ISOTHERMS OF SULPHUR HEXAFLUORIDE IN THE CRITICAL TEMPERATURE REGION

1951 ◽  
Vol 29 (8) ◽  
pp. 699-714 ◽  
Author(s):  
K. E. MacCormack ◽  
W. G. Schneider
Keyword(s):  
Critical Temperature ◽  
Temperature Region ◽  
Critical Density ◽  
Sulphur Hexafluoride ◽  
Small Temperature ◽  
Liquid Meniscus ◽  
Temperature Range ◽  
Horizontal Portion ◽  
Theoretical Considerations ◽  
Finite Slope

Measurements of the P-V isotherms for sulphur hexafluoride in a small temperature range of approximately 1.5°C. in the critical region have been made to determine the validity of some theoretical considerations recently proposed. No evidence has been found to support the postulates of Mayer with respect to anomalous second order transitions over a finite temperature range above the temperature of disappearance of a liquid meniscus designated Tm. All isotherms above the latter are found to have a finite slope and it is not possible to conclude that the Tm isotherm has a finite horizontal portion or "flat top". These conclusions are borne out by the nature of the isometrics which have been plotted and discussed qualitatively in relation to the existing theories.The temperature of meniscus disappearance Tm is estimated to be 45.547 ± 0.003°C. and at the previously determined critical density (1) of 0.7517 gm./cm.3 the corresponding pressure is found to be 37.113 ± 0.003 atm. The critical density was found to be approximately 0.73 gm./cm.3

Critical constants and density dependence of the Lorenz–Lorentz coefficient for germane

1978 ◽  
Vol 56 (9) ◽  
pp. 1140-1141 ◽  
Author(s):  
P. Palffy-Muhoray ◽  
D. Balzarini
Keyword(s):  
Critical Temperature ◽  
Density Dependence ◽  
Experimental Error ◽  
Critical Density ◽  
Coexistence Curve ◽  
Index Of Refraction ◽  
Density Range ◽  
Temperature Range ◽  
Critical Constants

The index of refraction at 6328 Å has been measured for germane in the density range 0.15 to 0.9 g/cm3. The temperature and density ranges over which measurements are made are near the coexistence curve. The coefficient in the Lorenz–Lorentz expression, [Formula: see text], is constant to within 0.5% within experimental error for the temperature range and density range studied. The coefficient is slightly higher near the critical density. The critical density is measured to be 0.503 g/cm3. The critical temperature is measured to be 38.92 °C.

scholarly journals SOUND VELOCITY AND SOUND ABSORPTION IN THE CRITICAL TEMPERATURE REGION

1951 ◽  
Vol 29 (3) ◽  
pp. 243-252 ◽  
Author(s):  
W. G. Schneider
Keyword(s):  
Critical Temperature ◽  
Liquid Phase ◽  
Sound Velocity ◽  
Temperature Region ◽  
Temperature Range ◽  
Maximum Value ◽  
Increasing Temperature ◽  
Very High ◽  
High Absorption ◽  
Liquid And Vapor Phases

The velocity and absorption of ultrasound (600 kc.) has been measured throughout the critical temperature region of sulphur hexafluoride. Measurements were carried out for the coexisting liquid phase and vapor phase below Tc, and for the supercritical gas, and simultaneously, observations of the meniscus behavior in the neighborhood of Tc were made. The sound velocity for both liquid and vapor phases below Tc decreased with increasing temperature and became equal at Tc, the velocity at this point being 121.5 m. per sec. In the temperature range from 0.6° below Tc to Tc the velocity in the vapor was greater than that in the liquid. A very high absorption of sound was observed, having a maximum value at Tc and extending over a temperature range of approximately 1°. In the temperature range from Tc to 0.6° below Tc, the absorption in the liquid phase was greater than that in the vapour.

