Atmospheric conditions

Zaera F, Fischer D A, Shen S and Gland J L 1998 Fluorescence yield near-edge X-ray absorption spectroscopy under atmospheric conditions CO and FI2 coadsorption on Ni(IOO) at pressures between 10 and 0.1 Torr Surf. Sc/. 194 205-16... 

Atmospheric Conditions. In addition to complete combustion, wastes may be destroyed by treatment at high temperatures either without oxygen (qv) (pyrolysis), usiag limited oxygea (partial combustioa), or ia reactive atmospheres (gasiftcatioa), such as those containing steam (qv), hydrogea (qv), or carboa dioxide (qv). 

Shielding and Stabilization. Inclusion compounds may be used as sources and reservoirs of unstable species. The inner phases of inclusion compounds uniquely constrain guest movements, provide a medium for reactions, and shelter molecules that self-destmct in the bulk phase or transform and react under atmospheric conditions. Clathrate hosts have been shown to stabiLhe molecules in unusual conformations that can only be obtained in the host lattice (138) and to stabiLhe free radicals (139) and other reactive species (1) similar to the use of matrix isolation techniques. Inclusion compounds do, however, have the great advantage that they can be used over a relatively wide temperature range. Cyclobutadiene, pursued for over a century has been generated photochemicaHy inside a carcerand container (see (17) Fig. 5) where it is protected from dimerization and from reactants by its surrounding shell (140). 

Metallic magnesium and water [7732-18-5] react. Under normal atmospheric conditions or in pure or chloride-free water of high pH, the reaction is suppressed by the formation of an insoluble magnesium hydroxide [1309-42-8] film. 

The rare-earth nitrides do not have any technical appHcations. These are high melting compounds but are hydrolyzed easily by moisture and are not stable under normal atmospheric conditions. 

The effluent from the reactor is a slurry of terephthaUc acid because it dissolves to a limited extent in almost all solvents, including the acetic acid—water solvent used here. This slurry passes through a surge vessel that operates at a lower pressure than the reactor. More terephthaUc acid crystallizes and the slurry is then ready to be processed at close to atmospheric conditions. The terephthaUc acid crystals are recovered by filtration, washed, dried, and conveyed to storage, from which they are in turn fed to the purification step. 

Aminophenol. This is the most stable of the isomers under atmospheric conditions. It forms white prisms when crystallized from water or toluene. The orthorhombic crystals have a tetramolecular unit and a density of 1.195 g/cm (1.206 and 1.269 also quoted) (15,16) (see Tables 3—5). 

Under atmospheric conditions, 3-aminophenol is the most stable of the three isomers. Both 2- and 4-aminophenol are unstable they darken on exposure to air and light and should be stored in brown glass containers, preferably in an atmosphere of nitrogen. The use of activated iron oxide in a separate cellophane bag inside the storage container (116), or the addition of staimous chloride (117), or sodium bisulfite (118) inhibits the discoloration of aminophenols. The salts, especially the hydrochlorides, are more resistant to oxidation and should be used where possible. 

With the exception of neopentyl alcohol (mp 53°C), the amyl alcohols are clear, colorless Hquids under atmospheric conditions, with characteristic, slightly pungent and penetrating odors. They have relatively higher boiling poiats than ketonic or hydrocarbon counterparts and are considered iatermediate boiling solvents for coating systems (Table 1) (1—16). 

Propylene is a colorless gas under normal conditions, has anesthetic properties at high concentrations, and can cause asphyxiation. It does not irritate the eyes and its odor is characteristic of olefins. Propjiene is a flammable gas under normal atmospheric conditions. Vapor-cloud formation from Hquid or vapor leaks is the main ha2ard that can lead to explosion. The autoignition temperature is 731 K in air and 696 K in oxygen (80). Evaporation of Hquid propylene can cause skin bums. Propylene also reacts vigorously with oxidising materials. Under unusual conditions, eg, 96.8 MPa (995 atm) and 600 K, it explodes. It reacts violentiy with NO2, N2O4, and N2O (81). Explosions have been reported when Hquid propylene contacts water at 315—348 K (82). Table 8 shows the ratio TJTp where is the initial water temperature, and T is the superheat limit temperature of the hydrocarbon. 

Cooling-Tower Plumes. An important consideration in the acceptabiHty of either a mechanical-draft or a natural-draft tower cooling system is the effect on the environment. The plume emitted by a cooling tower is seen by the surrounding community and can lead to trouble if it is a source of severe ground fog under some atmospheric conditions. The natural-draft tower is much less likely to produce fogging than is the mechanical-draft tower. Nonetheless, it is desirable to devise techniques for predicting plume trajectory and attenuation. 

The exposed surface area of a tank is relatively large, thus heated tanks are almost always insulated. Another reason for insulating is that the external corrosion rate of the steel owing to atmospheric conditions increases with increasing temperature. Insulation, if propedy installed, reduces external... 

