Critical azeotropic

R. B. Griffiths and Wheeler ( 2) have suggested that there are "anomalies" on a gas-liquid critical curve for a binary mixture, not only at the critical azeotrope but also at points where the critical curve passes through the extremum with respect to changes of pressure or temperature."... 

Chang, R. E, Doiron, T. Pegg, I. L. (1986). Decay rate of critical fluctuations in ethane + carbon dioxide mixtures near the critical line including the critical azeotrope, /nt. J. Thermophys., 7,295—304. 

Fig. 15. Isobaric vapor—liquid—liquid (VLLE) phase diagrams for the ethanol—water—benzene system at 101.3 kPa (D-D) representHquid—Hquid tie-lines (A—A), the vapor line I, homogeneous azeotropes , heterogeneous azeotropes Horsley s azeotropes, (a) Calculated, where A is the end poiat of the vapor line and the numbers correspond to boiling temperatures ia °C of 1, 70.50 2, 68.55 3, 67.46 4, 66.88 5, 66.59 6, 66.46 7, 66.47, and 8, the critical poiat, 66.48. (b) Experimental, where A is the critical poiat at 64.90°C and the numbers correspond to boiling temperatures ia °C of 1, 67 2, 65.5 3, 65.0 ...

Winn [99] proposes a modification to recognize temperature variation effects on relative volatility. The method does not apply to mixtures forming azeotropes or at conditions near the critical. Kister [94] proposes ... 

In cases where rAB>l and rBA>l or rAB<.l and rBAazeotropic composition1 or critical point where the copolymer composition will exactly reflect the monomer feed composition (Figure 7.1). 

In Figures 3b and c, there is a critical composition xg where the vapour has the same composition as the liquid, so that no change occurs on boiling. Such critical mixtures are called azeotropes. Special methods which are necessary to effect separation of these are discussed in Section 11.8. For compositions other than xg, the vapour formed has a... 

Colorless liquid commercial grade has a pungent disagreeable odor, in its purest form the odor is sweet and pleasant flammable refractive index 1.6295 density 1.261 g/mL at 20°C boils at 46.3°C freezes at -110.8°C critical temperature 279°C, critical pressure 77.97 atm, critical volume 173 cm3/mol slightly soluble in water, 0.29 g/lOOg at 20°C soluble in alcohol, ether, benzene, chloroform, and oils forms an azeotrope with water (CS2 H2O = 97.2%)... 

Colorless gas fumes in moist air pungent acrid odor nonflammable heavier than air density 2.71 (air=1.0) gas density 3.55 g/L at 25°C liquefies at -66.4°C solidifies at -86.8°C critical temperature 89.8°C critical pressure 84.5 atm highly soluble in water (saturated aqueous solution contains 66% HBr at 25°C) forms a constant-boiling azeotrope at 47.5% HBr in solution, boiling at 126°C at atmospheric pressure soluble in alcohol a O.IOM aqueous solution is 93% ionized to H and Br ions at 18°C. 

Water freezes to ice at 0°C expands by about 10% on freezing boils at 100°C vapor pressure at 0°, 20°, 50°, and 100°C are 4.6, 17.5, 92.5, and 760 torr, respectively dielectric constant 80.2 at 20°C and 76.6 at 30°C dipole moment in benzene at 25°C 1.76 critical temperature 373.99°C critical pressure 217.8 atm critical density 0.322 g/cm viscosity 0.01002 poise at 20°C surface tension 73 dynes/cm at 20°C dissolves ionic substances miscible with mineral acids, alkalies low molecular weight alcohols, aldehydes and ketones forms an azeotrope with several solvents immiscible with nonpolar solvents such as carbon tetrachloride, hexane, chloroform, benzene, toluene, and carbon disulfide. 

Binary System. The first task is to examine the characteristics of the 2-propanol—water-phase equilibria (VLE, LLE, SLE) to determine the compositions of interest and any critical features. 2-Propanol forms a minimum boiling azeotrope with water (80.4°C at 101.3 kPa (760 torr), 68 mol % 2-propanol). The azeotrope is between the feed and the IPA product and is a distillation boundary, thus it is impossible to obtain both desired products from any single-feed... 

According to this equation the maximum number of phases that can be in equilibrium in a binary system is = 4 (F= 0) and maximum number of degrees of freedom needed to describe the system = 3 (n=l). This means that all phase equilibria can be represented in a three-dimensional P,T,x-space. At equilibrium every phase participating in a phase equilibrium has the same P and T, but in principle a different composition x. This means that a four-phase-equilibrium (F=0) is given by four points in P, 7, x-space, a three-phase equilibrium (P=l) by three curves, a two-phase equilibrium (F=2) by two planes and a one phase state (F= 3) by a region. The critical state and the azeotropic state are represented by one curve. 

Often the essentials of phase diagrams in P,7,x-space are represented in a P,7-projection. In this type of diagrams only non-variant (F=0) and monovariant (F=l) equilibria can be represented. Since pressure and temperature of phases in equilibrium are equal, a four-phase equilibrium is now represented by one point and a three-phase equilibrium with one curve. Also the critical curve and the azeotropic curve are projected as a curve on the P, 7-plane. A four-phase point is the point of intersection of four three-phase curves. The point of intersection of a three-phase curve and a critical curve is a so-called critical endpoint. In this intersection point both the three-phase curve and the critical curve terminate. 

Figure 2.2-1. Two phase equilibria three cases were the composition of the two phase are equal, a Pure component boiling point, b Azeotropic point, c Critical point.

Another drying experiment, shown in Table III, narrows the critical range of porosity still further. In this series, one sample of another hydrogel was dried in an oven from water, while a second was dried by azeotropic... 

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