Migration numbers

In order to split the A values into the X% and 11 values for the individual ions, use is made of a property known variously as the transport number, the transference number, and the migration number. It is the fraction of the current carried by each of the ions present in solution. 

This fraction ti is the transport, transference, or migration number of the given ion in the particular solution. For the simplest case of a solution containing a single electrolyte yielding two ions the transport numbers of the two ions, t+ and are... 

The electrolysis of stannic acid bydrosol, or the purple of Cassius takes place in precisely the same manner as that of the crystalloids, methyl-orange, or the sodium salts of dyestuffs. In both cases under the microscope the separation of the alkali soluble constituent may be seen at the cathode. Where the particles are small enough no movement can be perceived even under the ultramicroscope. Determinations of the migration numbers have shown that in one case seven and in others ten gram mols of stannic acid were transported for every equivalent of silver deposited in the voltmeter. A portion of the stannic acid was deposited on the anode. 

When ethanoi is present, the risk of separation is much less than with methanol. Nevertheless, the ethanol should be relatively anhydrous (less than 3000 ppm water) moreover, if a fuel containing ethanol comes in contact with a water layer, a migration of ethanol toward the water is observed creating a fuel quality problem manifested by lower octane number and an environmental quality problem in that the water will need to be treated. Distribution of ethanol-based fuels requires extra precaution to ensure dryness in distribution systems. 

We can also visualise the subsurface as being made up of an enormous number of point scatterers or diffractors. (Fig b). Each contributes a diffraction curve (hyperbola) to the reflection section. Migration focuses the energy in these curves to a single point. 

Here t. is the intrinsic lifetime of tire excitation residing on molecule (i.e. tire fluorescence lifetime one would observe for tire isolated molecule), is tire pairwise energy transfer rate and F. is tire rate of excitation of tire molecule by the external source (tire photon flux multiplied by tire absorjDtion cross section). The master equation system (C3.4.4) allows one to calculate tire complete dynamics of energy migration between all molecules in an ensemble, but tire computation can become quite complicated if tire number of molecules is large. Moreover, it is commonly tire case that tire ensemble contains molecules of two, tliree or more spectral types, and experimentally it is practically impossible to distinguish tire contributions of individual molecules from each spectral pool. 

Adenosylcobalamin (coenzyme B 2) is required in a number of rearrangement reactions that occurring in humans is the methylmalonyl-Co A mutase-mediated conversion of (R)-methylmalonyl-Co A (6) to succinjl-CoA (7) (eq. 1). The mechanism of this reaction is poorly understood, although probably free radical in nature (29). The reaction is involved in the cataboHsm of valine and isoleucine. In bacterial systems, adenosylcobalamin drives many 1,2-migrations of the type exemplified by equation 1 (30). 

Waxes are one of the two general classes of commercial antiozonants. Waxes are derived from petroleum and are of two common types, paraffin and microcrystalline (20—23). Typical carbon numbers are n = 20 50 for paraffin waxes and n = 30 70 for microcrystalline materials. If a wax is present ia a vulcanizate at a concentration exceeding its solubiUty, some of it will migrate to the mbber surface where it can form a physical barrier to prevent the penetration of ozone. Waxes, of course, are essentially unreactive towards ozone so that there is no appreciable chemical protection. Commercial waxes are... 

Electrical conduction ia glasses is mainly attributed to the migration of mobile ions such as LE, Na", K", and OH under the influence of an appHed field. At higher temperatures, >250° C, divalent ions, eg, Ca " and Mg ", contribute to conduction, although their mobiUty is much less (14). Conduction ia glass is an activated process and thus the number of conducting ions iacreases with both temperature and field. The temperature—resistivity dependence is given... 

The dyes used in the ink sheet must satisfy various requirements (/) optimum color characteristics of the three primary colors (hue, color density, shape of absorption spectmm) (2) sensitivity, ie, sublimabiHty from ink sheet to acceptor sheet (3) fastness for light and migration and (4) compatibiHty with the resin in the ink sheet. With respect to these characteristics, a large number of anthraquinone dyes have been proposed particularly for magenta and cyan colors. Typical examples are given in Table 8 and Table 9. 

These three terms represent contributions to the flux from migration, diffusion, and convection, respectively. The bulk fluid velocity is determined from the equations of motion. Equation 25, with the convection term neglected, is frequently referred to as the Nemst-Planck equation. In systems containing charged species, ions experience a force from the electric field. This effect is called migration. The charge number of the ion is Eis Faraday s constant, is the ionic mobiUty, and O is the electric potential. The ionic mobiUty and the diffusion coefficient are related ... 

Particle diam., i Number of elementary electrical charges, Nq Particle migration velocity, u, ft/sec... 

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