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Movement of Water as Effected by Free Energy and Pressure Gradients III. Restriction of Solutes by Membranes
Author(s) -
Kemper W. D.,
Evans N. A.
Publication year - 1963
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1963.03615995002700050007x
Subject(s) - membrane , osmotic pressure , chemistry , osmosis , diffusion , water transport , water flow , flow (mathematics) , pressure gradient , volumetric flow rate , chromatography , thermodynamics , mechanics , environmental engineering , environmental science , biochemistry , physics
The validity and method of using the self‐diffusion coefficient of water to estimate movement in response to free energy gradients are outlined. The dominant mechanism of water transport through these membranes is viscous flow, even when osmotic pressure differences are causing the flow. Osmotic pressure and hydraulic pressure differences are equally effective in moving water through a membrane when the solutes are completely restricted by the membrane. When solutes are not completely restricted, osmotic pressure differences are less effective than hydraulic pressure differences in moving water through membranes. Equations including the sizes of the solute molecules and the pores are developed which predict the rate at which osmotic pressure differences move water through uncharged porous media.