PHASE EQUILIBRIA IN THE TWO COMPONENT SYSTEM, ETHYLENE-PROPYLENE, IN THE CRITICAL TEMPERATURE REGION

1941 ◽  
Vol 19b (10) ◽  
pp. 231-240 ◽  
Author(s):  
W. G. Schneider ◽  
O. Maass
Keyword(s):  
Critical Temperature ◽  
Phase Equilibria ◽  
Temperature Region ◽  
Critical Density ◽  
Dispersion Theory ◽  
Two Component System ◽  
Ethylene Propylene ◽  
Liquid Dispersion ◽  
Persistence Theory ◽  
Mass Volume

Phase equilibria measurements have been made for a 1:1 ethylene-propylene system in the critical temperature region by means of an equilibrium apparatus described by Holder and Maass (3). The critical density of the system was found to be 0.230 gm. per cc. and the critical temperature 58.30° ± 0.05 °C. For mass-volume ratios greater than 0.230, at constant volume, the temperature of liquid disappearance was lower than 58.30 °C., while for mass-volume ratios less than 0.230, the temperature of liquid disappearance was higher than 58.30 °C. With stirring, the phase compositions and phase densities of the liquid and vapour phases were shown to become equal at the critical temperature, whereas in the absence of stirring the attainment of equilibrium is slow and uncertain. The results are discussed on the basis of the liquid persistence theory (5), and the vapour-liquid dispersion theory (1, 9).

AN INVESTIGATION OF THE HYDROGEN-CHLORIDE-PROPYLENE REACTION IN THE REGION OF THE CRITICAL TEMPERATURE

1938 ◽  
Vol 16b (12) ◽  
pp. 453-467 ◽  
Author(s):  
C. H. Holder ◽  
O. Maass
Keyword(s):  
Critical Temperature ◽  
Temperature Coefficient ◽  
Hydrogen Chloride ◽  
Liquid State ◽  
Critical Density ◽  
Positive Temperature ◽  
Gaseous State ◽  
Gaseous Mixtures ◽  
Reaction Velocity ◽  
Temperature Range

The reaction between hydrogen chloride and propylene has been studied in the gaseous state above the critical temperature and in the liquid state just below the critical temperature. Pressures were used such that the density of the gaseous mixtures could be made as great as the density of the liquid mixture at some temperature.The rate of reaction above the critical temperature increases slowly with increasing pressure until a certain critical density is attained, after which the rate increases rapidly. In the liquid state the reaction has a positive temperature coefficient except for a 25° temperature range just below the critical temperature. In this region there is a rapid decrease in density of the medium with rise in temperature and a negative temperature coefficient occurs.The density of the liquid reactants at a number of temperatures just below the critical temperature (here defined as the temperature where the visible meniscus disappears) has been reproduced above the critical temperature for a small temperature range. The reaction velocity data obtained under these conditions show a minimum in passing through the critical temperature region.The above results have been interpreted on the basis of a "structure" characteristic of the liquid state which favors higher reaction velocity and which may exist above the critical temperature at sufficiently high densities.

scholarly journals Fast-Scanning Chip-Calorimetry Measurement of Crystallization Kinetics of Poly(Glycolic Acid)

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 891
Author(s):  
Yongxuan Chen ◽  
Kefeng Xie ◽  
Yucheng He ◽  
Wenbing Hu
Keyword(s):  
Crystallization Kinetics ◽  
Temperature Region ◽  
Glycolic Acid ◽  
Crystal Nucleation ◽  
Side Group ◽  
Half Time ◽  
Temperature Range ◽  
Chip Calorimetry ◽  
Kinetics Of ◽  
Fast Scanning Chip Calorimetry

