Demixing strength

Eqn. (8.6) describes the steady state concentration profile of an (A, B) alloy which has been exposed to the stationary vacancy flux j°. The result is particularly simple if the mobilities, b are independent of composition, that is, if P = constant. From Eqn. (8.6), we infer that, depending on the ratio of the mobilities P, demixing can occur in two directions (either A or B can concentrate at the surface acting as the vacancy source). The demixing strength is proportional toy°-(l-p)/RT, and thus directly proportional to the vacancy flux density j°, and to the reciprocal of the absolute temperature, 1/71 For p = 1, there is no demixing. 

The rule mentioned above is related to the so-called demixing effect20,24 which is explained as follows When the developer is composed of, e.g., two solvents with different polarity, the composition of the developer, hence, the solvent-strength, varies with proceeding of the development as a result of preferential adsorption of the more polar solvent component onto the adsorbent. Consequently, a concentra-... 

In the bed-development separation of sample mixtures which are not subject to the general elution problem (e.g., a two-component sample), solvent demixing is usually an unwelcome complication. The preceding relationships for describing the effect of the solvent on separation [e.g., Eqs. (8-4), (8-5), (8-10)] become inapplicable, and it is difficult to predict satisfactory separation conditions or to define the relative strength of a binary solvent. As in the case of polyzonal chromatography, there may be a tendency for two or more sample components to travel with one of the solvent fronts and hence remain unseparated. In extreme cases a satisfactory separation of a particular sample may be impossible with a given binary A-B of any composition, even where sample K° values are... 

Deactivation of adsorbent, see Adsorbent, HETP, Linear capacity Delocalized adsorption, 270 Demixing, see Solvent Detection of sample bands, 349-350 Development, see Bed development Diatomaceous earth, 172 Diazaaromatics, see Pyridine derivatives Dielectric constant, see Solvent strength Diffusion coefficient, calculation of, 102 Diffusion of sample, contribution to HETP, 102... 

In our recent study [137], it was confirmed that the droplet electrophoretic mobility increased with increasing drop diameter and the increase was explained based on the electro osmotic flow generated due to the additional internal diffuse double layer of the droplet. These values were compared with the predicted mobilities obtained from the electrophoresis theory. The effect of field strength, polarity, and pH on phase demixing rate was studied. These dependencies were found to be consistent with a model based on the electro-osmotic flow ... 

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