High pressure diffusion

At the third limit, above 3000 Torr, the mixture again enters an explosive region. At these high pressures, diffusion of H02 to the wall is so slow that this species has sufficient time to react in the gas phase. Thereby a new chain-propagating reaction pathway opens up, initiated by... 

The rate of diffusive separation, k, was determined from separate experimental measurements of iodine radical diffusion rates in the high pressure diffusion limited regime (19). The rate of excited state deactivation, k i, was calculated from the measured quantum yields at high densities where G> = kd/k i (18). It was assumed that k i is proportional to the inverse diffusion coefficient, D 1 (19,23) as both properties are related to the collision frequency. 

Due to its low solubility in magma, CO2 is able to exsolve from magma even at high pressures. Diffuse carbon dioxide emissions can... 

Figure 24.5 shows an optical setup for high-pressure diffusion measurement with a DAC. An H2O/D2O ice bilayer is already prepared in the sample chamber. The dimension of each ice layer is typically 120 pm in diameter and 20 pm in thickness. The detailed procedure for preparing the ice bilayer has been described in the literature [24]. The surface concentration of proton, Ch, at x = 1 can be... 

Diaphragm-cell techniques for high-pressure diffusion measurements... 

There is one complication in the bubble-point test referred to as "diffusional-flow." A small amount of gas-flow can result even through a pore is filled with liquid. The gas dissolves in the liquid in the pores at high pressure, diffuses across the liquid-filled pore in solution, and comes out of solution on the low-pressure side of the membrane. In practice, "diffusional-flow" is not even detected when small membrane areas are involved. Even for large areas, it is easily distinguished from the much larger gas-flow at the bubble point. 

In this relation, ki(Te) is the ionization rate coefficient and o is the neutral gas density. Criterion 4-15 actually restricts pressure, because Da a 1/p and o oc p. When pressure is low, non-equilibrium discharges are controlled by diffusion to the walls and surface recombination. When pressure exceeds 10-30 Torr (the so-called range of moderate and high pressures), diffusion is relatively slow and the balance of charge particles is due to volume processes ... 

D can be calculated by the methods outlined by Satterfield [99]. Under industrial conditions, i.e. at high pressures, diffusion occurs mainly in the bulk and D is thus the bulk diffusion coefficient of the components in the mixture. At low pressures Knudsen diffusion will also play a role, and the pore volume distribution must be known in order to calculate D. 

This determines the total flux at the li/nic of viscous flow. Equations (5.18 and (5.19) therefore describe the limiting form of the dusty gas model for high pressure or large pore diameters -- the limit of bulk diffusion control and viscous flow,... 

Finally, before leaving our exploration of the dusty gas model, we must compare the large pore (or high pressure) limiting form of its flux relations with the corresponding results derived in Chapter 4 by detailed solution of the continuum equations in a long capillary. The relevant equations are (4,23) and (4,25), to be compared with the corresponding scalar forms of equations (5.23) and (5.24). Equations (4.25) and (5.24).are seen to be identical, while (4,23) and (5.23) differ only in the pressure diffusion term, which takes the form... 

Boron and carbon form one compound, boron carbide [12069-32-8] B C, although excess boron may dissolve ia boron carbide, and a small amount of boron may dissolve ia graphite (5). Usually excess carbon appears as graphite, except for the special case of boron diffused iato diamonds at high pressures and temperatures, eg, 5 GPa (50 kbar) and 1500°C, where boron may occupy both iaterstitial and substitutional positions ia the diamond lattice, a property utilized ia synthetic diamonds (see Carbon, diamond, synthetic). 

If the power requirement of the gaseous diffusion process were no greater than the power required to recompress the stage upflow from the pressure on the low-pressure side of the barrier to that on the high-pressure side, then the power requirement of the stage would be Z RTLq (1 /r) for the case where the compression is performed isotherm ally. The power requirement per unit of separative capacity would then be given simply by the ratio... 

In the special case that A and B are similar in molecular weight, polarity, and so on, the self-diffusion coefficients of pure A and B will be approximately equal to the mutual diffusivity, D g. Second, when A and B are the less mobile and more mobile components, respectively, their self-diffusion coefficients can be used as rough lower and upper bounds of the mutual diffusion coefficient. That is, < D g < Dg g. Third, it is a common means for evaluating diffusion for gases at high pressure. Self-diffusion in liquids has been studied by many [Easteal AIChE]. 30, 641 (1984), Ertl and Dullien, AIChE J. 19, 1215 (1973), and Vadovic and Colver, AIChE J. 18, 1264 (1972)]. 

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