THE CHARACTERISTICS OF ULTRAFILTRATES OF PLASMA BY RAYMOND C. INGRAHAM, CHARLES LOMBARD, Am MAURICE B. VISSCHER
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چکیده
I t has been tacitly assumed by many investigators that the fluid formed by filtration through partially semipermeable membranes will be at diffusion equilibrium with the original fluid. In case one of the indiffusible constituents of the original fluid has an ion in common with a diffusible constituent, the so called Donnan membrane equilibrium would be set up if time adequate for the attainment of equilibrium be allowed. There is an important question as to whether the equilibrium would be set up within the time that the ultrafiltrate is passing through the pores of the filtering membrane. Under experimental conditions when a collodion membrane is used as the ultrafilter, the distance across the membrane is relatively great, that is, of the order of magnitude of tenths of a millimeter, and the time during which the filtered fluid remains on the membrane is so short, that is, a mat ter of minutes, that it might be supposed that equilibrium conditions would never be set up if they depended upon diffusion equilibrium being reached across the whole membrane. Actually, however, we must conceive of the diffusion equilibrium as being set up across the hypothetical plane bounding the region within which the indiffusible constituents can move freely, and separating that region from the region they cannot enter, presumably because of diminutive pore size. That is to say, looking at the membrane as a collection of pores between solid blocks the membrane equilibrium must be set up across the plane of entrance to the pores. Then, unless the fluid moves so rapidly through the pores that diffusion equilibrium cannot occur, we 637
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تاریخ انتشار 2003