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  • 1
    Electronic Resource
    Electronic Resource
    The concentration dependence of the diffusion and permeability in a homogeneous membrane (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 35-41 
    Details
    ISSN: 1435-1536
    Keywords: Chemical potential ; uniform membrane ; concentration depend sorption ; concentration depend diffusivity ; sorption transient ; permeation transient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract For the sorption and diffusion coefficient dependence on the concentration of the penetrant the transport properties of a homogeneous medium are calculated. The diffusion current is assumed to be proportional to the negative gradient of the chemical potential. This is in contrast with the first Fick's law that assumes this current to be proportional to the negative gradient of the concentration of the penetrant. The difference between the two cases depends on the concentration dependence of the sorption coefficient. In a homogeneous membrane the chemical potential formulation leads to an equation which is very similar to the Fickian expression. The apparent diffusion coefficient, however, depends not onlly on the transport resistance but also on the deviation of the sorption coefficient from constancy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01411246
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  • 2
    Electronic Resource
    Electronic Resource
    The concentration dependence of the diffusion and permeability in a homogeneous membrane (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 42-50 
    Details
    ISSN: 1435-1536
    Keywords: Chemical potential ; uniform membrane ; concentration dependent sorption ; concentration dependent diffusivity ; sorption transient ; permeation transient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In a linear dependence of the sorption coefficient S on the equivalent pressure of the penetrant the differences between the Fickian and chemical potential formulation of the diffusion current are very soon larger than 20%, the assumed and tolerated error limit of the experiment. It turns out that the zero concentration diffusion coefficientD o determined from the sorption or permeation transient on the basis of the chemical potential basis is larger than that determined on the basis of Fick's law. The exponential concentration dependence as measured byγ, however, is very little affected up toγc o=4. The steady state current of the permeation mulitplied by the time-lag yields the concentration dependent sorption practically independent of the formulation used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01411247
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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