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Updated: Jul 26, 2026
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A Method for Determination and Simulation of Permeability and Diffusion in a 3D Tissue Model in a Membrane Insert System for Multi-well Plates
Published on: February 23, 2018
Evolving ideas about osmosis and capillary fluid exchange
1Department of Physiology and Biophysics, Medical Sciences Program, Indiana University School of Medicine, Bloomington, Indiana 47405-4401, USA. hhammel@indiana.edu
Summary
Hulett's 1903 theory explains osmosis: solute alters water at the solution's surface, not the membrane. This reinterprets fluid exchange, particularly capillary protein influence, offering a valid view of osmosis.
Area of Science:
- Physical Chemistry
- Solution Thermodynamics
- Biophysics
Background:
- Osmosis is traditionally explained by solute-solvent interactions at a semipermeable membrane.
- Hulett's 1903 theory posits that solutes alter water properties at the solution's free surface.
- This fundamental difference impacts the understanding of osmotic pressure and fluid dynamics.
Purpose of the Study:
- To re-evaluate the physical basis of osmosis based on Hulett's neglected theory.
- To demonstrate that solute-induced changes in water properties occur at the solution surface.
- To reinterpret the role of colloidal proteins in capillary fluid exchange through the lens of Hulett's osmotic theory.
Main Methods:
- Theoretical deduction based on Hulett's 1903 thought experiment.
- Analysis of partial molar properties of water in solution versus pure water at equivalent pressures.
- Conceptual reinterpretation of fluid exchange mechanisms across capillary endothelium.
Main Results:
- Identical partial molar properties (vapor pressure, chemical potential, etc.) exist for water in solution and pure water at different applied pressures.
- Hulett's theory implies solutes exert an internal pressure at the solution boundary, altering water.
- Competing theories incorrectly localize solute action at the semipermeable membrane.
Conclusions:
- Hulett's theory provides the only valid explanation for osmosis, locating solute influence at the solution surface.
- The physical state of water in solution is equivalent to pure water under adjusted external pressure.
- Capillary fluid exchange, influenced by plasma proteins, requires reinterpretation based on this surface-interaction model of osmosis.
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