Vapor pressure units, 6, Table

Selected physical properties are given in Table 1 and some thermodynamic properties in Table 2. Vapor pressure (P) and enthalpy of vaporization (H) over the temperature range 178.45 to 508.2 K can be calculated with an error of less than 3% from the following equations wherein the units are P, kPa Pi, mj/ mol T, K and = reduced temperature, T/ T (1) ... 

The water-vapor transmission rate (WVTR) is another descriptor of barrier polymers. Strictly, it is not a permeabihty coefficient. The dimensions are quantity times thickness in the numerator and area times a time interval in the denominator. These dimensions do not have a pressure dimension in the denominator as does the permeabihty. Common commercial units for WVTR are (gmil)/(100 in. d). Table 2 contains conversion factors for several common units for WVTR. This text uses the preferred nmol/(m-s). The WVTR describes the rate that water molecules move through a film when one side has a humid environment and the other side is dry. The WVTR is a strong function of temperature because both the water content of the air and the permeabihty are direcdy related to temperature. Eor the WVTR to be useful, the water-vapor pressure difference for the value must be reported. Both these facts are recognized by specifying the relative humidity and temperature for the WVTR value. This enables the user to calculate the water-vapor pressure difference. Eor example, the common conditions are 90% relative humidity (rh) at 37.8°C, which means the pressure difference is 5.89 kPa (44 mm Hg). 

A wide variety of solubilities (in units of g/m3 or the equivalent mg/L) have been reported. Experimental data have the method of determination indicated. In other compilations of data the reported value has merely been quoted from another secondary source. In some cases the value has been calculated. The abbreviations are generally self-explanatory and usually include two entries, the method of equilibration followed by the method of determination. From these values a single value is selected for inclusion in the summary data table. Vapor pressures and octanol-water partition coefficients are selected similarly. 

Pesticides are characterized by a range of (saturation) vapor pressure and densities (Table 8.2) they therefore evaporate from the land surface in different patterns. Peck and Hombuckle (2005) studied atmospheric concentrations of currently used pesticides in Iowa (United States) during the years 2000-2002. The average detected concentrations of five heavily used herbicides were 0.52 ng/m ... 

The instruments consist of the actual sensor (gauge head, sensor) and the control unit required to operate it. The pressure scales or digital displays are usually based on nitrogen pressures if the true pressure pj of a gas (or vapor) has to be determined, the indicated pressure p, must be multiplied by a factor that is characteristic for this gas. These factors differ, depending on the type of instrument, and are either given in tabular form as factors independent of pressure (see Table 3.2) or, if they depend on the pressure, must be determined on the basis of a diagram (see Fig. 3.11). 

It can also be seen from Table 1 that the small amounts of light components have an even greater effect on true vapor pressure than on Reid vapor pressure. True vapor pressure more accurately measures the tendency of a crude oil to cause problems in the offshore loading of tankers, in pump stations of open system oil pipelines, and in increased vaporization losses in storage and in transit. True vapor pressure of crude oil will be fixed by the operating temperature and pressure of the last stage of oil-gas separation, or the bottom conditions of any crude stabilization unit, if no other liquids are added back to the crude stream. 

Table 1.1. Abundance of the metal in the earths s crust, optical band gap Es (d direct i indirect) [23,24], crystal structure and lattice parameters a and c [23,24], density, thermal conductivity k, thermal expansion coefficient at room temperature a [25-27], piezoelectric stress ea, e3i, eis and strain d33, dn, dig coefficients [28], electromechanical coupling factors IC33, ksi, fcis [29], static e(0) and optical e(oo) dielectric constants [23,30,31] (see also Sect. 3.3, Table 3.3), melting temperature of the compound Tm and of the metal Tm(metal), temperature Tvp at which the metal has a vapor pressure of 10 3 Pa, heat of formation AH per formula unit [32] of zinc oxide in comparison to other TCOs and to silicon...

