MEASUREMENT OF VISCOSITY IN THE CRITICAL REGION. ETHYLENE

1940 ◽  
Vol 18b (5) ◽  
pp. 128-137 ◽  
Author(s):  
S. G. Mason ◽  
O. Maass
Keyword(s):  
Critical Temperature ◽  
Critical Region ◽  
Critical Pressure ◽  
New Method

A precision oscillating disc viscometer has been constructed with a view to studying viscosities of systems at the critical temperature and critical pressure. A new method of computing logarithmic decrements is described and a number of results obtained with ethylene are presented. Of particular interest is the transition in viscosity on an isochore through the critical temperature.

PVT MEASUREMENTS IN THE CRITICAL REGION OF XENON

1954 ◽  
Vol 32 (2) ◽  
pp. 98-112 ◽  
Author(s):  
H. W. Habgood ◽  
W. G. Schneider
Keyword(s):  
Critical Temperature ◽  
Critical Point ◽  
Critical Region ◽  
Critical Pressure ◽  
Critical Density ◽  
Van Der Waals Equation ◽  
The Third ◽  
Critical Isotherm ◽  
Pvt Measurements ◽  
Derivatives Of

Extensive PVT measurements of xenon extending from 1.8° above the critical temperature to the critical temperature, and in a few cases to 4 ° below the critical temperature, have been carried out at densities ranging from somewhat above the critical density to well below. In order to make the corrections for hydrostatic head small and easily calculable, a bomb having a height of only 1.0 cm. was used in the present measurements. The previously reported value for the critical temperature 16.590° is confirmed. The critical density is estimated to be 1.099 ± 0.002 gm./ml. compared with 1.105 gm./ml. found previously. The critical pressure is found to be 57.636 ± 0.005 atm.The isotherms at temperatures above the temperatures of meniscus disappearance do not appear to have any flat portions. However, the critical isotherm is considerably flatter and broader over a range of densities than that corresponding to a van der Waals equation, and at the critical point the third and fourth derivatives of pressure with respect to volume appear to be zero.

Estimation of Critical Temperature and Critical Pressure Using Antoine Constants

2015 ◽  
Vol 48 (2) ◽  
pp. 104-106 ◽  
Author(s):  
Katsumi Tochigi ◽  
Satoru Ando ◽  
Kyohei Suginuma ◽  
Hiroyuki Matsuda ◽  
Kiyofumi Kurihara
Keyword(s):  
Critical Temperature ◽  
Critical Pressure

The Direct Determination of the Critical Temperature and Critical Pressure of Normal Hydrogen1

1950 ◽  
Vol 72 (8) ◽  
pp. 3565-3568 ◽  
Author(s):  
David White ◽  
Abraham Solomon Friedman ◽  
Herrick L. Johnston
Keyword(s):  
Critical Temperature ◽  
Critical Pressure ◽  
Direct Determination

ON THE LIQUID–VAPOR COEXISTENCE CURVE OF XENON IN THE REGION OF THE CRITICAL TEMPERATURE

1952 ◽  
Vol 30 (5) ◽  
pp. 422-437 ◽  
Author(s):  
M. A. Weinberger ◽  
W. G. Schneider
Keyword(s):  
Critical Temperature ◽  
Critical Region ◽  
Van Der Waals ◽  
Coexistence Curve ◽  
Packing Materials ◽  
Critical Data ◽  
Van Der Waals Theory ◽  
Liquid Vapor

The liquid–vapor coexistence curves of very pure xenon have been determined in bombs of vertical lengths 1.2 cm. and 19 cm. The longer bomb yielded a flat-topped coexistence curve, the shorter a more rounded curve. The classical van der Waals theory is capable of explaining a large portion of the flat top if effects of gravity are taken into account. Details of the theoretical variation of the width of the flat top with vertical bomb lengths are given. The critical data obtained for xenon are ρc = 1.105 gm./cc., Tc = 16.590 ±.001 °C. The danger of contamination of gases in the critical region on contact with gasket or packing materials is stressed.

Two Species/Nonideal Solution Model for Amorphous/Amorphous Phase Transitions

1996 ◽  
Vol 455 ◽  
Author(s):  
Cornelius T. Moynihan
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Critical Temperature ◽  
Amorphous Phase ◽  
Thermodynamic Model ◽  
Critical Pressure ◽  
Solution Model ◽  
Amorphous Phases ◽  
First Order ◽  
Temperature And Pressure

ABSTRACTA simple macroscopic thermodynamic model for first order transitions between two amorphous phases in a one component liquid is reviewed, augmented and evaluated. The model presumes the existence in the liquid of two species, whose concentrations are temperature and pressure dependent and which form a solution with large, positive deviations from ideality. Application of the model to recent data indicates that water can undergo an amorphous/amorphous phase transition below a critical temperature Tc of 217K and above a critical pressure Pc of 380 atm.

