Degassing coefficient

Radon is a noble gas and is therefore not readily ionized or chemically reactive. Its properties in terrestrial material will be controlled by its solubility in melt and fluid as well as its diffusion coefficients. Compared with the lighter noble gases, Rn diffuses more slowly and has a lower solubility in water. It will also more readily adsorb onto surface that the lighter rare gases. It can, however be lost by degassing in magmatic systems (Condomines et al. 2003). More information about the behavior of Rn can be found in Ivanovich and Harmon (1992). 

Let us assume that a sphere with radius a is immersed in a liquid of finite volume, e.g., a mineral in a hydrothermal fluid. Diffusion in liquids is normally fast compared to diffusion in solids, so that the liquid can be thought of as homogeneous. Similar conditions would apply to a sphere degassing into a finite enclosure, e.g., for radiogenic argon loss in a closed pore space. Given the diffusion equation with radial flux and constant diffusion coefficient... 

Interstitial Water. The differentiation between solutes and particles is of great importance in the sampling of interstitial water. Most conveniently so-called peepers are used. These consist usually of plexiglass plates in which small compartments (0.5 cm deep and 0.5 - 1 cm high) are separated from the sediments by a dialysis membrane. The compartments are initially filled with degassed distilled water. After 1 - 2 weeks for equilibration subsequent to the retrieval of the peeper, the "dissolved" components are measured in each component. For this type of application the pore size does not seem to be very critical colloids do not seem to accumulate in the compartments (low diffusion coefficients). 

These results were obtained, using hydrogen absorption into pure aluminum between 300 and 1050 °C and were calculated by temporal process degassing. Eichenauer et al. also reported that the square root Sievert s law is satisfied within the limit of error in the solid and in the liquid state. Utilizing the fact that diffusion in the metal is responsible for the hydrogen degassing rate of the solid aluminum they deduced the diffusion coefficient to be D = 0.11 exp (—9780/ RT) cm s . The heat of solution was calculated from these measurements by Birnbaum et al. [7] and Ichimura et al. [8] and found to be in the range of + 0.6 to + 0.7 eV. 

A major breakthrough in the study of gas and v or transport in polymer membranes was achieved by Daynes in 1920 He pointed out that steady-state permeability measurements could only lead to the determination of the product EMcd and not their separate values. He showed that, under boundary conditions which were easy to achieve experimentally, D is related to the time retired to achieve steady state permeation throu an initially degassed membrane. The so-called diffusion time lag , 6, is obtained by back-extrapolation to the time axis of the pseudo-steady-state portion of the pressure buildup in a low pressure downstream receiving vdume for a transient permeation experiment. As shown in Eq. (6), the time lag is quantitatively related to the diffusion coefficient and the membrane thickness, , for the simple case where both ko and D are constants. 

In the expressions for the gas exchange coefficient employed previously, it is evident that the air-water gas exchange flux density is proportional to the difference between a chemical concentration in the water (Cw) and the corresponding equilibrium concentration (Cw H) in air. Consequently, the difference between actual and equilibrium concentration in the water tends to decay exponentially, as expected for any first-order process. In many situations, exponential decay may provide a useful model of a volatile chemical concentration in a surface water. A classic example is degassing of a dissolved gas from a stream if the gas is present at concentration C0 upstream, atmospheric concentration of the gas is negligible, and flow is steady and uniform along the stream, then the gas concentration in the stream is given by... 

To better understand the changes taking place in the intermolecular interactions in the aqueous system, Table IV gives the calculated values of the coefficient X (the index of a peculiar structurization) for different modifications of water. The value X for equilibrium water was calculated from formula (505) for degassed structural water it was calculated from the formula X Cp/S and for degassed water with disordered structure, it was calculated from the formula X CpjS. 

The effect of ultrasonic degassing of liquid metal on the quality of ingots manifests itself by increased density, decreased coefficient of ultrasonic attenuation, and increased ductility at temperatures of plastic deformation. The data on the ductility of a flat-shaped ingot (1700 x 300 mm) from an AMg6 grade alloy at the temperature of hot deformation of 400 °C are given in Table 10. 

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