Of liquids at various temperatures

Figure 1. This nomograph helps estimate surface tension of liquids at various temperatures.

Vapor Pressure of Liquids at Various Temperatures in mmHg... 

Physical Properties.—Arsenic tribromide is a solid at ordinary temperatures, crystallising in beautiful colourless rhombic prisms6 which possess a feebly aromatic odour 7 and are stable in dry air. In the presence of moisture slight fuming occurs. The crystals melt sharply at 31° C.8 The density 9 at 15° C. is 3-66 after fusion and resolidification, the product has density 3-54 at 25° C.10 The density of the liquid at various temperatures may be obtained from the expression 11... 

The surface tension, a, and molecular surface energy, /x, of the liquid at various temperatures have been found 12 to be ... 

The chart shown in Fig. 3.4, is called a Cox, or vapor-pressure, chart. It shows the pressure developed by pure-component liquids, at various temperatures. The interesting aspect of this chart is that the sloped... 

PERCENTAGES OF OXYGEN IN EQUILIBRIUM IN GASEOUS AND LIQUID PHASES OF AIR AT VARIOUS TEMPERATURES UNDER ATMOSPHERIC PRESSURE. 

Ice exerts a definite vapour pressure which, at 0° C., is identical with that of water, so that at this point the three phases—solid, liquid, vapour—can co-exist. This is not the real triple point, because pressure lowers the melting-point of ice, and by definition 0° C. is the melting-point of ice under a pressure of one atmosphere. The true triple point therefore lies at +0 0076° C., and m the absence of air, OB, which represents the vapour pressure of ice at various temperatures, is termed the sublimation curve (fig. 43). 

The irregularities in the specific heats and densities of water at various temperatures, particularly the contraction observed when water is warmed from 0° to 4° C., led Rontgen1 to suggest m 1892 that liquid water is a mixture of two sets of molecules m equilibrium, namely, ice molecules and water molecules. Thus ... 

The System Phosphorus-Sulphur and Compounds.—The two elements mixed in various proportions were fused in sealed tubes at about 200° C. The solids so formed were heated and the temperatures determined at which complete liquefaction took place. These temperatures are the initial freezing-points of liquid at that temperature in equilibrium with the solid phases. 

The curved line from T to C in Figure 13-17a is a vapor pressure curve obtained experimentally by measuring the vapor pressures of water at various temperatures (Table 13-8). Points along this curve represent the temperature-pressure combinations for which liquid and gas (vapor) coexist in equilibrium. At points above AC, the stable form of water is liquid below the curve, it is vapor. 

A schematic plot of the variation of the pressure with volume, as predicted by the van der Waals equation of state, at various temperatures is given in Fig. 10.2. At temperatures above the critical temperature, the pressure-volume variation is monotonic and qualitatively similar to that of an ideal gas (see dotted-line). At temperatures below tire critical temperature, the pressure-volume curve begins to oscillate, exhibiting a van der Waals" loop (see dashed-line). This behavior is unphysical, but represents tire vapor-liquid transition, and should be replaced by the solid line. The precise location of the solid line is given by the Maxwell construction. 

Fig. 5. Temperature dependence of the entropy difference between various supercooled liquids and their stable crystals, A5. is the entropy change upon melting, and is the melting temperature. (Reprinted with permission from W. Kauzmann. The nature of the glassy state and the behavior of liquids at low temperatures. Chem. Rev. (1948) 43 219. Copyright 1948, American Chemical Society.)...

The figure-that follows for the ethanol + water sy.s-tem is an unusual one in that it shows both vapor-liquid equilibrium and the enthalpy concentration diagrams on a single plot. This is done as follows. The lower collection of heavy lines give the enthalpy concentration data for the liquid at various temperatures and the upper collection of lines is the enthalpy-concentration data for the vapor, each at two pressures, 0.1013 and 1 013 bar. (There are also enthalpy-concentration lines for several other temperatures.) The middle collection of lines connect the equilibrium compositions of liquid and vapor. For example, at a pressure of 1.013 bar, a saturated-vapor containing 71 wt % ethanol with an enthalpy of 1535 kJ/kg is in equilibrium with a liquid containing 29 wt % ethanol with an enthalpy of 315 kJ/kg at a temperature of 85°C. Note also that the azeotropes that form in the ethanol -f water system are indicated at each pressure. 