scholarly journals A new formation of diamond

1905 ◽  
Vol 76 (512) ◽  
pp. 458-461 ◽  
Keyword(s):  
Critical Temperature ◽  
Melting Point ◽  
Critical Point ◽  
Boiling Point ◽  
Critical Pressure ◽  
Carbonic Acid ◽  
Melting Points ◽  
Boiling Points ◽  
James Dewar ◽  
New Formation

On the average the critical point of a substance is 1·5 times its absolute boiling-point. Therefore the critical point of carbon should be about 5800° Ab. But the absolute critical temperature divided by the critical pressure is for all the elements so far examined never less than 2·5; this being about the value Sir James Dewar finds for hydrogen. So that, accepting this, we get the maximum critical pressure as follows, viz., 2320 atmospheres:— 5800° Ab./CrP = 2·5, or CrP = 5800° Ab./2·5, or 2320 atmospheres. Carbon and arsenic are the only two elements that have melting-point above the boiling-point; and among compounds carbonic acid and fluoride of silicium are the only other bodies with similar properties. Now the melting-point of arsenic is about 1·2 times its absolute boiling-point. With carbonic acid and fluoride of silicium the melting-points are about 1·1 times their boiling-points. Applying these ratios to carbon we find that its melting-point would be about 4400°.

THE VISCOSITY OF CARBON DIOXIDE IN THE CRITICAL REGION

1940 ◽  
Vol 18b (10) ◽  
pp. 322-332 ◽  
Author(s):  
S. N. Naldrett ◽  
O. Maass
Keyword(s):  
Carbon Dioxide ◽  
Critical Temperature ◽  
Lower Limit ◽  
Critical Region ◽  
Liquid State ◽  
Condensation Temperature ◽  
Constant Density ◽  
Time Lags ◽  
Great Precision ◽  
Temperature Time

Measurements of the viscosity of carbon dioxide in the critical region have been made with great precision by means of an oscillating disc viscosimeter. The variation of viscosity with temperature at constant density has been determined for 14 different densities. Isothermals have been evaluated from a plot of the isochores. One isothermal was determined directly and is in agreement with those determined indirectly.The form of the viscosity-temperature isochores is not the same as that found by Mason and Maass (12) for ethylene, in that there is no minimum at the critical temperature nor even up to 7 °C. above. For the region just above the condensation temperature, the viscosity is more dependent on density than on temperature; the isochores are almost flat and are well separated. However, the isothermals are spread between an upper and a lower limit of density, showing that viscosity is not entirely independent of temperature. Time lags were observed in the present investigation in the opposite direction to those observed by Geddes and Maass (9); this would appear to decrease the strength of their claims that the time lags that they observed are due to the formation of a structure in the liquid state.

Diffusion of a solute in dilute solution in a supercritical fluid

1991 ◽  
Vol 433 (1887) ◽  
pp. 63-79 ◽  
Keyword(s):  
Diffusion Coefficient ◽  
Critical Temperature ◽  
Equation Of State ◽  
Supercritical Fluid ◽  
Critical Region ◽  
Critical Density ◽  
Partial Molar Volumes ◽  
Dilute Solution ◽  
Binary Diffusion Coefficient ◽  
Binary Diffusion

The experimental evidence for the behaviour of the binary diffusion coefficient for a solute in dilute solution in a supercritical fluid (a fluid above its critical temperature and pressure) is reviewed. Measurements at very low dilution, particularly by the Taylor dispersion technique, indicate that, at constant temperature a few degrees above the critical temperature, the product of density and the diffusion coefficient exhibits a small, continuous and undramatic variation from zero density to well above the critical density. However, some measurements made at higher, but still very low concentrations (e.g. with mole fractions around 10 -3 ), show a lowering of the coefficient in the critical region. The equations, based on non-equilibrium thermodynamics, are put into a form in which the behaviour of the binary diffusion coefficient in the critical region, but not very close to the critical point, may be examined using an equation of state. Calculations for naphthalene in solution in carbon dioxide are carried out using the van der Waals equation of state for mixtures to indicate the form and order of magnitude of the ‘anomalous’ lowering of the coefficient, and especially its dependence on concentration. These indicate a substantial effect even at naphthalene mole fractions of 4.0 x 10 -4 or less and a temperatures 1, 3 and 9 K above the critical temperature of the pure solvent. In addition the flux of a solute in a supercritical fluid in the critical region with respect to space or cell-fixed coordinates is discussed. Because of the large and negative partial molar volumes of solutes like naphthalene in this region, the frames of reference, according to which the diffusion coefficients are defined, can be caused to move rapidly, commonly towards the source of concentration. Thus fluxes of solute with respect to space-fixed coordinates are further substantially reduced in the critical region. The combination of the lowering of the diffusion coefficient and barycentric motion can therefore cause a very significant reduction of solute mass transfer in the critical region and may be the explanation of the sometimes very large diffusion anomalies observed experimentally.

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