We report fast-scanning chip-calorimetry measurement of isothermal crystallization kinetics of poly(glycolic acid) (PGA) in a broad temperature range. We observed that PGA crystallization could be suppressed by cooling rates beyond -100 K s−1 and, after fast cooling, by heating rates beyond 50 K s-1. In addition, the parabolic curve of crystallization half-time versus crystallization temperature shows that PGA crystallizes the fastest at 130 °C with the minimum crystallization half-time of 4.28 s. We compared our results to those of poly(L-lactic acid) (PLLA) with nearby molecular weights previously reported by Androsch et al. We found that PGA crystallizes generally more quickly than PLLA. In comparison to PLLA, PGA has a much smaller hydrogen side group than the methyl side group in PLLA; therefore, crystal nucleation is favored by the higher molecular mobility of PGA in the low temperature region as well as by the denser molecular packing of PGA in the high temperature region, and the two factors together decide the higher crystallization rates of PGA in the whole temperature range.

A STUDY OF THE COEXISTENCE OF THE LIQUID AND GASEOUS STATES OF AGGREGATION IN THE CRITICAL TEMPERATURE REGION. ETHYLENE

1940 ◽  
Vol 18b (4) ◽  
pp. 118-121 ◽  
Author(s):  
S. N. Naldrett ◽  
O. Maass
Keyword(s):  
Critical Temperature ◽  
Temperature Region ◽  
Previous Investigation ◽  
Coexistence Curve

The coexistence curve of ethylene has been determined in a manner similar to that described in a previous investigation on ethane (9). It is found to lie entirely within the coexistence curve determined by P-V-T methods by other investigators (6). This is considered to be evidence for the formation of a dispersion of liquid and vapour before the critical temperature is reached. The term "critical dispersion temperature" is suggested for the temperature at the apex of the coexistence curve determined by the disappearance of the meniscus in a bomb shaken in the manner described in this investigation. The apex of the curve determined by P-V-T methods is the true critical temperature, beyond which liquid is not stable. The classical critical temperature, determined by the disappearance of the meniscus in a stationary bomb, is an indefinite point between these two.

scholarly journals The system CaO-MgO-FeO-SiO2 and its bearing on the origin of ultrabasic and basic rocks

1960 ◽  
Vol 32 (249) ◽  
pp. 459-470 ◽  
Author(s):  
Peter J. Wyllie
Keyword(s):  
Experimental Data ◽  
Temperature Interval ◽  
Wide Temperature Range ◽  
Multicomponent System ◽  
Small Temperature ◽  
Experimental Procedure ◽  
Temperature Range ◽  
A Value ◽  
Basaltic Magmas ◽  
Basic Rocks

SummaryExperimental data in the system CaO-MgO-FeO-SiO2 suggest that there may be a plateau on the liquidus and solidus of the multicomponent system basalt-peridotite. If this is so, fusion of peridotite would produce only basaltie magmas over a wide temperature range; when the temperature reached a value such that the liquid crossed the threshold of the plateau, there would be a rapid increase in the amount of fusion for small temperature increases, with the formation of picritic magmas; basaltic magmas containing suspended forsteritic olivine crystals could dissolve them if the temperature rose slightly above that of the plateau threshold; a high proportion of a picritic magma would crystallize in a small temperature interval, with the precipitation of forsteritic olivine that was only slightly zoned. These possibilities are compared with current theories, and it is concluded that several petrological axioms may require critical re-examination. An experimental procedure is outlined to determine the shape of the liquidus and solidus in the basalt-peridotite system.

SOLUBILITY MEASUREMENTS IN THE REGION OF THE CRITICAL TEMPERATURE

1940 ◽  
Vol 18b (9) ◽  
pp. 293-304 ◽  
Author(s):  
C. H. Holder ◽  
O. Maass
Keyword(s):  
Critical Temperature ◽  
Temperature Region ◽  
Pressure Change ◽  
Liquid Phases

An apparatus for the measurement of solubility in the critical temperature region has been constructed. This apparatus permits samples to be taken from the upper and lower regions (vapour and liquid phases, if below critical temperature) of a system without volume or pressure change so that equilibrium is not disturbed.Solubility measurements of hexachloroethane in ethane have been made through the critical temperature region.

Sign in / Sign up

Export Citation Format

Share Document