The aromatization of mixed-C4 hydrocarbons, prevalent by-products derived from petroleum refining processes, over HZSM-5 catalysts modified by both Zn and Ni cations via different impregnating methods has been systematically studied in two different sizes of reactors at various temperatures and space velocities of the feeds. The reaction mechanisms were discussed according to the liquid and gas product distributions. The acidity of the catalysts were also characterized using the frequency response (FR). 

Figure 10.12 shows the saturated vapour pressure of water at various temperatures. The figure also shows the way that the saturated vapour pressure of ethanol varies with temperature. The vapour pressure of water and ethanol (like that of all liquids) increases with temperature. This is expected, since at the higher temperature more liquid molecules have sufficient energy to escape the attractive forces holding molecules in the liquid. 

Figure 3.20 Dynamic viscosity of liquid R134a (l,lJ,2-tetrafluoroethane) as a function of pressure at various temperatures with the Lucas equation. (Data from Comunas et af. [74].)...

A recessed cup was mad to measure the effect of changing the temperature of the top surface on the heat input to the liquid nitrogen. The bottom of this cup, made of brass extended 5 in. below the top edge of the flask and was 1/16 in. smaller in diameter than the flask, so that it did not contact the walls. The body of the cup was about 1 in. smaller in diameter than the bottom plate to allow for gas passage while minimizing the effect of the cup wall temperature. Liquids at various temperatures were then put in the cup and the boil-off rates of the nitrogen were compared. Data were obtainedwith cup temperatures of 371 , 324 , 285 , 195 , and 146 K. These data are presented in Fig. 4. 

As Figure 11.7 demonstrates, the vapor pressure of a substance depends on the temperature. (Appendix B gives a table of the vapor pressures of water at various temperatures.) As the temperature increases, the kinetic energy of molecular motion becomes greater, and the vapor pressure increases. Liquids and solids with relatively high vapor pressure at normal temperatures arc said to be volatile. Chloroform and carbon tetrachloride are volatile liquids. Naphthalene, CioHg, and para-dichlorobenzene, C6H4CI2, are volatile solids they have appreciable vapor pressures at room temperature. Both arc used to make mothballs. 

The experimental values of the solvation Gibbs energies of water in water are obtainable from the densities of the liquid and the vapor pressure of water at various temperatures. It is assumed that the vapor at equilibrium with liquid water at most temperatures of interest may be viewed as ideal gas, in which we have (see section 6.13)... 

When liquid molecules with sufficient kinetic energy break away from the surface, they become gas particles or vapor. In an open container, all the liquid will eventually evaporate. In a closed container, the vapor accumulates and creates pressure called vapor pressure. Each liquid exerts its own vapor pressure at a given temperature. As temperature increases, more vapor forms, and vapor pressure increases. Table 11.4 lists the vapor pressure of water at various temperatures. 

Waldbaum and Thompson (1969). The mixing properties for sanidine -high albite solutions derived by Thompson and Waldbaum (1969a) are used to construct feldspar phase diagrams. The equations of state for alkali feldspar are used to predict equilibria involving reactions among feldspar and other phases (including feldspar liquids) at various temperatures and pressures. 

Vapor Pressures of Selected Liquids at Various Temperatures (°C)... 

In his fifth memoir, where he disregards differences in constitution between the surface layer and the remainder of the mass, Duprd found that, for the same liquid at various temperatures, the tension is proportional to the square of the density but, in his sixth memoir, where he takes account of the difference in question, he recognizes that this proportionality is not exact. 

When oil and gas are produced simultaneously into a separator a certain amount (mass fraction) of each component (e.g. butane) will be in the vapour phase and the rest in the liquid phase. This can be described using phase diagrams (such as those described in section 4.2) which describe the behaviour of multi-component mixtures at various temperatures and pressures. However to determine how much of each component goes into the gas or liquid phase the equilibrium constants (or equilibrium vapour liquid ratios) K must be known. 

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