Gases from chemical reactions

Are elements given off which are more hazardous, i.e. gases from chemical reactions ... 

By-product gases from chemical reactions in the process... 

Judging from our present knowledge, such a description is far from the whole story. The article of Benderskii and Goldanskii [1992] addressed mostly the vast amount of experimental data accumulated thus far. On the other hand, the major applications of QTST involved gas-phase chemical reactions, where quantum effects were not dominant. All this implies that there is a gap between the possibilities offered by modern quantum theory and the problems of low-temperature chemistry, which apparently are the natural arena for testing this theory. This prompted us to propose a new look at this field, and to consistently describe the theoretical approaches which are adequate even at T = 0. 

The heat capacity of gases is essential for some process engineering design involving gas-phase chemical reactions. Here, tlie heat capacities, Cp, for gases are required to determine the heat necessary to bring the chemical compound increase to the reaction temperature. The heat capacity of a mixture of gases may he found from the heat capacities of the individual components contained in the mixtures. 

We have already seen that the behavior of gases is important to a chemist. The pressure-volume behavior leads to the particle model of a gas. Differences among gases (in properties such as color, odor, and solubility) show that the particles of one gas differ from the particles of another gas. In chemical reactions, the simple combining volume relationships support Avo-gadro s Hypothesis and, hence, give us a way to measure molecular weights. 

Fig. 17. Influence of bubble size on NAj as affected by interaction between bubbles (as a function of a in subreactors and for constant gas holdup), chemical reaction rates, and contact times. NAJ was calculated from Eq. (176) with c, = 1.46 x 10-7 gr-mole/cm3 D= 2.3 x 10"5 cm2/sec G> =0.064 d = 0.1 cm 0 = 2.85 sec [after Gal-Or and Hoel-scher (G5)].

The mobile phase in LC-MS may play several roles active carrier (to be removed prior to MS), transfer medium (for nonvolatile and/or thermally labile analytes from the liquid to the gas state), or essential constituent (analyte ionisation). As LC is often selected for the separation of involatile and thermally labile samples, ionisation methods different from those predominantly used in GC-MS are required. Only a few of the ionisation methods originally developed in MS, notably El and Cl, have found application in LC-MS, whereas other methods have been modified (e.g. FAB, PI) or remained incompatible (e.g. FD). Other ionisation methods (TSP, ESI, APCI, SSI) have even emerged in close relationship to LC-MS interfacing. With these methods, ion formation is achieved within the LC-MS interface, i.e. during the liquid- to gas-phase transition process. LC-MS ionisation processes involve either gas-phase ionisation (El), gas-phase chemical reactions (Cl, APCI) or ion evaporation (TSP, ESP, SSI). Van Baar [519] has reviewed ionisation methods (TSP, APCI, ESI and CF-FAB) in LC-MS. 

Since the whole theme of this book is concerned with unexpected or concealed sources of energy, it is relevant to reiterate that compressed gases may contain a large content of kinetic energy over and above that potentially available from chemical reaction energy possibilities for the gas. A procedure for calculating available kinetic energy from rupture of compressed gas containers is found in... 

FUME. A suspension of fine solid ttr liquid panicles (0.2 to 1 micrometer in diameter) in a gas, Technically, fumes are colloidal systems formed from chemical reactions, such as combustion, distillation, sublimation, calcination, and condensation. 

Ion mobility spectrometry (IMS) is an instrumental method where sample vapors are ionized and gaseous ions derived from a sample are characterized for speed of movement as a swarm in an electric field [1], The steps for both ion formation and ion characterization occur in most analytical mobility spectrometers at ambient pressure in a purified air atmosphere, and one attraction of this method is the simplicity of instrumentation without vacuum systems as found in mass spectrometers. Another attraction with this method is the chemical information gleaned from an IMS measurement including quantitative information, often with low limits of detection [2 1], and structural information or classification by chemical family [5,6], Much of the value with a mobility spectrometer is the selectivity of response that is associated with gas-phase chemical reactions in air at ambient pressure where substance can be preferentially ionized and detected while matrix interferences can be eliminated or suppressed. In 2004, over 20000 IMS-based analyzers such as those shown in Fig. 1 are placed at airports and other sensitive locations worldwide as commercially available instruments for the determination of explosives at trace concentration [7],... 

The detonation cell size (the minimum volume in which the heat release effect from chemical reaction exceeds the gas expansion effects) is smaller than the minimum diameter of the tube or distance between obstacles (Glassman, 1987). 

A quantitative understanding of certain primary combustion phenomena, e.g., liquid fuel-droplet vaporization and burning, gas phase chemical reaction kinetics, radiation heat transfer from combustion products, and mixing of reactants and combustion products, is required to develop a rational approach for the effective utilization of synfuels in industrial boiler/furnace systems. Those processes are defined by the interaction of a number of mechanisms which are conveniently described in terms of physical and chemical related processes. The physical processes are ... 

Ion-molecular reactions are used to resolve isobaric interferences, as discussed, in ICP-MS with a collision/reaction cell or by utilizing ion traps. The mass spectra of Sr, Y and Zr (Fig. 6.10a) without O2 admitted into the collision cell and (Fig. 6.10b) with 10 Pa Oj are different. By introducing oxygen, selective formation of YO and ZrO, but not SrO, is observed. This behaviour of different oxide formation is relevant for an interference free determination of Sr. Ultrahigh mass resolving power ICP mass spectrometry (at m/Am 260 000) selectively removes unwanted ions prior to transfer to the FTICR analyzer cell by gas-phase chemical reactions, e.g., for separation of Ca from " Ar+ obtained with a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer equipped with a 3 tesla superconducting magnet. ... 

The first term in each case arises from bulk flow of gas into the floor of an isolated bubble and out the roof, as required by the hydrodynamic model of Davidson and Harrison (27). The weight of experimental evidence, from studies of cloud size (28,29), from chemical reaction studies (e.g. 30), and from interphase transfer studies (e.g. 31,32), is that this term is better described by the theory proposed by Murray (33). The latter leads to a reduction in the first term by a factor of 3. Some enhancement of the bulk flow component occurs for interacting bubbles (34,35), but this enhancement for a freely bubbling bed is only of the order of 20-30% (35), not the 300% that would be required for the bulk flow term Equations (1) and (2) to be valid. 

A model of filtration combustion in a thin porous layer, immersed in a bath of gaseous reactant, has also been investigated (Shkadinskii et al, 1992a). In this case, only filtration of gas from the surroundings to the sample, normal to the direction of combustion propagation (cross-flow filtration), should be considered. New pulsating instabilities associated with the gas-solid chemical reaction and mass transfer of gas to the porous medium were identified. 

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