studies.

(111) Monocrystalline Nickel Films

1972 ◽  
Vol 30 ◽  
pp. 512-513
Author(s):  
T.E. Pratt ◽  
R.W. Vook
Keyword(s):  
Film Thickness ◽  
Deposition Rate ◽  
Room Temperature ◽  
Narrow Range ◽  
High Vacuum ◽  
Residual Pressure ◽  
Temperature Dependent ◽  
Deposition Parameters ◽  
Transmission Electron ◽  
Substrate Temperatures

(111) oriented thin monocrystalline Ni films have been prepared by vacuum evaporation and examined by transmission electron microscopy and electron diffraction. In high vacuum, at room temperature, a layer of NaCl was first evaporated onto a freshly air-cleaved muscovite substrate clamped to a copper block with attached heater and thermocouple. Then, at various substrate temperatures, with other parameters held within a narrow range, Ni was evaporated from a tungsten filament. It had been shown previously that similar procedures would yield monocrystalline films of CU, Ag, and Au.For the films examined with respect to temperature dependent effects, typical deposition parameters were: Ni film thickness, 500-800 A; Ni deposition rate, 10 A/sec.; residual pressure, 10-6 torr; NaCl film thickness, 250 A; and NaCl deposition rate, 10 A/sec. Some additional evaporations involved higher deposition rates and lower film thicknesses.Monocrystalline films were obtained with substrate temperatures above 500° C. Below 450° C, the films were polycrystalline with a strong (111) preferred orientation.

Scanning electron microscopy of plant cells using a variable-pressure SEM and cryogenic techniques

1993 ◽  
Vol 51 ◽  
pp. 260-261
Author(s):  
M. Yamada ◽  
K. Ueda ◽  
K. Kuboki ◽  
H. Matsushima ◽  
S. Joens
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Saturated Vapor ◽  
Plant Cells ◽  
Variable Pressure ◽  
Specimen Preparation ◽  
Operating Pressure ◽  
Vapor Pressures ◽  
Low Temperature Microscopy ◽  
Scanning Electron

Use of variable Pressure SEMs is spreading among electron microscopists The variable Pressure SEM does not necessarily require specimen Preparation such as fixation, dehydration, coating, etc which have been required for conventional scanning electron microscopy. The variable Pressure SEM allows operating Pressure of 1˜270 Pa in specimen chamber It does not allow microscopy of water-containing specimens under a saturated vapor Pressure of water. Therefore, it may cause shrink or deformation of water-containing soft specimens such as plant cells due to evaporation of water. A solution to this Problem is to lower the specimen temperature and maintain saturated vapor Pressures of water at low as shown in Fig. 1 On this technique, there is a Published report of experiment to have sufficient signal to noise ratio for scondary electron imaging at a relatively long working distance using an environmental SEM. We report here a new low temperature microscopy of soft Plant cells using a variable Pressure SEM (Hitachi S-225ON).

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