Gaseous components

The separation of hydrogen fluoride, HF (see Fig. 91, curve 20) occurs inversely to the separation of water, H20, (see Fig. 91, curve 18) the peak in HF separation corresponds to the minimum water concentration. Residual water that is usually adsorbed by the material and the surface of the inner parts of the vacuum cell clearly indicate the hydrolysis of the compounds. 

it is possible to make a very important assumption that chain-type compounds decompose forming gaseous niobium-containing components, while island-type compounds release upon thermal decomposition only light atoms and molecules into the gaseous phase [383]. 

Nonetheless, the absence, from even the high range of the accelerating potential, of even very weak peaks corresponding to NbF5 ions was especially mentioned in [383]. 

It is possible that NbF5 separates due to NbOF3 decomposition according to the following known process, as evident from NbF5 deposits found on the cold parts of the vacuum chamber of the measuring equipment  

The ionic current intensity corresponding to the peak at 169 amu was analyzed under isothermal and polythermal conditions [383]. It was found that in a gaseous atmosphere, the intensity changes are in correlation with the CO content and in negative correlation with the C02 content. The presence of CO in vacuum systems equipped with heating elements is usually related to thermo-cycling and desorption of CO by nickel atoms [386]. Based on the above, the presence of NbF4+ ions in mass spectra is most probably related to the niobium reduction process, which can be represented as follows  

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Table 4.19 gives the Henry constants for a few common gaseous components. The chemical nature is also a dominant factor. The effect of temperature is moderate note that the solubility passes through a minimum that depends on the hydrocarbon in question and that it is around 100°C. 

There are two ways to express the fraction which one gaseous component contributes to the total mixture (1) the pressure fmction, pJP, and (2) the mole fraction, nfn. ... 

Industrial Hquid chlorine is routinely analy2ed for moisture, chlorine, other gaseous components, NCl, and mercury foUowing estabHshed procedures (10,79). Moisture and residue content in Hquid chlorine is determined by evaporation at 20°C foUowed by gravimetric measurement of the residue. Eree chlorine levels are estimated quantitatively by thiosulfate titration of iodine Hberated from addition of excess acidified potassium iodide to the gas mixture. 

A most widely used decomposable chemical blowing agent is azodicarbonamide. Its decomposition temperature and rate of evolution of gaseous components are greatly influenced by the stabilizers containing zinc. Lead and cadmium are considered moderate activators for, -oxybis benzenesulfonyl hydrazide (OBSH). OBSH can also be used as a blowing agent for PVC foams. 

Partial Concentration. The sum of the partial concentrations (pressures) in a free molecular gas is equal to the total concentration (pressure). However, all gaseous components, at the same partial pressure or absolute pressure or ratios thereof, are not likely to have the same significance to any or all vacuum appHcations. The significance of the condensed-phase concentrations must therefore be considered. 

In the course of mixture separation, the composition and properties of both mobile phase (MP) and stationary phase (SP) are purposefully altered by means of introduction of some active components into the MP, which are absorbed by it and then sorbed by the SP (e.g. on a silica gel layer). This procedure enables a new principle of control over chromatographic process to be implemented, which enhances the selectivity of separation. As a possible way of controlling the chromatographic system s properties in TLC, the pH of the mobile phase and sorbent surface may be changed by means of partial air replacement by ammonia (a basic gaseous component) or carbon dioxide (an acidic one). 

In most circumstances, it can be assumed diat die gas-solid reaction proceeds more rapidly diaii die gaseous transport, and dierefore diat local equilibrium exists between die solid and gaseous components at die source and sink. This implies diat die extent and direction of die transport reaction at each end of die temperature gradient may be assessed solely from diermodynamic data, and diat die rate of uansport across die interface between die gas and die solid phases, at bodi reactant and product sites, is not rate-determining. Transport of die gaseous species between die source of atoms and die sink where deposition takes place is die rate-determining process. 

The gaseous component typically contains hydrocarbons, hydrogen sulfide, ammonia, mercaptans, solvents, and other constituents, and is either discharged directly to the atmosphere or is combusted in a flare. The major air emissions from blowdown systems are hydrocarbons in the case of direct discharge to the atmosphere and sulfur oxides when flared. 

Light Extinction Budget the percent of total atmospheric extinction attributed to each aerosol and gaseous component of the atmosphere. 

Gibbs definition of the chemical potential of the gaseous component B in a mixture at constant temperature T and pressure p is given by... 

All the above deals with gases and gas phase processes. We now turn to non-gaseous components of the system. There are many ways of expressing this. Probably the simplest is to consider an ideal solution of a solute in a solvent. If the solution is ideal, the vapour pressure of the solute is proportional to its concentration, and we may write p = kc, where c is the concentration and k is the proportionality constant. Similarly, = Arc , which expresses the fact that the standard pressure is related to a standard concentration. Thus we may write from equation 20.198 for a particular component... 

Hydrofluoride synthesis is based on the simultaneous fluorination by ammonium hydrofluoride of niobium or tantalum oxides with other metals compounds (oxides, halides, carbonates etc.) [105]. Table 13 presents some properties of ammonium hydrofluoride, NH4HF2 [51, 71]. Ammonium hydrofluoride is similar to anhydrous HF in its reactivity, but possesses some indisputable advantages. The cost of ammonium hydrofluoride is relatively low, it can be dried and handled easily, recycled from gaseous components, and its processing requires no special equipment. 

Fig. 15. Mass spectral pattern Polytherms of total pressure (P) and ionic currents of gaseous components in the form of ions separating from a TaiOs -NH4HF2 system versus heating temperature (after Agulyansky et al. [114]).

Compound Initial composition and temperature, °C Gaseous components... 

Repeated attempts to obtain the band at 1030 cm 1 in spectra of the respective solids of various compositions did not furnish the desired result. Nevertheless, the band was observed in IR transmission spectra of gaseous components that separated from molten K2NbF7 and were collected in a standard gas phase cell with Csl windows appropriate for IR measurements. Fig. 85 presents the structure of the band and exact wave numbers of its components. Storage of the gas in the cell for several days resulted in a yellow deposit on the windows due to oxidation and subsequent separation of iodine. Analysis of available reported data [364 - 367] enables to assign the band observed at -1030 cm 1 to vibrations of OF radicals. It should be emphasized that a single mode was observed for OF in the argon matrix while in the case of nitrogen, two modes were indicated [367]. 

In both cases, the fluorination of the complex oxides of tantalum and niobium leads to the formation of the water-soluble compounds (NH4)2TaF7 and (NH4)3NbOF6, the insoluble lithium fluoride and die gaseous components H20, NH3 and HF. 

Decomposition following thermal treatment of the separated material yielding solid oxides and gaseous components (solid-gas interaction). 

Ammonia, hydrogen fluoride and carbon dioxide separate from the system in the form of gaseous components. 

No additional gaseous components that coming from gaseous heating source in the case of gas-flame process ... 

The interaction occurs in the reactor (4), which is equipped with exterior heaters and insulation. The coarsest parts of the solids are collected in the collector (5). The gaseous mixture is moved through the connecting tube to the filter (6), which is also equipped with a heater and heat shielding. The solid oxide powder is collected on the filter while the rest of the gaseous components are removed to the heat exchanger... 

Analysis of some experimental results [527, 528, 532] suggests that niobium oxides are first formed as gaseous components resulting from the pure gas-phase hydrolysis ... 

From this point of view, the filter serves not only as separator between the solid and gaseous components of the interaction, but also as a niobium oxide condenser . 

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