Heat vapor pressure

H.R. Bader, Jr et al, Rocket Engines — Liquid Propellant. Volume I—Small Engines , DO-114118-2-Vol 1, Boeing, Seattle (1968) (AD 843667) [The density, specific heat, vapor pressure and viscosity of UDMH and Aerozine-50 (UDMH/hydrazine, 50/50 wt %) over a temp range of —60° to +140°F are presented in Figs 3 4... 

These are properties that can be measured or observed without converting the chemical into a different substance. For example, boiling point temperature(s), density, specific heat, vapor pressures, and color may be determined without changing the chemical into a different substance. 

It will be assumed here that the equations for 2ero-pressure specific heat, vapor pressure, and the derivative of the vapor pressure with respect to temperature are all available. For example, the following forms have been found to be adequate for some fluids ... 

Stream properties required for solving material and energy balance equations and other process calculations are predicted from component properties. The properties of petroleum pseudocomponents can be estimated from their boiling points and specific gravities. The component properties include the molecular weight, critical constants, acentric factor, heat of formation, ideal gas enthalpy, latent heat, vapor pressure, and transport properties. These are predicted mainly by empirical correlations based on experimental data. Many of these correlations are documented in the American Petroleum Institute Technical Data Book (API, 1983). 

Figure 12.10 Liquid sources are supplied by bubbling a carrier gas such as H2 or Ar through the liquid. T refers indicates tri , M designates methyl and E is for ethyl . Al, Ga, and In sources are dashed, P, As, and Sb are solid lines. Ethyl compounds are the heavy lines while methyl compounds are narrow lines. Note that the ethyl compound pressures lie below the methyl vapor pressures. Heavier metals produce lower vapor pressure organic compounds. (TMA is an exception being elose to the TEA line.) Vapor pressures of divalent metal organics such as dimethyl tellurium generally lie below the most closely-related group III or group V compound. Note that the In compounds are solids under the conditions shown above and sublime upon heating. Vapor pressures shown here are plotted from data in Ref. 3.

Zwolinski, B. J., and R. C. Wilhoit "Vapor Pressures and Heats of Vaporization of Hydrocarbons and Related Compounds," Thermodynamic Research Center, Dept, of Chemistry, Texas A M University, College Station, Texas, 1971. 

Enthalpies are referred to the ideal vapor. The enthalpy of the real vapor is found from zero-pressure heat capacities and from the virial equation of state for non-associated species or, for vapors containing highly dimerized vapors (e.g. organic acids), from the chemical theory of vapor imperfections, as discussed in Chapter 3. For pure components, liquid-phase enthalpies (relative to the ideal vapor) are found from differentiation of the zero-pressure standard-state fugacities these, in turn, are determined from vapor-pressure data, from vapor-phase corrections and liquid-phase densities. If good experimental data are used to determine the standard-state fugacity, the derivative gives enthalpies of liquids to nearly the same precision as that obtained with calorimetric data, and provides reliable heats of vaporization. 

This chapter presents quantitative methods for calculation of enthalpies of vapor-phase and liquid-phase mixtures. These methods rely primarily on pure-component data, in particular ideal-vapor heat capacities and vapor-pressure data, both as functions of temperature. Vapor-phase corrections for nonideality are usually relatively small. Liquid-phase excess enthalpies are also usually not important. As indicated in Chapter 4, for mixtures containing noncondensable components, we restrict attention to liquid solutions which are dilute with respect to all noncondensable components. 

Liquid chromatography, having a resolving power generally less than that of gas phase chromatography, is often employed when the latter cannot be used, as in the case of samples containing heat-sensitive or low vapor-pressure compounds. 

For non-polar components like hydrocarbons, the results are very satisfactory for calculations of vapor pressure, density, enthalpy, and specific, heat and reasonably close for viscosity and conductivity provided that is greater than 0.10. 

Calculation of characteristics (density, vapor pressure, heating value) M 41-014... 

A heat of immersion may refer to the immersion of a clean solid surface, qs.imm. or to the immersion of a solid having an adsorbed film on the surface. If the immersion of this last is into liquid adsorbate, we then report qsv.imm if tbe adsorbed film is in equilibrium with the saturated vapor pressure of the adsorbate (i.e., the vapor pressure of the liquid adsorbate P ), we will write It follows from these definitions... 

The accurate determination of relative retention volumes and Kovats indices is of great utility to the analyst, for besides being tools of identification, they can also be related to thermodynamic properties of solutions (measurements of vapor pressure and heats of vaporization on nonpolar columns) and activity coefficients on polar columns by simple relationships (179). 

To achieve sufficient vapor pressure for El and Cl, a nonvolatile liquid will have to be heated strongly, but this heating may lead to its thermal degradation. If thermal instability is a problem, then inlet/ionization systems need to be considered, since these do not require prevolatilization of the sample before mass spectrometric analysis. This problem has led to the development of inlet/ionization systems that can operate at atmospheric pressure and ambient temperatures. Successive developments have led to the introduction of techniques such as fast-atom bombardment (FAB), fast-ion bombardment (FIB), dynamic FAB, thermospray, plasmaspray, electrospray, and APCI. Only the last two techniques are in common use. Further aspects of liquids in their role as solvents for samples are considered below. 

Reaction 1 is highly exothermic. The heat of reaction at 25°C and 101.3 kPa (1 atm) is ia the range of 159 kj/mol (38 kcal/mol) of soHd carbamate (9). The excess heat must be removed from the reaction. The rate and the equilibrium of reaction 1 depend gready upon pressure and temperature, because large volume changes take place. This reaction may only occur at a pressure that is below the pressure of ammonium carbamate at which dissociation begias or, conversely, the operating pressure of the reactor must be maintained above the vapor pressure of ammonium carbamate. Reaction 2 is endothermic by ca 31.4 kJ / mol (7.5 kcal/mol) of urea formed. It takes place mainly ia the Hquid phase the rate ia the soHd phase is much slower with minor variations ia volume. 

The common physical properties of acetyl chloride ate given in Table 1. The vapor pressure has been measured (2,7), but the experimental difficulties ate considerable. An equation has been worked out to represent the heat capacity (8), and the thermodynamic ideal gas properties have been conveniently organized (9). 

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). 

Physical Properties. Physical properties of anhydrous hydrogen fluoride are summarized in Table 1. Figure 1 shows the vapor pressure and latent heat of vaporization. The specific gravity of the Hquid decreases almost linearly from 1.1 at —40°C to 0.84 at 80°C (4). The specific heat of anhydrous HF is shown in Figure 2 and the heat of solution in Figure 3. 

Fig. 1. (---) Latent heat of vaporization (1,7) and (-) vapor pressure (1,4,7,15) of anhydrous hydrogen fluoride. To convert kPa to psi, multiply by...

Ucon HTF-500. Union Carbide Corp. manufactures Ucon HTE-500, a polyalkylene glycol suitable for Hquid-phase heat transfer. The fluid exhibits good thermal stabHity in the recommended temperature range and is inhibited against oxidation. The products of decomposition are soluble and viscosity increases as decomposition proceeds. The vapor pressure of the fluid is negligible and it is not feasible to recover the used fluid by distiHation. Also, because the degradation products are soluble in the fluid, it is not possible to remove them by filtration any spent fluid usuaHy must be burned as fuel or discarded. The fluid is soluble in water. 

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