J.m/h. Because the diamond growth takes place under atmospheric conditions, expensive vacuum chambers and associated equipment are not needed. The flame provides its own environment for diamond growth and the quaUty of the film is dependent on such process variables as the gas flow rates, gas flow ratios, substrate temperature and its distribution, purity of the gases, distance from the flame to the substrate, etc. 

The stmcture of boron phosphate prepared under normal atmospheric conditions consists of tetragonal bipyrimids analogous to the high cristobahte form of siUca. Both the boron and phosphoms are tetrahedraHy coordinated by oxygen. Similar siUcalike stmctures ate found for BAsO and TaBO (156). A quart2like form of boron phosphate can be prepared by heating the common form to 500°C at 5.07 GPa (50,000 atm) (157). 

GB decomposes thermally to form a variety of phosphoms-containing products as well as propjiene. The rate of decomposition increases with increase in temperature and in the presence of acids. At the boiling point of GB, under atmospheric conditions, decomposition is fairly rapid. 

The stainless steels contain appreciable amounts of Cr, Ni, or both. The straight chrome steels, types 410, 416, and 430, contain about 12, 13, and 16 wt % Cr respectively. The chrome—nickel steels include type 301 (18 wt % Cr and 9 wt % Ni), type 304 (19 wt % Cr and 10 wt % Ni), and type 316 (19 wt % Cr and 12 wt % Ni). Additionally, type 316 contains 2—3 wt % Mo which gready improves resistance to crevice corrosion in seawater as well as general corrosion resistance. AH of the stainless steels offer exceptional improvement in atmospheric conditions. The corrosion resistance results from the formation of a passive film and, for this reason, these materials are susceptible to pitting corrosion and to crevice corrosion. For example, type 304 stainless has very good resistance to moving seawater but does pit in stagnant seawater. 

Supercriticalfluid solvents are those formed by operating a system above the critical conditions of the solvent. SolubiHties of many solutes ia such fluids often is much greater than those found for the same solutes but with the fluid at sub atmospheric conditions. Recently, there has been considerable iaterest ia usiag supercritical fluids as solvents ia the production of certain crystalline materials because of the special properties of the product crystals. Rapid expansion of a supercritical system rapidly reduces the solubiHty of a solute throughout the entire mixture. The resulting high supersaturation produces fine crystals of relatively uniform size. Moreover, the solvent poses no purification problems because it simply becomes a gas as the system conditions are reduced below critical. 

Use for heat treating is also small compared to the past. It has been supplanted to a large extent by furnaces using special atmospheric conditions. Heat treatment salts containing sodium cyanide are used for small metal parts when selective case hardening is required. 

From the viewpoint of air pollution, both stable surface layers and low-level inversions are undesirable because they minimize the rate of dilution of contaminants in the atmosphere. Even though the surface layer may be unstable, a low-level inversion will act as abarrier to vertical mixing, and contaminants will accumulate in the surface layer below the inversion. Stable atmospheric conditions tend to be more frequent and longest in persistence in the autumn, but inversions and stable lapse rates are prevalent at all seasons of the year. 

The effective stack height (equivalent to the effective height of the emission) is the sum of the actual stack height, the plume rise due to the exhaust velocity (momentum) of the issuing gases, and the buoyancy rise, which is a function of the temperature of the gases being emitted and the atmospheric conditions. 

Introduction Gas dispersion (or vapor dispersion) is used to determine the consequences of a release of a toxic or flammable material. Typically, the calculations provide an estimate of the area affected and the average vapor concentrations expected. In order to make this determination, one must know the release rate of the gas (or the total quantity released) and the atmospheric conditions (wind speed, time of day, cloud cover). 

The problem with Eq, (26-60) is that the eddy diffusivity changes with position, time, wind velocity, and prevailing atmospheric conditions, to name a few, and must be specified prior to a solution to the equation, This approach, while important theoretically, does not provide a practical framework for the solution of vapor dispersion problems,... 

Sutton Micrometeorology, McGraw-Hill, 1953, p, 286) developed a solution to the above difficulty by defining dispersion coefficients, O, Gy, and O, defined as the standard deviation of the concentrations in the downwind, crosswind, and vertical x, y, z) directions, respectively, The dispersion coefficients are a function of atmospheric conditions and the distance downwind from the release. The atmospheric conditions are classified into six stability classes (A through F) for continuous releases and three stability classes (unstable, neutral, and stable) for instantaneous releases. The stability classes depend on wind speed and the amount of sunlight, as shown in Table 26-28,... 

The puff model describes near-instantaneous releases of material. The solution depends on the total quantity of material released, the atmospheric conditions, the height of the release above ground, and the distance from the release. The equation for the average concentration for this case is (Growl and Louvar, 1990, p, 143) ... 

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