Gaseous Constituents

The first application of FI gas-diffusion separation reported by Baadenhuijsen [II] was on the determination of carbon dioxide in plasma by spectrophotometry, resulting in a fast automated procedure. A dimethylsilicone rubber membrane was used for separating the carbon dioxide from the acidified sample. Fan et al.[12] described a similar procedure using a PTFE microporous membrane. The procedure is described in detail in Sec. 9.5.2. 

FI gas-diffusion separation systems with membrane separators have been used successfully for the determination of ammonia in whole blood and plasma both with a potentiometric [13] and a spectrophotometric detector [14]. 

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Absorption, or gas absorption, is a unit operation used in the chemical industry to separate gases by washing or scmbbing a gas mixture with a suitable hquid. One or more of the constituents of the gas mixture dissolves or is absorbed in the Hquid and can thus be removed from the mixture. In some systems, this gaseous constituent forms a physical solution with the Hquid or the solvent, and in other cases, it reacts with the Hquid chemically. 

Whereas the OVD, PCVD, and MCVD processes build a refractive index profile layer by layer, the VAD process uses gaseous constituents in the flame to control the shape and temperature distribution across the face of the growing soot boule. 

Coal can be converted to gas by several routes (2,6—11), but often a particular process is a combination of options chosen on the basis of the product desired, ie, low, medium, or high heat-value gas. In a very general sense, coal gas is the term appHed to the mixture of gaseous constituents that are produced during the thermal decomposition of coal at temperatures in excess of 500°C (>930°F), often in the absence of oxygen (air) (see Coal CONVERSION PROCESSES, gasification) (3). A soHd residue (coke, char), tars, and other Hquids are also produced in the process ... 

Roast. The heating of soflds, frequently to promote a reaction with a gaseous constituent in the furnace atmosphere. 

The gaseous constituents produced in a refinery give rise to a host of chemical intermediates that can be used for the manufacture of a wide variety of products (2). Synthesis gas (carbon monoxide, CO, and hydrogen, H2) mixtures are also used to produce valuable industrial chemicals (Pig. 13). 

Condensation Nuclei the small nuclei or particles which gaseous constituents in the atmosphere (e.g., water vapor) collide and adhere. 

Table 7-2 includes most of the main gaseous constituents of the troposphere with observed concentrations. In addition to gaseous species, the condensed phases of the atmosphere (i.e. aerosol particles and clouds) contain numerous other species. The physical characteristics and transformations of the aerosol state will be discussed later in Section 7.10. The list of major gaseous species can be organized in several different ways. In the table, it is in order of decreasing concentration. We can see that there are five approximate categories based simply on concentration ... 

The lattice enthalpy is defined as the standard change in enthalpy when a solid substance is converted from solid to form gaseous constituent ions. Accordingly, values of AH(iattice) are always positive. 

Post-flashover fire models calculate the time-temperature history in a compartment by solving simplified forms of the energy, mass, and species equations. The concentration of various gaseous constituents can be monitored as well as vent flows. Some post-flashover fire models allow mechanical ventilation to be factored in the calculation. These types of models are most useful for determining the time-temperature exposure to a structure for a specific compartment and fuel load. Such time-temperature histories can be used for assessing the possibility of structural failure or fire spread to adjacent compartments. 

This description of processes of burning necessarily led to a comparison of the gaseous constituent of the atmosphere which played so important a part in these processes, with... 

The negative values of the lattice enthalpies are plotted against the cation radii in Figure 3.3. The negative values represent the enthalpy changes accompanying the conversion of the solid compounds to their gaseous constituent ions (the opposite of lattice formation). 

Several methods are commonly used to specify the abundance of substances in the atmosphere. For gaseous constituents common practice is to specify abundances as mixing ratios, or equivalently as mole fractions of the species in air. This quantity is simply the ratio of the partial pressure of a substance to the total pressure. The advantage of this unit is that it is independent of pressure and temperature, and for an atmospheric component that is well mixed, the mixing ratio will be constant as the pressure or temperature changes. Common units for specifying mixing ratios are parts... 

Chu, W. and M.P. McCormick (1979) Inversion of stratospheric aerosol and gaseous constituents from space craft solar extinction data in die 0.38-1.0 micron region. Applied Optics 18 1404-1414. 

Vaporization. Maxima in n-alkane abundance ranging from C5 to Ci 1 in most crude oils probably result from the vaporization of normally gaseous constituents, primarily through reduction in pressure. The position of the maximum should depend primarily on the gas-to-oil ratio, greater ratios giving higher maxima. 

Natural gas the naturally occurring gaseous constituents that are found in many petroleum reservoirs also there are also those reservoirs in which natural gas may be the sole occupant. 

The instruments and techniques outlined in the Section on Quality assurance of NPL gas standards are used to check the concentrations of all gaseous constituents in the standards other than the specified minor and major components. This verifies that no impurities or extraneous species have become entrained into the cylinders during the preparation... 

In contrast to the decomposition of carbonates, which yield only a single gaseous product, and of sulfates, for which useful generalizations about gas composition can be made (Chapter 4), the situation for nitrates is more complex. Partial pressures of the gaseous constituents must be calculated by a rather complicated method (see below) and, even so, some compromises are required. For example, although it is known that over some temperature ranges alkali metal and alkaline earth nitrates decompose to nitrites as a first step, no high- temperature thermo-... 

With = 0, pq = 0, and - -1.3 kJ -mol-1 found in chemical handbooks, we then obtain the standard affinity equal to A0 = -/% = 1.3 kJ - mol-1. If the gas phase is an ideal gas, the activities are equal to the molar fraction of gaseous substances. Further, if solid I2is a pure substance, the activity of I2 is unity. The equilibrium constant K in the standard state will then be expressed by the molar fractions of gaseous constituents as shown in Eq. 6.9 ... 

The central idea in the laser-based method for detection of small quantities of H in restricted areas is that an intense laser strike can form a pothole in a metal. The metal of the pothole and the H it contains are vaporized. Both the H and some of the metallic atoms are withdrawn by a vacuum that pulls gaseous constituents out of the system. On the way, however, these constituents are made to fly through the space between the electrodes of a quadrupole mass spectrometer set to measure mass 2. Knowing the H2 produced from one laser strike, and the dimensions of the pothole, the H concentration in the metal—and within any restricted area to which the laser can be directed—can be measured. 

Analysis of gaseous constituents released by in vacuo crushing or by dissolution of the inorganic matrix in concentrated mineral acid. 

It is convenient at this stage to introduce a standard free energy change AGd for the reaction. This is the value of AGd when the reaction is advanced infinitesimally and reversibly under conditions where all gaseous constituents are at unit partial pressure (usually one atmosphere) at the temperature of interest. It may not be possible actually to execute the reaction of interest under such conditions, but this fact does not detract from the correctness of the assertion. The definition is also consistent with the fact that we had earlier... 

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