Vapor Pressures of Mixtures

In the discharged state of ZEBRA batteries NaCl is formed in the positive electrode, which is beside the NaAlCl4. In abuse experiments, e.g., overheating, less volatile material will be released in the discharged state compared with the charged state where no NaCl is present. This is due to the lower vapor pressure of mixtures with increased NaCl content. 

The vapor pressures of soybean oil-hexane mixtures between 75°C and 120°C were reported (108, 109), and similar data for soybean oil with commercial hexanes was reported by Smith (110). Arnold and Breuklander (83) measured the boiling point of dichloroethylene-soybean oil mixtures and found the log (V.P.) was a linear relation of the mole fraction of oil. Kusano (111, 112) measured the vapor pressure (P) of soybean oil-solvent mixtures that included hexane, benzene, and carbon tetrachloride between 20°C and 50°C and found linear relations between log P and 1/ T. Anikin et al. (113, 114) measured the vapor pressure of mixtures of soybean oil with the khladon 113 (trichlorotrifluoroethane) between 30°C and 100°C. Aeber-hard and Spekuljak (115, 116) measured the vapor pressure of hexane in hexane-soybean oil mixtures and found the vapor pressure at 25°C could be predicted by the equation... 

Figure 14.12(a) shows the partial-pressure curves and the total vapor pressure of mixtures of carbon disulfide and acetone. In this system the individual partial-pressure curves fall well above the Raoult s law predictions indicated by the dashed lines. The system exhibits positive deviations from Raoult s law. The total vapor pressure exhibits a maximum that lies above the vapor pressure of either component. 

The measured vapor pressures of mixtures of PH3 with SiH4 [18, 19] and ASH3 [20, 21] were used to calculate physicochemical parameters of the systems. The relative vapor pressure of infinitely diluted PH3 at the triple points and boiling points of the solvents CH4, SiH4, and ASH3 was calculated by a statistical method [22]. 

When discussing the vapor pressure of mixtures, we found the same situation and it is reasonable to adopt the same explanation for it now. 

Where p = vapor pressure of mixture, mj = molar fraction of component 1, and pi, p2 = vapor pressures of the components 1 and 2. 

This whole chapter is devoted to the vapor pressure (and related phenomena) of single pure species. We use that information, plus other information to estimate the vapor pressures of mixtures, discussed in detail in Chapters 8-10. 

Before proceeding with the paper which has become classical, it is pertinent to glance back at earlier work on the vapor pressure of mixtures. In 1836, Magnus observed that when alcohol was added to ether in the usual barometer assembly, the vapor pressure of both liquids is less than that of the ether alone. 

Regnault (1852) aimed at a general idea of the relations between the vapor pressure of mixtures and those of the components. Alcohol+water (1852) and HCN+water (1864) were examined. Duclaux (1878) used a distillation procedure to gather information about the relations between the composition of the liquid mixture to that of the vapor emitted. His mixtures were water+an n -alcohol ROH (R = CH3 to CgHiv) and water+a carboxylic acid RC02H(R = H, CH3, C2H5, C3H7) Konowalow (1881) also worked on similar mixtures. 

The Vapor pressure of mixtures can- bo computed accurately by siiib-ming thd j)irod soible fraction times the true vapor-pr each compqnehi in the blend. Howeve true rathby thatt... 

For our needs, the saturation pressure of a mixture will be defined as the vapor pressure of a pure component that has the same critical constants as the mixture ( JT... 

Significant vapor pressure of aluminum monofluoride [13595-82-9], AIF, has been observed when aluminum trifluoride [7784-18-1] is heated in the presence of reducing agents such as aluminum or magnesium metal, or is in contact with the cathode in the electrolysis of fused salt mixtures. AIF disproportionates into AIF. and aluminum at lower temperatures. The heat of formation at 25°C is —264 kJ/mol(—63.1 kcal/mol) and the free energy of formation is —290 kJ/mol(—69.3 kcal/mol) (1). Aluminum difluoride [13569-23-8] h.3.s been detected in the high temperature equihbrium between aluminum and its fluorides (2). 

In addition to H2, D2, and molecular tritium [100028-17-8] the following isotopic mixtures exist HD [13983-20-5] HT [14885-60-0] and DT [14885-61-1]. Table 5 Hsts the vapor pressures of normal H2, D2, and T2 at the respective boiling points and triple points. As the molecular weight of the isotope increases, the triple point and boiling point temperatures also increase. Other physical constants also differ for the heavy isotopes. A 98% ortho—25/q deuterium mixture (the low temperature form) has the following critical properties = 1.650 MPa(16.28 atm), = 38.26 K, 17 = 60.3 cm/mol3... 

Vapor pressure is the most important of the basic thermodynamic properties affec ting liquids and vapors. The vapor pressure is the pressure exerted by a pure component at equilibrium at any temperature when both liquid and vapor phases exist and thus extends from a minimum at the triple point temperature to a maximum at the critical temperature, the critical pressure. This section briefly reviews methods for both correlating vapor pressure data and for predicting vapor pressure of pure compounds. Except at very high total pressures (above about 10 MPa), there is no effect of total pressure on vapor pressure. If such an effect is present, a correction, the Poynting correction, can be applied. The pressure exerted above a solid-vapor mixture may also be called vapor pressure but is normallv only available as experimental data for common compounds that sublime. 

Relative humidity and dew point can be determined for other than atmospheric pressure from the partial pressure of water in the mixture and from the vapor pressure of water vapor. The partial pressure of water is calculated, if ideal-gas behavior is assumed, as... 

The equilibrium vapor pressure of a flammable hquid at its closed-cup flash point about equ s its LFL in percent by volume. Thus, the vapor pressure of toluene at its closed-cup flash point (4.4°C or 40°F) of 1.2 percent (1.2 kPa) is close to its LFL of 1.1 percent. The composite LFL of a mixture may be estimated by Le Cnatelier s Rule ... 

Raoult s law States that at equilibrium, the partial pressure of a solute vapor over a liquid mixture is equal to the vapor pressure of the pure solute at the given temperature times the mole fraction of the solute liquid component in the mixture. 

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