Vapor phase contributions

Vapor phase contribution of component Z Component Z in the liquid phase Total vapor pressure of all components. 

Equations (13-111) to (13-114), (13-118) and (13-119), contain terms, Njj, for rates of mass transfer of components from the vapor phase to the liquid phase (rates are negative if transfer is from the liquid phase to the vapor phase). These rates are estimated from diffusive and bulk-flow contributions, where the former are based on interfacial area, average mole-fraction driving forces, and mass-... 

The devolatilization of a component in an internal mixer can be described by a model based on the penetration theory [27,28]. The main characteristic of this model is the separation of the bulk of material into two parts A layer periodically wiped onto the wall of the mixing chamber, and a pool of material rotating in front of the rotor flights, as shown in Figure 29.15. This flow pattern results in a constant exposure time of the interface between the material and the vapor phase in the void space of the internal mixer. Devolatilization occurs according to two different mechanisms Molecular diffusion between the fluid elements in the surface layer of the wall film and the pool, and mass transport between the rubber phase and the vapor phase due to evaporation of the volatile component. As the diffusion rate of a liquid or a gas in a polymeric matrix is rather low, the main contribution to devolatilization is based on the mass transport between the surface layer of the polymeric material and the vapor phase. 

In fact, the horizontal component of liquid surface tension, 7 cos 0, is not without effect, since the triple-line region now protrudes from the bulk solid. This component leads to a stretching of the surface layer of solid on the vapor-phase side of the triple line for 0 < tt/2 or on the liquid side for 0 > 77/2. By analogy with Eq. (8), we have a second contribution to the work effected, E2. 

For a puncture, break, or pressure relief valve (PRV) opening from a reactor or distillation column, there may be no clear-cut level distinguishing the liquid and vapor phases. That is, the system is initially mixed. In this case, noncondensable gases, condensable vapors, and liquid plus solids are initially discharged. The value of (Xq is nonzero and less than unity, reflecting the contributions of the gases and vapors. 

At the same time, as the concentration decreases the exchange of water molecules by cooperative processes becomes easier and so significant fluctuations in the coordination numbers are observed, which are estimated to be about 1. At even lower concentrations, ion-water correlation patterns will become obscured and then undetectable. As an extrapolation, dynamic processes might contribute more and more to the description of the solution. The strong interaction between Li+ and OH2 (dH. i = 34 kcal/mole in the vapor phase 130>) may cause the cation-water complexes to remain quite well-defined tetrahydrates, on the average, despite all dynamic effects. 

In the condensed phase the sum is over all 3n frequencies, but in the ideal vapor phase the six external (zero) frequencies do not contribute to the IE s, the sum is over the remaining 3n — 6 internals. For condensed rare gases the harmonic assumption is highly approximate, and this is also true for the lattice modes of polyatomics. However as molecular size increases the relative contribution of the external modes becomes less and less important relative to internals. 

Figure 10.25 shows these mutagrams for the vapor and particle phases, respectively. Interestingly, the total direct mutagenicity of the vapor phase, 210 rev m-3, was actually greater than that of the particle phase, 160 rev m 3 furthermore, its mutagenicity profile was substantially different. Thus, fraction 4 is the major peak for the vapor-phase sample whereas most of the particle-phase mutagenicity is in the more polar peaks 6 and 7. Similar enhancements in the contributions of more polar species were reported for bioassay-directed fractionation of SRM 1649 urban air particulate matter (Schuetzle and Lewtas, 1986 Nishioka et al., 1988 ... 

Finally, in the context of the overall vapor-phase mutagenicity of ambient air, we note that significant fractions of the two powerful human cell and bacterial mutagens discussed earlier, cyclopen ta[c<7]pyrene (XXVIII) and 2-nitrodibenzopyranone (XI), have been found in the gas phase (i.e., trapped on PUF plugs) in samples collected during hot weather at sites in southern California (Fraser et al., 1998, and Arey et al., 1994, respectively). Flence the contributions of such species, which are normally considered to be primarily in the particle phase, to the gas-phase mutagenicity at high ambient temperatures should also be considered. 

As discussed earlier (see Fig. 10.26), the contributions of 1- and 2-nitronaphthalenes and the methylni-tronaphthalene isomers to the vapor-phase mutagenicity of extracts of daytime and nighttime samples of ambient air in Redlands, California, were determined by Gupta and co-workers (1996) and shown to be major contributors to the overall vapor-phase mutagenicity of ambient air. Furthermore, the researchers demonstrated that both daytime OH radical initiated and nighttime N03 radical initiated reactions of naphthalene and the methylnaphthalenes are important in pol-... 

Gupta, P., W. P. Harger, and J. Arey, The Contribution of Nitro-and Methylnitronaphthalenes to the Vapor-Phase Mutagenicity of Ambient Air Samples, Atmos. Environ., 30, 3157-3166 (1996). 

C Is XPS spectra for the treated surfaces are not well resolved. From the deconvoluted spectra, the decreases in the main contamination peak at 284.8 eV, and the other two peaks at 1.7 and 4.0 eV higher binding energy (BE) can be followed. The intensities of these peaks are notably much lower in the oxide samples as compared with those of Y58 wafers, consistent with the lower density of surface silanols or contamination adsorption sites between the two surfaces. After vapor-phase HMDS treatment, the contribution of these peaks is greatly reduced and a new main C Is peak centered at 284.6 eV appears, as for the Y58 samples, which is assigned to the —CH3 group, due to the HMDS stabilization reaction. 

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