The book is completed with Annexes on the analysis of reactive mixtures by residue curve maps, design of heat exchangers, selection of construction materials, steam tables, vapor pressure of typical chemical components and conversion table for the common physical units. 

Note that we expressed the properties in units that cancel each other in boiling heat transfer relalions. Also note that we used vapor properties al 1 atm pressure from Table A-16 instead of the properties of saturated vapor from Table A-9 at 225°C since the latter are at the saturation pressure of 2.55 MPa. 

The Kelvin equation can be combined with the relative humidity, RH, if water is involved as the fluid relative humidity indicates how moist the air is. The amount of water vapor in the air at any given time is usually less than that required to saturate the air. The relative humidity is the percentage of saturation humidity, generally calculated in relation to the saturated vapor density. Relative humidity may be defined as the ratio of the water vapor density (mass per unit volume) to the saturation water vapor density, usually expressed in percent. Relative humidity is also approximately equal (exactly equal when water is assumed as an ideal gas) to the ratio of the actual water vapor pressure to the saturation water vapor pressure, RH = PJP°. The P° values corresponding to each temperature are given in tables which can be found in handbooks. If RH is measured in an experiment, then Pv can be calculated by using the saturation water vapor pressure tables and can be inserted into the Kelvin equation. 

The effect of pressure on calculated pH, activities of several aqueous species, and saturation states of selected minerals for the seawater are listed in Table 4. The calculated pH at higher temperatures and 500 bars pressure is 0.1 unit lower than that calculated for pressures along the vapor saturation curve at 1000 bars pressure, the pH is lower by --0.2 units (Table 4). At 500 bars pressure, the predicted saturation states of calcite are greater by -200 cal (ASI=0.15) at 25°C, and 1800 cal (ASI=0.75) at 250°C, compared to those calculated without considering the effect of pressure on the ionization constants (Figure 7). Similar, but numerically larger, differences are seen for the saturation state of anhydrite. 

The most efficient way to use this index is to look for the pertinent property (e.g., vapor pressure, entropy),/process (e.g., disposal of chemicals, calibration), ov general concept (e.g., units, radiation). Most primary entries are subdivided into several secondary entries, e.g., under heat capacity there are 17 secondary entries such as air, metals, water, etc. Primary entries will be found for certain classes of substances, such as alloys, elements, organic compounds, refrigerants, semiconductors, etc. Primary entries are also given for the individual chemical elements and for a few compounds such as water and carbon dioxide. However, only the most important tables are listed under these substances. Therefore, the user will find in most cases that it is best to look first for the property of interest, then examine the table or tables that are referenced. 

This table gives the thermal conductivity of several gases as a function of temperature. Unless otherwise noted, the values refer to a pressure of 100 kPa (1 bar) or to the saturation vapor pressure if that is less than 100 kPa. The notation P = 0 indicates the low pressure limiting value is given. In general, theP = 0 andP = 100 kPa values differ by less than 1%. Units are milliwatts per meter kelvin. Substances are listed in the modified Hill... 

This table gives the thermal conductivity of some common liquids at temperatures between -25 and 100°C. All values are given in units of watts per meter kelvin (W/m K). Values refer to nominal atmospheric pressure (about 100 kPa) when an entry is given at a temperature above the normal boiling point of the substance, the pressure is understood to be the saturation vapor pressure at that temperature. 

The alkali metal halides, MX, fonn solids at room temperature. The best known member of the family, NaCl, melts at 801°, the vapor pressure reaches 1 torr at 865°, and the melt boils at 1413°. The dominant species in gaseous alkali metal halides is the monomeric formula unit, MX(g), but smaller amounts of dimers (M2X2), trimers (M3X3) and tetramers (M4X4) have also been detected by mass spectroscopy. Information about the monomeric molecules obtained by spectroscopic studies at high temperatures is collected in Table 5.1 [1]. 

---